Essential to our bodies, vitamins are often cited as the building blocks of our health. There are 13 vitamins involved in numerous physiological processes.
They are classified into two categories according to their chemical nature. Water-soluble vitamins, found in the bloodstream, such as the 8 group B vitamins and vitamin C. And the fat-soluble vitamins: vitamins A, D, E and K. Our bodies are able to store these vitamins in the liver and adipose tissue.
In this article, we introduce you to vitamins, with a focus on the fat-soluble vitamins A, D, K and E: their benefits, the intakes we need for good health, the risks of deficiencies, and their dietary sources.
What are vitamins?
Vitamins are organic elements essential to the proper functioning of our bodies. They have the particularity of being necessary in very small quantities to ensure our health.
Generally speaking, we must obtain vitamins from our food, as our bodies are unable to produce them on their own, with the exception of two of them, vitamins D and K.
Vitamins have no energy value, i.e. they have no calories. And for each of them, there are nutritional reference values indicating the target daily amount for our health (RNP: Référence Nutritionnelle pour la Population or AS: Apports Satisfaisants).
The functions of vitamins in the body
Vitamins are essential for the proper functioning of several physiological mechanisms. We can define two categories of vitamin benefits for our organism:
- A structural role: vitamins are essential to several structural elements of our body, such as the growth and health of our bones, the various cellular activities, the formation of our tissues and skin...
- A functional role : beyond their involvement in the structure of our body, vitamins ensure the functioning of numerous systems such as the nervous system, the muscular system, the immune system and the cardiac system. They are also involved in DNA synthesis, vision, digestion...
Fat-soluble vitamins: vitamin A
Vitamin A is also commonly known as retinol. It has a precursor, provitamin A (pro-retinol), which is found in the large family of carotenoids, the best known of which is beta-carotene.
The functions of vitamin A:
Immune system: vitamin A contributes to the normal functioning of the immune system.
Vision: vitamin A contributes to the maintenance of normal vision.
Cellular activity: vitamin A plays a role in the process of cellular specialization.
Iron metabolism : vitamin A contributes to the normal metabolism of iron.
Skin and mucous membrane health: vitamin A contributes to the maintenance of normal skin. Vitamin A helps maintain normal mucous membranes.
The risks of vitamin A deficiency:
Intra-uterine and post-natal growth retardation, congenital malformations, dry eyes, loss of twilight vision.
Reference intakes of vitamin A:
Value: RNP (Nutritional Reference for the Population)
Adult man: 580 μg / day
Adult woman: 490 μg / day
Pregnant woman: 540 μg / day
Nursing woman: 1,020 μg / day
Sources of vitamin A:
Foods of animal origin:
Cod liver oil (30,000 μg / 100 g), offal and liver (14,500 to 4,000 μg / 100 g), fish (1,100 to 285 μg / 100 g), butter (800 μg / 100 g), crème fraîche (390 μg / 100 g), cheeses (265 to 350 μg / 100 g), eggs (230 to 450 μg / 100 g).
Plant foods:
Sweet potato (10,500 μg / 100 g), carrot (7,200 μg / 100 g), squash (6,900 μg / 100 g), lettuce (5,300 μg / 100 g), spinach (4,000 μg / 100 g), apricot (2,100 μg / 100 g), melon (1,900 μg / 100 g), tomato (1,600 μg / 100 g), red bell pepper (1,500 μg / 100 g), mango (1,200 μg / 100 g).
Fat-soluble vitamins: vitamin D
Vitamin D is one of the two vitamins our body is able to synthesize. It has hormonal activity and exists in two forms: the D2 form, known as ergocalciferol and of plant origin, and the D3 form, known as cholecalciferol, essentially of animal origin. Exposure to the sun (15 to 20 minutes is enough) enables the synthesis of vitamin D3 in the epidermis of our skin.
The functions of vitamin D:
Bone health: vitamin D helps maintain normal bone structure. Vitamin D contributes to normal blood calcium levels.
Cellular activity: vitamin D plays a role in cell division.
Muscular system: vitamin D contributes to normal muscle function.
Immune system: vitamin D contributes to normal immune system function.
Pregnancy and children: vitamin D is necessary for normal growth and bone development in children.
The risks of vitamin D deficiency:
A vitamin D deficiency reduces bone density, weakening the skeleton and potentially promoting osteoporosis. A deficiency leads to an alteration in the bone mineralization process, resulting in rickets in children and osteomalacia in adults.
The reference vitamin D intake:
Value: AS (Satisfactory Intake)
Adult man: 15 μg / day
Adult woman: 15 μg / day
Pregnant woman: 15 μg / day
Nursing woman: 15 μg / day
Sources of vitamin D:
Foods of animal origin:
Cod liver oil (250 μg / 100 g), cod liver (54 μg / 100 g), fish roe (cod and salmon - 27 μg / 100 g), herring (22 μg / 100 g), fish (halibut, tilapia, trout, swordfish - between 21 and 15 μg / 100 g).
Foods of plant origin:
Margarine-type fats of plant origin (7.5 μg / 100 g).
Fat-soluble vitamins: vitamin E
Vitamin E groups together several compounds with antioxidant properties: tocopherols (alpha, beta, delta and gamma) and tocotrienols (alpha, beta, delta and gamma). Through its antioxidant action, it helps preserve the body by limiting aging.
The functions of vitamin E:
Cellular activity: vitamin E helps protect cells against oxidative stress. This makes it particularly useful for preserving cognitive functions, as well as muscle mass and recovery.
The risks of vitamin E deficiency:
Vitamin E deficiency can lead to neurological degeneration.
Vitamin E reference intakes:
Value: AS (Satisfactory Intake)
Adult men: 10 mg / day
Adult women: 9 mg / day
Pregnant women: 9 mg / day
Nursing women: 9 mg / day
Sources of vitamin E:
Plant foods:
Wheat germ oil (149 mg / 100 g), sunflower oil (57 mg / 100 g), avocado oil (45 mg / 100 g), vegetable fats such as margarine (23 mg / 100 g), olive oil (22 mg / 100 g).
Foods of animal origin:
Cod liver oil (30 mg / 100 g).
Fat-soluble vitamins: vitamin K
In humans, vitamin K comprises vitamins K1 (phylloquinone) and K2 (menaquinone).
The different roles and functions of vitamin K:
Cellular activity: vitamin K (K1) contributes to normal blood coagulation.
Bone health: vitamin K (K2) contributes to the maintenance of normal bone structure.
Risks of vitamin K deficiency:
A dietary vitamin K deficiency is rare, but can lead to poorer lipid absorption.
Vitamin K reference intakes:
Value: AS (Adequate Intake) for vitamin K1 (few data exist on K2 requirements).
Adult man: 79 μg / day
Adult woman: 79 μg / day
Pregnant woman: 79 μg / day
Nursing woman: 79 μg / day
Sources of vitamin K:
Vitamin K1 - Plant foods:
Dried herbs (basil, sage, thyme, parsley - 1,200 to 1,700 μg / day), kale (820 μg / day), spinach (500 μg / day), soybean oil (360 μg / day), Brussels sprouts (200 μg / day), broccoli (180 μg / day).
Vitamin K2 - Foods of animal origin:
Goose liver (360 μg / 100 g), chicken (34 μg / 100 g), raw egg yolk (32 μg / 100 g),
butter (15 μg / 100 g).
Other vitamins are also essential to our health: these are the water-soluble B-group vitamins (B1, B2, B3, B5, B6, B8, B9, B12) and vitamin C. Absorbed from the small intestine, they are not stored in the body. The bloodstream enables them to reach their sites of action, where they are used directly.
A varied diet, rich in fruit and vegetables, with adequate protein intake, and cereals, supports our various vitamin needs.