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Many people think that taking a daily cocktail of vitamins, minerals, antioxidants and other supplements is a prescription for a healthy diet. But it's also likely that they don’t know whether the nutrients they're taking are fat soluble, water soluble, or if they are getting more of some nutrients than they need. 

Supplements, in general, are viewed as good for you, and people may think, "If one is good, then more is probably better." But that’s not necessarily true.

Getting too many fat- or water-soluble nutrients, either from the food you eat or from supplements, can be dangerous. Vitamin and mineral supplements are serious business, and taking more than you need -- unless you are under the care of your doctor -- may be bad for your health.

The Dangers of Too Much Anything

Taking a vitamin or supplement as directed on the package label is considered to be safe, but not following directions can lead to problems.

"Excesses of all nutrients, from water, to iron, to water-soluble B vitamins, can potentially cause toxicities," says Norman Hord, PhD, MPH, RD, associate professor in the department of Food Science and Human Nutrition at Michigan State University. People who take vitamins and minerals in amounts above the established upper limits of the Dietary Reference Intakes (DRIs) may harm tissues where the vitamin is stored in their body, Hord explains. That’s why you shouldn’t take more than the recommended amount.

Vitamins and other nutrients play essential roles in maintaining good health, but they need to be consumed in the proper amounts. Vitamins are classified into two types: water-soluble vitamins and fat-soluble vitamins. They are divided into these groups according to how they are dissolved and stored in your body. Fat-soluble vitamins reside in your body's fatty tissue and liver and are used as needed by your body. By contrast, water-soluble vitamins dissolve in water and generally are not stored in your body. 

Water-Soluble Vitamins and Nutrients

Because water-soluble vitamins and nutrients dissolve in water, the continuous supply your body needs calls for a steady daily intake, from the foods you eat, from the supplements you take, or from a combination of foods and supplements. Vitamins C, B12, thiamin, niacin, riboflavin, tryptophan, pantothenic acid, biotin, and folic acid are all classified in the water-soluble category.

Water-soluble nutrients work best when you get them in the proper amounts. When you eat or take more than your body needs, the body adapts by absorbing just what it needs, and then it usually excretes the excess in your urine -- but not always. A study in the August 2010 Journal of Nutrition Science and Vitaminology found that urinary excretion of certain vitamins and other nutrients was reduced when study participants fasted.