The ABCs of Vitamins

When researchers reviewed more than a decade’s worth of findings, they found that megadoses of vitamin C don’t prevent colds for most people. Some studies suggest it might help you get over the symptoms a little faster. But it won't make them less severe.

Studies show that many different vitamins and minerals may lower your risk for an eye problem called macular degeneration, the leading cause of vision loss in people over 65. A balanced diet loaded with fruits and vegetables should give you all you need. If your risk is still high, your doctor may recommend a supplement along with lifestyle changes. And don't smoke!

Scientists first thought that vitamins were amino acids, the building blocks of protein. Today, we know of 13 types that are essential for good health. You can usually get all you need from a balanced diet. But some people, especially those who limit certain foods, may benefit from supplements. How much do you need? The government recommends a daily amount for most vitamins and minerals, as well as the maximum amount that scientists think is safe.

It's definitely important to get enough B12. Too little of it can cause anemia, memory loss, confusion, and tingling in your arms and legs. But there’s little evidence that taking it makes you a better athlete or gives you more energy. A diet that includes meat, fish, or dairy products should give you enough.

Most people know that calcium and vitamin D are important for healthy bones. But new research shows that other nutrients, including magnesium, potassium, and vitamin K, help, too. If you have a high risk of brittle, thinning bones, called osteoporosis, your doctor may recommend a calcium and vitamin D supplement.

Your body needs vitamins for growth, digestion, and nerve function. Minerals support cells and help different parts of your body do their jobs. Vitamins are known by letters of the alphabet: A, B, C, D, E, and K. Examples of minerals include calcium, which builds bone and makes blood clot, and iron, which helps your blood carry oxygen.

Some vitamins, including C and B, turn your pee a bright orange or even yellow-green if you take more than you need. That’s your kidneys getting rid of the excess. (Don't test it out -- it can be dangerous to get too much of some nutrients.) But the recommended amounts of most vitamins and minerals don't color your urine.

Pregnant and breastfeeding women often need more nutrients. Other people may take vitamin or mineral supplements to fill a specific gap. Those on special diets, such as vegans, may not get enough from food. Other people may have trouble absorbing all the nutrients they need, including: 

• Those with some medical conditions, such as inflammatory bowel disease
• People who have had some types of weight loss surgery
• Anyone who takes some medications for seizures or heartburn
• Those who use aspirin often 

Talk to your doctor if you think you need a supplement.

Supplements can be a good way to make sure you get enough nutrients, but many vitamins and minerals can be toxic if you take too much. A lot of vitamin A can cause nausea, vomiting, and liver damage, for example. Too much vitamin D can cause weakness, heart rhythm problems, and confusion. Because the body stores vitamins A, D, E, and K and iron, the excess can build up in your organs and tissues and damage your kidneys or liver.

Citrus fruits may be the best-known source of vitamin C, but many other fruits and vegetables have it, too. Most adults need between 75 and 90 milligrams a day. A half-cup of sweet red pepper does the trick -- about the same as a 6-ounce glass of orange juice.

This crucial B vitamin is mostly in foods from animal sources, including meat, eggs, and dairy products. If you don't eat these, you may not be getting enough B12. Talk to your doctor about whether you should take a supplement.

Researchers continue to study whether some antioxidants prevent the kind of genetic damage that can turn cells into cancer. But there is no evidence that taking these supplements will lower your risk for the disease. If you’re getting cancer treatment, talk to your doctor before you take any. Some research suggests that antioxidant supplements may keep some cancer-fighting medicines from working.

Women who still have their periods usually need more iron because they lose a little with each menstrual cycle. Experts say premenopausal women should get 18 milligrams a day. Men usually need only 8 milligrams a day. Pregnant women should get 27 milligrams a day.

Experts are deeply divided on multivitamins. A lot of recent studies have found that healthy people don't benefit from them. Even those who have taken one every day for years don't appear to be healthier or to live longer. But other scientists believe that they can help fill in for what's missing in many people's diets. Experts do agree that the best source for vitamins and minerals is food, not pills.

These are all different forms of B vitamins. They help your body with many important jobs, including changing food into energy. Whole grains, beans, nuts, meat, eggs, and fish are good sources of many different forms of B vitamins. Vitamin B12, on the other hand, is found almost exclusively in foods from animal sources.

People with dark skin may be more likely to have low vitamin D levels. Older people also might not have enough because skin gets less efficient at converting sunlight to vitamin D as you age. If you stay out of the sun because of sensitive skin or the risk of cancer, you may also need extra D. Talk to your doctor. A simple blood test can show whether you have as much as you need.

Folic acid helps prevent birth defects, specifically problems with the brain and spinal cord. Because it's so important during pregnancy, doctors say pregnant women and those who want to have a baby should take a supplement to make sure they get enough.

This mineral helps keep your heart beating regularly, and one study found that taking it lowered systolic blood pressure (the top number). Reducing blood pressure lowers the risk of stroke, heart disease, heart failure, and kidney disease.

Teens and adults should get 4,700 milligrams of potassium a day. Many foods have this nutrient, so it's rare that people don't get enough from their diet. Potassium-rich foods include many fruits and vegetables, milk, meat, and whole grains. In addition to potassium, there are other supplements as well, such as magnesium, that appear to have benefits for lowering blood pressure. More study is needed.