Among the essential nutrients, so defined because their relative or absolute absence from the diet causes symptoms and often diseases, we must remember the vitamins.
They are organic compounds, are found in many foods and are necessary for regular metabolic functions. They are divided into fat-soluble ones, which can be stored in the liver, in adipose tissue and in the endocrine glands, and in water-soluble ones that instead are distributed in the intra and extracellular liquids and are eliminated, after a certain threshold,in the urine.
Vitamin A is distinguished in retinol from animal sources and carotenoids from plant sources. Beta-carotene has a powerful antioxidant action aimed at neutralizing free radicals, while retinol is essential for vision, skin, hair and mucous membranes. It is contained in eggs, liver, fish and orange-yellow fruit. Among the most important carotenoids we remember the lutein present in cabbage, lettuce, spinach, green beans, zeaxanthin present in tomato, watermelon and grapefruit. From the latest research has also come to know about astaxanthin present in crustaceans and salmon.
Under normal conditions about 80% of the vitamin is absorbed following the path of lipid absorption, remembering that the retinol storage site is the liver.
Vitamin D regulates the growth of bone tissue by controlling the absorption of calcium and phosphorus in the small intestine. Cod liver oil is very rich but difficult to palatilize, among the fish, herring and salmon contain moderate quantities, between meat, liver, dairy products only butter and particularly fatty cheeses.
Vitamin E is naturally occurring in eight forms, but the most important is alfatocopherol. Absorption of tocopherols occurs in the small intestine by means of bile acids. From the intestinal mucosa they first pass into the lymphatic circulation, then into the systemic one where they are conveyed by lipoproteins. The most significant deposits are in adipose tissue, muscle and liver.
The action of the vitamin is due to its anti-oxidant properties, as it protects the poly-unsaturated fatty acids from oxidation. This function is present in cell membranes where tocopherol is associated with PUFAs in phospholipids. It is present in olive oil, in some cereals and in fruit, but some domestic preparations, such as boiling, frying and baking, can lead to significant losses.
Vitamin K present in green leafy vegetables such as spinach, lettuce, broccoli and cabbage, is absorbed at the level of the proximal ileum and passes with chylomicrons in the lymphatic circulation. As with other vitamins it requires normal pancreatic and biliary functions for absorption, which is therefore favored by the presence of fats. In cases where there is malabsorption of lipids, a compromise in the use of the vitamin can occur.
Vitamin B1, called Tiamina, is found in foods of vegetable and animal origin, among these we recall brewer’s yeast, legumes, pork and eggs. It is absorbed into the small intestine and its deficiency affects the cardiovascular, muscular and gastrointestinal system. In Asian countries the most important cause of deficit is linked to the use of poor carbohydrates in vitamins such as rice, while in western Europe it is linked to alcoholism. The chemical resistance of thiamine depends on the pH of the medium, below a pH 5 it is stable to heat and oxidation, with higher pH is destroyed. Since the thiamine fears therefore ph alkaline, the addition of bicarbonate to keep the legumes green leads to the destruction of vitamin and due to its water solubility it can melt in the washing or boiling water.
Vitamin B5, called pantothenic acid, is known to be the component of coenzymeA, the main factor in the metabolism of carbohydrates and amino acids. The food sources are the liver, kidney, brewer’s yeast, egg yolk and considerable quantities even in royal jelly, shortages are very rare. In multivitamin preparations pantothenate is not used, but pantothenol is used instead, as it is more stable and in any case it is transformed into pantothenate from the human body.
Vitamin B8, Biotin, cooperates in the metabolism of amino acids and carbohydrates. It is present in the yolk, liver, soy, brewer’s yeast and tea. The biotin not absorbed in the small intestine is excreted in the feces as the large intestine has very limited absorption capacity.
Vitamin C, ascorbic acid, has an antioxidant action, enhanced by vit E and beta carotene, it acts above all as a vasoprotector. It is absorbed in the small intestine, but the absorption capacity is individual and however quite limited. For this it is recommended to administer small daily doses, considering that for doses of 1 gram you can count on a 50% absorption, while for doses of 5 grams this absorption decreases to 25%. Fresh fruits and vegetables contain the largest percentage, the preservation of these, however, frequently implies the loss. It must be borne in mind that oxidation of the ascorbate occurs when cooking or storing food.
Folate is a coenzyme of numerous metabolic reactions and is involved in the synthesis of nucleic acids and in the formation of blood and nerve cells; their deficiency can cause megaloblastic anemia and malformations in the newborn. Deposits in the body are limited, so is their availability in food. Not being very stable, the cooking inactivates a large part of vitamin labile to heat. About three quarters of folate present in food are hydrolyzed and absorbed in the small intestine. Folate can be found in tomatoes, offal, beans and oranges.
Vitamin B12 includes a group of substances characterized by a cobalt atom: cobalamine. It is essential for the growth and formation of blood cells and nerve sheaths. The food sources are legumes, seafood such as mussels and oysters, in nature can be synthesized by bacteria, fungi and algae. About two thirds of the introduced vitamin are absorbed, this reaches the intestine through biliary secretion. Vegetarian diets are at high risk of deficiency.
In addition to vitamins, other essential nutrients called oligoelements also exist, But that will make for an entire new post.
Sarah is part of the Team ELC and she helps people discover what makes their life happy, meaningful, and full of ease. She is a writer, meditator and loves painting, an art she happily gets to practice a lot in her spare time.