Is the Adherence to the Mediterranean Diet the Right Choice?
There hardly is another field better defined by an abundance of knowledge paralleled with a striking level of ignorance than that of nutrition. Take reductionism as an example. Introduced in the 1960s, this is the use of a building blocks approach to nutrition. Here we break foods down to the sum of their parts, isolating their key constituents and declaring that these individual nutrients are responsible for delivering that food’s observed effects. We consider the nutritional qualities of food being largely attributable to their macronutrient composition. The best example of reductionism is its use in distributing healthy eating advice for preventing heart disease i.e. to reduce intakes of dietary fat and cholesterol. However, the evidence never existed to support the condemnation of a singular nutrient whether it is fat or its subclass saturated fat. In fact the questionable link of high fat intakes with heart disease was largely, and wrongly, constructed around the remarkably low prevalence of heart disease among those habitually consuming the Mediterranean diet.
The traditional Mediterranean diet is characterized by a high consumption of vegetables, fruits, legumes and whole-grains, with a moderate consumption of fish and the consumption of olive oil and nuts as the main source of fats and a low-to-moderate amount of red wine during meals. Increased adherence to the Mediterranean diet is associated with substantial reductions in cardiovascular and neurodegenerative diseases and cancer. Balanced in its composition, experts were unable to reduce the benefits of this diet to its singular nutrients and instead decided to look at what the diet did not contain. Generally low in fat and specifically low in saturated fat, compared to the Western diet, it was decided that this must be the distinguishing feature. Instead of being a diet of inclusion, the heart healthy diet now became a diet of omission and the food industry embraced it.
The publication of a landmark randomised controlled trial of the Mediterranean diet shows just how erroneous this assumption was. The PREDIMED trial, conducted in Spain, randomly assigned 7447 persons at high risk for cardiovascular disease to one of three groups: participants who received advice on a Mediterranean diet and provision of fat rich extra-virgin olive oil, those who received advice on a Mediterranean diet and provision of fat rich mixed nuts, and those who received advice to reduce dietary fat only. The results were astonishing. Compared to the control group, both Mediterranean groups reduced their incidence of cardiovascular disease by approximately 30%.
This trial turned things on its head. The Mediterranean diet was no longer the low fat diet, the control group was. Suddenly the headlines proclaimed that a high fat intake was now shown to be cardioprotective and not harmful. But, when you read the research carefully you will notice that the control group were not very praise worthy. In fact, they failed miserably in their attempts at a low fat diet as total fat made up 37% of energy intake in the control group and 41% of energy intake in the Mediterranean groups. OK, so saturated fat must be the culprit. Wrong. Saturated fat intakes were practically uniform in all three test groups (around 9%). OK then, well it must be proof that the omega 9 mono-unsaturated fats, which are particularly abundant in olive oil are the unrecognized hero. No, wrong again! The omega 6 fat rich nuts produced the same effect. Unsaturated fats as a whole then? Maybe, but unlikely. Remember there was only 4% difference within all three groups as all were consuming high unsaturated fat diets.
This is really confusing, isn’t it? Well to a supporter of reductionism it is. Not so much to those who understand food. Take olive oil for example. The intervention group received extra virgin olive oil while the control group mostly used standard olive oil. Although macronutrient-wise they seem comparable, there is far more to olive oil than just its lipid composition. Extra virgin olive oil is a richer source of phytonutrients such as oleuropein- and ligstroside glycosides and aglycones and their derivatives, including hydroxytyrosol and tyrosol, luteolin, apigenin, caffeic acid, ferulic acid, cinnamic acid, coumaric acid, peonidins, cyanidins, kaempferol, quercetin, rutin, pinoresinol, syringic acid, vanillic acid as well as carotenoids, tocopherols and chlorophylls. This is an extensive list of nutrients beneficial for our health. We should not ignore all these health promoting ingredients and simply make olive oil a substitute for mono-unsaturated fat intake. And before we now make a conclusion that extra virgin olive oil is a super healthy food, let us not forget that nuts, with their own unique composition, showed the same effect.
We can conclude by saying that diet is never down to a single nutrient or a single food. We cannot isolate nutritional benefit. Instead, we form food patterns, ignoring individual nutrients. We speak of diets rich in fruits, vegetables, nuts, whole grains, oils, fish etc. When combined together these constituent foods can interact synergistically and provide a real benefit to our health.