Quote:
Originally Posted by JacktheThriller
upper limits are established for most vitamins
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Yes - there is information about acute toxicity of vitamins ("if you take more than x mg in a day it may not be safe"), but the problem is that it's really hard to tell what a safe dose is taken over a long period of time.
For example, take this study:
http:
//www.ncbi.nlm.nih.gov/pubmed/8901854
Here's a quote:
Quote:
A total of 29,133 men aged 50-69 years who smoked five or more cigarettes daily were randomly assigned to receive alpha-tocopherol (50 mg), beta-carotene (20 mg), alpha-tocopherol and beta-carotene, or a placebo daily for 5-8 years (median, 6.1 years)...
Incident cases of lung cancer (n = 894) were identified through the Finnish Cancer Registry and death certificates.
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Here're the results:
Quote:
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No overall effect was observed for lung cancer from alpha-tocopherol supplementation (relative risk [RR] = 0.99; 95% confidence interval [CI] = 0.87-1.13; P = .86, logrank test). beta-Carotene supplementation was associated with increased lung cancer risk (RR = 1.16; 95% CI = 1.02-1.33; P = .02, logrank test).
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So taking 20my beta-carotene a day significantly increased their risk of developing lung cancer. 20 mg didn't seem a lot, and when I googled it, the first lot of capsules I saw were 14mg each, not a million miles away from that 20mg.
Now, these were smokers in the study, so the results may not generalise. But all the same I think the point holds true: we don't really know what even moderate doses of vitamins do over the long term.Personally, I took industrial amounts of vitamins for longer than their 6.1 years - I now wonder if I'll regret it.