It seems as if each day there's a new product that promises to provide you with extra nutritional support, a boost of immunity or a host of antioxidants to fight off diseases.

Take a walk down the pharmacy aisle and you'll see so many vitamin bottles, it can leave you confused: Which ones are necessary? Will taking them actually do anything helpful?

“Here’s the point about vitamins,” said Dr. Marc Siegel, an internist and FOX News Channel contributor. “Most people who eat a well-balanced diet in an upscale socio-economic environment do not need vitamin supplements, with the exception of calcium and vitamin D. Those are usually deficient in our diets.”

So here’s a breakdown of what each vitamin does, how much your body needs, and in what form the vitamin is best taken:

Vitamins A & E

Siegel said vitamin A and E supplements are not necessary. Instead, people should seek natural sources of these antioxidants.

“They are overused,” Siegel said. “These are are antioxidants that were trendy for many years, and it was thought they protected you from heart disease and cancers, but it turns out they don’t. So, I don’t recommend those.”

Vitamin A is found in carrots, sweet potatoes and broccoli, while vitamin E is found in cucumbers, milk and vegetable oils.

Vitamin B12

Siegel said a lack of vitamin B12 can cause peripheral neuropathy, stroke or anemia, yet it can easily be replaced by an injection.

“You’ve got to keep a check on your B12 levels, you can be tested,” Siegel said.

Vitamin B12 is found naturally in liver, shellfish, milk and eggs.

Vitamin C

When it comes to vitamin C, 500 milligrams is enough, Siegel said. “But, be careful, you should be getting that already. It’s not just in orange juice, it’s also in meat.”

Also, don’t be fooled by the popular myth that vitamin C prevents colds. Its main purpose is to help bones regrow and heal wounds, Siegel said.

Fruits that contain the highest amounts of vitamin C include papayas, strawberries and oranges.

Vitamin D

A lack of vitamin D is associated with heart disease, muscle problems, a loss of mental acuity and fertility problems, Siegel said.

“Everybody should consider taking a vitamin D supplement,” Siegel said. “You need at least 400 international units per day. You should have your doctor check your levels (through a blood test).”

Siegel said proton pump inhibitors (medicines like Nexium or Protonix), which treat acid reflux symptoms, may block the body's absorption of vitamins B12 and D, so anyone on those medicines should have their levels checked regularly.

Vitamin D is also known as the sunshine vitamin, because it is produced naturally in the body through exposure to the sun's ultraviolet rays. It can be found in salmon, tuna and eggs.

Vitamin K

Vitamin K, which helps the body clot blood, is found in leafy green vegetables. If you are eating enough salads, you should be all set, Siegel said.

Calcium

You should take 500 to 1,000 milligrams of calcium every day, especially if you are a post-menopausal female, Siegel said. Calcium is essential for keeping bones strong and preventing them from breaking.

Women should continue to get their calcium from outside sources, even if they are taking a supplement, Siegel said.

Calcium can be found in dairy products such as milk and cheese, as well as in almonds, figs, collard greens and kale.

Folic Acid

Not everyone is aware of how important folic acid is, especially to pregnant women as it can prevent major birth defects in the baby’s spine and brain, Siegel said. It is found in all prenatal vitamins.

Foods such as liver, peas, spinach and sunflower seeds are high in folate.

Iron

Most people do not need iron supplements.

“If you are iron-deficient, we want to know why,” Siegel said. “But, maybe a menstruating woman or someone who is iron-deficient should take a prescribed dose, in which case I would recommend 325 milligrams of Ferrosulfate twice a day.”

Red meats, poultry, fish, beans and tofu are rich in iron.

Magnesium

Magnesium is essential to the body’s heart and muscle function, as well as your nerves, but you usually do not have to supplement magnesium, Siegel said. If you think you may be deficient, ask your doctor to check your magnesium levels through a simple blood test.

Magnesium is found in foods like bananas, coconut, peanuts and shrimp.

Thiamine

People who are heavy drinkers — and are not willing to give up on the booze — should consider taking 100 milligrams of thiamine per day, Siegel said, as alcohol can lead to a thiamine deficiency.

A deficiency in thiamine can lead to psychosis and brain disorders such as encephalopathy, which can be caused by cirrhosis of the liver.

Foods rich in thiamine include pork, oatmeal, brown rice, cauliflower and oranges.

Zinc

“I’m not suggesting you take zinc unless you have a poor diet,” Siegel said. “It is good for the skin, and there is some evidence it may decrease the severity of colds, but I think that needs more studying. So, if you are going to take zinc, take 1 milligram each day.”

Beef, lamb and liver have the highest concentrations of zinc in food.

Siegel added that if you really feel your diet is “horrendous,” you may benefit from a multivitamin, but otherwise, a diet rich in vegetables and fruits should do the trick.