You may have been encouraged to eat your broccoli when you were a kid, but you may not have been told that it’s better to eat it raw than cooked. Broccoli contains high amounts of an antioxidant compound called sulforaphane, which may help prevent cancer, type 2 diabetes, heart disease, inflammation, depression, and more harmful health conditions. And a study published in 2008 in Journal of Agricultural Food and Chemistry found that our bodies absorb sulforaphane more quickly when we eat broccoli raw instead of cooked.
Another study from 2009 found that cooking the veggie in a variety of ways—including microwaving, boiling, and stir-frying it—lowered its vitamin C levels. If you can’t stand the thought of raw broccoli, try steaming it. That cooking method had the least effect on nutrients.
Don’t cry for onions! They’re loaded with health benefits, including some major cancer-fighting benefits, thanks to high concentrations of the flavonoid quercetin. “When eaten raw, you maximize on [onions’] cancer-fighting properties,” says Ashley Walter, nutritionist, chef, and creator of Living with Ashley. “Cooking reduces the benefits of the phytochemicals in onions that fight cancers.”
What’s more, onions are in the allium family of vegetables, which means they contain antiplatelet agents that can prevent cardiovascular disease. A study published in the Journal of Agricultural and Food Chemistry found that when raw onions were heated in an oven, those heart-healthy properties completely disappeared in 30 minutes or less, depending on whether the onions were whole, quartered, or crushed.
Like onions, garlic is an allium vegetable that also has antiplatelet agents, but that means its properties that fight cardiovascular disease are also affected by heat. A study published in the Journal of Agricultural and Food Chemistry found that heating garlic at 392 degrees for six minutes completely suppressed antiplatelet activity in uncrushed garlic and significantly reduced it in crushed garlic.
Among the other unexpected health benefits to using raw garlic: Research, including a study published in 2019 in Journal of Food Process Engineering, show that heat inactivates the alliinase enzyme. Boiling garlic for 20 minutes completely suppressed antibacterial activity, and only one minute of microwave heat destroyed 100 per cent of its cancer-fighting ability. Crushing garlic and allowing it to sit 10 minutes before heating it partially restored its anti-carcinogenic power, but the cooked garlic was still 30 per cent less potent than raw garlic.