By Dr. Christopher R. Mohr, R.D., PhD

There are more than 29,000 dietary supplements on the market today. It’s a multibillion dollar market.

But how do you know what’s in your supplements? How do you know if they're effective? And, most importantly, how do you know if they're safe?

With so many people interested in taking dietary supplements and so many out there, first you need to do your homework. Putting your trust in an ad or infomercial is clearly not the best way to find out what's right for you. Instead, use these four strategies to cut through the hype.

1. Will the supplement actually work?

The purpose of dietary supplements is to improve an aspect of your health, reduce the risk of developing a health condition or ease symptoms associated with a disease. So when evaluating the product, ask yourself, “Is it possible for the supplement to actually help me?”

For example, omega-3 fatty acids are powerful in reducing blood fat, also known as triglycerides, and therefore reducing the risk of heart disease. Is this your goal?

If the answer is yes, the next step is to consider whether the supplement in question is necessary, and whether it will lower your triglycerides faster than you could if you didn't take the supplements.

Do you need the omega-3 supplements to reduce your triglycerides, or is there another way that you could do that, such as losing weight, increasing your exercise and/or making some dietary changes?

2. Is this product useful for me?

Certain supplements are designed for specific issues or disease states, such as diabetes, heart disease, etc. Therefore, if you don't have those diseases or health conditions, you don't need to consider supplements to treat them.

Similarly, the market is now flooded with weight loss supplements. Research--and common sense--tells us that all these supposed “weight loss supplements” are useless. At this time, there aren't data to support their use. On the flip side, we know that clean eating and exercise do work. So why go for the expensive and unproven quick fix product that’s not going to cause change--and could potentially cause harmful side effects--when we actually know what does work? Ditch the fat loss supplements, and, if you suffer from a condition such as diabetes or heart disease, talk to your health care provider to see whether your specific situation could benefit from a supplement.

3. Are there scientific, placebo-controlled studies to support or refute the claims being made for the supplement? Have the results been duplicated?

Dietary supplements are being developed, improved, and launched all the time. Unfortunately, well-conducted scientific studies take much longer to carry out, and in the meantime, consumers are buying and trying those supplements. Dietary supplements do not have to endure the same rigor as prescription and over-the-counter medications; however, some supplements have had a number of safety and efficacy studies conducted on them. Such studies are published in peer-reviewed, scientific journals. Access to thousands of well-respected journals can be found for free on PubMed.gov, a resource of the National Library of Medicine at this website.

4. Where are you getting your information? Is this supplement safe?

Unfortunately all too often dietary supplements are recalled. Earlier this year, more than 150 fat loss supplements and other similar products were pulled from the market.

Where did you hear about the dietary supplement in question--a friend, trainer, magazine, infomercial? Ideally the information should come from a registered dietitian with a specific knowledge about dietary supplements. Don't trust everything you hear from a friend, read in the back of your fitness magazine or see on TV.

It’s crucial to talk to a health professional who knows about dietary supplements to make sure you have all the information before taking any supplement. The clerk at the vitamin store is not a reliable source for information on the safety and efficacy of supplements; he or she is in the business of marketing and selling supplements, not protecting your health. Nor is your trainer. (If your trainer tries to sell you supplements, it might be time to find a new one.)

This is a basic list of questions and concerns that should be answered prior to consuming any dietary supplements. What’s most important, though, is to remember that dietary supplements are called supplements for a reason—they are intended to supplement whole foods in the diet. No dietary supplement can or will ever be able to replace what can be obtained through a healthy diet. Consuming adequate calories and fluids should be your first concern. Dietary supplements should then fill in the very gaps in your nutritional needs--but only if they are proven to be safe, legal, and beneficial.

Dr. Christopher R. Mohr of Mohr Results is a weight loss and nutrition expert. He has a weight loss column in "Men’s Fitness" and has written more than 500 articles for magazines and websites. His expertise has been sought out by LL Cool J, Denise Austin, Emeril Lagasse, the Washington Redskins, and thousands of regular people. As a registered dietitian with a doctorate in exercise physiology, Dr. Mohr has the tools and strategies to help people get into the best shape of their life.

Do you take any dietary supplements? Which ones? Where do you get your information on supplements?