miércoles, 14 de marzo de 2012

Mejor no suplementar megadosis de antioxidantes


Bjelakovic et al (2007) JAMA 297: 842-857

Mortality in randomized trials of antioxidant supplements for

primary and secondary prevention - Systematic review and metaanalysis.

- 47 low-bias trials with 180 938 participants,

- antioxidant supplements (BC, vit A, C, E, Se)

- significantly increased mortality (RR, 1.05; 95% CI, 1.02-1.08).

After exclusion of selenium trials:

beta carotene (RR, 1.07; 95% CI, 1.02-1.11),

vitamin A (RR, 1.16; 95% CI, 1.10-1.24), and

vitamin E (RR, 1.04; 95% CI, 1.01-1.07),

singly or combined, significantly increased mortality.

Vitamin C and selenium had no significant effect on mortality.

Conclusions: Treatment with beta carotene, vitamin A, and

vitamin E may increase mortality. The potential roles of vitamin C

and selenium on mortality need further study.

Beta-carotene supplements increase mortality risk



But…

- Increased intake of vegetables and fruits rich in carotenoids

reduced the risk of lung cancer.

High levels of ß-carotene in the blood were consistently associated

with reduced incidence of lung cancer.



TOLERABLE UPPER INTAKE LEVELS FOR VITAMINS AND MINERALS

European Food Safety Authority, February 2006

Scientific Committee on Food and Scientific Panel on Dietetic Products,

Nutrition and Allergies



High natural intake: reduced risk.

Intervention with supplements: no confirmation, indications for

possible adverse effects

Questions:

What is the difference between intake from food and intake from

supplements?

Possible reasons:

- Modifying factors (smokers, timing, genes, age, sex, etc)

- Isolated components, while food is complex

- Concentration

- Metabolism

HUMAN AND ANIMAL PHYSIOLOGY

We have to establish the window of benefit

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