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Q: Can the artificial sweetener aspartame cause depression? I know a psychiatrist who tells people to avoid it.

A: No well-designed human studies have ever found that aspartame causes neurological or psychiatric problems, including migraines, depression, insomnia, or memory loss. Hundreds of studies have exonerated aspartame. In 2007, for example, a massive review (500 studies) by a panel of experts from medical schools and research institutions in the U.S., Britain, and the Netherlands found no evidence that aspartame has negative effects in the body or mind, even when consumed at high levels.

It’s true that this review was funded by a Japanese company that makes aspartame, but the company did not have any influence on the published results, which appeared in Critical Reviews in Toxicology, a respected journal. One small and poorly controlled study in 1993 did conclude that people with mood disorders should not use aspartame, but this was the sole study with such findings. There were only eight people in the treatment group, and five in the control group—not enough to provide statistically valid conclusions. Some went into the study believing they were prone to adverse reactions to aspartame. The trial lasted only 20 days. Despite its dubious quality, the psychiatrist who conducted it wants the Senate to pass legislation rescinding the approval of aspartame. Of course, this has generated a lot of publicity.

Aspartame remains controversial, in spite of clear evidence that it is safe. Its chief ingredients, phenylalanine and aspartic acid, are amino acids that occur naturally in foods and in the body. As the warning label states, people with the rare genetic disorder phenylketonuria, which keeps them from properly processing phenylalanine, should avoid aspartame as well as foods rich in this amino acid.

Q: Are shrimp off limits if I have high blood cholesterol?

A: No. Though higher in cholesterol than fish, shrimp don’t have as much cholesterol as you may think—190 milligrams in a 3.5-ounce cooked serving (about 17 medium shrimp). That’s about the same as in a large egg, and within the daily limit of 200 milligrams of cholesterol set by the American Heart Association for people with heart disease, high cholesterol, or other coronary risk factors. (If you’re healthy, we advise limiting cholesterol to an average of 500 milligrams a day.)

Moreover, some studies suggest that shrimp’s effects on blood cholesterol aren’t all bad. First of all, saturated fat raises blood cholesterol more than dietary cholesterol does, and shrimp have virtually no saturated fat. The small amounts of fat in shrimp also include some heart-healthy omega-3 fats. And as seen in research from Rockefeller University in New York City several years ago, even though shrimp (10 ounces a day) raise LDL ("bad") cholesterol, they raise HDL ("good") cholesterol more, thereby improving the cholesterol ratio; plus, they help reduce triglycerides (fats in the blood). Note: The effects of dietary cholesterol vary considerably from person to person, and probably no one should eat 10 ounces of shrimp a day.

How you cook shrimp, however, can add lots of calories and affect your blood cholesterol. Instead of breading and frying or broiling shrimp with butter or margarine, try steaming or grilling.

Q: What do you think about jojoba supplements for weight loss? I have tried everything else, and my doctor wants me to lose 30 pounds.

A: We advise you to stay away from these supplements—promoted on the Internet under such names as Jojoba Diet capsules and Size Zero Diet Pills. Jojoba oil, widely used industrially and especially in cosmetics, is extracted from the seed of the jojoba shrub, which grows in Mexico, Arizona, Israel, and other arid regions worldwide. You may have noted it as an ingredient in shampoos and conditioners. It is a good cleanser.

Native American tribes are known to have used the seeds as an appetite suppressant in times of food scarcity. Two subsidiaries of the R. J. Reynolds Tobacco Company now hold a patent on a jojoba extract called simmondsin, which is said to suppress appetite. That, perhaps, is what the supplements contain, though you can’t be sure.

The only published studies of jojoba as an appetite suppressant and weight-loss aid have been done in animals. There is simply no evidence that the substance is safe and effective for people. The animal studies showed a number of adverse effects, including damage to the digestive tract, changes in hormone levels, and other potentially serious problems. No responsible researcher has ever recommended jojoba for weight loss in humans.

Until well-designed clinical studies show that jojoba is safe and effective for weight loss, don’t risk it. All supplements currently promoted for weight loss have potentially serious side effects. And prescription drugs for weight loss have had similar problems. Only a few of the drugs remain on the market, and they are only minimally effective.

Q: Does gargling with warm saltwater help a sore throat? Can it prevent one?

A: Many people find it helps a sore throat, at least a little, though scientific proof is lacking. Gargling with any solution—even water mixed with sugar or corn syrup—may temporarily relieve dryness and be soothing. Gargling won’t shorten the duration of your sore throat, though. And a better way to keep your throat moist when you’re sick is to drink plenty of water or other fluids.

As for gargling as a preventive, research is limited. A Japanese study in the American Journal of Preventive Medicine in 2005 did find that a simple tap water gargle, done at least three times a day, prevented colds by 40% in healthy volunteers over 60 days, compared to a group that didn’t gargle. And those who got a cold had less severe bronchial symptoms. Part of the benefit may come from the chlorine in the water, the authors noted.

UC Berkeley Wellness Letter, February 2010