Wondering about the side effects of that new drug your doctor prescribed? Want advice on how to cope with a new diagnosis? Should you believe reports that calcium can prevent colon cancer?

If you're like tens of millions of Americans, you're more likely to look for answers on the Internet

What's more, search engines dredge up commercial and non-commercial sites in no apparent order. And it's not always easy to tell the difference (unless you hit a page with a hard sales pitch).

To save you the aggravation, we searched the Web for reliable, consumer-friendly health and nutrition sites. We found some first-class places to start your searches from, and some sites that aren't as helpful as you might think (see boxes). We also found a handful of other sites that are worth bookmarking:

* To see what's in any food. For the calories, calcium, folate, saturated fat, or just about any other nutrient in any of 10,000 (mostly non-brand-name) foods, go to www.nal.usda.gov/fnic/ foodcomp. The U.S. Department of Agriculture has been collecting data on what's in food for more than 100 years. You'll probably make the most use of the nutrient breakdowns under "Search the Nutrient Database," but the site also contains separate listings of vitamin K, carotenoids, trans fats, and much more.

* To calculate your body mass index (BMI). To see if you're underweight, overweight, or just right, go to www.nhlbisupport.com/bmi. The site, which is part of the National Institutes of Health, also explains how your BMI affects your risk of heart attack and stroke.

* To look up scientific studies. The world's largest database of published medical research is at www.ncbi.nlm .nih.gov/entrez/query.fcgi. You can search through more than nine million scientific articles (most have just abstracts; a few have the full text).

* To participate in a study. At www.clinicaltrials.gov you'll find which government-sponsored studies are recruiting and what the requirements are. In early 2003, for example, 162 clinical trials on prostate cancer and six on osteoarthritis were looking for volunteers.

RELATED ARTICLE: The best all around site.

At WebMD (www.webmd.com) we were able to quickly locate top-notch information. A good place to start: the "Newly Diagnosed," "Stay Healthy," or "Living with Illness" buttons on the WebMD Health page. Each opens up a world of resources.

The site is loaded with feature articles, news items, advice columns, recipes, charts and guides, and links to support groups. Some of the material is written by WebMD, and some comes from experts in the field. (For example, a recent visit turned up a Q&A with weight-loss researcher Kelly Brownell and a guide to prostate cancer by The Cleveland Clinic.)

Advertisements and material from the site's sponsors (who are identified on the Home page) are clearly marked.

For links to the Web sites mentioned in this article, go to www.cspinet.org/nah.

The use of information from this article for commercial purposes is strictly prohibited without written permission from CSPI.