Q: I thought mushrooms were kind of a nonstarter from a nutritional standpoint, but now I read they are the best source of the antioxidants linked to anti-aging. Have I underestimated their health benefits? They're kind of icky, but I'll eat them if I have to.
A: "Icky and slimy" was the way I described mushrooms as a kid. I would push them to the edge of my plate, hoping my mom wouldn't notice my disgust for the fungi. Eventually, however, I started to like them and now enjoy many species of edible mushrooms.
They're low in calories, have a small degree of protein, are a good source of fiber and contain multiple B vitamins and selenium. But decrease aging?
It's true that mushrooms contain many antioxidants, including glutathione and ergothioneine. That seems to be where these claims start.
Glutathione helps protect and repair cells damaged by everyday life, pollution and harmful influences. Although deficiency can lead to multiple health problems, it isn't known whether supplementation can help people without a deficiency.
Ergothioneine is found throughout the human body and in black beans, kidney beans -- even mushrooms. Although ergothioneine has shown antioxidant properties in the laboratory, little is known of its physiological role in humans.
One recent study, likely the one you read about, measured the amounts of these antioxidants in different mushrooms. The authors found that higher levels of ergothioneine correlated with higher levels of glutathione.
Maitake mushrooms had high levels of glutathione, for example, while chanterelles had the lowest amounts of both glutathione and ergothioneine. Porcini and yellow oyster mushrooms had the highest amounts of ergothioneine.
Regular white, crimini and portabella mushrooms had relatively low levels of both antioxidants. Some news coverage of this study extrapolated by linking levels of antioxidants to an impact on aging.
That may be a stretch, but mushrooms do have immune-stimulating and anti-inflammatory properties. For example, mushrooms contain arginine, which has been shown to inhibit the growth of tumor cells and decrease the rate of cancer metastasis.
Some edible mushrooms also contain fatty acids and lectins that decrease inflammation and may inhibit growth of tumors such as breast cancer.
Further, phytochemicals in mushrooms such as indoles, phenols and terpenoids have been shown to decrease inflammation. All these compounds are potentially important because chronic inflammation can lead to cancer and vascular disease, even as inflammation and oxidation can lead to harmful effects on nerve cells in the brain.
The effects on the brain bring us to one of the biggest worries in aging: the risk of dementia. Countries such as Italy and France, which have high dietary amounts of ergothioniene, have substantially lower rates of Alzheimer's and Parkinson's disease compared to countries such as the United States with low amounts of dietary ergothionene.
Now, all this information about mushrooms and their link to health and aging is far from conclusive. In fact, it may be wishful thinking.
Yes, mushrooms contain many compounds, including antioxidants, which are good for your health, but so do many foods, such as berries, oranges, plums, grapes, kale, spinach, Brussels sprouts and broccoli. Perhaps you should simply add mushrooms to this list.
In other words, give them a try. You may find some varieties more appealing than the typical white mushrooms, and you may be surprised, as I was, that you like the taste.
• Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles. Send your questions to firstname.lastname@example.org.