Vitamins provide essential nutrients needed to perform all basic tasks in the body. The movement of muscles, production of blood and synthesis of energy all require vitamins. We can obtain vitamins from the foods we eat and from vitamin supplements. Deficiency or excess of vitamins can cause severe symptomsm and individuals have different needs for vitamin intakes based on age, gender, activity level, lifestyle factors such as smoking and presence of disease. Your physician or registered dietitian can provide expert advice as to what specific needs you may have to achieve optimum health.
Natural Regulation
Your body naturally regulates vitamin absorption and customizes how much or little is absorbed based on the body's need. When needs are high, the body ramps up absorption. If the body has adequate amounts of a nutrient, absorption decreases. The body always functions to preserve energy when possible. Absorbing unnecessary nutrients is a waste of resources as it requires energy to absorb and to excrete nutrients. For example, if you supplement more than 1,000 milligrams, or mg, of vitamin C per day, your body only absorbs about two percent. Taking too many vitamin supplements can become a waste to your body and your wallet.
Avoid Toxicity
Consuming a variety of fruits and vegetables, provides the best means for obtaining adequate nutrition without risk of toxicity, since the body regulates what is absorbed. Water-soluble vitamins, such as vitamin C and B vitamins, are excreted in the urine once the body absorbs what is needed and in most cases, pose a low risk of toxicity. Excess amounts of vitamins A, D, E, and K are stored in fat tissue not excreted from the body. This can cause toxic amounts to accumulate. The Food and Nutrition Board of the Institutes of Medicine examined nutrients and established Tolerable Upper Intake Levels, or ULs, which are the highest dose researched as safe for adult consumption.
Pair Up
Some vitamins are absorbed best when paired with another nutrient. Iron requires vitamin C for absorption into the body's cells. Vitamin D and calcium are another example as vitamin D is needed to promote calcium uptake into the bone. Even with adequate calcium intake, if vitamin D is deficient, calcium cannot be properly absorbed and risk of osteoporosis or osteomalacia is increased.
Timing Is Everything
Avoid taking vitamin supplements with high fiber meals, tea or alcohol. Fiber and tannins, found in tea and alcoholm can bind nutrients and prevent them from being absorbed. To avoid this, take supplements at least an hour before or after a consumption of fiber, tea or alcohol.
Vitamin Forms
Some forms of vitamins are better absorbed than others. Iron has two types: heme and non-heme iron. Heme iron is present in meat and is nearly three times more absorbed than non-heme iron, which is found in plant products such as tofu, soybeans, dark green vegetables and legumes. Folate has a naturally occurring form found in food and a synthetic form, folic acid, found in fortified cereals and supplements. Folic acid has a much higher rate of absorption compared to dietary folate.
References
- "Annual Review Pharmacology"; Vitamin Toxicity; Joseph DiPalma; April 1977
- Vitamins: The Basics
- "American Society for Nutrition"; Setting Tolerable Upper Intake Levels of Nutrients; Ian Munro; February 2006.
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