5 Popular Supplements Scrutinized

There are a lot of unknowns about some of the most used supplements

By Michael Smith, MD
WebMD Weight Loss Clinic - Feature

Reviewed By Cynthia Haines, MD

When it comes to supplements, "buyer beware" only goes so far these days. Patients have been interested in supplements for years, but doctors have been slow to recommend them. Don't be too hard on doctors. It's ingrained in us to look for strong evidence that a treatment works without doing harm. That's a good thing.

But as more research comes out, more doctors are getting on board. But we still know very little about supplement effectiveness, and what we do know doesn't look all that great.

So, if you're going to take supplements, which ones are most likely to give you the effect that you're looking for without causing you harm?

Here's a summary of what we do -- and don't -- know about five of the most popular supplements based on current research.

Glucosamine and Chondroitin

These two supplements -- both components of natural joint cartilage -- have been fairly well-studied in the treatment of osteoarthritis -- also called degenerative arthritis.


  • It may improve pain, mobility, and quality of life for people suffering from osteoarthritis.
  • These supplements may slow progression of osteoarthritis by controlling inflammation. They are believed to stimulate the growth of cartilage cells which have been broken down in this arthritis. Chondroitin may also provide cartilage with strength and resilience.
  • They are generally safe.


  • Derived from shellfish so people with shellfish allergies should check with their doctor first
  • May be linked to higher blood sugar in people with type 2 diabetes (glucosamine only)

There are many different brands of glucosamine and chondroitin. Do your research and find a reputable brand. Take it for at least four to eight weeks before deciding if it works for you.


If bigger muscles are what you're looking for, creatine may be the supplement for you.


  • Can help build muscle size and even improve athletic performance -- at least a little -- when combined with exercise


  • Unknown effects in kids
  • Can build up in the bloodstream and may cause kidney and liver damage
  • Linked to muscle cramps when taken immediately before exercise or when exercising in intense heat

A few years back, St. John's wort was looking like one herb that might effectively treat a common medical problem -- depression.
But as more research was unveiled, a different story unfolded.

What we don't know:

  • How creatine works. Theories range from increasing water content in the muscle -- thus increasing muscle size -- to improvements in energy production. Naysayers believe the increase in muscle size from water buildup only encourages athletes to work harder -- thereby improving performance.

Creatine does appear to increase muscle size -- at least in young men who hit the gym pretty hard -- but the question remains if it's from the creatine or just harder work.


DHEA (dehydroepiandrosterone) is a naturally occurring hormone in the body produced by the adrenal glands, which are located on top of the kidneys. DHEA supplements are made from plant chemicals.


  • There are some positive effects, but mostly in people who have certain conditions, such as lupus and advanced HIV.
  • It might help fight heart disease. One study shows an improvement in blood vessel function and in the body's ability to handle sugars -- both factors in the development of heart disease. But some studies have suggested an increase in heart disease linked to DHEA so more research is needed.
  • Might improve sexual spontaneity, arousal, and enjoyment for women. Sexual problems have been linked to a fall in certain male-type hormones (androgens), which are derived from DHEA.


  • There are uncertain benefits for the average, healthy person.
  • There are uncertain effects on memory and muscle-building.
  • There are potential increased risks of breast and prostate cancers because, in the body, DHEA is converted to estrogen and testosterone, which feed these cancers and can help them grow.

Since DHEA levels fall as we age, the theory is that DHEA supplements might help fight the effects of aging. But there's still way too little research at this point to claim much of anything.


Red, white, Korean, Siberian... ginseng comes in many varieties and is accompanied by even more health claims.