A low-calorie artificial sweetener 180 times sweeter than sugar was approved yesterday by the Food and Drug Administration, which overruled a panel that urged long-term study to make sure it won't cause brain tumors.

The sweetener, aspartame, is safe, FDA Commissioner Arthur Hull Hayes Jr. ruled after reviewing all the evidence, including the scientific panel's recommendation for more study in animals.

Aspartame is the first chemical sweetneer the FDA has approved since it banned cyclamates, once the dominant artificial sweetener, in 1970. In 1977, it tried to restrict the use of saccharin but was overruled by the Congress.

Aspartame may be used, Dr. Hayes said, as a table-top sugar substitute, as a tablet or as an additive in cereals, drink mixes, instant coffee and tea, gelatins, puddings, fillings, dairy products and toppings.

It won't be used in soft drinks, where saccharin will remain the low-calorie ingredient by an expected order of Congress even though the FDA declared it a "weak," that is, infrequent, promoter of bladder cancer. G.D. Searle & Co., aspartame's manufacturer, did not seek approval of aspartame in soft drinks, though the beverage industry has said it is exploring aspartame use.

Aspartame's approval comes eight years after Searle first sought FDA approval. The FDA approved it in 1974, but stayed that approval after Dr. John Olney of Washington University, St. Louis, said feeding studies produced brain lesions in test animals.

Questions were then raised about the accuracy of other animal studies that Searle used to back its application. So FDA ordered a two-year independent audit, which found them authentic.

FDA then referred the Olney, and other, allegations to a board of inquiry, a scientific panel headed by Dr. Walle J.H. Nauta of Massachusetts Institute of Technology. It said Olney's and other evidence failed to support the belief that aspartame might cause immediate brain damage.

But the Nauta group did urge the further, long-term animal testing.

FDA's Bureau of Foods and Office of Health Affairs disagreed on the need for such testing, and Dr. Hayes yesterday concurred.

FDA warned, however, that persons with the hereditary disease phenylketonuria, of PKU, must avoid protein foods like meat that contain phenylalanine, one of aspartame's components. And FDA ordered food-makers to put a warning label on packages saying: "Phenylketonurics: Contains Aspartame."

FDA will also require manufacturers to monitor aspartame consumption levels.

A Searle spokesman said aspartame is more expensive than saccharin, but the company nonetheless hopes to create a large market and bring down the cost with increased production. He said an aspartame table-top sweetener is "doing extremely well" in popular sales in France.

Searle said it will begin marketing aspartame under the brand names "NutraSweet" and "Equal." It said aspartame has no after-tastes, does not promote tooth decay and can reduce calories in many products by as much as 95 percent.