A draft guidance document stresses the importance of human intervention studies.

WASHINGTON — Human intervention studies may prove crucial whenever the Food and Drug Administration determines whether an ingredient meets its fiber definition, according to a draft guidance document released by the F.D.A. on Nov. 22.

The F.D.A. on Nov. 22 also said it is publishing a request for scientific data, information and comments to help it determine whether certain fibers should be added to a dietary fiber definition published as part of a Nutrition Facts Panel final rule in the May 27 edition of the Federal Register. The F.D.A. in the final rule said naturally occurring dietary fibers meet the definition as do added isolated or synthetic fibers that the F.D.A. has determined have a physiological effect beneficial to human health.

The F.D.A. on Nov. 22 said it had conducted a scientific literature review of clinical studies associated with 26 isolated or synthetic non-digestible carbohydrates not listed as dietary fiber. Among the carbohydrates were acacia gum, carboxymethyl cellulose, inulin, polydextrose and xanthan gum. The F.D.A. said it had identified the main physiological endpoints, such as cholesterol or glucose levels, but now is asking for scientific data on additional physiological endpoints for which a non-digestible carbohydrate may have a beneficial effect, thus potentially meeting the definition for fiber.

The F.D.A. is inviting interested parties to submit additional scientific data, information and comments on physiological benefits of carbohydrates that the parties believe qualify for the fiber definition. A manufacturer who wants the F.D.A. to amend the definition of dietary fiber to include another non-digestible carbohydrate may submit a citizen petition.

The draft guidance document is open for public comment and may be found here.

It gives the F.D.A.’s thoughts on submitting a citizen petition and the scientific review approach it plans to take. The F.D.A., according to the draft guidance document, will address three issues: identifying published scientific articles that evaluate a physiological effect of an added non-digestible carbohydrate, evaluating the studies from which scientific conclusions may be drawn, and evaluating the strength of the scientific evidence on whether there is a physiological effect.

The F.D.A. said it primarily will focus its review on articles reporting human intervention studies. These studies provide evidence from which scientific conclusions may be drawn about the beneficial physiological effect of a specific isolated or synthetic non-digestible carbohydrate in humans, according to the F.D.A. Within human intervention studies, randomized controlled trials offer the best assessment of a causal relationship between a non-digestible carbohydrate and a physiological effect.

When evaluating the human intervention studies, the F.D.A. may eliminate some of them. For example, the design, data collection and data analysis may be so flawed that they make it impossible to draw scientific conclusions, according to the F.D.A.

The guidance document also addresses how the F.D.A. plans to examine such issues as blood glucose levels, laxation, satiety, control groups, baseline data and study length. For example, the F.D.A. considers three weeks to be the minimum duration for evaluating a dietary intervention effect on serum L.D.L. cholesterol concentration. Studies on bowel function generally should be conducted for at least one week.

When evaluating the strength of the scientific evidence, the F.D.A. said it will consider the number of studies and the sample sizes of each study, the relevance of the body of the scientific evidence to the U.S. population or target subgroup, whether the results supporting the beneficial physiological effect have been replicated, and the overall consistency of the total body of evidence.

The F.D.A. plans to accept public comments for the draft guidance document as well as in regard to its request for scientific data, information and comments on whether certain fibers should be added to the definition of dietary fiber.

Electronic scientific data, information and comments may be sent through the web site. Written/paper submissions should be sent to Divisions of Dockets Management (HFA-305), Food and Drug Administration, 5630 Fishers Lane, rm. 1061, Rockville MD 20852.

The request for scientific data, information and comments opens Nov. 23 and will be open for 45 days. All submissions must include Docket No. FDA-2016-N-3389 for “Evaluation of the Beneficial Physiological Effects of Isolated or Synthetic Non-Digestible Carbohydrates; Request for Scientific Data, Information, and Comments.”

The F.D.A. will accept comments on its draft guidance document for 60 days following publication in the Federal Register. All comments should be identified with the docket number FDA-2016-D-3401 listed in the notice of availability that publishes in the Federal Register.