The paper “Pathways and mechanisms linking dietary components
to cardiometabolic disease: thinking beyond calories” summarises the presentations and discussions at the 2017 CrossFit Foundation Academic Conference “Diet and Cardiometabolic Health – Beyond Calories”. I am pleased to see that there is some specific focus on this issue, namely that not all calories are equal, which I think is of great importance.
When you start reading the article, there does seem to be a bias though: the introduction clearly states that “there is no doubt that positive energy balance, due to excessive caloric consumption and/or inadequate physical activity, is the main driver of the obesity and cardiometabolic epidemics”. So if this seems to be clear, then the purpose of the conference, the presentations and this paper would be to look at other, less important, additional drivers of obesity and cardiometabolic disease. I think this sets the stage in a poor way, because if there really is no doubt in this matter, you are discrediting from the start anyone who says otherwise, and you are establishing that any findings to follow in this paper are of less consequence than calorie balance. If there really is no doubt, then why hold this conference at all?
I invite you to check out the paper yourselves here.
But because this is a fairly long and information-dense paper, I will go through its parts in separate posts.
The first objective of the conference was to determine whether certain dietary components increase the risk of cardiometabolic disease in a way other than positive energy balance (more energy in than out). There were two approaches: one looking at dietary fat, and the other at added sugars.
The author of the presentation of fats, Ronald Krauss, made some excellent points when it comes to research design and presentation. Studies focusing on fat consumption, as well as on carbohydrate consumption, do not always make the difference between the types of macronutrients the participants were consuming. What he calls the “food context” is of great significance too, because different processing or preparation methods can have different effects on the body. When using data from multiple large-scale studies, the investigators will decide which studies are admitted and this may lead to conflicting results. All these need to be kept in mind when reading about studies on food.
He also highlighted the need for more biomarkers to be used in studies. A simple example of this is the following: most studies look at the dietary effects on LDL cholesterol, which are less strongly associated with cardiovascular disease (CVD) than small dense LDL. The former seem to be increased by consumption of dietary saturated fatty acids (SFA), while the latter have been reduced by a lower carbohydrate intake. I know, definitive conclusions cannot be drawn from studies on lowering one biomarker and others on the increase in another biomarker. Maybe this is a direction for future studies.
Another study mentioned that I found of interest was one conducted in Spain on 7,000 participants with type 2 diabetes or with three risk factors for cardiovascular disease. They were divided into three groups, all of them following a Mediterranean diet with a focus on reducing fat intake, but one group would supplement it with olive oil, a second group with mixed nuts, and a third with nothing (the control group). After 4 years, the first two groups showed a relative risk reduction in major CVD events by 30% compared to the control group, which the researchers associated with the consumption of olive oil or nuts, since those were the only significant differences between the diets. Another find, and which contradicts the introduction’s “no doubt” statement, was that despite consuming more calories due to the olive oil or the nuts, neither group of participants gained any weight.
The presentation on sugars shows some very interesting finds, again going against the lack of doubt of the authors of the introduction (seriously, no editor actually read that and thought that it doesn’t work well with the contents of the article?). Kimber Stanhope and Jean-Marc Schwarz presented the results of multiple studies on both adults and children, showing that the consumption of glucose, fructose or sucrose (glucose + fructose, present in our lives mainly as table sugar and high fructose corn syrup) had different effects on the amount of fat in the liver, on de novo lipogenesis (production of new fat, basically), on fat oxidation, on LDL cholesterol, on small dense LDL, insulin sensitivity, uric acid. Fructose here is not to be understood as the sugar in whole fruit, but as added sugar. Most studies used glucose and fructose only, all of them showing that consumption of glucose resulted in improved biomarkers compared to fructose, even in the absence of weight loss (really, there is no doubt that energy balance is the main driver of cardiometabolic disease? None whatsoever?). The study looking at glucose, fructose and sucrose showed that sucrose had a more significant effect on fasting (on an empty stomach) and post-prandial (after a meal) LDL cholesterol, non-HDL cholesterol and apoB (apolipoprotein), all of which are considered risk factors for CVD. This means that not only do glucose and fructose have different effects on our bodies, but their combined consumption has yet other effects.
Evidence has shown that added sugar in beverages seems to be more detrimental to the body than added sugars in solid food, but there is not enough data on this and more studies need to be conducted before any conclusions can be drawn.
The main take from the studies summarised in this presentation is that the reduction in fructose and sucrose consumption has positive effects on the body, which are not related to energy balance and weight gain or loss. It is also worth keeping in mind that the individual micro or macro nutrients are not just relevant in themselves, but also in the combination consumed and their food context.