Vitamins are substances in food that are “vital to life” and are involved in numerous body functions. There are 13 known vitamins needed to support sound nutritional health.
Keep in mind that all vitamins are different from each other and one vitamin cannot substitute for another. Many vitamins have several different, but closely related, forms that occur naturally in the foods we consume. Because vitamins can have various forms, consumers may see several different names for the same vitamin. This can be confusing when trying to maintain a healthy diet.
Vitamins are classified into two groups based on their solubility - fat-soluble and water-soluble. The solubility affects how vitamins are lost in cooking as well as how they are absorbed, stored and excreted by the body.
The fat-soluble vitamins include A, D, E, and K. Hermann said these vitamins are usually found with fats in food. Because fat-soluble vitamins are soluble in fat, not water, these vitamins are not easily lost from foods when cooked in water. The body absorbs fat-soluble vitamins best with some fat. However, only a small amount of fat is needed.
The fat-soluble vitamins are stored in the body rather than excreted, thus they do not need to be consumed on a daily basis. Because fat-soluble vitamins are stored, toxicity is more likely to occur when they are consumed in excess.
Water-soluble vitamins include the B vitamins, or “B complex,” as well as vitamin C. Because they are water-soluble, these vitamins can be lost when foods are cooked in water. The best way to prevent loss of water-soluble vitamins when cooking is to use as little water as possible and cook for as short a time as possible.
Water-soluble vitamins are easily absorbed and excreted by the body. As a result, water-soluble vitamins must be consumed on a more regular basis than the fat-soluble vitamins. Although water-soluble vitamins are not stored, excess amounts may overwhelm the body, creating adverse effects.
Tolerable Upper Intake Levels have been established for many vitamins in an effort to address the possibility of adverse effects from high intakes. An Upper Level is the highest amount of a nutrient that is likely not to cause harm for most healthy people when consumed daily.
Most foods contain a variety of vitamins, but no single food has enough of all the vitamins to meet the total requirement.
Eating the recommended amount of foods from each of the USDA Daily Food Plan food groups is the best way to get the vitamins you need.