Niacin (Vitamin B3)

Niacin is a water-soluble B vitamin important for DNA repair and energy metabolism. Also known as vitamin B3. Niacin is the generic term for nicotinic acid (pyridine 3-carboxylic acid) and nicotinamide (nicotinic acid amide) and the coenzyme forms of the vitamin.

In 1867, nicotinic acid was produced from nicotine in tobacco. In the early 1940s, with its role as a vitamin established, it was renamed “niacin” so people wouldn’t confuse it with nicotine.

Nicotinic acid and nicotinamide are colorless crystalline substances; each is insoluble or only sparingly soluble in organic solvents.

Nicotinamide is the active form, which functions as a constituent of two coenzymes, namely, nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP).

Niacin is part of coenzyme that participates in the production and breakdown of carbohydrates, fatty acids, and amino acids. It involved in at least 200 metabolic pathways. It is also a compound that dilates blood vessel.

A sufficient intake of vitamin B3 (niacin) is important as it helps the body to
• convert food into glucose, used to produce energy
• produce macromolecules, including fatty acids and cholesterol
• DNA repair and stress responses.

Clinical evidence of niacin deficiency includes fatigue, poor appetite, diarrhea, irritability, headache, emotional instability and possible memory loss. These may lead to changes in the skin, mucosa of the mouth, stomach and intestinal tract and the nervous system. These changes are called “pellagra”, which means “raw skin”.

Pellagra is characteristically associated with maize based diets. The disease pellagra has been known since the introduction of corn to Europe in the 1770s. The connection between pellagra and niacin was confirm in 1937 by an American scientist who reaching for the cause of pellagra.

In industrialized country, particularly among alcoholics, niacin deficiency may present with only encephalopathy.

Niacin comes from the diet, but the body can also manufacture it from the amino acid tryptophan, with riboflavin helping out in the process.

Adults require 13-20 mg niacin. In pregnancy, lactation and active muscular work, niacin requirement is further increased by 3-4 mg. Children require 5-16 mg niacin.

Yeast, liver, poultry, lean meats, nuts and legumes contribute most of the niacin obtained from food. In cereal products (e.g., corn, wheat), niacin is bound to certain components of the cereal and is thus not bioavailable.

The amino acid tryptophan contributes as much as two thirds of the niacin activity required by adults in typical diets. Important food sources of tryptophan are meat, milk and eggs.
Niacin (Vitamin B3)

Manifestation of iodine deficiency

Iodine is an essential constituent of the hormones of the thyroid gland, namely, triodothyronine (T3) and thyroxine (T4). These hormones are essential for normal growth and physical and mental development in animals and man.

Iodine deficiency is the result of insufficient dietary iodine intake, which can lead to inadequate production of thyroid hormones and many adverse effects at all life stages, collectively known as iodine deficiency disorders.

The diet is likely to be deficient whenever the soil content of iodine is low, which is often the case in mountainous regions. The most severe deficient soils are those of the European Alps, the Himalayas, the Andes and the vast mountains of China.

WHO recommends that the daily intake of iodine should be 90 μg for preschool children (0 to 59 months), 120 μg for schoolchildren (6 to 12 years, 150 μgfor adults (those older than 12 years) and 200 μg for pregnant and lactating women.

Iodine deficiency leads to inadequate production of thyroid hormone that indispensible for brain growth and development. The iodine deficiency disorders consist of wide spectrum, including mental retardation, impaired physical development, increased prenatal and infant mortality, hypothyroidism, cretinism and goiter.

The most visible manifestation of iodine deficiency is goiter. Goiter is defined as an enlargement of the thyroid gland and cretinism is a term used for a severe form of iodine deficiency characterized by severe mental retardation. Thyroid function is dependent upon the availability of iodine and several other trace elements, The relationship between the iodine intake level of a population and the occurrence of thyroid disease is U-shaped, with an increase in risk associated with both low and high iodine intake.

Iodine deficiency during pregnancy remains a common cause of preventable cognitive of impairment worldwide. The most severe damage due to iodine deficiency occurs from the fetal period to the third month after birth, during which iodine deficiency can produce cretinism, an irreversible form of mental retardation.
Manifestation of iodine deficiency

Daily requirement for vitamin A

The requirement for vitamin A can be considered as those amounts which allow certain defend states of nutriture to exist.

Because the absorption efficiency of preformed vitamin in foods is equal to a greater than 90 percent, the dietary requirement is 10 percent higher than the requirement for absorbed vitamin A.

The US recommended Daily Allowance (RDA) of vitamin A for adults is 5000 IU (1000 retinol equivalents).

Main dietary sources of vitamin A are the carotenoids from fruits and vegetables. Rich dietary sources of retinol (preformed vitamin A) include dairy products, eggs and organ meats.

About 100 g of carrots or any of a large variety of green leafy vegetables can meet the daily requirement of vitamin A.

Some carotenoids (found in deep-yellow and dark green vegetables) can be converted to vitamin A during digestion. In the US diet, approximately half of the vitamin A activity is derived from B-carotene and other carotenoids. It is not essential to meet the daily basis requirement on a daily basis because the liver can store about 50 day’s supply of vitamin A.

Excess of vitamin A can cause defects in the fetal bones and central nervous system. Rarely should adult doses exceeding 25,000 IU daily be taken unless a deficiency is especially severe.
Daily requirement for vitamin A