DEAR DR. ROACH: I will be having a full knee replacement in early November. Because I am metal-sensitive, my surgeon will be using a titanium knee. He told me he would be using the Zimmer product. In researching on the Internet, I found that there are several lawsuits pending on the company’s products. Is the Internet overstating the problems with these products? Is there a substitute that I can talk to my surgeon about? — L.C.S.

ANSWER: There are a few issues here. The first is metal sensitivity. In people with a metal sensitivity or allergy (which is usually to nickel), a titanium device is a good choice.

Second, you can find scary stories about anything on the Internet. I have no doubt that there are many people who have had bad experiences with any particular brand of prosthesis, and because Zimmer is the most widely used manufacturer, it does not surprise me that its products are commonly listed. Two recent studies showed a need for revision using Zimmer products to be between 0.5 percent and 1.9 percent, which is as good as or better than other products. There has not been a Food and Drug Administration recall of its current knee prostheses, although, as is the case with other manufacturers, some components have been recalled. I did a search on a competing company and found multiple lawsuits there, too.

Third, the opinion that is most informed is that of your surgeon, who has a great deal of experience. I think it is entirely reasonable to share with him your concerns and ask if he thinks there is a better product for you.

DR. ROACH WRITES: Several readers have asked or assumed, but I do not endorse any particular product, and never accept any gifts, travel, cash or anything from pharmaceutical companies.

DEAR DR. ROACH: I have heard that garcinia cambogia, along with diet and exercise, helps with weight loss, as well as with lowering cholesterol and triglycerides. Please advise. — S.M.A.

ANSWER: This plant has been in the news recently, and the extract has been recommended as being useful for weight loss. However, the paper usually cited is about the theoretical benefits of a purified compound, hydroxycitric acid. There is always the concern that the extract you buy doesn’t have as much of the active substance you want as it says it does.

There is at least one report of liver damage from the plant, and the only study I could find looking at the plant’s ability to help people lose weight failed to show benefit.

So, based on this, I do not recommend using this plant extract for weight loss.

The booklet on cholesterol and its subtypes covers all aspects of cholesterol control. Readers can obtain a copy by writing: Dr. Roach — No. 201, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. ROACH: Why is Lactaid effective? Since it is an enzyme, why isn’t it denatured by stomach acid, then digested like other proteins? I do know from experience that it works, but the biologist and chemist in me doesn’t understand how. — D.M.

ANSWER: Lactase, the enzyme in Lactaid, breaks down the milk sugar lactose, which many people can’t digest, into smaller sugars, glucose and galactose. The symptoms of lactose intolerance include bloating, gas and diarrhea. It works best in a slightly acidic environment, but will indeed be digested like other enzymes in the stomach once stomach acid can bring the pH in the stomach to the very acidic range. It works only because it is able to break down sugar faster than it is itself broken down. Clever people have designed lactase in forms that resist stomach acid and are active in the small intestine, which ought to work better. However, Lactaid works well enough for many people intolerant of milk.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Health newsletters may be ordered from www.rbmamall.com.

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