Scientists Wednesday Wednesday said big doses of the nutrient beta carotene fail to prevent skin cancer but that Mom's advice still holds: Eat your vegetables.

People who eat plenty of fruits and vegetables are less likely to get cancer, and experts had suspected that their intake of beta carotene might explain this.But a study published today in the New England Journal of Medicine found that beta carotene does not seem to be the key ingredient, at least as far as skin cancer is concerned.

"This conclusion should not, however, deter people from eating fruits and vegetables," the researchers wrote.

Beta carotene is the nutrient that makes carrots yellow and is found in varying degrees in many fruits and vegetables. The body uses it to manufacture vitamin A, which some believe can prevent cancer, perhaps by trapping chemical compounds known as free radicals that can harm the body's cells.

The researchers tested beta carotene pills on people who had been treated for basal-cell or squamous-cell skin cancer. None had melanoma, the far more dangerous malignant form of skin cancer. The treatment did nothing to slow the growth of new skin cancers.

"Although our results provide no support for an anti-cancer effect of oral beta carotene on non-melanoma skin cancer, it would be unwise to conclude on the basis of this study alone that beta carotene is ineffective against all cancers," the researchers wrote.

They noted other evidence to suggest that it might prevent lung cancer. Several other studies of beta carotene are also under way.

The study was directed by Dr. E. Robert Greenberg of Dartmouth Medical School.

In the study, 1,805 people were randomly assigned to take 50 milligrams of beta carotene or placebos each day for a year. After five years of follow-up, 362 people who took beta carotene and 340 in the comparison group had at least one new skin cancer.