Posted by Larry Hoover on October 12, 2004, at 16:40:57
In reply to Re: Riboflavin warning » Simus, posted by JLx on October 12, 2004, at 13:05:30
> I ran across this recently and it really gave me pause:
>
> "the nutrition industry has failed to heed the warning that damage may be caused by high doses of riboflavin supplements.
>
> As always, the dose makes the poison, and this means that if you take nutritional supplements you should make sure you consume an adequate amount of riboflavin daily, rather than an excess of riboflavin.
>
> The human requirement for riboflavin is less than 2 milligrams a day, but many common vitamin supplements contain 10s or 100s of milligrams. There is little (if any) scientific justification for taking supplements of riboflavin greatly in excess of the known dietary requirement. However, there is a lot of scientific evidence and speculation that the combination of abnormally high blood, eye and skin levels of riboflavin, combined with a lifetime of sun exposure, may have serious negative consequences, and actually cause the damage we are trying to prevent. The combination of sunlight and abnormally high tissue levels of riboflavin from excess supplementation is a toxic combination that should be avoided."
>
> http://www.townsendletter.com/June2003/riboflavin0603.htmI suppose that it is wise to listen to cautionary advice, but.....
1. "The human requirement... (of) less than 2 mg a day" is not an accurate statement. That is the RDA, which is that amount that prevents *overt* deficiency symptoms in 97.5% of the normal, healthy population.
We do not know that more than that sub-2 mg dose would not optimize riboflavin-dependent biochemical processes. We only know that most people do not display overt deficiency symptoms at that intake level. I would also want to argue about the intake requirement of abnormal or unhealthy people, but that is somewhat tougher to quantify.
2. Riboflavin is not well absorbed, and probably has a finite uptake capacity. Your body can only take so much up. Riboflavin is so poorly absorbed that it is sometimes used to "mark" food to determine gut transit time before excretion as feces. Plasma riboflavin is also rapidly excreted in urine (it's the yellow stain from B-complex).
3. Patients with melanoma are demonstrably riboflavin deficient. Riboflavin deficiency is also associated with the promotion of squamous-cell skin cancers, including tissues which are never exposed to sunlight (e.g. the esophagus).
4. Riboflavin deficiency causes an induced B6-deficiency disorder.
5. There is no Tolerable Daily Intake level established for this nutrient, according to the National Institutes of Health. That means there is no defined toxic threshold. Migraine prophylaxis studies employing 400 mg/day for a minimum of three months found no adverse effects of note.
http://books.nap.edu/books/0309065542/html/115.html#pagetop
I suppose it is wise to take counsel from precautionary statements. I think optimal might lie somewhere between the extremes, but I'm not sure just where.
Lar
poster:Larry Hoover
thread:401626
URL: http://www.dr-bob.org/babble/alter/20040928/msgs/402247.html