Cuba is receiving assistance from the U.N. World Food Program that exceeds its true needs at a time when such help would do more good in poorer countries, according to a prominent American nutritionist.

Dr. George G. Graham of Johns Hopkins said that the amount of dried skim milk now scheduled or tentatively earmarked for delivery to Cuba by the World Food Program -- 60,000 metric tons -- is enough to provide a glass of milk daily to 10 million children for a year.

Dr. Graham cited studies that show that if a glass of milk was added to daily diet of rice consumed by the children of Bangladesh it "would increase rates of weight gain by more than 100 percent."

Dr. Graham, who said Cuba's achievements in the field of nutrition are regarded as outstanding, cited a major study of children's growth rates in that Caribbean island nation that found it coming close to U.S. levels by the early 1970s. The study pointed out that one problem already encountered in the United States was developing there: childhood obesity.

A report of Cuba's use of the 10,000 metric tons of dried milk already delivered to Cuba under World Food Program auspeces said that it had been turned into 614,000 gallons of ice cream and 2,120 tons of yogurt in addition to 84,748 tons of fluid milk.

Referring to the $53 million in diary products supplied to Cuba by the World Food Program over the past four years, Dr. Graham called it "a brazen income supplement," adding that it spares Havana "the cost of importing [milk] commercially, particularly at a time when they have assumed the heavy burden of exporting armies of 'liberation.'"

The policy of the Rome-based World Food Program has been justified on the ground of serving "vulnerable groups" in Cuba and helping that country become self-sufficient in milk products.

Most experts agree that Cuba's record in health standards and food production -- which even before the 1959 revolution was the highest in Latin America -- has continued to show progress, particularly in making the benefits universally available.

Yet, the World Food Program has provided more assistance to Cuba than to any country in Latin America except the far more populous Colombia and Mexico.

Dr. Graham concluded that this seeming anomaly was the result of political influence on the 30-nation committee overseeing the massive but little known program. It has administered $4 billion in cash and commodities since its creation in 1962.

U.S. and international officials in related programs, consulted about Dr. Graham's charges, defended the U.N. effort in general while failing to come up with a precise explanation for the size of the effort in Cuba.

The United States is the heaviest contributor to the World Food Program, supplying about $100 million annually in commodities, cash and services in recent years. By informal agreement none of that goes to Cuba, but the United States provides almost 30 percent of the program's resources.

The Rome headquarters of the World Food Program, asked to explain the emphasis on Cuba, noted that it "has been the largest Latin American donor."

The statement added that "Cuba is a large importer of protein-rich food" and that "the budgetary savings made possible by the World Food Program food aid projects . . . are used to support livestock and dairy development projects."

Indeed, a document summarizing the original Cuban application in 1971, noted that the country expected to become self-sufficient in dairy products by 1977, with the donated milk helping to keep new installations operating at capacity in the interim.

Although Cuban production has increased, the goal of self-sufficiency remains distant. The staff's latest request submitted to the operating committee in Rome, successfully seeking renewal through 1980, indicates Cuba will not be able to produce its own dairy requirements until at least 1993.

Dr. Graham disagrees with the contention that the skim milk surplus stocks provided Cuba would be of limited use elsewhere. According to Graham, there is no nutritionist on the committee directing the World Food Program.

A professor of nutrition and pediatrics, Graham serves on the faculties of both the School of Hygiene and Public Health and the School of Medicine at the Johns Hopkins University in Baltimore.

Graham, 56, has published frequently on research projects and was cited by the American Academy of Pediatrics in 1977 for "significant contributions to human nutrition with particular emphasis on infants and young children."

The doctor expressed incredulity that U.S. officials attending Program meetings in Rome failed to question the Cuban project. The nearest thing to criticism in the documents came in a report on the session held in April 1978, attended by six U.S. officials.

"There was agreement that the WFP assistance to the more advanced developing countries needed to be particularly carefully examined" on the question of duration, the report said. Nevertheless, the Cuban project was subsequently extended.

"One delegation, while agreeing to the project, suggested that consideration should be given in due course to the phasing out of WFP assistance in a foreseeable future," it concluded.

Fred Welz of the Agriculture Department, Peggy Sheehan of the Agency for International Development and Edmund Parsons of the State Department, who attended the session, said they did not know if it was the U.S. delegation that made that point. None was familiar with the Cuban project but each defended the program in some measure.

"The World Food Program is better run than some of the other agencies," said Welz, adding that one problem arose from the program being jointly directed by the United Nations itself and by the subsidiary Food and Agriculture Organization. FAO, with a broader range of agricultural activities "is always wanting to ride herd," he said. Western nations generally are critical of FAO.