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Daily Dose: The Vitamins You Should or Shouldn't Be Taking

By August McLaughlin

In the early 1900s, Americans consumed all of their nutrients by eating food. In 2007, vitamin supplement sales topped $23.7 billion in the United States, according to the American Dietetic Association. But consuming more vitamins does not necessarily add up to improved health. How do you know what vitamins you need to take, if any, and what amount is appropriate?

For years I thought I was just a grumpy, low-energy person. I wish I'd known sooner that I just lacked vitamin D.

Heidi Smith, night-shift worker

Find Out What You're Missing

After moving from Florida to New York and starting a night job, Heidi Smith felt like she was always running on empty. "For years I thought I was just a grumpy, low-energy person," Smith explained. "I wish I'd known sooner that I just lacked vitamin D."

Working at night limited her exposure to the UV rays that help the body synthesize vitamin D. "Plus," she admitted, "I was eating pretty badly." When therapy and antidepressants failed to do the trick, she visited her physician, who tested her vitamin D levels and discovered a severe deficiency -- one that dietary changes alone would not rectify. Since being treated for a vitamin D deficiency, Smith has seen huge improvements in her energy level, "as though a cloud has been lifted," she said.

Most health-care practitioners agree that whole, natural foods remain the optimum source of nutrients. If your diet is lousy or your body's ability to absorb vitamins is compromised, however, you may require supplements. Registered dietitian Lauren Schmitt recommends that populations at risk for not meeting their nutrient needs, such as elderly adults, pregnant women and children, consider a basic multi-vitamin supplement. Women who experience heavy menstrual bleeding, strict vegans and vegetarians, and anyone who consumes fewer than 1,600 calories daily or can't stick to a balanced diet may also require supplements.

Various medical conditions, such as chronic digestive diseases and food intolerances, also create a need for vitamin supplements. Though numerous natural health-care practitioners use blood tests that supposedly check your nutrient levels, the tests lack scientific validity. If your doctor suspects a vitamin deficiency, he will likely run standard health tests, such as checking your blood cell counts, glucose levels, electrolytes and organ function. He will also ask you questions about your diet and lifestyle. In other words, vitamin deficiencies are diagnosed based on the symptoms they present and confirmed by your doctor's assessment of your overall health and dietary habits.

Common Deficiencies

Though people's specific dietary needs vary, certain nutrients are commonly lacking in the typical American diet.

Even if you consume a relatively healthy diet, you may be missing particular nutrients. The vitamin supplement most people should consider taking is vitamin D, according to Luigi Gratton, clinical nutrition specialist at the UCLA Risk Factor Obesity Program—the nutrient that had such a powerful impact on Smith's life. “Most folks in North America are deficient,” Gratton explains. The U.S. Institute of Medicine of the National Academy of Sciences recommends 5 micrograms of Vitamin D daily for those under 50.

Vitamin D is essential for proper calcium absorption and healthy bones. It also enhances your immune system and, for severely deficient people like Smith, your moods. If you rarely spend time outside and do not consume vitamin D-fortified dairy products, fish and other seafood regularly, discuss your need for vitamin D supplementation with your doctor.

Deficiencies of other vitamins are uncommon in people who live in the United States. If you consume a strict vegetarian or vegan diet, or suffer from the autoimmune disorder known as pernicious anemia, you may lack vitamin B12. The nutrient is found mainly in animal-derived foods and plays a major role in brain function, blood cell production and fatigue prevention. If you have a disorder that causes nutrient malabsorption, such as celiac disease or Crohn's disease, you may have difficulty absorbing all nutrients, particularly if you fail to manage your disorder appropriately.

The American Dietetic Association recommends consuming more of the B vitamin folate -- or the synthetic form, folic acid -- if you are pregnant, nursing or may become pregnant. Prenatal vitamins generally contain sufficient amounts of folate, as do whole grains.

Mega Bad

Consuming plentiful amounts of nutrients from food sources rarely causes problems. Excessive intake of most any vitamin supplement, however, can lead to a broad range of side effects, some of which are serious.

Vitamin supplements have been linked to nausea, diarrhea, stomach cramping, reduced cognitive abilities, interactions with medications and even death. For example, taking excessive doses of vitamin A in supplement form causes hypervitaminosis A -- a condition characterized by liver abnormalities, reduced bone density and birth defects. Excessive intake of vitamin B12, though not associated with toxic effects, can interact with medications, such as certain antibiotics and diabetes medications. Schmitt also describes taking unnecessary supplements as “not good use of your hard-earned money.”

To prevent unwanted side effects, avoid vitamin supplements that contain mega amounts -- more than 100 percent of the recommended daily allowance -- of particular nutrients and those that promise miraculous benefits. By law, the standard RDA is always listed on product packaging. Find that fine print and read it before taking any new supplement.

Maximizing Vitamin Absorption

Take fat-soluble vitamins with healthy fat. Because fat-soluble vitamins, such as vitamins E and K, are best absorbed when consumed with some fat, take your multivitamin supplement with a meal that contains a healthy fat source, such as olive oil, nuts or fish oil. Taking vitamins with food can also help prevent mild nausea, which is possible particularly with B vitamins.

Divide your doses. Selecting vitamins that can be divided into two smaller doses can enhance your absorption, according to Dr. Mahmet Oz, television medical expert and author of "You: The Owner's Manual.” To reap maximum benefits, select "mini" vitamins that require two to three capsules per day or large vitamins that can be cut into two.

Maintain freshness. If your vitamins have expired, toss them out. Keeping your vitamins in the refrigerator may help preserve their freshness and effectiveness.

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