We geven de conclusie weer, er werden geen duidelijke aanwijzingen gevonden dat de supplementen een zinvolle bijdrage leverden. Voor vitamine C en selenium waren de resultaten minder negatief, en er wordt aanbevolen die twee supplementen verder te onderzoeken.^[1]

Overall, the antioxidant supplements did not seem to reduce mortality. A total of 17880 of 136,023 participants (13.1%) randomised to antioxidant supplements and 10136 of 96527 participants (10.5%) randomised to placebo or no intervention died. In the analyses of the trials with low risk of bias, beta-carotene, vitamin A, and vitamin E significantly increased mortality.

There were no significant differences between the effects of antioxidant supplements in healthy participants (primary prevention trials) or participants with various diseases (secondary prevention trials).

Randomised trials with adequate bias control found no significant effect of vitamin C. In some of our analyses, selenium seems to reduce mortality.

The current evidence does not support the use of antioxidant supplements in the general population or in patients with certain diseases.

The combined evidence suggests that additional research on antioxidant supplements is needed.

The evidence on vitamin C and selenium was not conclusive. Future trials could focus on vitamin C and selenium and should assess both potential beneficial and harmful effects.

Conduct of additional primary and secondary prevention trials on vitamin A, beta-carotene, and vitamin E seems questionable, at least in the dosage range examined.

The present review does not assess antioxidant supplements for treatment of specific diseases (tertiary prevention), antioxidant supplements for patients with demonstrated specific needs of antioxidants, or the effects of antioxidants contained in fruits or vegetables. Further research and systematic reviews on these types of interventions are therefore warranted. 

Sterfte juist hoger! 

Verder in het oorspronkelijke document een bespreking door de auteurs van de verhoogde mortaliteit bij het chronisch innemen van bepaalde supplementen. We citeren:

Our systematic review contains a number of findings. Beta-carotene, vitamin A, and vitamin E given singly or combined with other antioxidant supplements significantly increase mortality. There is no evidence that vitamin C may increase longevity.

We lack evidence to refute a potential negative effect of vitamin C on survival.

Selenium tended to reduce mortality but only when high-bias risk trials were considered.

Accordingly, we need more research on vitamin C and selenium.

We confirmed that trials with inadequate bias control significantly overestimate intervention effects (Schulz 1995; Moher 1998; Kjaergard 2001; Bjelakovic 2004; Bjelakovic 2006).

The detrimental effect of antioxidant supplements became significantly more pronounced when we excluded all trials with potential confounding.

Our findings support and extend our previous findings regarding antioxidant supplements and increased mortality (Bjelakovic 2004). 

Commentaar

Er zijn wel heel veel studies uitgesloten van de meta-analyse omdat die studies niet voldeden aan alle methodologische criteria. Dat is natuulijk altijd wat lastig, zeker als er honderden minder goed opgezette studies uitgesloten worden. Om te begrijpen hoe streng de studie was, voegen we een aantal literatuur referenties toe van de studies die niet in de meta-analyse werden meegnomen, omdat ze niet strak genoeg waren. En we beperken ons tot alleen de studies, waarvan de auteur met een A begon... Die slecht opgezette studies kwamen in het algemeen tot uitspraken die het geven van supplementen juist ondersteunen, aldus de auteurs. Nogmaals dat citaat: We confirmed that trials with inadequate bias control significantly overestimate intervention effects (Schulz 1995; Moher 1998; Kjaergard 2001; Bjelakovic 2004; Bjelakovic 2006).

Een ander meet biologisch aspect is ook belangrijk bij het interpreteren van de gegevens.

Wij zijn opgebouwd uit duizenden molecuulsoorten, en die komen ook in vruchten, noten, groenten en vlees voor. Al die moleculen hebben met elkaar een bepaalde relatie, en van sommigen zijn er veel, en van anderen minder. Om uit dat hele palet een enkele molecuulsoort te halen, en daar veel van te geven is natuurlijk ook wat kort door de bocht. De moderne systeembiologische visie op supplementen is ook, om meer volle of totale extracten van bepaalde planten  te geven, om zo de natuurlijke balans tussen al die verschillende stoffen niet te veel te veranderen. 

De uitkomsten van deze meta-analyse is in ieder geval voer voor discussie! 

Uitgesloten literatuur van auteurs beginnend met A

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Erik - Toch nuttig? 04-02-2009 22:53:08 Toch wel zinvol: AHA: Omega-6 Beneficial for Heart Health The American Heart Association (AHA) released a new science advisory recommending that at least 5-10 percent of daily calories come from omega-6 polyunsaturated fatty acids. Other groups, including the European Commission (EU) and World Health Organization (WHO), have similar guidelines. According to the advisory, published in Circulation: Journal of the American Heart Association, human and animal trials have shown that consuming this amount of omega-6 is associated with a decreased risk of coronary artery disease. The safety of omega-6 fatty acids has been debated, as some researchers suggested that they might actually increase the risk of heart disease. This is because a major component of omega-6 fatty acids is linoleic acid, which can be converted to arachidonic acid, a building block for some inflammation-related molecules. William Harris, director of the Metabolism and Nutrition Research Center of the University of South Dakota Sanford School of Medicine, led the AHA's two-year assessment. The authors analyzed a meta-analysis of randomized, controlled trials and more than two dozen observational, cohort, case/control and ecological studies. The AHA committee found that in most trials, omega-6 fatty acids either did not change or lowered levels of inflammatory markers. According to observational trials, people who consumed the most omega-6 fatty acids typically developed the fewest cases of heart disease. Other studies found that patients with heart disease generally had lower levels of omega-6 in their blood. In controlled trials comparing the number of heart attacks in patients eating high or low levels of omega-6, those who ate more omega-6 fatty acids developed fewer cases of heart disease. According to the AHA advisory, most Americans already eat the recommended amount of omega-6 fatty acids. Recommended daily doses range from 12 to 22 grams, depending on a person's age, gender and level of physical activity. For more information about omega-6 fatty acids, please visit Natural Standard's Foods, Herbs & Supplements database. To comment on this story, please click here to enter Natural Standard's blog. References: American Heart Association (AHA). www.americanheart.org Harris WS, Mozaffarian D, Rimm E, et al. Omega-6 Fatty Acids and Risk for Cardiovascular Disease. A Science Advisory From the American Heart Association Nutrition Subcommittee of the Council on Nutrition, Physical Activity, and Metabolism; Council on Cardiovascular Nursing; and Council on Epidemiology and Prevention. Circulation. 2009 Jan 26. View Abstract Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com. Copyright © 2009.