Miracle fruit isn't just a party trick. The tropical berries that can turn bitter into sweet could also make food taste better for chemotherapy patients.

An oncologist at Mount Sinai's Comprehensive Cancer Center is conducting the first clinical study of the benefits of miracle fruit for cancer patients whose chemo drugs leave an unpleasant metallic taste in their mouth.

''Taste alteration is one of the most common side effects of chemo,'' said Dr. Mike Cusnir, a Mount Sinai oncologist. "A metallic taste is very common, as is a complete lack of taste. One patient told me he could order a pizza and eat the box and not know the difference.''

His study is examining whether miracle fruit -- Synsepalum dulcificum -- helps cancer patients for whom chemotherapy has changed their sense of taste.

Masking is the secret of the fruit, says Linda Bartoshuk, a researcher at the University of Florida's Center for Smell and Taste. A miracle fruit protein called miraculin stimulates the sweet taste receptor whenever there is acid in the mouth.

The idea of giving miracle fruit to chemo patients sprang from Don Blechman, a cancer patient and a volunteer at Fairchild Tropical Botanic Garden.

Blechman was talking to a tropical fruit expert at Fairchild, hoping for some botanical anecdotes he could tell visitors taking his tram tour of the grounds. The curator of the tropical fruit conservatory introduced Blechman to the miracle fruit. On his next visit with Cusnir for chemo, Blechman showed the oncologist how eating a lemon after the miracle fruit turned the lemon's taste from sour to sweet.

Cusnir met with Mike Maunder, then director at Fairchild, and Richard Campbell, senior curator of tropical fruit, and arranged to take berries -- and lemon slices -- to the protocol committee at the hospital. He got the go-ahead to explore using miracle fruit in a study.

That series of events set in motion what would become a $100,000 experimental study in which Cusnir hopes to reach a minimum of 40 patients, using miracle fruit supplied by Fairchild.

It's not just a matter of bitter vs. sweet on the palate. The taste-changing effects of chemo can often result in a loss of appetite, causing patients to eat less and sometimes lose weight they can't afford to lose.

''Calorie intake is important for a better prognosis,'' Cusnir said. "If patients become malnourished, they lose their resistance and their organs can suffer.''

Cusnir got approval from Food and Drug Administration to conduct an initial clinical trial, with hopes of expanding it if the results are promising. An anonymous donor has underwritten the cost of his study.

Each patient must go through a chemo cycle using the fruit and a cycle without the fruit.

Then, each gets a questionnaire about taste.

Several patients have found the miracle fruit beneficial.

With chemo, ''you have a bad taste all the time,'' said Carlos Novela, a Miami Beach chemo patient. "I tried the fruit Dr. Cusnir recommended to me as a trial. Right after I took that, the taste disappeared. It doesn't mean [a sense of taste] totally comes back to normal, but the flavor is masked; you don't really feel it.''

The fruit's magic doesn't work for everyone. Linda Rosa said it did not curb the metallic taste she got from a cocktail of five chemicals she was taking for colon cancer.