Onion Powder Tested for Alzheimer’s

In 1936, Albert Szent-Györgyi, who won the Nobel Prize for discovering vitamin C, suggested that a class of phytonutrients called flavonols should also be considered a vitamin. The most common flavonol in the diet is called quercetin, which is concentrated in onions, kale, and apples.
Quercetin is said to have “antidiabetic, anti-inflammatory, antioxidant, antimicrobial, anti-Alzheimer’s, antiarthritic, cardiovascular, and wound-healing effects…as well as its anticancer activity….” But much of that was derived from preclinical data, meaning animal models and petri dishes. Some properties, like the anti-inflammatory, antioxidant, and cardiovascular benefits, have been confirmed, as I documented in the cellular senescence chapter of my book How Not to Age, but what about its purported anti-Alzheimer’s effects?

Consistent neuroprotective effects of quercetin have been demonstrated in different animal models of Alzheimer’s Disease, but when nearly a thousand healthy men and women were randomized to 12 weeks of quercetin supplements or placebo, no improvements in cognitive function were found. Maybe it’s because the researchers used the purified compound rather than a whole-food source? Onions are the leading food source of quercetin in the United States. The problem is how could you design a placebo onion? Researchers in Japan figured out an elegant solution.

Realizing that some onion varieties had more quercetin than others (for example, red onions have twice as much), they selectively bred high-quercetin and low-quercetin cultivars. That’s how the researchers could publish a study entitled “A Randomized, Double-Blind, Placebo-Controlled Study Evaluating the Effects of Quercetin-Rich Onions on Cognitive Function in Elderly Subjects.” For six months, men and women aged 65 to 84 were randomized to 10 daily grams of one or the other onion powders (equivalent to eating about a half cup (120 ml) of fresh onion a day). Overall, the study appeared to be a wash, but the younger half of the study subjects (those under 72 years of age) did show a significant improvement in the most commonly used assessment of cognitive function. The more pressing question, though, is can it help those actively suffering from Alzheimer’s disease?

The same research team had five early-stage Alzheimer’s patients consume a month of the high-quercetin onion powder versus low-quercetin onion powder. On the high-quercetin powder, the study subjects had significantly higher scores on a memory recall component of one of the assessments, but overall, no changes in global cognitive function were found. Such post-hoc subcategory analyses are always suspect, but since quercetin-rich foods are healthy anyway, and cardiovascular disease is still a leading killer among Alzheimer’s patients, it can’t hurt to start eating healthier.