Tuesday, December 16, 2008

Vitamins and Minerals: How Much Does Your Body Need?

They line the shelves of every pharmacy and health store, thousands of tiny bottles, claiming everything from improving memory and providing energy to preventing cancer and aging. In fact, chances are you take one or two, maybe a handful, daily. And if you don’t, maybe you should. What are these super pills? You guessed it – vitamin and mineral supplements. The biggest question in nutrition these days isn’t who needs vitamins and minerals, but how much.

In simplest terms, everyone requires vitamins and minerals. They are essential for life, fueling virtually every biochemical reaction in our bodies. It has long been realized that certain groups of people such as pregnant and breastfeeding women, chronic dieters, vegetarians, alcoholics, the elderly, and athletes often have increased nutrient needs and may require supplements. But for the most part, it has been assumed that the average, healthy adult can get all the vitamins and minerals their body needs from a healthy diet. The fact is most of us don’t.

Even if you are one of the few people who manage to eat a varied and healthy diet each and every day, factors such as environmental pollutants in our air and water; food filled with uncountable additives and preservatives; destructive agricultural practices which rob the soil of essential nutrients; food processing, storage and preparation – all reduce the nutrient content of food.

If that isn’t enough, physical and mental stress, illness, certain drugs, and a genetic predisposition towards certain diseases increase our nutrient needs. And taking into consideration the newest research, which suggests that higher doses of certain vitamins may protect against the development of chronic diseases such as cancer and heart disease, it might be a good time to visit a dietician or talk with your doctor about whether or not you might benefit from supplements.

What Are Vitamins and Minerals?

What Are Vitamins?
Vitamins are organic compounds essential for life that, with the exception of vitamin D, can only be obtained from food or supplements. While vitamin D can be found in dietary sources, the body also synthesizes it when sunlight meets the skin.

Fat-soluble Vitamins
Vitamins can be divided into two broad categories based on whether they dissolve in water or fat. The fat-soluble vitamins include A, E, D, and K. These vitamins are stored in the liver and fatty tissues, and therefore, it is not necessary to get a fresh supply every day. However, the fact that they can be stored also means that they can accumulate to toxic levels if taken in excess.

Water-soluble Vitamins
The rest of the vitamins, the family of B-vitamins (including thiamin, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid and cobalamin) and vitamin C, dissolve in water. Any excess is harmlessly excreted in your urine, making toxic levels virtually impossible. But note that this also means that you need a fresh supply of these vitamins every day to maintain adequate levels.

Remember that while vitamins help you extract energy from food, they themselves provide no calories and thus no energy.

What Are Minerals?
Minerals are inorganic compounds found in rocks and metals, although we get them from plants grown in mineral-rich soil or animals that have eaten mineral-rich plants. There are at least 10 minerals essential for life and a few others we house in minute levels, although scientists haven’t pinned down an exact role for all of them in the body.

Minerals are divided into two groups based on how much our bodies need. The major minerals, or macrominerals, are required in comparatively large amounts and include calcium, phosphorus, magnesium, potassium, sodium and chloride.

Trace Elements or Microminerals
Minerals required in very small amounts, less than 100mg/day, are called trace elements or microminerals. These include: boron, chromium, cobalt, copper, fluoride, iodine, iron, manganese, molybdenum, nickel, selenium, silicon, tin, vanadium, and zinc.

How Much Does Your Body Need?

Recommended Dietary Allowances
So now you know that you need 13 vitamins and some 15+ minerals, but how much does your body need? The Food and Nutrition Board of the Institute of Medicine developed the Recommended Dietary Allowances (RDAs) to help you out. These values reflect the amounts of vitamins and minerals you need daily to prevent deficiency diseases and are "safe and adequate" to meet the needs of most healthy people. They are the minimum values you need to prevent overt signs of deficiency diseases and are updated approximately every five years or so to reflect current research. A newer term, Reference Daily Intakes (RDIs), represents an average value recommended for children and adults over the age of four and will replace the complex RDAs. The RDIs and RDAs are basically the same.

Many nutritionists now think that the current values are too low and it is expected that future RDAs will be increased to address the issues of optimum health and disease prevention. In a position statement released by the American Dietetic Association, the criteria for establishing a recommended intake for a nutrient should not "assume that the recommended amounts can be met from dietary sources."

Meeting Your RDAs

According to Melanie Polk, RD, Director of Nutrition Education at the American Institute for Cancer Research, the best way to meet your RDAs is through a careful diet based on the Food Guide Pyramid. "Eating at least five servings of fruits and vegetables each day is essential," she says. Unfortunately, only one in ten people actually consume their recommended five servings.

Nutritionists agree that supplements are not a replacement for a healthy diet, but may be beneficial in addition to a healthy, varied diet. Carolyn Manning, Mag RD, and professor of nutrition and dietetics at the University of Delaware warns that relying too much on supplements can cause people to become irresponsible about their eating habits. Her motto, "Food first!"

There are additional health benefits from getting many of your nutrients from food. A group of recently discovered compounds found in plants called phytochemicals, are thought to protect against certain cancers. A few have been discovered but scientists think that there may be thousands of these compounds. "We don’t know exactly how they work, or if they work as a team with other phytochemicals or nutrients," says Polk, but they can’t be found in a pill.

Both Manning and Polk agree, that some groups require more nutrients than a healthy diet alone can provide.

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