A deficiency of riboflavin can be primary - poor vitamin sources in one's daily diet - or secondary, which may be a result of conditions that affect absorption in the intestine, the body not being able to use the vitamin, or an increase in the excretion of the vitamin from the body.
Substantial evidence means more than a mere scintilla. It means such relevant evidence as a reasonable mind might accept as adequate to support a conclusion.. Richardson v. Perales, 402 U.S. 389, 401 (1971).
substantial adjective (LARGE) B2 large in size, value, or importance: The findings show a substantial difference between the opinions of men and women. She inherited a substantial fortune from her grandmother. The first draft of his novel needed a substantial amount of rewriting.