Vitamins - Overview

Blood Flow Physics

Circulation

Dehydration

Diabetes And Cardiovascular Disease

Energetics

Energy

Energy Fuels

Hunger

Muscle Protein

Nutrition

Powering The Body

Shoes

Trans Fatty Acids

Vitamins

Weight Control

Weight Loss And Exercise

Weight Loss: Physiology And Psychology

Vitamins are substances needed by the body in tiny amounts and are complex chemical entities which the body cannot make for itself, certainly in sufficient quantities. They act principally as regulators of a wide range of essential processes for normal metabolism, growth and human body development. Vitamins are divided into two categories, the fat-soluble (A) and water-soluble (B). Later the C (water soluble) and D (fat soluble) vitamins were identified. The B vitamin was discovered to be a group of many different components but many were incorrectly identified. The original B1, B2 up to B20 have now been reduced to a few specific and distinct compounds. The subscript of a particular B group vitamin

• Vitamin B₁ (thiamine)
• Vitamin B₂ (riboflavin)
• Vitamin B₃ (niacin, includes nicotinic acid and nicotinamide)
• Vitamin B₅ (pantothenic acid)
• Vitamin B₆ (pyridoxine, pyridoxal, and pyridoxamine)
• Vitamin B₇ (biotin), also known as vitamin H
• Vitamin B₉ (folic acid), also, vitamin M
• Vitamin B₁₂ (various cobalamins; commonly cyanocobalamin in vitamin supplements)

has been replaced by a name now that the identification has been verified. Also, the E vitamin group is a series of functionally and metabolically related compounds - the tocopherols.

• A Retinol (carotene)
  
• Visual processes, connective tissue and skin

• B1 Thiamine
• Carbohydrate metabolism. CNS function

• B2 Riboflavin
• Carbohydrate metabolism, vision and skin

• B3 Niacin
• Carbohydrate and fat metabolism

• B6 Pyridoxine
• Protein metabolism, red blood cell formation. CNS function

• B9 Folic acid
• Cell growth regulation, including red blood cells

• B12 Cyanocobalamin
• Red blood cell formation. CNS function

• C Ascorbic Acid
• Connective tissue, iron absorption, metabolism, healing, infection
  

• D Calciferols
• Calcium metabolism, bones and teeth

• E Tocopherols
• Protects vit A, C and fatty acids from destruction (antioxidant)

• K

The water-soluble vitamins (B family and C) pass across the mucosa by diffusion and also by association with specialised membrane carriers. Vitamin B12 (Cyanocobalamin) is the largest of the vitamins and its transport utilises yet another mechanism involving a specific mucoprotein in the stomach. Fat-soluble (A, D and K) are absorbed in the chylomicrons which are protein-bound fat droplets (lipoprotein particles) in the blood along with the fatty nutrients. These chylomicrons have a protein coating with a fat core allowing the fat to be transported in the bloodstream without clumping together.

Iron is transported across the mucosa from the intestinal lumen and into the plasma by an iron-binding protein called transferrin. When iron is in excess, it is combined with the protein ferritin and stored in the mucosal cells. In iron deficiency, this iron is given up and delivered to the blood.

Calcium is actively taken up by a calcium binding protein for blood delivery. This protein is made in the mucosal cells under vitamin D3 stimulation. This vitamin (cholecalciferol) can be obtained in the diet or produced from cholesterol in the skin by the action of ultraviolet radiation in sunlight. To become active, vitamin D3 must be first converted in the liver to calcidiol and then in the kidney to calcitriol. This is a much more active than vitamin D. Parathormone is necessary for this conversion of calcidiol to calcitriol in the kidney. Calcitriol stimulates the intestinal epithelium to synthesise more carrier protein molecules for calcium transport thus elevating the levels of calcium in the plasma. Calcitriol further enhances the action of parathormone on bone cells which normally acts on bone tissue by increasing the resorption of calcium from the bone matrix and elevating plasma calcium levels.

The fat soluble vitamins (A, D, E and K) are stored in large amounts within tissue, particularly the liver. These stores amount to many months or even years of supply under normal conditions. Any fat-soluble vitamin deficiency is very unlikely to occur for a very long time in a well nourished individual. If these vitamins are taken in excess it is very easy to accumulate too much saturating the body stores causing cellular damage. Liver damage can result from the ingestion of too much vitamin A or cellular damage can occur as a result of over consumption of vitamin D causing an increase in the body's absorption and handling of calcium.

Water soluble vitamins are not well stored in the body and pass through more easily, any excess mostly in the urine. Deficiency is much more likely (one-two months) but over consumption of these generally non-toxic vitamins can lead to interference with the absorption and utilisation of other nutrients (vitamin C), impair liver function (nicotinic acid) and nerve function (B6).

There is little evidence to show that the diets of athletes are specifically low in any particular vitamin or that athletes show any clinical or biochemical signs of deficiency. Surveys have shown that the vast majority of athletes (up to 80%) take vitamin and mineral supplements in some form throughout training and competition believing performance will be enhanced. This belief stems from an assumption that since certain vitamins are necessary for the energy processes to work then more vitamins means more energy. The outcome from nutrition research demonstrates that there is no significant effect. Importantly, since vitamin deficiency does impair performance, and there was no effect on performance, then there was no indication that diet was lacking in vitamin intake. Performance improvements have been reported but there are two other possible explanations for this. Either a real performance effect was noted by taking supplements or a deficiency of certain vitamins was restored to levels to allow normal performance to occur. The placebo effect should also not be overlooked. The psychological effects of supplementation can be very powerful. Just the belief that performance will be enhanced can make it so. Nevertheless, the jury is still out regarding vitamin supplementation.

Little evidence is available to indicate that high levels of exercise causes the destruction, excessive use by the body or increased excretion of vitamins. It is possible that the B (mostly B2 - Riboflavin) requirements may increase but generally the consumption of food will increase proportionally to exercise intensity. Those with poor diet and high intensity exercise are certainly at risk. It should be noted that high alcohol intake can impair absorption of B1 (Thiamine), B9 (Folic acid), B12 and C and that large doses of aspirin and other anti-imflammatories may reduce vitamin C levels. Smoking increases the need for vitamin C and interferes with B1 and B12 metabolism. Oral contraceptives tend to deplete the body stores of vitamins B1, B2, B6, C and folic acid.

The problem probably lies with the associative factors which manifest as vitamin depletion. Fatigue, depression, muscular aches are most likely caused through training and not any deficiency. Though the belief is that the cause is a lack of vitamins and not as a consequence of training. Supplementation of vitamins is not likely to reduce the severity of these factors or suddenly produce any boost in energy levels. Hope and aggressive promotional campaigns by the vitamin manufacturers is responsible for the high incidence of athletes taking the supplements. The advertising code prohibits manufacturers from suggesting that vitamins will cure or prevent disease but they must provide evidence of any claims they do make. Many products do go completely unchallenged though due to word of mouth and in-house promotion of such products in limited circulation magazines. Great powers are believed to exist within these products even though there is no scientific evidence in support. The exploitation of ignorance in the whole area of nutrition creates vast profits.

Sub-optimal nutrient levels can exist in individuals. Those exposed to higher risk are usually involved in weight division sports. Attempting to stay in a certain weight class by manipulating body weight has its own set of problems. Obviously high nutrient density (vitamins and iron) are essential to prevent the consequences of hyponutrition. Before any use of supplementation careful considerations of diet should be made to correct poor diet and the insufficiency of vitamin intake caused by it. Any shortage of nutrient is probably a result of diet rather than increased requirement through exercise.

Large doses of vitamins can be harmful or even fatal. Small excesses are probably acceptable. Relatively small amounts of vitamins are present in most foods except certain ones such as polar bear liver, cod liver oil, red palm oil which are high in the fat-soluble vitamins. It is difficult to overdose on vitamins through normal diet. However, synthetic vitamins can be produced in large quantities so it is very easy to ingest far in excess of safe levels. The megavitamin preparations can expose the body to levels way above normal physiological levels, maybe 10-1000 times the levels of normal diet. The capability of the body to deal with such levels is pushed to (or over) the limit leading to cellular damage and possibly even death. Synthetic, natural or organic vitamins equally describe essentially the same quality.

Minerals constitute about 5% of the body composition. They are essential to life for basic structure (skeleton: calcium), nerve and muscle function and for correct enzymatic function, vital for normal metabolism processes to occur. Some macrominerals, minerals required in relatively large amounts (100mg daily), are calcium, magnesium, and sodium and potassium chlorides. Others in trace amounts (2-5mg or less) include iron, copper, zinc, manganese, iodine, cobalt, chromium and selenium. Often these interact with the macrominerals.