Melissa Juried Kriebel
Many women know her especially for her presence in products dedicated to skin care: the vitamin A it is in fact widely used in cosmetics. But its function goes far beyond an aesthetic need e you skin health. Why Vitamin A (retinol, retinoic acid, retinaldehyde) is a substance underlying many body functionscome vision, tissue growth and differentiation, cell division, reproduction and immunity. As well as fundamental for its properties antioxidants. Vitamin A, fat-soluble molecule, along with some carotenoids, helps the immune system work properly, helping to control infections. In the West, vitamin A deficiency problems are very rare, since it can be taken directly from foods of animal origin; while it is not present in plant foods, but is assimilated through its precursors, carotenoids, which are converted into vitamin A by the small intestine, then deposited in the liver which, according to the needs of the body, stores it or releases it little by little into the body. One element should be underlined: not all carotenoids in foods are converted into vitamin A, even if they have fundamental properties: they are lycopene, lutein and zeaxanthin. “Carotenoids are found in plant foods (fruits and vegetables) and are responsible for their pigment, red-yellow-orange. Spinach is also rich in itdespite being green because they are covered in chlorophyll”, explains the professor Pier Luigi Rossispecialist in food science and professor at the University of Siena, “both vitamin A and carotenoids have genomic functions”.
Can you explain this concept to us?
“Vitamin A it is the epigenetic key in human cells. We must think that within our cells there are natural biological systems capable, for example, of resisting the accumulation of excess fat, eliminating it. Food is no longer just a consumption of daily calories, but a vehicle of information for our genes. Stimulating positive genes and curbing dangerous ones is the goal of a diet that takes into account genomic activity on cells to reduce excess fat stored inside adipocytes, and thus lose weight in a healthy way. Some carotenoids are then transformed into retinoic acid in the cells. This it has a direct and positive action on DNA and genes. If absent or deficient, DNA is not efficient and you can see and feel it”.
How is this deficiency highlighted?
“Con decreased vision and night blindness, chapped lips, brittle nails, impaired protein synthesis and compromised immune system (increases susceptibility to infectious diseases)”.
Where is vitamin A mostly found?
“In fish, fatty meats, eggs, cheeses…”.
So vegetarians who expect an intake of meat derivatives have no problems. What about vegans, given that vitamin A can only be taken through the transformation of carotenoids?
“They have to deal with the problem of bioavailability, ie the ability to absorb nutrients in the body. And cooking promotes the absorption of carotenoids. Let’s take an example with a raw tomato: if I eat it I take only 7-8% of an important carotenoid, lycopene; if I consume instead a tomato cream, I absorb 40% of it! Same speech with carrots: raw they give me a carotene intake of about 10%; eaten cooked, I reach 37%”.
On closer inspection, the problem of the bioavailability of carotenoids could concern everyone, including omnivores.
“Yes, because while on the one hand the risk of A deficiency is very remote, the same cannot be said for carotenoids”.
What is the cause?
“First, we don’t eat enough plant products and then, based on what was said before, we don’t create the conditions at the table to have sufficient bioavailability of these elements, in other words: to allow the molecules of these foods to pass from intestine to blood. It is for this reason, I insist, that vegetables must be eaten cooked, if one wants to guarantee adequate absorption of carotenoids, also favored by the consumption of extra virgin olive oil”.
However, if we eat only cooked vegetables we lose a part of other water-soluble vitamins, i.e. those that dissolve in water. How should we adjust then?
“By eating a plate of raw vegetables (intake of water-soluble vitamins, B complex and vitamin C), and a plate of cooked vegetables in the same meal. Start the meal with a plate of raw vegetables and end the meal with a plate of cooked vegetables”.
If we have carotenoid deficiency, what happens?
“The eye meets blindness, the retinal maculopathy it’s at an alteration of the metabolism as a whole leading to fat accumulation and lack of energy.”
Are vitamin A supplements recommended?
“Supplements need to be absorbed. For instance, a supplement of lutein and zeaxanthin used to combat vision loss in the elderly, it must be bioavailable, i.e. be transported in the blood by a vehicle, from the fatty molecule HDL, the one defined as ‘good cholesterol’. If I have a low HDL, this step does not occur and therefore I do not assimilate lutein or zeaxanthin, not even in the form of a supplement”.