Almost every day, patients and their physicians are confronted with new wisdom about nutrition and its resulting consequences. So far, however, the advice for healthy eating has always been quite unanimous in the same direction. But the PURE study questions some of the previous dogmas of nutritional science and thus very probably creates greater uncertainty.
The PURE study is a large-scale, global study that looked at the impact of healthy lifestyle interventions on people's health. More than 200,000 people from industrial nations and low to middle-income countries took part. One aspect of the study concerned human nutrition and was discussed at the ESC 2018 in Munich.
The ESC guideline recommends patients with cardiovascular risk to adapt their diet as a cornerstone of prevention (recommendation level 1B). A basic problem of all guideline recommendations for healthy nutrition and also the nutritional recommendations themselves: Certain amounts of the nutrients fat, carbohydrates and protein are recommended. Consumers, however, do not consume nutrients, but foods which, as is well known, rarely meet the requirements and recommendations for healthy nutrient composition.
Too many fats in food are unhealthy, yet most recommendations are not about further reducing the fat, but about the composition of fats. According to the previous black-and-white thinking, there are good fats (mono- and polyunsaturated fatty acids) and there are bad fats (saturated fatty acids, trans fatty acids).
The PURE study now turns this classification upside down. If carbohydrates were energetically replaced by saturated fatty acids, the patients achieved an 11 % risk reduction for overall mortality and up to 20 % for stroke. If the saturated fatty acids are finally replaced by polyunsaturated fatty acids, the risk is even reduced by 25%. So you'd rather have fat than sugar? Such a question was almost unthinkable before the PURE study.
Salt and the cardiovascular risk
The European guidelines and the World Health Organization (WHO) recommend < 5 g of salt per day. In fact, however, a European absorbs > 10 g of salt per day on average. But is it better to limit salt consumption more?
The PURE study also provides a surprising answer to this question: According to the study, reduced salt consumption of < 3 g sodium/day leads to a higher cardiovascular risk, as does the intake of > 5 g sodium salt per day. It is important to note that high sodium chloride consumption is particularly dangerous for patients with hypertension. People with normal blood pressure, therefore, do not have to limit their salt consumption any further. This is supported by the fact that there is still a lively discussion as to whether the salt reduction in healthy people really reduces the risk of cardiovascular disease and stroke.
Sugars, in particular, simple sugars, such as those found in soft drinks, sweets, and cakes, are often rightly considered to be harmful to health. However, this stigmatization of sugar generally led to the germination of sugar-free diets, such as the low carb diet. However human consumption of healthier sugars, like starch from potatoes, noodles, and rice - is not completely without health consequences, as the PURE study proved recently.
Accordingly, both diets with a high sugar content (> 70 % sugar content in the diet; HR = 1.20 [95%-KI: 1.09-1.32]) and diets with a reduced sugar content (< 40 % sugar content in the diet; HR = 1.23 [1.11-1.36]) increase the mortality risk. According to the study, the smallest risk was actually in the range between 50 % and 55 % sugar content in food, which is in line with the current recommendation for sugar consumption.
Mediterranean cuisine is regarded as a prime example of healthy nutrition. It is rich in fish and vegetable foods and uses only a little red meat as well as moderate amounts of alcohol, e.g. red wine. Studies, such as the PREDIMED study, previously showed that the Mediterranean diet reduces the risk of cardiovascular disease, heart attack, and stroke.
Wood et al. (2018) also presented data in The Lancet on the risk thresholds of alcohol, above which health consequences are to be expected. It is interesting to note that moderate alcohol consumption of up to about 100 g per week, as part of the Mediterranean diet, for example, even reduced the risk of cardiovascular disease. On the other hand, the risk of disease above the 100-gram threshold increases slightly, the mortality risk even exponentially.
The human diet is far more than the intake of nutrients. For example, it goes hand in hand with rituals and cultural education. Diet is an important part of our lifestyle.
In the past decades, the valid nutritional recommendations have undergone specific changes almost with every new study - countless trends have emerged. The given recommendation direction was not always confirmed. The PURE study also brought new findings that can reverse prevailing doctrines on how to deal with nutrition.
This makes it all the more important to continue discussing the results of the PURE study without, however, continuing to unsettle patients. Patients are not only confused by constant, partial changes of direction in the dietary recommendations but also tend to accept advice regarding their diet less and less willingly.
Do not unsettle your patients with details that have not yet been confirmed by further suitable studies. Based on the study situation, give more general nutritional recommendations that support the prevention of cardiovascular diseases, but leave enough leeway not to be distressed by every new study result.
These include, for example:
How to eat right: should PURE results influence dietary guidelines?, 27.08.2018, ESC Munich