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).
evidence that cannot be disputed and that, as a matter of law, must be taken to establish some fact in issue. CONCLUSIVE EVIDENCE. That which cannot be contradicted by any other evidence,; for example, a record, unless impeached for fraud, is conclusive evidence between the parties. 3 Bouv. Inst.