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Friday, 18 September 2015

How dairy fats and coconut protect against type 2 diabetes

Type 2 diabetes, in the etiology laid out by Professor Roy Taylor, is (in its usual form at any rate) a condition of fat accumulation in the pancreas, liver, and muscle cells, which causes insulin resistance, hyperinsulinaemia, hyperglucagonaemia, and a vicious cycle of glucotoxicity and lipotoxicity.[1]

It is thus one of a constellation of associated lipid accumulation disorders connected with hyperinsulinaemia, the others including atherosclerosis, NAFLD, obesity. That these conditions are linked in some way was recognised as early as the 1880s by the great German physiologist Wilhelm Ebstein, the father of the modern LCHF diet.[2]

In the recent saturated fat and disease meta-analysis by de Souza et al, higher intake of ruminant trans-palmitoleic acid, a marker of dairy fat consumption, was inversely associated with type 2 diabetes (0.58, 0.46 to 0.74).[3] This is consistent with many studies of serum biomarkers of dairy fat consumption, also including odd-chain saturated fatty acids.

The recent results from Malmö, the third largest city in Sweden, give more detail about these correlations. The Malmö Diet and Cancer cohort was studied using a 7-day food diary and a 1 hour interview as well as an FFQ. This makes the results more reliable than other epidemiological diet studies, which normally use only the FFQ. In
Malmö, greater consumption of dairy fat (including butter) had a protective association with T2D. The association was strongest for shorter-chain fatty acids (from 4:0, butyrate, to 14:0, myristic acid) and there was also a protective effect of a higher ALA/LA ratio.[4]

In a separate analysis of the Malmö cohort, it was found that adherence to dietary recommendations to limit saturated fat to 14% or less of energy was associated with a 15% increased risk of T2D in men and a slightly smaller increase in women. There was a small association in men between adherence to recommendations to limit added sucrose and T2D.[5] (I see a future paper here titled “food sources of sucrose may clarify the inconsistent role of dietary sucrose intake for incidence of type 2 diabetes”. After all, chocolate consumption has beneficial associations not seen with sugar sweetened beverages.)

Is there some simple, mechanical explanation that begins to explain the relationship? If T2D is the result of excess lipid storage, are some lipids easier to store than others? NAFLD research suggests that short- to medium-chain fatty acids are not easily stored. Wistar rats fed coconut oil under NAFLD-generating conditions ate an incredible 143% extra calories across the board with no increase in hepatic lipid accumulation, while butter-fed rats managed an extra 30%.[6]

A team led by George Bray looked at rates of fatty acid oxidation in humans, and made two findings - 1) the shorter the chain length of a saturated fat, the faster the rate of oxidation, 2) the more double bonds in an unsaturated fat, the faster the rate of oxidation. Thus, lauric acid (12:0) was oxidised at a much higher rate than stearate (18:0), and ALA (18:3) was oxidised at a faster rate than LA (18:2).[7]
The faster a fatty acid is oxidised the harder it is to store; this phenomenon discourages lipid accumulation, with benefits to the risk of lipid accumulation disorders.

A second consideration is that fat displaces carbohydrate in the diet, and carbohydrate is the nutrient that, by inducing insulin secretion, increases lipid synthesis and lipid conservation, something that (without the insulin bit) Wilhelm Ebstein understood in the 1880s. Levels of serum triglycerides are directly associated with %E from carbohydrate, and this triglyceride component is the source of pancreatic fat in the model of Professor Roy Taylor.[1]

A third consideration is that saturated fats are resistant to peroxidation and oxidative stress plays a role in promoting beta-cell failure. Saturated fats are protective against beta-cell failure in the alloxan-treated rat.


[1] Taylor, R. Type 2 Diabetes. Etiology and reversibility. Diabetes Care April 2013;36(4): 1047-1055

[2] Wilhelm Ebstein. Corpulence and its treatment on physiological principles. 1882.

[3] de Souza, RJ, Mente, A, Maroleanu, A, Cozma, AI, Ha, V, Kishibe,T, et al.  Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ 2015;351:h3978

[4] Ericson, U, Hellstrand, S, Brunkwall, L, Schulz, C-A, Sonestedt, E, Wallström, P, et al. Food sources of fat may clarify the inconsistent role of dietary fat intake for incidence of type 2 diabetes. AJCN 2015;114.103010v1

[5] Sonestedt, E et al. A high diet quality based on dietary recommendations does not reduce the incidence of type 2 diabetes in the Malmo Diet and Cancer cohort. EADS2015 ePoster #322

[6] Romestaing, C, Piquet, MA, Bedu, E, Rouleau, V, Dautresme, M, Hourmand-Ollivier, I et al. Long term highly saturated fat diet does not induce NASH in Wistar rats. Nutr Metab (Lond). 2007; 4: 4

[7] DeLany, JP, Windhauser, MW, Champagne, CM, Bray, GA. Differential oxidation of individual dietary fatty acids in humans. Am J Clin Nutr October 2000;72(4):  905-911

Sunday, 6 September 2015

This Mendelian Randomisation - I think it does not mean what you think it means.

"LDL may or may not correlate to cardiovascular outcomes,”

-  Dr. Kim Allan Williams, president of the American College of Cardiologists

“God, grant me the serenity to accept the things I cannot change,
The courage to change the things I can,
And the wisdom to know the difference.”

- Reinhold Niebuhr’s Serenity Prayer

Last year there was a good discussion of the saturated fat issue on Otago University's Public Health Expert blog (here) that continued into the comments.
David Brown pointed out that
"Evaluation of the overall health effects of saturated fat requires consideration of markers in addition to LDL-cholesterol. Isocaloric replacement of carbohydrate with any type of fat results in decreased triglycerides and increased HDL-cholesterol, the effect on HDL-cholesterol being greater for saturated fat compared to unsaturated fat. Reductions in saturated fat also adversely affect HDL subpopulations by decreasing larger HDL2-cholesterol concentrations, whereas increases in saturated fat increase this antiatherogenic fraction. "

In response to this, Tony Blakely, professor of public health, commented
"A note of caution on HDL. An important and massive analysis of many studies published in the Lancet in 2012 found no association of HDL with myocardial infarction (or heart attacks). This study used a genetic technique call Mendelian Randomisation, which strips away (in theory, and I believe in practice in this paper) all the confounding that plagues observational studies. Thus, it appears that it is LDL – not HDL – that has a causal association with coronary heart disease.
Reference: Voight BF, Peloso GM, Orho-Melander M, et al. Plasma HDL cholesterol and risk of myocardial infarction: a mendelian randomisation study. The Lancet 2012;380(9841):572-80 doi: 10.1016/s0140-6736(12)60312-2[published Online First: Epub Date]|."

At the time I thought fine, when the evidence runs against your hypothesis, invent a new statistical method that obscures the fact. Nothing to see here. Then a few weeks ago Bill Barendse tweeted a paper that used Mendelian Randomisation and Bill to put it mildly has expertise in the field of genetics, so I thought it might not hurt to look into this again.

Though I am doing so in a superficial way, using logic rather than any deep understanding of the genome, I want to question whether the idea that HDL is not causal in CVD, if it is true, should make any difference at all to how we interpret risk factors or the effect of dietary or lifestyle changes.

Mendelian Randomisation is a method for identifying drug targets. If people with X polymorphism have the same cardiovascular risk as everyone else, then there's not much point in developing a drug that targets X. Fair enough - drugs that elevate HDL by tweaking the enzymes associated with it have been a big disappointment.
The problem is, the cardioprotective association of HDL remains for all that. And, as for "all the confounding that plagues observational studies", HDL is measured directly, whereas LDL is calculated in diverse ways; and it's hard to see how confounding applies to blood tests in the sense that it applies to diet epidemiology. The examples here involve controlled conditions and short-term hard outcomes in secondary prevention. This is as good as it gets - high HDL is indeed a solid marker for cardioprotection and lots of other good things (albeit the HDL increase in response to alcohol probably weakens this in some populations). Does it matter whether the HDL particle itself is protective in a causal fashion? (and, if the particle that removes cholesterol from foam cells is really a dud, where does that leave the lipid hypothesis?)
Should we rely on LDL alone to assess cardiovascular risk? (TG isn't convincingly associated with risk in Mendelian Randomisation either) Well, not if we have those other CVD risk factors, insulin resistance or type 2 diabetes.

"When compared with IS, the IR and diabetes subgroups exhibited a two- to threefold increase in large VLDL particle concentrations (no change in medium or small VLDL), which produced an increase in serum triglycerides; a decrease in LDL size as a result of an increase in small and a reduction in large LDL subclasses, plus an increase in overall LDL particle concentration, which together led to no difference (IS versus IR) or a minimal difference (IS versus diabetes) in LDL cholesterol; and a decrease in large cardioprotective HDL combined with an increase in the small HDL subclass such that there was no net significant difference in HDL cholesterol. We conclude that 1) insulin resistance had profound effects on lipoprotein size and subclass particle concentrations for VLDL, LDL, and HDL when measured by NMR; 2) in type 2 diabetes, the lipoprotein subclass alterations are moderately exacerbated but can be attributed primarily to the underlying insulin resistance; and 3) these insulin resistance-induced changes in the NMR lipoprotein subclass profile predictably increase risk of cardiovascular disease but were not fully apparent in the conventional lipid panel."

("LDL may or may not correlate to cardiovascular outcomes")

Garvey WT et al. Effects of insulin resistance and type 2 diabetes on lipoprotein subclass particle size and concentration determined by nuclear magnetic resonance. Diabetes. 2003 Feb;52(2):453-62.

Are there other interpretations of Mendelian Randomisation in the literature?

"Observed associations between serum CRP and insulin resistance, glycemia, and diabetes are likely to be noncausal. Inflammation may play a causal role via upstream effectors rather than the downstream marker CRP."

Brunner EJ et al. Inflammation, Insulin Resistance, and Diabetes—Mendelian Randomization Using CRP Haplotypes Points Upstream. Plos Medicine August 12, 2008 DOI: 10.1371/journal.pmed.0050155

In other words, those markers that don’t have genetic links to the incidence of a condition should be considered as downstream effects of the true cause. A drug that blocks CRP synthesis won’t prevent diabetes (or any other inflammatory condition) – why should it? Most likely CRP is just doing its job, and things would not suddenly be brilliant if it was removed.
Let’s walk this idea back to lipids and CVD. The TG/HDL ratio isn’t determined by your lipid genes, it’s a downstream effect of dietary carbohydrate (non-genetic) and insulin resistance (genes linked to IR and hyperglycaemia do correspond to CVD). The association between LDL and cardiovascular risk is modified by carbohydrate which increases TG-rich VLDL, the end product of which is the small, dense LDL particle, which is cleared more slowly than larger LDL particles and is thus exposed to peroxidation. Another effect of having a high output of TG-rich VLDL being that HDL gets loaded with TGs and is cleared from circulation faster (hence high TG, low HDL). Half of your LDL-associated risk can be traced to genes (like ApoE4) which you can try to tweak with drugs if you like, and half belongs to Beta-apolipoprotein, sdLDL, oxLDL etc, which are modified by the carbohydrate factor. Saturated fat effects on VLDL and LDL may differ depending on the foods they are in or the other macronutrients , especially carbohydrate.

From Siri-Tarino et al 2015

Your liver is downstream from your gut and has first pass at the nutrients you absorb there; its uptake of fats, sugars and proteins determines the triglycerides, cholesteryl esters, and apolipoptoteins the liver produces and its types of HDL and LDL species. Genetics has more influence on the LDL species than on the HDL or TG, and if you are insulin-resistant the effect of high-carbohydrate diet on HDL, TG-rich VLDL, and atherogenic LDL subspecies is magnified; this is the pathology that hyperlipidaemia, MetSyn, and diabetic lipid patterns have in common.

This is how Mendelian Randomization of LDL and HDL was presented in a recent butter and cholesterol paper [here]
“The LDL-cholesterol concentration is a true risk factor for CVD. A meta-analysis of 26 trials showed that, for every 1-mmol/L reduction in LDL cholesterol, there was a 20% relative reduction in deaths that were due to coronary heart disease (RR: 0.80; 99% CI: 0.74, 0.87) (30). Thus, our result of an increase in LDL-cholesterol concentration of 0.16 mmol/L was not negligible. In addition, butter resulted in a concomitant increase in HDL cholesterol compared with the habitual diet. An increase in HDL cholesterol of the butter diet rich in long-chain SFAs was expected because these SFAs are known to increase HDL cholesterol…
 According to the literature, the HDL cholesterol concentration is associated with a protective effect on CVD (31, 32). However, studies that used Mendelian randomization showed that genetically decreased HDL cholesterol did not increase risk of myocardial infarction and questioned a causal association between the HDL concentration and CVD (33–35). Thus, it is necessary to be careful with interpreting low HDL-cholesterol concentrations as a CVD risk factor. However, as a marker of cardiovascular health, changes in HDL cholesterol concentrations need to be included when interpreting the effect of SFAs in the diet. It is possible to speculate that an unbeneficial increase in LDL cholesterol may partly be counteracted by the beneficial effect of SFAs on HDL cholesterol, which suggests that dairy and saturated fat may be less harmful in relation to CVD than previously thought, as reported in recent meta-analysis (8, 9).”
Engel S and Thorstrup T (2015) Butter increased total and LDL cholesterol compared with olive oil however resulted in higher HDL cholesterol than habitual diet. Am J Clin Nutr. ajcn112227

Another suggestion is that HDL functionality is the important variable. HDL functionality is increased by CLA in butter and ruminant fat, olive oil polyphenols,[1] and the action of vitamin E (found in nuts and vegetable oils and other sources of linoleic acid) on protein kinase-C.[2] As substitution of all fats for carbohydrates tends to raise HDL, there will be a correspondence between intake of natural fats, HDL, and HDL functionality. Polyphenols administered without fat reduce inflammation but do not increase HDL or HDL functionality.[3]

Thus there is evidence for a rather neat correspondence between the quality of dietary fat and the cardioprotection associated with HDL -

[1] Hernáez Á et al (2014) Olive oil polyphenols enhance high-density lipoprotein function in humans: a randomized controlled trial. Arterioscler Thromb Vasc Biol. 2014 Sep;34(9):2115-9. doi: 10.1161/ATVBAHA.114.303374. Epub 2014 Jul 24.[2] Mendez AJ et al (1990) Protein Kinase C as a Mediator of High Density Lipoprotein Receptor dependent Efflux of Intracellular Cholesterol (1990) Journal of Biological Chemistry Vol. 266, No. 16, Issue of June 5, pp. 10104-10111,199

[3] Nicod N et al (2014) Green tea, cocoa, and red wine polyphenols moderately modulate intestinal inflammation and do not increase high-density lipoprotein (HDL) production. J Agric Food Chem. 2014 Mar 12;62(10):2228-32. doi: 10.1021/jf500348u. Epub 2014 Mar 4.

From a 2014 paper that failed to find a causal relationship between HDL and CVD:

The estimates of LDL-C from instrumental variable analysis showed that a long-term genetically increased LDL-C, regardless of the analytical strategy used (unrestricted, restricted, or unrestricted score plus sequential adjustments) resulted in an increased causal OR for CHD, which is similar in magnitude to that reported in randomized trials of statin-lowering therapies in individuals at low risk of vascular disease1 and is further evidence of the validity of our various analytical approaches.For triglycerides, the findings for the unrestricted and restricted allele scores were concordant, with both showing association with CHD. However, the unrestricted score adjusted for HDL-C diminished the association to null.This could mean that a treatment that targets a triglyceride pathway that has no effect on HDL-C may not be beneficial, whereas a treatment that targets a triglyceride pathway that both reduces triglycerides and increases HDL-C could have a role in prevention of CHD events. An alternative explanation is that HDL-C could mark long-term triglyceride concentrations, but this hypothesis requires further investigation.

Holmes, MV, et al. Mendelian randomization of blood lipids for coronary heart disease. 2014. DOI:

Clearly, the complete implications of mendelian randomization for cardiovascular risk related to diet are far from clear.
But I'd putting money on this; these analyses don’t change the meanings of metabolic risk factors that are affected by diet and lifestyle, and if anything they support their usefulness as measures of improvement.

Thursday, 16 July 2015

Oliver and Boyd 1953 - lessons from the early history of the lipid hypothesis.

The introduction to Hooper et al. 2015 gives a good potted history of the lipid hypothesis. It's well worth reading to get some background as to why this idea that saturated fat causes heart disease took off the way it did. (Hooper 2015)
There's a chain of logic involved. There is cholesterol in atherosclerotic plaques. There was a correlation between high cholesterol and heart disease. Eating saturated fat tends to elevate serum cholesterol. Join the dots.
The assumption is that the high cholesterol that correlates with heart disease and the effect of saturated fat on serum cholesterol are the same thing. 

In 1949 Ryle and Russell in Oxford documented a dramatic increase in coronary heart disease (CHD), and the Registrar General’s Statistical Tables of 1920 to 1955 showed that there had been a 70-fold increase in coronary deaths during this 35-year period (Oliver 2000Ryle 1949). This sudden surge in coronary heart disease sparked research into its causes. A case-control study published in 1953 of 200 post-myocardial infarction patients and age-matched controls established that those with disease had higher low density lipoprotein (LDL) cholesterol levels (Oliver 1953).

The 70 fold rise seen by Ryle and Russell seems to have been mainly due to vagaries in coding cause of deaths during the period, plus a decrease in mortality; in large part, more people were dying of CHD because more people were living to a suitable age, and CHD was becoming a popular diagnosis, replacing other similar causes on death certificates. CHD almost certainly did rise, but probably not nearly so fast. And of course it's ridiculous to think that people didn't eat much saturated fat before the 1920s. There's a small mistake in Hooper et al.'s citation of Oliver and Boyd 1953; this paper doesn't mention LDL cholesterol, just serum cholesterol. The reviewers would have picked this up if they'd been interested in the early history of the lipid hypothesis.The Plasma Lipids in Coronary Artery Disease. Oliver MF, Boyd GS. 
Br Heart J. 1953 Oct;15(4):387-92. Free text.
Oliver and Boyd 1953 does show a significant difference in cholesterol levels between MI patients and case-controls. That's true (except that strangely there was absolutely no correlation in women in the 50-59 age group). Peak decade for MI in men (largest % of cases) was 50-59, for women 60-69. 

The subjects were 200 consecutive admissions with coronary artery disease and 200 miscellaneous inpatient controls. In the coronary artery disease group, there was electrocardiographic confirmation of myocardial infarction in 170, and of ischaemia before or after the Master two-step test in 30 who presented clinically with angina of effort; any subject who lacked cardiographic confirmation of coronary artery disease was excluded. Adequate controls were very difficult to obtain from a hospital population, but were carefully selected from convalescent in-patients, who had no history or clinical features of atherosclerosis, cardiac, hepatic, metabolic, or renal disease, nor of any other condition known to influence the plasma lipids.
The coronary artery disease group was completed first, and the mean age of each decade of both sexes was determined; the control group was then completed so that the mean age, and number of cases in each decade, would correspond with the coronary artery disease group.

Does this study indicate in any way that saturated fat in the diet was linked to the high cholesterol associated with CHD?

In a small pilot study an irregular diurnal variation in plasma cholesterol was observed thus it was decided that all samples should be withdrawn between 8 and 8.30 a.m. in the fasting state. No blood sample taken during anticoagulant therapy has been included in this series. Similarly, no blood sample taken within five weeks of the occurrence of myocardial infarction has been included. All subjects were receiving a light ward or weight-reducing diet. 

So - the MI cases had been receiving the "light ward or weight-reducing diet" for at least 5 weeks. The controls were "convalescent", and as convalescence was still a leisurely process in hospitals in the UK in 1953, we can safely assume their exposure to hospital food was similar. Indeed, the study indicates that there was no age-related obesity in controls: 

Hypertension and obesity are more common after the menopause, but neither would seem 
to influence these observations; all the control subjects had a diastolic pressure of less than 90, and a morphological study employing a ponderal index assessment (Sheldon et al., 1940), did not show any tendency to endomorphy in this decade in the controls.

Though the text is not clear on this, the MI cases were probably more likely to be on the weight reducing diets than controls.

So what does Oliver and Boyd 1953 tell us about saturated fat and heart disease? Surely it demonstrates either 1) that the serum cholesterol level in MI cases has nothing to do with diet, or 2) that the serum cholesterol level in MI cases relates to a response to diet which is unique to MI cases, and which does not go away on light hospital or weight-reducing rations. There are three possible explanations of this; 1) that genetic determinants of serum cholesterol, such as FH phenotype, are related to MI (which seems pretty uncontroversial), 2) that cholesterol is elevated in response to an MI, and that this effect plays out over many weeks, 3) that cholesterol response to diet is influenced by either a recent MI or by genetic conditions predisposing to MI.
That saturated fat can cause heart disease in healthy people doesn't seem a logical conclusion to draw from Oliver and Boyd and is not a possibility mentioned in the text.

Any other explanations? 1953 was one year after the killer smog of London. The Oliver and Boyd study took place in Edinburgh, historically known as Auld Reekie for its air pollution. The Clean Air Act 1956 was the first attempt to limit air pollution in the UK. These and similar later Acts, the publication of and response to Silent Spring (1962), and the decline in cigarette smoking following (in the U.S.) the Surgeon General's report and Consumer Union reports into smoking (1963) seem to match the rapid decline in CHD after 1970 in the English speaking world and those countries that undertook similar public health measures in the same historical period (including Scandinavia and Japan).
Oliver and Boyd didn't ask questions about smoking, which might have been revealing, but they did at least set up their experiment to control for diet. It's just a pity that Keys and Hegsted ignored that.

See also: 
Flaws, Fallacies and Facts: Reviewing the 
Early History of the Lipid and Diet/Heart
Hypotheses. Elliott J. Food and Nutrition Sciences, 2014, 5, 1886-1903

Tuesday, 23 June 2015

Lee Hooper et al., 2015 - the latest Cochrane meta-analysis of saturated fat reduction RCTs

A new Cochrane meta-analysis of saturated fat reduction trials by Lee Hooper et al. has barely made a splash in the blogosphere, and my mention of it on Twitter barely merited a retweet.
This is a pity, because this is a question that is not really resolved.
A matter of particular interest to me about RCT meta-analysis is whether it agrees with prospective cohort meta-analysis. Another feature of Hooper's work that's instructive, which I intend to discuss, is her ongoing disagreement with Dariush Mozzafarian's analysis of fatty acid substitution.

Reduction in saturated fat intake for cardiovascular disease, The Cochrane Library, June 10 2015. Hooper L, Martin N, Abdelhamid A, Smith GD. DOI: 10.1002/14651858.CD011737

We include 15 randomised controlled trials (RCTs) (17 comparisons, ˜59,000 participants), which used a variety of interventions from providing all food to advice on how to reduce saturated fat. The included long-term trials suggested that reducing dietary saturated fat reduced the risk of cardiovascular events by 17% (risk ratio (RR) 0.83; 95% confidence interval (CI) 0.72 to 0.96, 13 comparisons, 53,300 participants of whom 8% had a cardiovascular event, I² 65%, GRADE moderate quality of evidence), but effects on all-cause mortality (RR 0.97; 95% CI 0.90 to 1.05; 12 trials, 55,858 participants) and cardiovascular mortality (RR 0.95; 95% CI 0.80 to 1.12, 12 trials, 53,421 participants) were less clear (both GRADE moderate quality of evidence). There was some evidence that reducing saturated fats reduced the risk of myocardial infarction (fatal and non-fatal, RR 0.90; 95% CI 0.80 to 1.01; 11 trials, 53,167 participants), but evidence for non-fatal myocardial infarction (RR 0.95; 95% CI 0.80 to 1.13; 9 trials, 52,834 participants) was unclear and there were no clear effects on stroke (any stroke, RR 1.00; 95% CI 0.89 to 1.12; 8 trials, 50,952 participants). These relationships did not alter with sensitivity analysis. Subgrouping suggested that the reduction in cardiovascular events was seen in studies that primarily replaced saturated fat calories with polyunsaturated fat, and no effects were seen in studies replacing saturated fat with carbohydrate or protein, but effects in studies replacing with monounsaturated fats were unclear (as we located only one small trial). Subgrouping and meta-regression suggested that the degree of reduction in cardiovascular events was related to the degree of reduction of serum total cholesterol, and there were suggestions of greater protection with greater saturated fat reduction or greater increase in polyunsaturated and monounsaturated fats. There was no evidence of harmful effects of reducing saturated fat intakes on cancer mortality, cancer diagnoses or blood pressure, while there was some evidence of improvements in weight and BMI.

In other words, no benefit from reducing SFA per se (some non-significant trends towards small benefits) on mortality and hard endpoints such as heart attacks. Non-significant trends and even null associations have been written up here as if they are meaningful. The Cochrane Collaboration surely wouldn't allow this in a review of drug trials, so why is it okay here?
Beneficial association between reduced SFA and cardiovascular events (17% RR), which is dependent on what SFA is replaced with, i.e. only PUFA. Because there is no reduction in individual classes of serious events, it's possible that the symptomatic relief of angina is the main benefit being shown here, but those figures aren't presented. In any case, this is almost certainly an effect of higher PUFA intakes and not SFA reduction.

An interesting point here is that this is the opposite of the prospective cohort data. Jakobsen et al. and Farvid et al. state that replacing SFA with PUFA (5%E) is associated with a 13% lower rate of CHD mortality, yet has (in Farvid et al.) non-significant effects on cardiovascular events in the randomised model. Non-randomised results from Farvid et al.:

“When the highest category was compared with the lowest category, dietary LA was associated with a 15% lower risk of CHD events (pooled RR, 0.85; 95% confidence intervals, 0.78-0.92; I(2)=35.5%) and a 21% lower risk of CHD deaths (pooled RR, 0.79; 95% confidence intervals, 0.71-0.89; I(2)=0.0%). A 5% of energy increment in LA intake replacing energy from saturated fat intake was associated with a 9% lower risk of CHD events (RR, 0.91; 95% confidence intervals, 0.87-0.96) and a 13% lower risk of CHD deaths (RR, 0.87; 95% confidence intervals, 0.82-0.94).”

Results from Jakobsen et al.

“For a 5% lower energy intake from SFAs and a concomitant higher energy intake from PUFAs, there was a significant inverse association between PUFAs and risk of coronary events (hazard ratio: 0.87; 95% CI: 0.77, 0.97); the hazard ratio for coronary deaths was 0.74 (95% CI: 0.61, 0.89).”

Subgroup analysis reveals that this effect on cardiovascular events in Hooper et al. 2015 is specific to PUFA and, though it is related to LDL, it depends on PUFA, not CHO, being the LDL-lowering replacement for SFA.

We found no important effects of reducing SFA compared to usual or control diets on mortality when we subgrouped studies by SFA replacement (with PUFA, MUFA, CHO, or protein), mean duration, baseline SFA intake, or difference in SFA between intervention and control arms, decade of publication, or degree of reduction of serum total cholesterol. "
"There was a reduction in LDL in participants with reduced SFA compared to usual diet (MD -0.19 mmol/L, 95% CI -0.33 to -0.05, I² 37%, 5 RCTs, 3291 participants, P 0.006). There was no clear differential effect on LDL depending on the replacement for SFA (PUFA, MUFA, CHO or a mixture). "

- " the subgroup of studies which achieved a reduction in serum total cholesterol of at least 0.2 mmol/L reduced cardiovascular events by 26%, while studies that did not achieve this cholesterol reduction showed no clear effect."


"When we subgrouped according to replacement for SFA, the PUFA replacement group suggested a 27% reduction in cardiovascular events, while there were no clear effects of other replacement groups."

So - lowering LDL has no association with benefit except when PUFA is increased, and no association with mortality even so.

This is not evidence of harms from SFA. 

This is consistent with an effect of the PUFA foods (possibly confounded by anti-atherogenic effects of their significant alpha-tocopherol, gamma-tocopherol, and Co-enzyme q10 content, and the anticoagulant effects of the hydrogenated vitamin K analogues formed during oil processing) being distinct from the effects of SFA lowering.

A substitution of PUFA for SFA in the context of a diet high in refined carbohydrate, which was the norm for most trials in Hooper at al., would produce a less atherogenic lipoprotein protein - less ApoCIII, for example (See anything by Ron Krauss). You would get the same effect by reducing carbohydrate without cutting SFA (ditto), which is why substitution of PUFA for CHO, even the small increments measured in prospective cohort meta-analysis, shows more benefit than substitution of PUFA for SFA . But substituting PUFA for CHO wasn't the (intentional) plan of any of the studies in Hooper et al. though it may well have happened incidentally as a result of calorie lowering or better food choices due to the educational aspect of these trials. (N.B. trials included were potentially biased by the intervention arms having education and support not available to controls, and by the SFA-lowering advice meaning less cakes, biscuits, more fish, veges, but the Finnish Mental Hospital trial where controls were handicapped by cardiotoxic drugs was excluded - EDITED - Excellent discussion of this paper by Steve Hamley here).

"The number of cardiovascular deaths was relatively small (1096), so while we can be quite confident in reporting a reduction in cardiovascular events (4377 events) with SFA reduction, and a lack of effect on total mortality (3276 deaths) within the studies' time scales, the effect on cardiovascular mortality is less clear. The risk ratio of 0.95 (95% CI 0.80 to 1.12) may translate into a small protective effect, but this is unclear. The lack of effect on individual cardiovascular events is harder to explain; there were 1714 MIs, 1125 strokes and 1348 non-fatal MIs, 2472 cancer deaths, 3342 diabetes diagnoses and 5476 cancer diagnoses. Lack of clear effects on any of these outcomes is surprising, given the effects on total cardiovascular events, but may be due to the relatively short timescale of the included studies, compared to a usual lifespan during which risks of chronic illnesses develop over decades."

By the same token, harmful effects of higher PUFA intakes may also take years to develop.

Where is the table for all-cause non-CHD mortality? Trend for cancer diagnoses = 0.94 (NS), trend for cancer deaths = 1.00 - no sub-group analysis. 

"One surprising element of this review is the lack of ongoing trials. In all previous reviews we have been aware of ongoing trials, the results of which were likely to inform the review, but for this review we have not noted any new trials on the horizon and so perhaps the current evidence set is as definitive as we will achieve during the 'statin era'."

I predict that towards the end of the "statin era" we will begin to see RCTs of LCHF and Paleo diets in the primary and secondary prevention of CVD/CHD. And I predict that, given the very low bar set by SFA restricted diets - which seem here to be not much better for you than the rubbish people normally eat before they end up in hospital, which was after all the composition of the control diets - LCHF and Paleo diets will do pretty well in this regard.

Hooper disputes Mozzafarian's exaggerated analysis still.  "A recent review by Mozaffarian 2010, which again included very similar studies to the last version of this review, with the Finnish Mental Hospital study and Women's Health Initiative data added, stated that their findings provided evidence that consuming PUFAs in place of saturated fat would reduce coronary heart disease. However, their evidence for this was limited and circumstantial, as they found that modifying fat reduced the risk of myocardial infarction or coronary heart disease death (combined) by 19% (similar to our result). As the mean increase in PUFAs in these studies was 9.9% of energy, they infer an effect of increasing PUFAs by 5% of energy of 10% reduction in risk of myocardial infarction or coronary heart disease death. "

According to Hooper's 2010 editorial she thinks this back-dated evidence, from times when PUFA baselines were lower than today, justifies current PUFA intakes - it does not necessarily warrant an increase on the scale suggested by Mozaffarian.

"Mozaffarian and colleagues go further in presenting
their results as a 10% risk reduction for each additional
5% of PUFA consumption, although they present no evidence
of a dose-response relationship (not presenting
subgrouping or meta-regression by PUFA intake) and do
not explain how much of the PUFA consist of ω-3 fats
in each trial.
This review addresses an important question and
re-opening the debate on the effectiveness of replacing saturated
by polyunsaturated fats on coronary heart disease
is very welcome. However, dietary patterns have changed
over the 20–50 years since these studies ware carried out.
It would be useful to examine the full data set, including
more recent trials before concluding, as the abstract does,
that “a shift toward greater population PUFA consumption
in place of SFA would significantly reduce rates of CHD.”
Such a shift has already occurred since these trials were

carried out, and further shifts may be unhelpful."

Hooper L. Meta-analysis of RCTs finds that increasing consumption of polyunsaturated fat as a replacement for saturated fat reduces the risk of coronary heart disease. Evid Based Med2010;15:108–109doi:10.1136/ebm1093.

C-enzyme Q10 and tocopherols as confounders in PUFA oils

Coenzyme Q10 consumption promotes ABCG1-mediated macrophage cholesterol efflux: A randomized, double-blind, placebo-controlled, crossover study in healthy volunteers

This shows that consumption of Co-Q10 improves HDL functionality, e.g. is anti-atherogenic. There is likely a separate effect on oxLDL as well.
Dose was 100mg 2x daily.

Vegetable oils are among the richest dietary sources of CoQ10.
the amount is much lower than in the experiment above, but enough to boost intake for most people. Absorption of coenzyme Q10 decreases with increasing supplemental dose.

Do oils raise serum co-Q10 levels?
Serum Co-Q10, alpha-tocopherol, and gamma-tocopherol are associated in women

"CoQ10 was significantly and positively correlated to α- and γ-tocopherol, and BMI was positively associated with CRP and γ-tocopherol in both groups."
Gamma tocopherol is generally considered to be a reliable marker of soy and corn oil consumption; soy and corn oils supply all 3 nutrients. It is most likely that the increase in Co-Q10 has the same origin as the increase in tocopherols. And maybe the same origin as the increased BMI, i.e. those of these oils that are highest in gamma-tocopherol - soy and corn.

Thursday, 4 June 2015

Statins and cancer stories - the stupidest thing you'll read this week.

If this isn't the stupidest thing I've read since that "high-protein diets kill mice fed lots of casein, ergo humans shouldn't eat paleo diet (which a priori eliminates casein)" story last week.

Statins 'could halve the risk of dying from cancer'

Apparently, people taking statins have much lower rates of cancer mortality. Cue more research and RCTs aimed at proving a new use for this class of drugs and sell even more prescriptions.

However, there are reasons why this claim (or carefully couched suggestion) amounts to quackery of the "false hope" sort. False hope for gullible GPs especially.

The studies did not show statins would prevent cancer. But they suggest taking them daily could save thousands of lives, by slowing the spread of diseases.
Doctors said it was not clear why they had such an effect, but the drugs reduce cholesterol, which is known to help the spread of disease.

Please do not bang your head quite so hard on your desk, no doctor recommends that (yet).

There are some basic things these "experts", and I use the inverted commas wisely, don't seem to know, or at least don't admit to knowing in a press release.

I summed up two of them in a letter to the Herald yesterday (unpublished so far).

Dear Sir/Ma'am,

According to a study reported in yesterday's Herald, people who take statin drugs are less likely to die from cancer. However, this effect has not been seen in 27 randomised, controlled trials. Statins are prescribed to people with high cholesterol. People with low cholesterol have an increased risk of cancer, and a greatly decreased likelihood of being prescribed statins. This might help to explain what is being presented as a possible protective effect of statins against cancer.

Yours sincerely,

George Henderson

References: (who includes references in letters to the Editor? I do. Maybe that's why they don't get published)

Serum cholesterol and cancer risk: an epidemiologic perspective.

Lack of Effect of Lowering LDL Cholesterol on Cancer: Meta-Analysis of Individual Data from 175,000 People in 27 Randomised Trials of Statin Therapy

I wanted to save space to increase the odds of publication, so left out two other confounders;

1) People who take statins are goodie-goods. If the doctor tells them to take pills, they take them. If the doctor tells them to stop smoking, they stop. And so on. In fact doctors are less likely to prescribe statins to smokers.

2) Lots of people stop taking statins because of their side effects. Side effects - the inability to tolerate statins - could signify underlying diseases of ageing or nutritional deficiencies that also increase cancer risk or mortality.

If statins reduced cancer mortality an effect would be seen in RCTs. Statins cannot reduce cancer mortality by lowering LDL cholesterol, which is a protective risk factor for many common cancers, and for non-coronary mortality in ageing populations.

I'm not ruling out a cytotoxic effect of statins in certain cancers or a potentiating effect with specific cancer meds, but that's not what's being touted here, and were there a general effect of this sort with regard to more common cancers it would have shown in the RCTs.

Monday, 1 June 2015

Japanese epidemiology puts another hole in the lipid hypothesis

Everyone is reading this masterful analysis (PDF) of the lipid hypothesis from Japan, a country where it doesn't even seem true, which hasn't stopped the Japanese authorities from recommending cholesterol limits. The whole thing is worth reading, and sections of it are particularly congruent with the reverse lipid hypothesis of hepatology - that saturated fat protects the liver.

That this reversal comes from Japan is particularly interesting, because Japan is the poster boy of the lipid hypothesis - low intake of saturated fat (2.2%E in the Seven Countries Study), low CHD mortality, and has long been used to support the pious hope that if our SFA intakes were only low enough we'd see a comparable reduction in CHD. The reason there's no correlation between SFA and CHD in meta-analysis is, so they say, because we all eat too much SFA, except for the Japanese (oh, and the people of the former USSR and its satellites, who have fantastically high CHD mortality, but let's ignore that). The limbo argument - you can't get under the CHD bar if you're not low enough - is one of those last-ditch defenses of lipid hypothesis epidemiology.
Another is the undisputable truth that in many countries, the ones we know best, CHD mortality did fall at around the same time that SFA intakes declined. Steven Hamley makes the valid point that this SFA was in practice mostly replaced with refined carbohydrate, which no epidemiologist would predict to have lowered CHD based on any data we have. I'll link to this post of Steven's here and recommend regular reading of his blog for anyone interested in this topic.

Here's the mortality trend graph for the USA, typical of NZ, Australia, Canada, Finland and other big dairy and meat countries. SFA goes down a little, CHO goes up, CHD goes down a lot and keeps falling after 1972. Okay.

Here's the same data for Japan.

Ignore the glitch in the coding; it's obvious that CHD mortality fell from about 1970 or 1971. What happened to Japanese fat intake? Saturated fat intake doubled between 1965 and 1975, kept climbing thereafter. Serum cholesterol levels have been going up too.
What we see here is exactly the same CHD mortality pattern in two countries with directly opposing saturated fat and serum cholesterol trends. Two countries which were placed by Keys et al. at opposite extremes, kept apart by their difference in SFA intakes and serum cholesterol.

There are two or three possible explanations. One is that there is an optimal SFA intake, higher than 1965 Japan, lower than 1965 USA, pretty much where both countries are today. This has a certain biological plausibility (though it does require belief in Paleo just-so-stories), but it doesn't match other epidemiology (replacing dietary SFA with CHO elevates serum SFA, reduces LDL particle size, increases CHD events, and doesn't alter CHD mortality. Which higher or lower SFA doesn't correlate with anyway within any population band, be it Japan or Finland).

The second explanation is an improvement in treatment. This is usually countered with the objection that statins weren't available till the 1980's. So - warfarin, nitrates, beta-blockers - were those all being prescribed for no reason? Sure they didn't lower cholesterol, but if that isn't the dominant factor in CHD it's plausible that they had a significant effect as doctors got better at using them.

The third explanation is that this was an epidemic with an unknown or unappreciated cause, and it passed like historical epidemics do. For example, a pathogen wiped out by vaccination or other changes. Smoking, which does fit the trends and which does get some credit. Smog and industrial and agricultural pollution; the mortality trends closely match the beginnings of environmental and workplace regulation of pollutant exposure in both the USA and Japan. Silent Spring was published in 1962 and the period 67-72 represents a tipping point during which restrictions on household smoke, industrial emissions, agricultural residues, workplace exposures, and vehicular emissions began, and after which they became increasingly strict. Another consideration is that 1972 or thereabouts marked the end of national conscription in many western countries. After that date there was a growing expectation that people wouldn't and couldn't be expected to do things any longer if they didn't want to. Turn on, tune in, drop out. The decline of the stress-driven West began, though how this played out in Japan I have no idea. Micronutrition also improved, with the availability of out-of-season foods, new cultivars and imports. Increased PUFA intakes should be seen as part of this trend - the PUFA aspect of the lipid hypothesis was really a proposal for nutrient megadosing to achieve a pharmacological effect not seen, according to Keys et al., with normal intakes of PUFA.

What are we left with today as primary causes of CHD? A significant residue of chemical atherogenesis from pollution and smoking; the effects of malnutrition and the oxidative stress of deficiency, made worse by high-energy diets and the adulterants and contaminants of food processing technology; and above all the effects of metabolic diseases - MetSyn, hyperinsulinaemia, type 2 diabetes, and so on.
The disease patterns of the present are not just those of the past repeated with more or less intensity.

Friday, 22 May 2015

How a high fat ketogenic diet prevents diabetic ketoacidosis – somatostatin

Karl Petren 1868-1927
How a high fat ketogenic diet prevents diabetic ketoacidosis – somatostatin

It is pretty well-accepted now that nutritional ketosis and diabetic ketoacidosis are quite different things, but it is not yet understood how nutritional ketosis prevents diabetic ketoacidosis. That it does so was clear in 1923; both Newbugh and Marsh[1] and Karl Petren[2] reported in that year from their respective diabetes clinics that a diet high in fat, restricted in protein, and very low in carbohydrate, fed to diabetic patients, including (certainly in the case of Newburgh and Marsh) those with juvenile-onset, or type 1 diabetes, prior to the introduction of insulin, resulted in no cases of DKA developing. Newburgh and Marsh also reported DKA developing in a fasting case, so the inhibition of DKA was not a result of carbohydrate restriction alone.
DKA is the result of the unrestrained action of glucagon, which stimulates lipolysis and proteolysis, flooding the liver with substrates for ketogenesis (fat and ketogenic amino acids) and gluconeogenesis (glycerol and glucogenic amino acids), in the absence of insulin. Glucose, in the absence of insulin, is also a glucogenic substrate and increases both glucagon release and hepatic gluconeogenesis. The combination of hyperglycaemia and hyperketonaemia that ensues produces a loss of fluid volume and a life-threatening acidosis.
How might feeding fat prevent this?

Raphi Sirt, in response to my restatement of this question recently, tweeted a paper that cited another paper referring to a 1970’s experiment in which people with insulin-dependent diabetes were withdrawn off insulin and given a peptide called somatostatin by researchers happily free from modern ethics committee constraints.[3] This hormone prevented DKA by inhibiting glucagon release from the pancreatic alpha-cells. Somatostatin exists in two main forms in human metabolism, as 14 and 28 length peptides, and somatostatin 28 is released from the delta cells of the gut and pancreas proportionately in response to the ingestion of fat; there is a partial response to protein and no response to carbohydrate, making the somatostatin 28 ratio of macronutrients the inverse of the insulin ratio.[4]
In normal metabolism somatostatin inhibits both insulin and glucagon release. It is probably responsible for mediating the slower digestive response needed when fat is consumed in a meal. But if you have no insulin to begin with, somatostatin is just a glucagon inhibitor. If you have too much insulin and low insulin sensitivity (and hence too much hepatic glucagon activity) it’s probably helpful too, as long as you aren’t also eating carbohydrate.

Unusually I could not find full-text version of references 3 and 4, so there are still some very unanswered questions. Did Gerich et al. know of the findings of Newburgh and Marsh in designing their experiment? What was the form of somatostatin they used? And, did the serum concentrations of somatostatin approximate those that might be attained with high fat feeding? If not, does the paracrine release of somatostatin 28 that inhibits glucagon necessarily result in such high serum levels?
All your help, as always, is appreciated.

[Update 23-05-15] The somatostatin that prevents DKA in the Gerich study is somatostatin 14, whereas that which is elevated by dietary fat is somatostatin 28. How might this work? Somatostatin 14 has a higher affinity for the distribution of receptors on alpha cells, somatostatin 28 for that in beta cells. So in normal physiology somatostatin 28 is mainly inhibiting insulin, more so than glucagon. However, in physiology without functioning beta cells, the weaker effect on alpha cells is all that there is, and somatostatin 28 is inhibiting glucagon.

[1] Further observations on the use of a high fat diet in diabetes mellitus. Newburgh LH and Marsh PL. Archives of Internal Medicine April 1923 Vol. 31 No. 4.

[2] Über Eiweissbeschränkung in der Behandlung des Diabetes gravis, Petren K, 1923 - On protein restriction in the treatment of diabetes gravis. Cited in: A Substance in Animal Tissues which stimulates Ketone-Body Excretion, Stewart FB and Young HG, Nature 1952; 170, 976 - 977 doi:10.1038/170976b0

[3] Prevention of Human Diabetic Ketoacidosis by Somatostatin — Evidence for an Essential Role of Glucagon. Gerich JE, Lorenzi M, Bier DM et al. N Engl J Med 1975; 292:985-989. DOI: 10.1056/NEJM197505082921901

[4] Effect of ingested carbohydrate, fat, and protein on the release of somatostatin-28 in humans. Ensinck JW, Vogel RE, Laschansky EC, Francis BH. Gastroenterology 1990 Mar;98(3):633-8