And, he says, wild swings in dietary regulation haven't always worked out.
The first rule bans the use of risky cattle tissue in dietary supplements and cosmetics.
It is also found in dietary supplements favored by many young athletes.
Tests were negative on steroids, alcohol, cocaine and ephedrine, a substance commonly found in dietary supplements banned by some sports.
Strictness can manifest itself in dietary restrictions, distinctive clothing, geographical separation or prohibitions on activities like dancing or drinking.
The F.D.A. does not specify maximum acceptable concentrations or daily dose limits for contaminants in dietary supplements.
The authors stress that this should not be a cause for panic measures or a change in dietary habits.
They are also high in dietary fibre, protein, calcium, iron, magnesium, zinc, and antioxidants.
Inconsistency in dietary supplement efficacy can often be traced to variability in product quality.
Perhaps the cardiovascular benefits previously ascribed to folic acid in dietary surveys relate to other components of diets rich in fruits and leafy vegetables.
Materials from some of the most potentially infectious parts of a cow, including brains, eyes and spleen, sometimes end up in dietary supplements.
