Think "natural" sex supplements are safer than prescription drugs like Cialis and Viagra? In many cases, the answer is no, and for a simple reason: The supplements sold online are often spiked with the real thing.

If you've been blamed for giving Mom gray hair, here's what not to give her this Mother's Day: a bottle of Go Away Gray, a supplement that claims to "prevent and reverse gray hair" via a daily dose of catalase, an enzyme produced by hair cells that naturally declines with age.

Fish-oil pills and supplements of lutein and zeaxanthin, nutrients found in many fruits and vegetables, don't boost the effectiveness of a popular vitamin and mineral combination previously found to help fight macular degeneration, the leading cause of blindness.

If you're hoping to boost your athletic performance, don't be tempted by supplement claims. On Monday, researchers reported that supplements account for more than half of all FDA drug recalls known as "Class I"—those for which serious adverse health consequences or death are a reasonable probability. Most of the supplements recalled are bodybuilding, weight-loss, or sexual-enhancement products that contain unapproved medicinal ingredients, according to researchers who analyzed FDA Enforcement Reports since 2004. The findings were published online yesterday in JAMA Internal Medicine.

Some do. Because most breast milk does not contain much vitamin D, the American Academy of Pediatrics says breast-fed infants should get 400 IU daily from supplement drops. Our new Ratings of vitamin D supplements included four children's supplements.

Some common Chinese herbal remedies contain aristolochic acid, which has been linked to kidney disease and cancer. And despite efforts by the Food and Drug Administration to keep the ingredient out of herbal products sold in this country, you can still purchase products with the dangerous ingredient online, according to a new report.

Q. I've read lately that supplements made from unroasted coffee beans can help you lose weight. Is that true?

Q. I've heard that squid oil is a good source of omega-3 fatty acids. Is it better than oil from salmon and other fatty fish?

On these short winter days, some people might find themselves eyeing caffeinated energy drinks for a little boost. But perk up your ears: Emergency room visits for problems related to energy drinks have risen sharply, particularly for people age 40 and older, according to a new government study.

If you're taking vitamin D pills to ease arthritis in your knee, you might want to reconsider. The supplement didn't stand up to rigorous testing in a clinical study out this week.

There's been a lot of buzz lately about the safety of energy drinks and shots. Following reports of harmful reactions and even deaths possibly associated with the products, two U.S. senators recently released a letter from the FDA stating that the agency is conducting a safety review of energy drinks and is considering requiring that labels disclose the amount of caffeine the products pack, limitations on use, and warnings about possible adverse effects. That makes sense, since our recent investigation found that the products sometimes have more caffeine than they claim.

Do you think of taking a daily multivitamin as a form of "health insurance"? More evidence suggests that you may be wasting your money.

Incident reports filed with the Food and Drug Administration linking the energy drink Monster with five deaths in recent years have cast doubts on the safety of these highly caffeinated beverages. And rightly so. Other research suggests that more than 13,000 people a year visit U.S. emergency rooms because of symptoms associated with these drinks, and thousands more call regional poison control centers. And our tests of energy drinks, out today, found that, per serving, some energy drinks contain as much as twice the caffeine in a typical 8 oz cup of coffee. Often, labels don't reveal the caffeine levels.

A study out today in the Journal of the American Medical Association suggests that multivitamins might help prevent cancer. Does that mean you should start popping the pills? Not so fast, say our medical experts.

Vitamin D is a hot seller in the supplement aisles, but it won't help you ward off or recover faster from the common cold in adults.