National Academy of Sciences' Reports on Diet and Health--Are They Credible and Consistent?

RCED-84-109: Published: Aug 21, 1984. Publicly Released: Sep 18, 1984.

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Pursuant to a congressional request, GAO examined issues relating to two reports issued by the National Academy of Sciences (NAS). Because the reports differed about whether the risk of chronic disease can be reduced through dietary modification, GAO was asked to: (1) study NAS processes of providing reports on controversial subjects; and (2) determine the range of issues pertaining to the relationship of diet to cancer.

GAO noted that one study was criticized because it minimized the benefit of dietary modification in reducing the risk of chronic disease, and that the other study was criticized because it suggested, allegedly without sufficient evidence, that dietary modifications can reduce the risk of cancer. GAO found that NAS has standard processes for: (1) reviewing study proposals; (2) appointing scientists to study groups; (3) reviewing proposed reports; and (4) ensuring that proposed reports are scientifically credible. GAO believes that NAS followed its standard processes in issuing the two reports. GAO also found that: (1) while the two reports differed as to whether dietary changes can reduce the risk of chronic disease, both offered dietary advice consistent with that offered by other groups; and (2) the reports differed because they were written for different purposes and audiences by different groups within NAS. In addition, GAO found that the reports were representative of two different schools of thought with respect to what scientific evidence is sufficient for providing dietary advice to the public. According to scientists and NAS officials, this legitimate difference of opinion stems from the fact that nutrition science is not thoroughly developed. GAO believes that, to aid public understanding of its reports, NAS may want to consider: (1) ensuring that study groups clearly set forth the basis for their conclusions and recommendations; and (2) delineating in future reports the extent of scientific disagreement over subjects reported upon.

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