Ich unterbreche meine Lernenklave für eine kleine Meldung aus angrenzenden Wissenschaften: Es geht um Ernährung und um die viel diskutierten Vitaminpräparate. Ein Artikel in der NYTimes berichtet ausführlich, das Fazit ist:

1. Vitamine sind gut und wichtig in der Kombination, wie sie in natürlichen Lebensmitteln vorkommen
2. Extragaben von Vitaminen nützen in der Regel nichts
3. Dafür bergen sie einige ernstzunehmende gesundheitliche Risiken

Hier sind ein paar interessante Stellen zum Nachlesen:

Vitamine an sich sind toll, und — natürlich — vor allem Obst und Gemüse

While people who eat lots of nutrient-rich fruits and vegetables have long been known to have lower rates of heart disease and cancer, it hasn’t been clear whether ingesting high doses of those same nutrients in pill form results in a similar benefit.

Vitaminpräparate bringen es nicht:

In the past few years, several high-quality studies have failed to show that extra vitamins, at least in pill form, help prevent chronic disease or prolong life.

The latest news came last week after researchers in the Women’s Health Initiative study tracked eight years of multivitamin use among more than 161,000 older women. Despite earlier findings suggesting that multivitamins might lower the risk for heart disease and certain cancers, the study, published in The Archives of Internal Medicine, found no such benefit.

Last year, a study that tracked almost 15,000 male physicians for a decade reported no differences in cancer or heart disease rates among those using vitamins E and C compared with those taking a placebo. And in October, a study of 35,000 men dashed hopes that high doses of vitamin E and selenium could lower the risk of prostate cancer.

Soweit eigentlich wenig Neues. Spannender wird es, wenn es um schädliche Wirkungen geht:

But some vitamin studies have also shown unexpected harm, like higher lung cancer rates in two studies of beta carotene use. Another study suggested a higher risk of precancerous polyps among users of folic acid compared with those in a placebo group.

In 2007, The Journal of the American Medical Association reviewed mortality rates in randomized trials of antioxidant supplements. In 47 trials of 181,000 participants, the rate was 5 percent higher among the antioxidant users. The main culprits were vitamin A, beta carotene and vitamin E; vitamin C and selenium seemed to have no meaningful effect.

Erklärungen sind noch nicht richtig etabliert, aber es gibt Ansätze:

The selling point of antioxidant vitamins is that they mop up free radicals, the damaging molecular fragments linked to aging and disease. But some free radicals are essential to proper immune function, and wiping them out may inadvertently cause harm.

In a study at the University of North Carolina, mice with brain cancer were given both normal and vitamin-depleted diets. The ones who were deprived of antioxidants had smaller tumors, and 20 percent of the tumor cells were undergoing a type of cell death called apoptosis, which is fueled by free radicals. In the fully nourished mice, only 3 percent of tumor cells were dying.

“Most antioxidants are also pro-oxidants,” said Dr. Peter H. Gann, professor and director of research in the department of pathology at the University of Illinois at Chicago. “In the right context and the right dose, they may be able to cause problems rather than prevent them.”

Das Fazit scheint dagegen schon fast wieder trivial:

Scientists suspect that the benefits of a healthful diet come from eating the whole fruit or vegetable, not just the individual vitamins found in it. “There may not be a single component of broccoli or green leafy vegetables that is responsible for the health benefits,” Dr. Gann said. “Why are we taking a reductionist approach and plucking out one or two chemicals given in isolation?”