Water-Soluble Vitamins; B-Vitamins

By Syeda Hajra

Water-Soluble Vitamins

Like fat-soluble vitamins, water-soluble vitamins are essential organic substances needed in small amounts for the normal function, growth, and maintenance of body tissues. For example, thiamin, riboflavin, niacin, pantothenic acid, and biotin are especially important for energy metabolism. Vitamin B-6, folate, and vitamin B-12 are important for amino acid metabolism and red blood synthesis. Vitamin C participates in the synthesis of numerous compounds, including collagen, and choline is required for nervous system function and aids amino acid and lipid metabolism.
 In contrast to the fat-soluble vitamins, only small amount of water-soluble vitamins are stored in the body. The risk of water-soluble vitamin toxicity tends to be low because, unlike fat-soluble vitamins, water-soluble vitamins are readily removed by the kidneys and excreted in the urine. In fact, Tolerable Upper Intake Levels have been set only 4 of the water-soluble vitamins and choline.
 Compared with fat-soluble vitamins, water-soluble vitamins are more easily destroyed during cooking. A food's vitamin content can be decreased by exposure to heat, light, air, and alkaline substances. Water-soluble vitamins can leach into cooking water, whereas fat-soluble vitamins can leach into cooking fats and oils. Retention of the B-vitamins and whereas vitamin C is greatest in foods that are prepared by steaming, stir-frying, and microwaving. These cooking methods limit exposure to heat and water. Fruits and vegetables are especially important sources of many vitamins.

Tips for Preservation of Vitamins in Fruits & Vegetables:

⦿Keep fruits and vegetables cool until eaten. Because the enzymes in fruits and vegetables begin to degrade vitamins once they are harvested. Chilling limits the process.
⦿Refrigerate fruits and vegetables (except bananas, onions, potatoes, tomatoes, and fruit that is not fully ripened) in the vegetable crisper drawer or in plastic bags with tiny holes that allow food to breathe. Nutrients keep best at temperatures near freezing, at high humidity, and away from air.
⦿Trim, peel, and cut fruits and vegetables minimally just before serving. This is because oxygen breaks down vitamins faster when more of the food surface is exposed.
⦿Microwave, steam, stir-fry, or lightly cook most fruits and vegetables. More nutrients are retained when there is less contact with water and a shorter cooking time.
⦿Reduce cooking time and reheating. Because prolonged cooking (slow simmering) and heat speed breakdown of vitamin.
⦿Do not add baking soda to vegetables to enhance the green color. Alkalinity destroys vitamin D, thiamin, and other vitamins.
⦿Store canned foods in a cool, dry location at zero degree Fahrenheit or colder. Eat canned and frozen foods within 12 months. Because vitamin content declines as storage time increases.

Role of B-Vitamins

Vitamin B; All types 

All B-vitamins form coenzymes which are small, organic molecules that are a type of cofactor. Metals are another type of cofactor. Cofactors combine with inactive enzymes (called apoenzymes) to form active enzymes (called holoenzymes) that are able to catalyze specific reactions. All 8 B-vitamins participate in energy metabolism; some also have other roles within cells. Because of the role of B-vitamins in energy metabolism, the need for many of them increases somewhat with higher amounts of physical activity. Still, this is not a major concern because the higher food intake that usually accompanies an increase in energy expenditure contributes more B-vitamins to the diet.
In foods, B-Vitamins are present as vitamins or as coenzymes, both of which are sometimes bound to protein. Digestion frees B-vitamins from coenzymes or protein. Unbound or free vitamins are the main form absorbed in the small intestine. Typically, about 50 to 90% of the B-vitamins in the diet are absorbed. Once inside cells, the coenzyme forms of the vitamins are resynthesized. Vitamin supplements sold in the coenzyme form have no specific benefits to consumers because vitamins must be released from the coenzyme before they can be absorbed.

Enrichment of Grains:

Grains are an important source of B-vitamins, minerals, and fiber. However, when grains  are milled, the seeds are crushed and the germ, bran, and husk layers are removed. This refining process leaves just the starch-containing endosperm, which is the only portion of the grain used to make white flour, as well as many bread and cereal products. Because the discarded parts are rich in nutrients, milling leas to a loss of vitamins, minerals, and fiber.
  To counteract this nutrient loss, in the U.S. nearly all bread and cereal products made from milled grains are enriched with 4 B-vitamins __thiamin, riboflavin, niacin, and folic acid __and with the mineral iron. According to a national survey of dietary intakes, only about half of the folate and thiamin, and three quarters of the niacin and riboflavin we ingest occurs naturally in foods. Foods made with enriched and fortified grains have less vitamin B-6, potassium, magnesium, zinc, fiber, and phytochemicals than those from whole grains contain the germ and the bran, as well as the endosperm. Nutrition experts therefore recommend daily be whole grain, such as brown rice, oatmeal, popcorn and whole wheat bread and pasta.












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