Vitamin B – Types, Sources, Deficient and Excess States
Vitamin B is a part of our everyday diet and play an important role in our body especially in some biochemical reactions. The different types of vitamin B are involved in major reactions in the body and thus are important in our everyday lives. Let us glance at the different type of vitamin B, their sources, and their deficient and excess states.
Types of Vitamin B, Sources, Deficient and Excess States
Vitamin B1 (Thiamine) – plays a role in the metabolism of amino acids and in peripheral nerve conduction. Sources of Vitamin B1 include yeast, meat, pork, legumes, beef, whole grains and nuts. Tea and coffee contain thiaminases (an enzyme) which could destroy thiamine thus drinking a lot of coffee or tea could reduce stores of vitamin B1. Deficiency with theses vitamin is usually secondary to decrease dietary intake, alcoholism and chronic diseases like cancer. Vitamin B1 deficiency leads to beri-beri. Beri-beriproduces cardiovascular and neurologic symptoms and peripheral neuropathy. Allergic reactions have been reported after high doses of this vitamin.
Vitamin B2 (Riboflavin) – this vitamin is important for the metabolism of protein, fat, and carbohydrates and in detoxification reactions. Sources of Vitamin B2 include milk, dairy products, breads, cereals, lean meat, eggs and legumes. Deficiency in Riboflavin may manifest as magenta tongue, angular stomatitis, cheilosis, and seborrhea. Anemia and personal changes have also been associated with Vitamin B2 deficiency. Riboflavin toxicity have not been reported.
Vitamin B3 (Niacin) – Vitamin B3 or Niacin serve as a precursor for two important coenzymes namely nicotinamide adenine dinucleotide (NAD) and NAD phosphate (NADP), which are involve in many oxidation and reduction reactions in the body. Sources of niacin include beans, milk, meats and eggs. Flour is also a rich source of niacin. Niacin deficiency would lead to pellagra which is common among people with corn-based diets and among alcoholics. The syndrome of pellagra includes dermatitis, diarrhea, dementia and eventually death. Hepatic toxicity is the most serious effect of niacin and could present with yellowish discoloration of the skin and elevated liver enzymes. Other symptoms of toxicity include glucose intolerance, macular edema and cysts and hyperurimia. Skin flushing have been noted with oral niacin supplements but are not seen from food sources of niacin.
Vitamin B5 (Pantothenic Acid) – pantothenic acid is involved in fatty acid and cholesterol metabolism. Liver, yeast, egg yolks, whole grains and vegetables are good sources of this vitamin. Symptoms of vitamin B5 deficiency include: depression, muscle cramps, paresthesia and hypoglycemia. Toxicity with this vitamin has not been reported.
Vitamin B6 (Pyridoxine) – Vitamin B6 is involved in amino acid metabolism, heme and neurotransmitter synthesis, metabolism of glycogen, lipids, steroids, sphingoid bases and of several vitamins. Rich sources of vitamin B6 include legumes, nuts, wheat bran and meat. Vitamin B6 deficiency can lead to peripheral neuropathy and personality changes like depression and confusion. Anemia and platelet dysfunction are also manifestations of vitamin B6 deficiency. Toxicity of this vitamin could manifest as severe sensory neuropathy, photosensitivity and dermatitis.
Vitamin B12 (Cobalamin) – this vitamin serves as a co-factor for certain important enzymes in the body. Sources of cobalamin come from food of animal origin like meat, fish and dairy products. Deficiency of this vitamin would lead to megaloblastic anemia, abnormal gait, dementia, impotence, and loss of vibratory and position sense.
Harrison's Principles of Internal Medicine 18th ed