The chief nutrition official at the National Institutes of Health, who is helping to run a private foundation sponsored by the food and beverage industries, is doing so as part of her government job, according to a let- ter from the NIH director to a consumer group.

Responding to conflict-of-interest charges raised in August by the Center for Science and the Public Interest, the director, Dr. James B. Wyngaarden, said in the letter obtained by The Washington Post that Dr. Artemis P. Simopoulos would remain on the governing board of the International Life Sciences Institute (ILSI) as part of her official NIH duties. However, he said he had asked her to resign from ILSI's executive committee.

Simopoulos heads the NIH's nutrition coordinating committee, a high-level body that oversees all nutrition research at the various government institutes.

ILSI, according to its brochure, funds its own research on caffeine, sweeteners and other food additives, and "maintains dialogue with regulatory agencies."

Its annual budget of more than $3 million comes almost entirely from member corporations, which include most of the major food and soft drink manufacturers in the United States.

Regulations of NIH's parent department, Health and Human Services, forbid employes from being on the board of any organization to which their duties are sufficientlyrelated to cause even an apparent conflict of interest.

However, if such membership is considered part of an employe's job, this rule does not apply, according to an HHS source familiar with the case.

Wyngaarden defended Simopoulos' involvement with ILSI in a letter, dated Oct. 17, to Michael Jacobson, director of the consumer group. He wrote that Simopoulos obtained NIH approval before joining ILSI's board of trustees in 1982. "NIH determined that due to the close connection between the nutrition research functions of ILSI and the nutrition research functions of the NIH Nutrition Coordinating Committee," her work for ILSI would be considered part of her government duties.

He also said that ILSI was not a lobbying group and did not try to influence decisions by regulatory agencies.

Jacobson said the fact that Wyngaarden had asked Simopoulos to resign from ILSI's executive committee, which she joined this year, "acknowledges that a conflict of interest exists."

ILSI "is hardly an objective scientific organization," Jacobson said. "When it makes pronouncements, they tend to be totally consistent with the food industry's interests on an issue like caffeine."

Close ties between government health officials and private foundations have raised similar questions in the past. In 1977, a congressional subcommittee investigated the membership of top National Cancer Institute officials on American Cancer Society panels. The NCI ordered its officials to resign from the panels, and changed its policy to forbid such involvement.

"We are pleased that the matter has been resolved and that Dr. Simopoulos will continue to serve on our board of trustees," said Sharon Senzik, an ILSI administrator.

Wyngaarden and Simopoulos were out of the country and could not be reached yesterday. NIH officials had no further comment.