Vitamins and dietary supplements are a $20 billion industry, and according to industry data, about half of all adult Americans take a daily multivitamin, but medical experts have questioned whether they really do any good.
While much is known about the link between vitamin deficiencies and related diseases, it doesn't automatically follow that taking extra vitamins is a good thing, Dr. Richard Besser, ABC News' senior health and medical editor, said on "Good Morning America."
For most people, eating a well-balanced diet from all the food groups is the best way to ensure you get the vitamins you need, Besser said.
Besser himself doesn't take vitamins.
"I eat a very balanced diet," he said, adding that "not everyone falls into that category."
Besser favors a balanced diet of fruits and vegetables, which, he said, provides him with all the nutrients he needs, including those he wouldn't get from supplements. He also doesn't recommend vitamins for his patients who have a well-balanced diet and aren't in any particular risk groups.
But, he added, the decision to take vitamins should be made after a patient has discussed his or her particular health needs with a doctor.
Doctors will consider the health, diet and age of a patient, and when those factors are taken into account, some people will need to take vitamins, Besser said.
Pregnant Women, Some Elderly, Should Consider Vitamins
On "GMA," Besser discussed three vitamins he recommends for certain groups: folic acid, vitamin D and calcium.
Women who are pregnant or who are considering becoming pregnant need to take a folic acid supplement. Besser said folic acid is vital to the baby's early development.
"If you're in the child-bearing age, you need to take folic acid," Besser said. "It's really early in pregnancy that you need to have those high levels of folic acid.
"Start taking it now and take it through the period where you may have children," he added.
Pregnant women should also talk to their doctors about getting a comprehensive prenatal vitamin, Besser said.
People for whom bone health is an issue should also talk to their doctors about getting a supplement, Besser said.
Vitamin D is essential for bone health and people become deficient as they age. While many people get enough Vitamin D by normal sun exposure, those who live in northern climates might not.
"Vitamin D is extremely important," Besser said. "I am convinced about the importance of vitamin D in your bone health."
In older people, the skin loses its ability to make vitamin D, so those who are older and who live in northern climates should consult with their doctors about whether they might need a vitamin D supplement.
"Your ability to store vitamin D in your body goes down" as you age, Besser said. "Knowing your vitamin D status … can be extremely important."
Besser said calcium, especially in combination with vitamin D, is beneficial to many.
"When you mix calcium and vitamin D, that's when you get those strong bones," he said.
Watch "GMA" Thursday for more on multi-vitamins and vitamins for your children.