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Does Roasting Veggies Ruin Nutrients?

Sharon Palmer

Roasting veggies is as hot as ever. The art of roasting fresh veggies, such as asparagus, cauliflower, and brussels sprouts, on a pan over high heat with a touch of olive oil and seasonings makes them taste simply divine. The carbohydrates in the veggies caramelize, mellowing out strong flavors into golden, toasty perfection—all with a nice pleasant crunch! What’s not to like? You can serve roasted veggies as a side-dish, and on salads, kebabs, grain bowls, sandwiches, wraps, pita, and the list goes on.

Roasted Asparagus Salad with Harissa-Spiced Sorghum

But does the roasting process destroy nutrients? Today, I’m answering your top questions on whether roasting veggies ruins nutrients.

Question: I love roasted vegetables, but does roasting them at high heat destroy their nutrients?


No, you don’t need to forgo roasted veggies because of high heat. The fact is that all forms of cooking can destroy some of the nutrients (such as vitamin C and B vitamins) in vegetables. But the flip side is that some nutrients actually become more bioavailable when vegetables are cooked, since cooking helps release the nutrients from the cell walls of the plant. These include nutrients in the carotenoid family, such as lycopene (found in tomatoes and red peppers) and beta-carotene (in carrots, spinach and kale). Mushrooms, asparagus and cabbage supply more antioxidant compounds when cooked compared with raw. And antioxidant compounds in foods we eat may help protect against cancer and other diseases.

Cauliflower Steaks with Puttanesca Sauce

One caveat: Charring can cause the formation of acrylamides (potential cancer-causing chemicals), particularly in starchy foods such as potatoes. Instead, roast your starchy veggies to a golden brown. Meanwhile, some nutrients, such as vitamin B-6 and folate in broccoli and the polyphenols (micronutrients that help protect against cancer and cardiovascular disease) in onions are better preserved in raw fruits and vegetables. So, it’s good to enjoy a diet that has some raw and some cooked foods to gain the benefits of each. If you like roasted vegetables, continue to enjoy them. Steaming, microwaving and boiling vegetables are also fine methods, but minimize the water you use and length of time you cook them to preserve nutrients. Try to avoid frying them to keep calorie levels in check and reduce overall nutrient loss.

Roasted Orange Ginger Carrots

Here are some of my favorite recipes featuring roasted vegetables:

Roasted Kohlrabi with Pumpkin Seeds
Maple and Balsamic Roasted Brussels Sprouts
Roasted Rosemary Potatoes and Tomatoes

Another good way to enjoy veggies is to grill them. Check out this step-by-step guide for grilling vegetables here.

Check out the other nutrition questions I’m answering at The Plant-Powered Dietitian:

How to Prepare Dried Beans to Avoid Antinutrients
How Can I Choose Sustainable Foods?
Is “Clean Eating” a Healthy Lifestyle?

About Ask Sharon:

As part of my program “Ask Sharon”, I am answering the top question of the month submitted through my blog, Facebook, Twitter or Instagram to answer here. You can even win a prize! Don’t forget to submit your burning nutrition question this month via my blog, or other social media. 

Main image: Roasted Sesame Broccolini from my upcoming book in 2021. 

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