Dietary supplements for men are big business in this country. Each year, more than six billion dollars are spent on pills and powders that promise to make people healthier, thinner, more energetic and happier.

The marketing barrage is constant, and conflicting studies about safety and efficacy often leave consumers confused. The question is, do most men need supplements, and if they do, which ones should they take and in what quantities?

Below, two nutritionists discuss the realities and myths that surround nutritional supplements for men. Doug Kalman is the Director of Clinical Research at Peak Wellness, a private health center in Greenwich, Connecticut that combines traditional and integrated medicine. Heidi Skolnik is the team nutritionist for both the New York Mets and the New York Giants.

We are taught growing up that eating a balanced diet is enough to sustain us nutritionally. Is this true?
HEIDI SKOLNIK: It starts with food first. Nothing is going to replace a good, healthy diet. Vitamins and minerals can be used to prevent deficiencies, or for health promotion and staying healthy for a longer amount of time. Supplements can also be used to lower the risk of certain diseases.

Who do you think should be taking vitamin and mineral supplements?
HEIDI SKOLNIK: I think everybody would benefit from taking a general one-a-day vitamin that doesn't exceed the recommended dietary guidelines for each day.

But still nothing will replace eating fruits and vegetables.

Why can't a supplement replace the actual fruit or vegetable?
DOUG KALMAN: Here's an example. A tomato is a great source of vitamin C, but it's also very high in something called lycopene. Lycopene is a water-soluble antioxidant that is thought to reduce risk of prostate cancer. But studies measured the levels of lycopene in people taking it in a supplement-and they did not seem to measure up to the levels in people that have a high lycopene intake from the vegetable or fruits that contain it.

So supplements should not replace. They should supplement a good diet.

With that said, how do you know if a supplement pill is effective and approved? What should you look for? DOUG KALMAN: The bottle should have a U.S. pharmacopeia U.S.P. stamp on it. When a vitamin or mineral or a combination product has a U.S.P. stamp or it says in some form that the product has been tested and meets U.S.P. standards, it means that that pill will dissolve within a certain period of time. We know when you take a vitamin, after it goes into your stomach and then into your small intestine, there's only a small timeframe where your body's going to absorb it, and what it does not absorb is excreted. Thus, you want something that has been tested, and is going to break down in your body within fifteen to twenty minutes or one hour.

How are supplements used to address heart disease risk?
DOUG KALMAN: People at risk of heart disease should be taking a multivitamin that includes folate, also called folic acid, and vitamins B6 and B12.

Folic acid is used to lower homocysteine, which is an enzyme byproduct in the body that can be detrimental and cause progression of heart disease. Studies have shown that 800 micrograms of folic acid is an effective amount, which is double the amount in an average multivitamin.

Of course, people at risk of heart disease should also be getting adequate fiber in their diets, and they should have daily exercise routines.

What is the role of iron in the body, and must it be supplemented in both women and men?
HEIDI SKOLNIK: Iron supplementation will differ based on your age, your gender and on your history. Women may need to supplement with iron because they lose iron in their blood each month during their child-bearing years. Men actually want to be careful not to overload on iron because it can lead to hemochromatosis, a condition of iron-overload in the body, which can lead to heart disease risk.

So, men actually want to be careful about taking in too much iron, either through a multivitamin or through a lot of fortified products, like energy bars or powders.

Should most men try to take iron out of the equation by just taking a multivitamin without iron?
DOUG KALMAN: I would say yes, take the multivitamin without iron. Iron in these supplements also can cause constipation. While constipation can be treated by extra fluids and extra fiber in the diet, it's just a pain. So we try to avoid it.

What are the omega 3 and 6 fatty acids we hear so much about?
DOUG KALMAN: These are types of fats that are generally found in fatty fish, and contain essential fatty acids. These are very important for the immune system, hormone production, testosterone and estrogen and many other things, as well as acting as natural anti-inflammatories.

HEIDI SKOLNIK: Eating fish even as little as one time a week has been shown to decrease the incidence of heart disease in men. So although four times a week would be ideal, even one time a week makes a big difference. That's how powerful these omega-3s are. It's not clear to me that the science has shown that supplementing with fish oil tablets has the same benefits. There may be other factors that are found in fatty fish that could provide some heart healthy benefits.

It has to do with endothelial function, brachial artery constriction, platelet aggregation-all of these different factors. There are multiple factors that foods have on your body-there is usually more than one nutrient or phytochemical within foods that provide the benefit.

DOUG KALMAN: But if you're not getting enough omega-3s in your diet, then a supplement of omega-3s may be indicated.

What is the role of zinc in supplementation?
DOUG KALMAN: Zinc is important for processes of the immune system in the body, as well as hormone production and sperm production. As you age, sometimes your testosterone production wanes, and so does your sexual desire. There are some indications that zinc supplementation, since it does have some involvement in testosterone and sperm production, helps increase libido. There are some concerns if you take too much zinc that you can inhibit copper absorption. However, on 15mg or less per day of zinc, it appears to be safe and do the trick. 50mg would be the cutoff amount.

HEIDI SKOLNIK: You'll probably find the amount that you need in a multivitamin; they usually put in 15mg or more.

What would be your parting words to men who are interested in using nutritional supplements?
HEIDI SKOLNIK: Become as informed as you can be, which is always easier said than done. Seek out the advice of people who are educated in these things, and don't self-diagnose. If you're really looking for an effect that will help your health, you have to understand that there is potential that a supplement could hurt your health. So the same way you don't self-medicate, you really want to find out what the right dose is and what the dose response rate would be. It's the same with vitamins and minerals. Be wary of easy marketing schemes. Become informed and find out, based on your health profile and your patterns of exercise and diet, what makes sense for you.