Adapted from BMJ: Hiding unhealthy heart outcomes in a low fat diet trial: The Women’s health initiative randomised controlled dietary modification trial finds that post menopausal women with established coronary heart disease were at increased risk of an adverse outcome if they consumed a low fat “heart healthy” diet. by Timothy David Noakes. Open Heart. 2021.
The WHI trial was designed to test with the US Department of Agriculture’s 1977 Dietary Guidelines for Americans protects against coronary heart disease (CHD) and other chronic diseases.
The only significant finding was that post menopausal women with CHD randomised to a low fat diet in 1993 were at a 26% greater risk of developing additional CHD events compared to women eating the control diet. In 2017 an additional 5 years of follow up data was published. It found that the risk for this group of women had increased to 47-61%.
The authors sought to explain why this was but author Tim Noakes has looked at the evidence and his opinion is that the women who had consumed 13 years of a low fat/high carbohydrate diet had inadvertently succumbed to the features of insulin resistance. Their risk of type 2 diabetes went up almost eleven fold and metabolic syndrome went up six fold.
Dr Noakes advises that according to the principle of “do no harm” the practice of putting women on low carb diets if they are diagnosed with cardiovascular disease is certainly not evidence based and probably not ethical.
The WHI is one of the most expensive long term dietary intervention trials ever undertaken. It started in 1993. Although the advice was given to cut dietary fat, particularly saturated fat in 1977, the policy had never actually been tested regarding its effects on weight, CHD, cancer and type two diabetes.
The idea was to replace the calories from saturated fat with increased carbohydrates from grains, fruits and vegetables. The effect of this was to lower blood cholesterol concentrations. The trial did not seek to replace saturated fat with polyunsaturated fat as studies of this had been published in 2013 and 2016.
Nutritionists led the first year 18 group sessions followed by individual follow up every 3 months. Feedback was given so as to encourage low fat intake.
A low fat diet was not found to improve rates of breast cancer, colorectal cancer, and only resulted in 0.4 kg weight loss over the first 8 years of the trial. The more women adhered to the low fat diet, the more weight they gained. The women who ate high fat, lower carb diets, the more weight they lost.
Blood sugar started to deteriorate in the first year of the trial for the low fat diet group. Post menopausal women who went on statins were at a 49% increased risk of developing type two diabetes. A prior meta-analysis had found that there was a 9% chance of developing type two diabetes with statin use.
The 2017 report analysed women in subgroups: No CHD or hypertension. Hypertension only. and pre-existing CHD. The idea was to see who may benefit or lose the most from the low fat intervention.
Women with hypertension only had neither benefit or harm from the low fat diet. Women who had no pre-existing hypertension or CHD had a small reduction in CHD risk but this was off set by a higher risk of stroke.
Regarding another study, the ERA trial, women who were on HRT who reported that they ate the most saturated fat over the trial time of three years, found that their coronary atheroma did not progress. In fact there was a modest regression in coronary artery narrowing. Both those who ate the most polyunsaturated fat, and those who ate the highest amount of carbohyrate and therefore the lowest amount of total fat showed worsening of their coronary atheroma.
Statin use was similar in both groups who were randomised to each diet, low fat versus usual. Indeed more than 40 percent of the women in each group were on statins.
Only post menopausal women who do not have CHD or hypertension are safe to eat the low fat diet, the others can expect some negative effects.
The Women’s health study (WHS) was established between 1992 and 1995 at Harvard Medical School to look into the effects of aspirin and vitamin E on the risks of developing CHD or cancer in women who started off with neither condition.
The study showed no benefit for either treatment.
A 21 year follow up programme of over 2,800 of these women evaluated more than 50 different clinical, lipid, inflammatory and metabolic factors.
Results showed that the development of Type two diabetes, and not high cholesterol levels were important factors in the development of CHD. Hypertension gives a 4.58 fold increase in CHD. Obesity gives a 4.33 fold risk. These factors as well as type two diabetes and metabolic syndrome were more predictive of CVD than smoking.
A Lipoprotein Resistance Score was developed looking at various factors particularly VLDL and HDL and a high level produced a 6.4 fold risk of cardiovascular disease. This is worsened in insulin resistance. LDL scores only gave a 1.38 fold risk of CVD by comparison.
The Progression of Early Subclinical Atherosclerosis Study looked at HbA1c in people who did not have type two diabetes. The higher the HbA1c, the higher the risk of CVD and the risk even started below HbA1c levels of 5.5%.
Women who had low HDL levels was associated with a higher breast cancer incidence and all cause mortality after breast cancer as well as an increased risk of cancer specific and all cause mortality.
The Recovered Minnesota Coronary Experiment (RMCE) study found that people randomised to eat more polyunsaturated fat in place of saturated fat were at a 22% higher risk of death with each 0.78 mmol/L reduction in blood cholesterol. This effect was worse in the over 65s.
The Recovered Sydney Diet Heart Study (RSDHS) showed that replacement of dietary saturated fat with linoleic acid was also associated with raised all cause mortality with increased deaths from cardiovascular disease and coronary heart disease.
Lawrence ( Lawrence GD Perspective: the saturated fat- unsaturated oil dilemma: relations of dietary fatty acids and serum cholesterol, atherosclerosis, inflammation, cancer and all cause mortality. Adv Nutr. 2021; 12: 647-56) concluded: PUVAs are unstable to chemical oxidation and their oxidation products are harmful in a variety of ways. They can initiate inflammation that can have dire health consequences. If saturated fats are replaced by carbohydrates in the diet there would be no significant improvement in serum cholesterol and it can result in a more atherogenic lipoprotein profile. …It appears that saturated fats are less harmful than the common alternatives.
This set of findings from four different studies effectively ends the debate about which diet should be eaten to lower the risk of CVD, especially in those with insulin resistance.
Two diets shown to prevent the clinical features of IR leading to type two diabetes are the restricted low calorie diet developed by Lim et al (Lim et al. Reversal of type two diabetes; normalisation of beta cell function in association with decreased pancreas and liver triacylglycerol. Diabetalogica 2011;54:2506-14.) and the ad libitum low carbohydrate higher healthy fat ketogenic diet.(Hite AH et al. In the face of contradictory evidence: report of the dietary guidelines for Americans Committee. Nutrition 2010;26:915-24.)
It is the ethical responsibility of those who manage those with cardiovascular disease or diabetes or other insulin resistance that they should NOT prescribe the never proven and now disproven low fat “heart healthy” DGA diet.