2015-11-08 08:52:32
It has been science that, thanks to the efforts of, often, anonymous champions of knowledge, has discovered that not everything we eat has similar effects on our well-being and general health. Without a doubt, today almost everyone in the developed world knows that eating saturated fat in excess is harmful. This type of fat, present especially in products derived from farm animals, such as meat or milk, increases the risk of obesity, increases blood cholesterol levels and increases the probability of developing cancer, cardiovascular diseases and diabetes. .
It is probably also well known that polyunsaturated fats, present especially in animal foods of marine or plant origin, exert beneficial effects on health, generally precisely the opposite of those produced by saturated fats. Numerous studies carried out with both laboratory animals and humans have therefore confirmed the fact that the chemical structure of fats, that is, that they have more or fewer hydrogen atoms (saturation) in the carbon atom chains that form them, it can be a matter of life or death.
However, nothing is truly known until we understand not only why, but also how things work and are produced. Molecular and medical biologists have not only spent a lot of effort establishing what happens to both types of fats, but also trying to understand why it happens.
Initially, data were obtained indicating that the difference between the health effects of saturated and unsaturated fats was due to their different metabolism. This different metabolism involved different transport proteins in the blood in each case and produced different cellular intermediates, different metabolites, as they are known in scientific language, before their complete oxidation to obtain energy. These metabolites appeared to be responsible for the very different health effects of saturated and unsaturated fats.
However, it soon became clear that this did not explain everything. Other studies showed that saturated fats produced inflammation of adipose tissue, which is responsible for storing excess fat, while unsaturated fats protected the development of inflammation in said tissue. Inflammation is not the adipose tissue “getting fat,” but rather an immunological process, in which both fluids and cells of the immune system go, in this case, to the adipose tissue and inflame it, swell it. This inflammation, therefore, is not due to a greater accumulation of fats, but rather to an activation of the immune system for unknown reasons.
Looking at the flora
About two years ago, a study showed that the composition of the diet had an important influence on the bacterial species of the intestinal flora. Since inflammation is a process that has evolved to fight against the attack of microorganisms, such as bacteria, this data suggested to researchers at the University of Gothenburg, in Sweden, the possibility that perhaps the fat composition of the diet caused vary the bacterial populations of the intestinal flora. This modification of bacteria populations could perhaps cause the activation of the immune system in a different way depending on the type of fat, which could lead to inflammation of adipose tissue.
The researchers got “mice to work” and fed these friendly little laboratory animals for 11 weeks either a diet rich in bacon or a diet rich in fish oil. It goes without saying that normally mice, not even laboratory ones, eat bacon or fish. However, the different diets caused a significant change in the bacterial populations of their intestinal flora. The mice fed with bacon fat, in addition to gaining more weight than the others, even if both types of diet administered had the same amount of calories and fiber (the main food for the bacteria of the flora), saw an increase in the population of the genera of Bacteroides, Turicibacter, and Bilophila bacteria, which are associated with greater induction of inflammation. In contrast, feeding fish fat increased populations of completely different bacterial genera, not associated with inflammation.
They were interesting results, but they still didn’t prove anything. True, dietary fats seemed to affect the intestinal flora, however this did not mean that these changes were the cause of the different metabolic (obesity) and inflammatory status of the mice. Association does not mean that there is a cause-effect relationship. To test it, the researchers used mice raised in conditions of total sterility, lacking intestinal flora. These mice were “transplanted” with the intestinal flora of mice fed either the diet rich in bacon or the diet rich in fish fat.
This is when they get the most interesting result. It turns out that bacteria from mice fed fish fat were able to protect mice transplanted with them from the effects of a diet rich in bacon. It therefore seemed proven that the beneficial or harmful effects of the different types of dietary fats are mediated, at least in part, by the intestinal flora and not by metabolic changes independent of it.
These surprising studies suggest that a dietary supplement in “healthy” bacteria could be very beneficial to counteract the effects of a diet that is too un-Mediterranean. More studies will have to be done to confirm this, but for now, it seems like good news.
Reference:
Caesar et al., Crosstalk between Gut Microbiota and Dietary Lipids Aggravates WAT Inflammation through TLR Signaling, Cell Metabolism (2015),
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