There are a large variety of vitamins in the B group, the more important being B1 or thiamine, B2 or riboflavin, B3 or niacin or nicotinic acid, B6 or pyridoxine, B9 or folic acid, B12 and B5 or pantothenic acid. B vitamins are synergistic. They are more potent together than when used separately.

Whole grains and dark, leafy vegetables are excellent supplies of vitamin B1, also known as thiamine. Known as anti-beriberi, anti-neuritic and anti-ageing vitamin, thiamine plays an important role in the normal functioning of the nervous system, the regulation of carbohydrates and good digestion. It protects heart muscle, stimulates brain action and helps prevent constipation. It has a mild diuretic effect. Valuable sources of this vitamin are wheat germ, yeast, the outer layer of whole grains, cereals, pulses, nuts, peas, legumes, dark green leafy vegetables, milk, egg, banana and apple. The deficiency of thiamine can cause serious impairment of the digestive system and chronic constipation, loss of weight, diabetes, mental depression, nervous exhaustion and weakness of the heart. 

The recommended daily allowance for this vitamin is about two milligrams for adults and 1.2 mg for children. The need for this vitamin increases during illness, stress and surgery as well as during pregnancy and lactation. When taken in a large quantity, say up to 50 mg, it is beneficial in the treatment of digestive disorders, neuritis and other nervous troubles as well as mental depression. For best results, all other vitamins of B group should be administered simultaneously. Prolonged ingestion of large doses of any one of the isolated B complex vitamins may result in high urinary losses of other B-vitamins and lead to deficiencies of these vitamins.