DEAR DR. ROACH: I love fish and chips. I eat them once a month. I have tuna and other fish throughout the month as well. Quite often, the fishy odors linger for days until all remnants have left my body. Is there anything I can do to counteract the smell? I feel that others can tell when I have eaten fish. The odor comes from my mouth, my urine and my feces. — J.C.A.

ANSWER: Fish, particularly deep-saltwater fish, contain a substance called trimethylamine oxide. After fish die, it is converted by bacteria and enzymes in the fish to trimethylamine, which is largely responsible for the “fishy” odor; it gets stronger over time. Trimethylamine in humans is excreted through sweat in addition to urine and feces.

People have different amounts of the enzyme that breaks down TMA so there’s a variance in the noticeable effect of fishy breath and sweat after consuming fish. A very few people lack the enzyme entirely.

TMA can be washed off of fish, and also can be broken down by acid, such as in lemons. Rinsing fish before cooking or using lemon during or after cooking will lessen the odor effect on you.

Other foods also may cause an evident odor in the sweat and urine. Cruciferous vegetables like broccoli and asparagus can change the odor of urine and sweat, as can garlic, onions and some spices. Alcohol, especially in excess, can be picked up by people with sharp noses. Men who ate no meat for two weeks were found to have a “more pleasant” body odor than those who did.

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DEAR DR. ROACH: A friend told me she was given a bowel regimen for a minimally invasive procedure. She said that she didn’t have to drink any solution the night before, and her doctor and nurse practitioner never discussed the issue. Can you tell us what a “bowel regimen” is? — K.C.H.

ANSWER: A regimen (not “regime,” that’s a government; and not “regiment,” that’s an army unit) is simply a prescribed treatment. In the context of an upcoming procedure like a colonoscopy, a bowel regimen means using medication to evacuate the colon. The colon needs to be empty so the examiner can see the lining of the wall.

The most common bowel regimens are nonabsorbable large molecules in a solution that has a salt balance similar to that of the body. These pass through the colon fast enough to wash away all the contents of the colon, preferably without affecting the salt levels of the blood, which must be kept tightly regulated. These can be low volume (2 liters) or high volume (4 liters). They are effective, but don’t taste particularly pleasant (drinking them cold or with flavoring agents can help). In practical terms, this means a fair amount of diarrhea.

If your friend didn’t drink a solution, she probably had sodium phosphate tablets. These are not recommended for people over 65; those who have heart or kidney problems; or people who take diuretics, some heart medicines or anti-inflammatories. They also can damage the lining of the intestines. Given all of the concerns with this preparation, I seldom see it used.

READERS: The booklet on constipation explains this common disorder and its treatments. Readers can order a copy by writing:

Dr. Roach

Book No. 504

628 Virginia Dr.

Orlando, FL 32803

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.

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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 628 Virginia Dr., Orlando, FL 32803. Health newsletters may be ordered from www.rbmamall.com.