Vitamins

What are vitamins

Vitamins are nutrients that are essential for maintenance of normal metabolic function. Vitamins cannot be synthesized by mammalian cells and function as cofactors for enzymatic reactions. The water-soluble vitamins play vital roles in the conversion of carbohydrate, protein, and fat into tissue and energy. 

Vitamins are needed for a variety of biologic processes, among them growth, digestion, mental alertness and resistance to infection. They also enable your body to use carbohydrates, fats and proteins, and they act as catalysts — initiating or speeding up chemical reactions. Though vitamins are involved in converting food into energy, they supply no calories.

Types of vitamins

The water-soluble vitamins (B-complex and C) are not significantly stored by the body; excess is excreted in the urine. They must be replenished regularly through diet or other means to maintain essential tissue levels. They are rapidly depleted in conditions interfering with their intake or absorption. Lipid-soluble vitamins (A, D, E, K) are better stored in the body. If they are not excreted, as in renal failure excess may accumulate and cause toxicity. Synthetic and natural vitamins are equivalent in action and exert similar kinetics.

• Water-soluble vitamins. Vitamin C, biotin and the seven B vitamins — thiamin (B-1), riboflavin (B-2), niacin (B-3), pantothenic acid (B-5), pyridoxine (B-6), folic acid (B-9) and cobalamin (B-12) — dissolve in water (water-soluble) and aren't stored in your body in any significant amounts. Surplus water-soluble vitamins are simply excreted in urine.

• Fat-soluble vitamins. Any extra vitamin A, D, E or K not used by the body right after ingestion is stored in the body fat and liver. Excess fat-soluble vitamins can accumulate in the body and become toxic. The body is especially sensitive to excess amounts of vitamins A and D.

Role of vitamins in our body

Vitamin A

Vitamin A is essential for night vision and improves effectiveness of the immune system. It can be found in many dairy products, and especially in carrots.

Vitamin B12

This vitamin is essential in the formation of red blood cells and lack of this may cause anemia.

Vitamin C

Scurvy is caused by a lack of vitamin C in the diet. Vitamin C is essential in the formation of red blood cells, antibodies and a healthy circulatory system. Symptoms of scurvy include bleeding gums and dizziness caused by the deficient blood supply.

Vitamin D

Essential part of the diet required in the absorption of minerals in food, where a lack of vitamin D in the diet leads to a condition called rickets, where softening of the bones cause them to bend from the lack of calcium. Humans have the ability to synthesize vitamin D from sunlight

Vitamin E

Important in preventing the oxidation of fatty acids in cells, and is commonly found in cereals and green vegetables

Vitamin K

Vitamin K is important for the blood clotting process and can be synthesized in the human gut, and found in green vegetables.

Daily requirement of vitamins

The requirements for Vitamins are as follows:

Iu = international units; mg = milligram; g = micrograms.

Requirements in Older Persons

The water-soluble vitamins of particular interest for older adults include C, B₆, B₁₂ and folate. Although there is no evidence to suggest vitamin C absorption or utilization is impaired in older persons, this vitamin may be effective in protecting against stress-related and degenerative diseases. Vitamin B₆ deficiencies have been observed in those taking antagonistic medications or abusing alcohol. This vitamin has a significant role in immune function, so replacement therapy is warranted.

Vitamin B₁₂ deficiency is a concern in older persons because it may be associated with megaloblastic anemia, impaired cognitive function, dementia, neuropsychiatry disorders or nonspecific complaints of lethargy and malaise. Older persons often eliminate red and organ meats from their diet, fearing the fat and cholesterol content, but these foods are a major dietary source of B_12. Physiological changes may decrease the absorption or bioavailability of B_12.

Folate deficiency is common among older adults and megaloblastic anemia may result. Typical causes include inadequate intake, alcoholism, medications or malabsorption syndromes.

Elevated homocysteine concentrations have been found to be associated with low levels of folate, vitamin B₆ or vitamin B₁₂. Hyperhomocysteinemia may be related to increased risk of coronary and vascular diseases, so there may be opportunity to decrease disease burden by supplementation of these vitamins.

Vitamin D is the most common fat-soluble vitamin deficiency for older persons. Homebound or institutionalized persons are particularly at risk. Low dietary intake, especially of milk products, and decreased sun exposure contribute to low levels. The roles of vitamin D in maintaining bone health and facilitating calcium absorption make it a very important dietary component.