Vitamins and Micronutrients

Vitamins

• Vitamins are organic compounds required in trace amounts (microgram to milligram quantities per day) in the diet for health, growth, and reproduction.
• They cannot be synthesized in adequate quantities by humans.
• Vitamins are classified as micronutrients because they are required in lesser amounts than macronutrients (carbohydrates, proteins, and lipids).

Classification of Vitamins

• Vitamins are classified into two categories: water-soluble and fat-soluble.
• Water-soluble vitamins: include folic acid, cobalamin, ascorbic acid, pyridoxine, thiamine, niacin, riboflavin, biotin, and pantothenic acid.
• Fat-soluble vitamins: include vitamins A, D, K, and E.
• Fat-soluble vitamins are released, absorbed, and transported with dietary fat, and are not readily excreted.

Water-Soluble Vitamins

• Water-soluble vitamins are readily excreted in the urine, and toxicity is rare.
• Deficiencies can occur quickly.
• Many water-soluble vitamins are precursors of coenzymes for the enzymes of intermediary metabolism.

Fat-Soluble Vitamins

• Fat-soluble vitamins are stored in the liver and adipose tissue.
• Consumption of vitamins A and D in excess of the Dietary Reference Intakes can lead to accumulation of toxic quantities of these compounds.
• Only one fat-soluble vitamin (vitamin K) has a coenzyme function.

Vitamin A

• Vitamin A serves many important functions in the body, including its role in vision, reproduction, growth, and embryonic development, as well as immune function.
• Dietary sources: animal-derived foods, such as liver, other organ meats, and fish oils, and plant sources like pumpkin, carrots, and most green vegetables.
• Deficiency: may cause night blindness, very dry, rough skin, decreased resistance to infections, faulty tooth development, and slower bone growth.
• Toxicity: nausea, vomiting, diarrhea, dizziness, drowsiness, and fatigue.

Vitamin D

• Vitamin D plays an essential role as a hormone in the control of calcium and phosphorous metabolism.
• Vitamin D is also essential for dental health, preventing tooth decay and loss, strengthening the gums, and reducing the risk of oral infections.
• Dietary sources: vegetables like mushrooms, fortified foods like breakfast cereals and oatmeal, and animal sources like egg yolk, cod liver oil, salmon, and tuna.
• RDA: 600 IU (15 mcg) daily for adults 19 years and older, and 800 IU (20 mcg) daily for adults >70 years.
• Deficiency: may cause rickets, osteomalacia, osteoporosis, alopecia areata, type 2 diabetes, and depression.

Learn about vitamins, organic compounds required in small quantities for health, growth, and reproduction. Understand how they differ from macronutrients and their role in the human body.