The Mediterranean diet has always been valued for its health properties. The characteristics of the Mediterranean diet are the following: high consumption of olive oil; high consumption of legumes; high consumption of unrefined cereals (including bread); high fruit consumption; high consumption of vegetables; moderate consumption of dairy products, mainly such as cheese and yogurt; moderate to high consumption of fish; low consumption of meat and meat products; moderate consumption of wine. Some studies have indicated that promoting the Mediterranean diet as a model of healthy eating can help prevent weight gain and the development of obesity. Within the group of cereals, bread is an important constituent from a nutritional point of view. However, a long-standing belief held by the general public is that bread makes you fat. This encourages many people to limit or even eliminate bread from their diet. Therefore, the consumption of bread, which was part of the traditional Mediterranean diet, continued to fall in the Mediterranean area and in the rest of the world. However, although the consumption of bread has decreased in recent decades, the global obesity epidemic has increased.
Some studies have specifically studied the associations between grain consumption and BMI (body mass index). They showed inverse associations with anthropometric variables for the consumption of whole grains, but gave conflicting results for the consumption of refined grains. Factors such as postprandial insulin responses, gastric emptying after consuming a high-glycemic index (GI) meal and other factors could be implicated in a potential differential effect of refined grains versus whole grains on adiposity. Indeed, from the latest scientific reviews, scholars agree that a constant consumption of whole wheat bread or other whole grains is not associated with the onset of general or abdominal obesity; which, on the other hand, seems to be associated with the consumption of white or refined bread. Scientists are generally in agreement in stating that there are at least four factors that could act (even in concert) in determining the “obesogenic” power of bread: a) the quantities, b) the fiber content, c) the glycemic index and d) the intervention of the intestinal microbiota.
If it is true that bread potentially makes you fat, it could depend primarily on the daily quantities consumed. Here the cultural factor comes into play which is certainly very marked in specific areas of the Mediterranean. Taking as an example in the Italian panorama, it is known that while some areas or regions have standard types of bread with rare variations on the theme, others are rich in types of bakery products that can vary even between neighboring cities. In many rural and non-rural Mediterranean areas, bread has a deep cultural content that is rooted in the population. For the most “devout”, if we can define them that way, bread often represents the main food source of the day, even at the expense of a second course of meat or fish and a complete meal with a portion of fruit. Similar attitudes are found in relation to pasta, this subject being not addressed here. It is clear that such a food choice is not healthy, because (a) it prefers a high consumption of carbohydrates (b) derived from a high glycemic index food, which is often not in the integral form, but (c) refined and therefore poor of fibers.
What a similar type of diet can do over time on the composition of the intestinal bacterial flora is not difficult to imagine. If we add the incorrect eating habits dependent on work commitments, the skipping of central meals for commitments of any kind, the component of daily emotional stress that often “close” the appetite or, exactly the opposite, “amplify it”, we can say that the intestine is facing a mixed cataclysm that will have strong negative effects on the metabolism. One of the ways to alleviate this danger would be to maintain, at least, a constant intake of vegetable fibers. Whether they are wholemeal stuff, vegetables, fruit or whatever, it doesn’t matter. Science has now proved that the intestinal microbiota is strongly affected by the presence of fibers. They represent a first line bacterial nourishment, from whose transformation derive many substances that have a positive action on the health of the intestinal mucous membranes, as well as on its local immune system and on the hormonal component. From the reflection of the good functioning of this complex, the pancreas and liver (which manage carbohydrates and fats) maintain a good management of body weight.
There is a still poorly understood factor on the relationship between bread intake and the appearance of obesity: that of insulin resistance. This para-metabolic state prevents insulin from functioning properly and managing the metabolism of carbohydrates, fats and even proteins. Several mechanisms have been invoked that would determine the appearance of insulin resistance. These include cellular toxicity caused by excess triglycerides, the intervention of oxidative stress (free radicals), poor coordination between insulin and antagonistic hormones (eg glucagon), to name a few. There is evidence, however, that gluten protein fragments can be directly toxic to the beta cells of the pancreas (the ones that produce insulin). Gluten is the main protein complex in bread, which however does not undergo total intestinal digestion. It has been shown that a very small but significant amount of bread protein does not undergo digestive enzymatic attack. These residual fragments seem to be able to cross the intestinal mucosa (especially when the intestine is inflamed or in dysbiosis), enter the bloodstream and exert an antagonistic action on the cellular functions of insulin.
The first site of attack would be the functioning of the insulin receptor on beta cells, which are the sensor of blood glucose levels. Over time, these fragments (peptides) can cause a sort of “atrophy” of the beta cells, which reduce their production of insulin and thus aggravate the urge to manage carbohydrates. There are scientific publications that demonstrate how a strong reduction in the intake of refined bread can improve pancreatic function in both healthy and diabetic subjects. Here we do not intend to stigmatize or demonize for any reason the consumption of such an important food as bread, which must not be kept aside or totally eliminated from the daily diet. It is included in the Mediterranean diet, the health effects of which are appreciated by the scientific community. Banning it would already be impossible for those who have a real culinary “dedication” to this food, it is easy to imagine how difficult it can be for those coming from the Mediterranean area to accept it. The ultimate message here is not to eliminate bread from the diet; whether or not it makes you fat depends essentially not on who uses it, but on abuse.
- Edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
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Dott. Gianfrancesco Cormaci
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