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).
cogent evidence - any factual evidence that helps to establish the truth of something; if you have any proof for what you say, now is the time to produce it. proof. evidence, grounds - your basis for belief or disbelief; knowledge on which to base belief; the evidence that smoking causes lung cancer is very compelling.