By Dr. Giovanni Chetta
Diet in Physiological Conditions
Obesity
Recent studies have shown that the best way to avoid obesity is to reduce total calories, not fat calories. The critical point, more than the highest calories per gram and the greatest efficacy of fat accumulation, therefore seems to be: does taking fat stimulate the appetite more than carbohydrates and proteins?
Studies that lasted more than a year showed that hypolipid diets (low in fat) did not result in a certain weight loss. Furthermore, sedentary and overweight people can become more resistant to the effects of insulin thus requiring more hormone to regulate blood glucose.
Old food pyramid
In 1992, the US Department of Agriculture (USDA) officially created a food guide with the aim of reducing the risk of chronic diseases in the population: the old food pyramid (preferred foods occupied the base and gradually to the top those to consume less): reduced consumption of fats and oils, 2-3 servings of protein foods per day (milk, cheese, yogurt, meat, legumes, fish, nuts), 3-5 portions of fruit and vegetables, 6-11 portions of carbohydrates (bread, pasta, rice, etc.). The message was therefore to minimize fats and to consume carbohydrates, fruit and vegetables in abundance. At that time, US calorie consumption was 45% carbohydrate, 40% fat, 15% protein. The guidelines of the American Hearth Association and other institutions recommended taking at least 50% carbohydrates, 30% fat (today it is backing down).
In fact, no study has shown long-term benefits attributable to a low-fat diet. The validity of these guidelines became even more questionable after the researchers showed that by increasing the ratio between the two main chemical formulas of cholesterol (total cholesterol 150-200 mg / dl in plasma of a healthy subject), low density lipoprotein (LDL ) corresponding to bad cholesterol, and high density (HDL) or good cholesterol, the risk of cardiovascular disease rises, while a beneficial effect is obtained by reversing the relationship. Although limited, studies have unequivocally indicated the advantage of replacing saturated fats with polyunsaturated fats but not with carbohydrates. Replacing fats with carbohydrates leads to a decrease in LDL and HDL and an increase in triglycerides (fats present in the blood in physiological amounts of 72-170 mg / dl).
In truth it was already known that some fats (unsaturated fats) are indispensable to the body and can reduce the risk of cardiovascular diseases. In fact, dietary advice has always led to the replacement of saturated fats (dairy products and meats), which raise cholesterol with the risk of heart attacks, with the unsaturated (vegetable and fish oils) that lower cholesterol. In the USA the incidence of heart disease has been halved and the consumption of polyunsaturated fats doubled in the decade 1970-1980. This is confirmed with what happens in countries where oil is predominantly used (in Crete it represents 40% of caloric intake) or little use of fat (10% in Japan).
From 1992 onwards further studies have shown that this pyramid had many defects.
We now propose, according to the indications of the authoritative journal Le Scienze - Scientific American (n. 414, February 2003), a new food pyramid that better reflects the current knowledge on food.
New Food Pyramid
Starchy foods
(bread, pasta, rice, cereals and starchy foods in general, potatoes, snacks and baked goods in general, snacks, chips etc.)
They are rich in carbohydrates and, if refined, or as normally consumed, they do not provide vitamins, minerals or fiber and are quickly absorbed by the body. They therefore increase the level of glucose in the blood much more than the integrals with a consequent insulin spike in the blood and drop in the level of glucose in the blood (even below the basal level). The consequences are: increased sense of hunger (with a tendency to overweight and obesity) and vitamin depletion (in particular of the B vitamins). Furthermore, high levels of glucose and insulin can have negative effects on the cardiovascular system by increasing triglycerides and decreasing HDL (good cholesterol).
Epidemiological studies show that high intakes of refined flours and starches and potatoes are associated with a high risk of type 2 diabetes and cardiovascular diseases and that this risk is higher in sedentary and less active people. Conversely, an increase in fiber consumption is associated with a lower risk of such diseases.
As for baked goods and snacks (snacks, chips, etc.), the risks described above in the following paragraph must be added to the hydrogenated fats often present.
It is therefore evident the healthy advantage in replacing refined grains with whole grains even if, in this case, it will be appropriate to opt for organic foods in order to avoid the risk of greater contamination by pesticides, more abundant, inevitably, in whole grains (in the refining process, eliminating the surface layers of the grain also eliminates part of the contaminants).
Food fats
Among the category of dietary fats, hydrogenated fats are actually the only significantly more deleterious than refined carbohydrates. They are made up of trans-unsaturated fatty acids (obtained by partial hydrogenation of the vegetable oil making it solidify) and are present in margarines and in many baked products and fried snacks: they raise LDL (bad cholesterol) and triglycerides, reduce HDL (good cholesterol ).
Extensive epidemiological studies have shown no particular role for fats against colon and breast cancers. Other studies have associated prostate cancer with the consumption of animal fats (rich in saturated fatty acids) but have shown no role for vegetable oils, which on the contrary can slightly reduce the risk. Finally, regarding cardiovascular problems, studies have unequivocally indicated the advantage of replacing saturated fats (animal fats) with polyunsaturated fats (vegetable and fish oils).
Fresh fruit and vegetables
They reduce the risk of vascular diseases (thanks, in particular, to their content in folic acid and potassium). Folic acid (present in green leafy vegetables) can also reduce the risk of colon cancer and its inadequate intake is responsible for birth defects. Lycopene (contained in tomatoes) reduces the risk of prostate cancer. Low consumption of lutein (pigment present in green leaves) increases the risk of cataracts and retinal degeneration.
We know that we get the maximum benefit from fruit and vegetables if we consume them fresh and raw, because they allow the maximum use of their vitamins and mineral salts, but even if they have been harvested ripe. Often, unfortunately, these precious foods are harvested as "harvested" or, for speculative reasons, as soon as possible, thus becoming food of little value.
