Nutrition Note: Vitamins, more is not always better.

Vitamins are a nutrient group everyone talks about, but of which many misconceptions exist. One major misconception is what is really considered vitamins. A second major misconception is that an excessive vitamin intake will make a person even healthier. This article will address these two issues.

Vitamins are organic substances that are required by the body in very small quantities, but are essential for normal health and growth. They are essential because they cannot be made in the body or in sufficient quantities required by the body. Prior to the development of precision measuring technology in the 1980"s, the quantity and bioavailability of vitamins was hard to determine⁴. Bioavailability refers to the amount of a substance that can actually be utilized in the body. Current units of measurements for vitamins are milligrams (mg) or micrograms (ug), although the older international units (IU) may still be used at times.

Vitamins can dissolved in either fat or water, therefore they are classified as either fat soluble or water soluble vitamins. In general, fat soluble vitamins can be stored in the body for a period of time and are at greater risk of toxicity at high intake levels^{2 4}.

When vitamins were first discovered, a sequential naming system was established, starting with A². However, over time certain substances that were thought to be vitamins were found not to be and this has led to the missing of alphabetical names we now have (i.e. Vitamin F does not exist).

At the present time, the following are considered the fat soluble vitamins:

Water soluble vitamins are:

Too little or too much vitamins will result in ill health. The vitamins that must not be consumed in excess are ^{1 2 3 4} :

Table 1 gives the levels of vitamins that should not be exceeded. Please be aware of the different measuring units used for the various vitamins^{2 3 4}.

Table 1

Vitamin A is necessary for proper vision, the formation of mucous membranes, and the differentiation of rapidly growing cells in the body ^{2 4}. Beta carotene is converted to Vitamin A in the body. Beta carotene is found in most yellow fruits and vegetables. 90% of vitamin A is stored in the liver⁴, while excess intake of beta carotene results in a yellow colour to the skin because of the carotene being stored in the subcutaneous fat below the skin. Vitamin A is obtained from animal foods, such as milk, cream, cheese, egg yolks, and fortified ready to eat cereals. A deficiency in vitamin A leads to the inability to replace old cells and results in tissue damage. Vitamin A deficiency also increases a person’s susceptibility to infection. Blindness can also be caused by a Vitamin A deficiency ^{2 4}.

On the other hand, too much Vitamin A is also harmful. Eskimos that eat polar bear liver were at times found to develop hypervitamosis A². Symptoms of excess Vitamin A intake may mimic a brain tumor or liver disease. Other symptoms include nausea, vomiting, headaches, and failure to grow, bone abnormalities, dry scaly skin, and mucous membrane.

Vitamin D is required for proper bone and teeth development, and the regulation of blood levels of calcium and phosphorus. Vitamin D is found in small amount in food, such as fish and eggs. Fortified food such as milk and ready to eat cereal are a good source. Vitamin D is also made in the body from exposure to the skin to ultraviolet light. Deficiencies in vitamin D cause soft pliable bones in children, known as rickets, and deformed bones with spontaneous fractures in adults, also known as osteomalacia. Excess Vitamin D intake in children results in calcium accumulation in the kidney and heart, which cause irreversible damage^{1 3}. It can also lead to mental retardation².

Vitamin E functions as an antioxidant to protect the body’s cells from damage from free radicles. The ability to decrease LDL cholesterol ability to form plaque in the arteries is another role². Vitamin E is found in vegetable oils, whole grains, dark green leafy vegetables, nuts and seeds, legumes and egg yolks. Too little vitamin E in infants can lead to poor vision or blindness⁴. Muscle loss, nerve damage and weakness are also symptoms of deficiencies². Excess Vitamin E increases blood lipid levels, interferes with blood clotting, and impairs white blood cell activity⁴.

Vitamin C is an antioxidant and is important in wound healing and the immune system⁴. Vitamin C is known to decrease the symptoms and duration of a cold, but does not affect the frequency of getting a cold². Vitamin C is found in fruit and vegetables, especially citrus fruit. Vitamin C deficiency causes scurvy. In the past, sailors at sea lacked fresh fruit and overtime developed swollen and bleeding gums, loosened teeth and an increased susceptibility to infection. By giving sailors lime, which contained Vitamin C, scurvy or "lime disease" was prevented on the high seas.

Excessive levels of Vitamin C interfere with anticoagulants, and increases uric acid excretion, which is an issue for people with gout. Excess Vitamin C can also cause false negatives on urinary glucose levels in diabetic patients and causes the formation of kidney stones.

Vitamin B6 or pyridoxine is necessary for the breakdown and synthesis of protein. It is also required for the formation of heme, the oxygen carry compound of the red blood cell, and is needed for the formation of the nervous system⁴. Vitamin B6 is found in chicken, liver, meats, milk, green and leafy vegetables, bananas, prunes, tomato, potatoes and ready to eat cereals. A deficiency in Vitamin B6 results in symptoms such as nervous irritability, muscular weakness, and decreased growth rate. An excess intake of Vitamin B6 results in numbness in the hands and feet, loss of balance, difficulty walking, and bone pain^{2 4}.

Folate is necessary for proper neural development. The vitamin is found in dark green leafy vegetables, oranges, bananas, grapefruit, and ready to eat cereal. Deficiencies in pregnant women are known to cause neural tube defects. Excessive Folate intake interferes with zinc absorption, and masks a vitamin B12 deficiency^{2 4}.

Niacin is required for proper nerve function and the release of energy⁶. This vitamin can be found in meat, fish and poultry, milk products, grains, and some vegetables. A deficiency results in sensitivity to the sun, skin changes, fatigue, mental changes, and death. High levels are used to decrease blood cholesterol levels. Excessive levels result in dilation of the vascular system resulting in a flushing appearance and redness in the skin. Excess Niacin can also cause heart burn, gastric ulcers, elevated blood glucose, a rapid heart beat and decrease liver function².

Vitamins are essential nutrient, but like all nutrients, a balanced approach to consumption provides the most benefits.

Reference for Nutrition Note: Vitamins, more is not always better.

1. Brody, T. Nutritional Biochemistry. 1994. Academic Press, New York
2. Brown, J. E. 1999. Nutrition Now. 2^nd ed. West/Wadsworth Publishing. Ca
3. RDA. Recommended Dietary Allowances. 1989. National Academy of Science, Washington, D. C.
4. Weigley E. S., Mueller, D. H and Robinson, C. H. 1993. Robinson’s Basic Nutrition and Diet Therapy. 8^th ed. Prentice Hall, Columbus, Ohio

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