This refreshing use of the ancient grain quinoa (pronounced KEEN-wah) is both low-calorie and full of phytochemicals, from sulfides in onions and garlic to lycopene in tomatoes and β-carotene in carrots. Though refreshing in summer, enjoy it any time of year. Used by the Incas, quinoa’s unique properties, including ease of cultivation and high protein content, make it newly appealing to nutritionists!

Overall healthy ingredient profile

Aside from being a complete protein and fiber-rich, quinoa contains a lot of the antioxidant flavonol quercetin plus a wide variety of other anti-inflammatory compounds. Bell peppers and carrots have β-carotene, vitamin A, lutein, zeaxanthin, falcarinol, and fiber. The capsaicin in chiles is believed to have antiinflammatory properties.

Evidence for cancer prevention by quercetin

Here we focus on the evidence for cancer prevention for quercetin found in quinoa. Studies with quercetin in animal models of breast, prostate, and skin cancer among others have shown promise for cancer prevention. Interestingly, in a mammary model, there was an inverted U dose-dependent effect of quercetin on tumor number and volume; the moderate dose was most efficacious and reduced the tumor number by 20% and tumor volume by 78% compared to control mice.

Sources of quercetin

Besides being found in high concentrations in quinoa, quercetin is found in apples (with skin), tea, onions, red wine, broccoli, kale, tomatoes, and capers. Food preparation and storage can affect quercetin concentrations; heating and long storage in some cases can lower quercetin content.

Safety suggestions

Quercetin is generally considered safe when taken in food. People typically get between 5 and 40 milligrams a day from food. You can get as much as 500 milligrams daily if you eat lots of fruits and vegetables. 

Quercetin as a supplement may be safe if taken in reasonable amounts for short periods, such as 500 milligrams twice a day for 12 weeks.  There are side effects (headache and tingling in arms and legs) and risks with higher doses. Drug interactions with the supplement form are also possible.

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