Microwaves get a bad rap. Microwaves heat food by causing water molecules in it to vibrate more rapidly, which then causes friction between nearby molecules and turns into heat. Of course, microwaves are convenient—they can cook food fast and evenly without wasting energy like conventional ovens do.
Some people believe microwaving changes the structure of food and makes it harmful to eat but there’s no evidence of that. Others believe microwaving destroys the nutrient content of food. What is the truth about microwaving foods, particularly healthy foods like vegetables? Is it a smart way to cook your veggies or not?
How Microwaving Works
Microwaves use radiofrequency waves to heat food. The waves cause water molecules in the food to vibrate and create heat. The heat cooks the food from the inside out, while the outside remains cool to the touch. When you put food in a microwave, the microwaves bounce around inside the oven and collide with water molecules in the food. The water molecules absorb some of the energy from the microwaves. This raises their temperature and cooks your food.
Microwaves are very efficient at heating water molecules in food and heating them up. This makes it easier for you to cook your food quickly. In fact, the microwave can heat up your food up to six times faster than conventional methods like boiling or roasting.
Microwaving vegetables is fast and convenient
One of the biggest benefits of microwaving vegetables is convenience. The trusty microwave will cook your veggies in minutes, so you can get them onto your plate faster than boiling or steaming. They also require little added water or other liquids, which means you don’t have to worry about the liquid being absorbed by the vegetable and making it soggy—a common complaint among boiled veggies.
If you have a convenient method for cooking vegetables, you’re likely to eat more of them and that’s never a bad thing. If you don’t prepare veggies due to lack of time, the microwave will help you change that and get more nutrient and fiber-rich vegetables on the table. The best cooking method is the one that helps you get healthy foods on the table.
Another benefit of microwaving vegetables is it frees up your stovetop for cooking other ingredients. If you’re making soup or chili, for example, you can use the microwave to cook some or all your vegetables while you prepare the rest of the meal on the stove.
How microwaving affects the nutrient content of vegetables
There’s a misconception that microwaving destroys nutrients. While every cooking method can lead to some nutrient loss, microwaving is one of the best strategies for preserving vitamins and minerals. The opposite is true: microwaving is one of the best methods for preserving the nutrient content of vegetables.
The key to cooking vegetables without losing nutrients is to cook them quickly, so they have less time to lose nutrients. When you cook vegetables in water, some of the water-soluble nutrients, especially vitamin C and thiamin (a B-vitamin) leach into the cooking water. That’s why boiling is such a bad method of cooking vegetables.
Microwaving is one of the fastest ways to cook vegetables and get them on the table. They cook quickly and there’s less time for nutrient loss. Plus, you can choose how much water you use when you microwave. That amount will be far less than what you would use to boil them.
Broccoli Can Be a Problem Child if You Microwave
One vegetable you should reconsider microwaving is broccoli. Research shows microwaving broccoli destroys an enzyme called myrosinase that converts compounds in broccoli (glucosinolates) to other compounds with potential anti-cancer and anti-inflammatory properties. (sulforaphane) If you microwave broccoli, you can add another source of myrosinase to make up for this loss. For example, add broccoli sprouts (a rich source of myrosinase) to a salad during the same meal or add another source of myrosinase, like brown mustard powder. A study found that powdered brown mustard boosted the bioavailability of sulforaphane by four-fold.
Also, a study in Journal of the Science of Food and Agriculture found that microwaving broccoli was linked to a sharp drop in its flavonoid (a type of antioxidant) content, more than other common cooking methods. However, they used 10 tablespoons of water when they microwaved the broccoli, and the flavonoids entered the water. So, if you microwave broccoli use a small quantity of water to limit nutrient loss.
Another study conducted by Spanish researchers compared cooking methods and their effect on the antioxidant content of a variety of vegetables. They found that the veggies retained the most antioxidants when they were baked, cooked on a griddle, or microwaved. Boiling and preparing in a pressure cooker led to the greatest loss.
Tips for Healthy Microwaving
- Use as little water as possible
- Save the water you use to microwave and add it to soups, stews, or smoothies to preserve nutrients.
- Steam rather than microwave broccoli to preserve myrosinase.
- Don’t microwave vegetables in plastic bags. Elements of the plastic could leach into the vegetables.
- Don’t overcook veggies in a microwave or anywhere else.
The Bottom Line
Microwaving is quick and convenient, and for most vegetables, it preserves their nutrient and antioxidant content well. The key is to use as little water as possible and keep your microwave time short. If a microwave helps you get more veggies ion the table, it’s a good investment. The worst method is boiling, as many of the nutrients end up in the boiling water. At the very least, save the water you boil vegetables in and use them in soups or smoothies.
References:
- “Microwave Ovens and Health: To Nuke, or Not to Nuke?.” 18 Feb. 2022, https://www.healthline.com/nutrition/microwave-ovens-and-health.
- “Microwaving vegetables – Harvard Health.” 01 Jun. 2004, https://www.health.harvard.edu/nutrition/microwaving-vegetables.
- “Does Microwaving Vegetables Destroy Their Nutrients? – Live Science.” 15 Jul. 2010, https://www.livescience.com/32704-does-microwaving-vegetables-destroy-their-nutrients.html.
- Okunade O, Niranjan K, Ghawi SK, Kuhnle G, Methven L. Supplementation of the Diet by Exogenous Myrosinase via Mustard Seeds to Increase the Bioavailability of Sulforaphane in Healthy Human Subjects after the Consumption of Cooked Broccoli. Mol Nutr Food Res. 2018 Sep;62(18):e1700980. doi: 10.1002/mnfr.201700980. Epub 2018 Jul 26. PMID: 29806738.
- Cross GA, Fung DY. The effect of microwaves on nutrient value of foods. Crit Rev Food Sci Nutr. 1982;16(4):355-81. doi: 10.1080/10408398209527340. PMID: 7047080.
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