.Every 5 years the Dietary Guidelines in the USA are reviewed. The latest exercise is in progress and the first draft was released in February 2015 (1). The crucial and potentially contentious aspects relate to fat, sugars and salt. The position of the Dietary Guidelines Advisory Committee (DGAC) was that it:
“…encourages the consumption of healthy dietary patterns that are low in saturated fat, added sugars, and sodium. The goals for the general population are: less than 2,300 mg dietary sodium per day (or age-appropriate Dietary Reference Intake amount), less than 10 percent of total calories from saturated fat per day, and a maximum of 10 percent of total calories from added sugars per day.”
“Sources of saturated fat should be replaced with unsaturated fat, particularly polyunsaturated fatty acids.”
Essentially this is in line with the conventional approach which has been in place in a great many countries since the 1980s. However there are growing doubts about the validity of this strategy particularly because of the growing incidence of obesity and Type 2 Diabetes (T2D) despite the fact that the advice to reduce fat, especially the saturated fat (SFA), is actually being implemented. Furthermore a number of systematic evaluations have been conducted, which have shown that there were fundamental flaws in the original evidence used to justify these recommendations. In addition, there have been investigations which demonstrate that the level of cholesterol in the blood (TC) is not a reliable indicator of the risks of heart disease. In a recent comprehensive study in Norway the TC levels in 52,087 men and women aged 20-74 years were measured over a 10-year period and any deaths were recorded. The results showed that in both men and women there was no statistically significant increase in the risk of death at higher TC levels. In men it was found that with those low TC levels, which comply with current official advice that the total death rate was actually increased. For women the results were even more striking: the higher the TC levels, the lower the risk of dying from all causes.
The authors commented as follows:
‘’If our findings are generalizable, clinical and public health recommendations regarding the ‘dangers’ of cholesterol should be revised. This is especially true for women, for whom moderately elevated cholesterol (by current standards) may prove to be not only harmless but beneficial.’’
They went on to conclude:
‘’Our results contradict the guidelines’ well-established demarcation line (5 mmol /L) between‘good’ and ‘too high’ levels of cholesterol. They also contradict the popularized idea of a positive, linear relationship between cholesterol and fatal disease. Guideline-based advice regarding CVD prevention may thus be outdated and misleading, particularly regarding many women who have cholesterol levels in the range of 5–7 mmol/Litre and are currently encouraged to take better care of their health’’(2).
The latest development is the growing acceptance and awareness that excessive consumption of sugar and carbohydrates is a critical factor contributing to T2D, heart disease and various cancers. The research which demonstrates this is convincing (3). In addition there are large numbers of individuals who have effectively cured their own T2D by switching to a diet which is low in carbohydrates and high in fat (LCHF) which is in direct contradiction of the conventional recommendations (4).
However things may be starting to change. The USA Academy of Nutrition and Dietetics has over 75,000 members made up of registered dietitian nutritionists, dietetic technicians, registered, and other dietetics professionals holding undergraduate and advanced degrees in nutrition and dietetics, and students. The Academy is committed to improving the nation’s health and advancing the profession of dietetics through research, education and advocacy. In a response to the latest draft version it has made a number of key points including the following:
- Genuine doubts about the advisability of making a recommendation on sodium intake which would apply to everyone. More specifically it draws attention to studies and reviews which demonstrate an increase in mortality at the recommended intakes. In fact, the optimal ranges for sodium intake are significantly greater than the DGAC’s recommended maximum intake. In other words there is a distinct danger that those who conscientiously follow the guidelines and lower their intake of sodium may actually be damaging their health. The Academy urges the DGAC to exercise caution in drafting the recommendation on sodium intake. In particular it expresses concern that the Scientific Report’s section on sodium intake appears to use the conclusions of several studies which were limited to those “who would benefit from blood pressure lowering” as a basis for making a general recommendation that all American adults consume less than 2,300 mg/day of sodium. Clearly it would not be valid to extrapolate such results to the population as a whole.
- The recommendation to reduce the intake of saturated fat (SFA) is based on the assumptions that TC and LDL Cholesterol are significant risk factors for heart disease and that these are raised by the SFA. The Academy comments that even if the SFAs increase the TC and LDL Cholesterol levels, this is essentially irrelevant to the question of the relationship between diet and risk for cardiovascular disease. In 2010 the USA Institute of Medicine concluded unequivocally that these markers were not suitable for use as surrogates for the impact of diet on heart disease. In the light of these conclusions the Academy was concerned that the evidence does not lead to the conclusion that saturated fats should be replaced with polyunsaturated fats (PUFAs) for the greatest health benefit. It is highly significant that the Academy should take this position because it paves the way for abandoning the advice to lower the SFA and provides an opportunity to advise an increase, which can be justified on the basis of extensive evidence (5).
- The Academy goes on to recognize that the SFAs should not be replaced by carbohydrates but despite the above comment after a rather convoluted argument finally reaches the conclusion that:This is surprising because there has been no attempt to distinguish between the omega-3s and the omega-6s even though the difference is absolutely crucial. In fact there is extensive reliable evidence which indicates that omega-6:omega-3 ratio is far too high in many countries and can reach values as high as 50. Ideally the ratio should close to unity and certainly no higher than 4 (6). A very high omega-6:omega-3 ratio promotes the pathogenesis of many diseases, including cardiovascular disease, cancer, and inflammatory and autoimmune diseases. As most of the normally available PUFAs are omega-6s the advice to increase them will only exacerbate the current position (7, 8). The only sound advice which can be given on the basis of current knowledge is that sugar and other sources of carbohydrates should be replaced by SFAs.
- “Therefore, it appears that the evidence summarized by the DGAC suggests that the most effective recommendation for the reduction in cardiovascular disease would be a reduction in carbohydrate intake with replacement by polyunsaturated fat.”
The Academy report certainly represents progress. The stances on salt and SFAs are an important step forward but it is particularly unfortunate that the input on PUFAs is so pedestrian and simply ignores much relevant evidence which demonstrates why recommending an increase is likely to be harmful. Nevertheless it is important to see this in a positive light. At the very least it will help to persuade more people that cholesterol can no longer be regarded as a major risk factor for heart disease.
- H Petursson et al (2012). Journal of Evaluation in Clinical Practice 18 (1) pp 159-168
- A P Simonopoulos (2002) http://www.ncbi.nlm.nih.gov/pubmed/12442909