You already ask you at what can be useful a supplément of multivitamine ?
let’s take a look close of each one.
Vitamin A is also known as retinol and retinal; retinoic acid is a by-product
of retinal. “Provitamin A” refers to beta-carotene, which can be converted to retinol in the body. The roles of vitamin A include the visual cycle, cellular differentiation (affects gene expression to control cell development), growth (appears to increase the number of receptors for growth factors), reproductive processes, bone development, and proper immune function. By boosting immune function, vitamin A may create a more favorable environment for muscle growth to occur. Vitamin A works synergistically with zinc and vitamins K and E; a deficiency of these nutrients may impair the function of vitamin A.Dosage: Up to 10,000 IU (international units) in divided doses daily.
Vitamin C (ascorbic acid) is an essential water-soluble vitamin for any intensely training athlete or dieter. It has several functions in the body, including antioxidant properties, collagen synthesis, immuno-enhancing effects, and decreasing cortisol levels. Vitamin C helps fight free radicals, which are responsible for oxidative damage in the body. Vitamin C has been shown to considerably decrease the duration of cold episodes and the severity of symptoms. If you’re sick, you cannot train properly and you may lose hard-earned muscle. Vitamin C may help reduce unwanted cortisol levels. Cortisol is a catabolic hormone that is secreted in times of stress, such as strenuous weight training. Vitamin C also aids in collagen synthesis. Collagen is a very important substance in the human body: it strengthens the skin, muscles, and bones, and is a primary component of ligaments and tendons. There are many studies that document vitamin C’s importance for healthy ligaments and tendons, which can be critical for preventing injury and speeding recovery. Vitamin C also plays a role in fat loss—it is important in the synthesis of the amino acid carnitine. Sufficient carnitine is important in fat metabolism, because carnitine helps transport long-chain fatty acids into the mitochondria for their breakdown to occur. Vitamin C also plays a key role in neurotransmitter synthesis and cholesterol catabolism. Dosage: 1–3 g (grams) in divided doses daily.
Vitamin D is associated with skeletal growth and strong bones. Calcitriol is considered the active form of vitamin D and functions like a steroid hormone. It plays a key role in parathyroid hormone, which directs the homeostasis of blood calcium. Parathyroid hormone also stimulates calcium and phosphorus reabsorption in the kidneys. When exposed to sunlight, the body can produce its own vitamin D. Dosage: 400 IU daily.
Vitamin E includes eight different compounds synthesized by plants. Vitamin E activity is greatest in the alpha-tocopherol form (more specifically, d-alpha-tocopherol). It is a fat-soluble vitamin necessary to maintain membrane integrity in body cells and acts as a powerful antioxidant, preventing the oxidation of unsaturated fatty acids in the cellular membranes. Vitamin E helps fight free radicals: there is an interrelationship between vitamin E and the mineral selenium, as both are tied closely in the function of glutathione peroxidase, a powerful antioxidant. The less muscle breakdown you have by stopping damaging free radicals, the more potential muscle building that can occur. Vitamin E can be regenerated with the help of vitamin C. There was some controversy over a study on vitamin E showing damaging effects, but the study was shown to have many deficiencies. Plus, the overwhelming evidence suggests vitamin E can be beneficial, especially to someone exercising regularly. Dosage: 400–800 IU in divided doses daily. High intakes of vitamin E can interfere with the functions of other fat-soluble vitamins, so I would not recommend taking amounts in excess of 1,200 IU daily. Look for the better absorbed d-alpha-tocopherol form.
Thiamin (Vitamin B1)
Thiamin is found primarily in the form of thiamin monophosphate in the blood. Thiamin can also be converted to its phosphorylated form, thiamin diphosphate (TDP), in the body. TDP functions as a coenzyme that is necessary for generating ATP (adenosine triphosphate, the primary form of energy used by cells). This is obviously important for promoting muscle function. Vitamin B1 is also important in nerve conduction and appears to mimic and potentiate the effects of acetylcholine, a neurotransmitter involved in memory. Dosage: 5–10 mg (milligrams) daily. Water-soluble vitamins rarelyshow any toxicity because excess water-soluble vitamins are excreted in the urine.
Riboflavin (Vitamin B2)
Riboflavin has two coenzyme forms, flavin mononucleotide (FMN) and flavin Vitamins and Minerals 41 adenine dinucleotide (FAD), which function in many metabolic reactions in the body. They can act as oxidizing agents and are a part of choline metabolism. Neurotransmitters such as dopamine require FAD for their metabolism: this can stimulate energy levels during exercise, since dopamine can convert to the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline). Dosage: 5–10 mg daily.
Niacin (Vitamin B3)
Niacin, also called nicotinic acid and nicotinamide, can occur as two nucleotides, NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate). It can also be formed in the liver from the amino acid tryptophan. NAD helps produce ATP (energy), while NADP is used in a variety of processes, including fatty acid synthesis, cholesterol and steroid hormone synthesis, and oxidation of glutamate. It may also help reduce the oxidized form of vitamin C. Niacin has also been shown to decrease cholesterol levels. Since it acts as a vasodilator, niacin also increases vascularity. It may increase energy during a workout. Dosage: 50–100 mg in divided doses daily. Niacin may cause a flush (redness and vasodilation), especially when taken on an empty stomach. Very high doses of niacin may also be hard on the liver. If you are concerned about these problems, you may want to try the inositol hexonicotinate form, which is easier on the liver. Niacinamide is also a flush-free form of niacin, but a small percentage of the population still seems to have a problem even with this form.
Pantothenic Acid (Vitamin B5)
Pantothenic acid plays an important role in energy storage as well as energy release in the body. It is used, along with cysteine and ATP, to form coenzyme A. As a component of coenzyme A, it is essential for the production of energy from carbohydrates, fat, and protein. Some studies suggest it may also accelerate the healing process, which is important during training. Dosage: 5 mg daily.
Pyridoxine (Vitamin B6)
The coenzyme form of vitamin B6 is associated with a vast number enzymes as part of amino acid metabolism. Vitamin B6 is also necessary to synthesize heme, the form of iron necessary for optimal blood flow and oxygenation. Niacin synthesis from tryptophan requires pyridoxal phosphate, which is one of the forms of vitamin B6. It is necessary in glycogen catabolism to “unlock” carbohydrate energy. Vitamin B6 has also been shown to diminish the actions of glucocorticoid hormones (such as cortisol). Dosage: 5–10 mg daily.
Folic acid (folate) is necessary in amino acid metabolism and is also required for histidine metabolism (to prevent this amino acid from accumulating in the body). Deficiencies in this vitamin can cause muscle weakness. Ascorbic acid (vitamin C) helps to protect folate from oxidative destruction and there is a synergistic relationship between folate and vitamin B12 (cobalamin). This relationship is sometimes called the “methyl-folate trap” because, without vitamin B12, folate is rendered useless in the body. Dosage: 500 mcg (micrograms) daily.
Biotin helps many enzymes function in the body, promotes energy metabolism, and is important in the utilization of fats and amino acids. Egg yolks contain a high amount of biotin. Egg whites contain a protein called avidin, which is unstable in heat; it binds to biotin and inhibits its absorption. That is why it is very important to cook egg whites before eating. Dosage: 300–500 mcg daily.
Vitamin B12 (cobalamin) may boost energy levels and enhance exercise performance. Vitamin B12 deficiency can lead to anemia. B12 shots are still popular for boosting energy levels. Dosage: 10–15 mcg daily.
Vitamin K is a fat-soluble vitamin that plays an integral part in blood coagulation. It may also strengthen the bone matrix. Dosage: 50–100 mcg daily.