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).
Proof of fact(s) presented at a judicial hearing such as a trial. Proof of fact(s) presented at a trial. Neatly divided into the most prevalent, direct evidence, and the slightly more difficult, circumstantial evidence. A judge, at the commencement of a trial, is like an empty scale - the scales of justice!