Does Microwaving Your Food Destroy Its Nutrients? Here's What Dietitians Say

Microwaving is a quick way to cook your food safely.

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Reviewed by Dietitian Maria Laura Haddad-Garcia

Cooking is an art form that has evolved over centuries, incorporating a diverse range of techniques and methods to prepare food. From the traditional practices of baking, grilling, and boiling to the more modern techniques like sous-vide and molecular gastronomy, each method uniquely enhances the flavor, texture and nutritional value of ingredients. Amidst this culinary diversity, microwaving stands out for its convenience and popularity. It offers a quick, efficient and energy-saving option for heating and cooking a wide variety of dishes, making it an indispensable tool in today’s fast-paced lifestyle.

While it is true that cooking with a microwave makes heating meals easy-breezy, you may have wondered if leaning on this cooking method impacts the nutrients in your food. This article will break this topic down for you so you can know exactly what happens to your food when you nuke it.

How Microwaves Work

Microwave technology is like magic for the modern kitchen, turning cold leftovers into hot, tasty meals in minutes. It’s a culinary quick-step that has revolutionized how we heat our eats, making meal prep as easy as pushing a button.

Microwaving harnesses the power of microwave radiation to heat and cook food, offering a swift and convenient method of meal preparation. This technology was developed in the mid-20th century and has become a staple in kitchens worldwide, with around 90% of American households having at least one. It has been prized for its ability to drastically reduce cooking times compared to traditional methods. Microwaves use electromagnetic waves, which fall within a specific frequency range, to agitate water molecules in food, thereby generating heat.

When food is placed inside a microwave oven, and the device is activated, it emits microwaves that penetrate the food. These waves cause water molecules within the food to vibrate millions of times per second, creating friction that produces heat. This internal heating mechanism allows the food to cook evenly and more quickly from the inside out, unlike traditional ovens that heat food from the outside in.

Do Nutrients Get Lost During Cooking?

Different cooking methods can impact food nutrients, leading to varying degrees of nutrient loss. For instance, water-based cooking methods like boiling or poaching may result in the leaching of water-soluble vitamins (such as vitamin C and some B vitamins) into the cooking water, which is often discarded. Conversely, methods that use lower temperatures for shorter periods, such as steaming and microwaving, tend to preserve more of these sensitive nutrients.

“Any cooking method that involves heat is going to cause some nutrient loss—this is just the reality of how heat can break down certain vitamins and minerals and denature proteins as well,” Chrissy Arsenault, M.B.A., RDN, a dietitian at Trainer Academy, explains. However, different cooking methods may result in differences in nutrient retention.

One study evaluated the effects of four different cooking methods (boiling, blanching, steaming and microwaving) on ten different vegetables. Results showed that:

• Boiling destroyed vitamin C in almost all the samples
• Blanching also destroyed vitamin C in the samples, but not to the same extent as boiling. 
• Steaming treatment significantly reduced the retention of vitamin C in all vegetables except broccoli.
• Microwaving had less of an impact on vitamin C content.

The authors suggested that steaming and microwaving retained higher concentrations of vitamin C than boiling because of the reduced contact with water at relatively low temperatures. Using minimal cooking water and cooking for shorter time periods should result in higher vitamin C retention.

In the same study, the vitamin K content after cooking varied, depending on the food. For example, microwaving caused the highest loss of vitamin K in crown daisy and mallow but the lowest loss in spinach and chard. Regardless of cooking method, cooking fresh broccoli, chard, mallow, crown daisy, perilla leaf, spinach and zucchini led to a significant increase in α-tocopherol (a form of vitamin E). The authors suggest this effect occurred because any cooking method would soften the cells of the food, potentially releasing vitamin E from the fat cells and making it more available. In other words, cooking food, regardless of the method, may increase the availability of the alpha-tocopherol form of vitamin E.

Does Microwaving Retain Nutrients?

Microwaving is actually one of the cooking methods that preserves nutrients the most effectively. “The short cooking time and lower temperatures used in microwaving might actually help retain water-soluble vitamins like vitamin C and B vitamins that can be lost through other cooking methods like boiling or frying,” Wan Na Chun, M.P.H., RD, an Indiana-based registered dietitian, explains. “The main factors that affect nutrient retention are cooking time and temperature, not the specific cooking method. Microwaving tends to cook food quickly at lower temperatures, which helps preserve nutrients compared to longer cooking times at higher temperatures. In contrast, other cooking methods like boiling, frying, or baking often require longer cooking times, which leads to greater nutrient losses,” she adds.

Data has shown that thanks to water avoidance and short cooking time requirements, microwaving can prevent the loss of vitamins A and C. Microwaving also results in less breakdown of certain forms of vitamin E.

Microwaving food may also preserve its mineral content. For example, older data showed that raw trout’s sodium, potassium and phosphorus content was preserved after microwaving. Microwaving may also increase the antioxidant activity of certain foods. Another older study showed that when microwaved, celery increased its antioxidant capacity.

One factor to note is that microwaving and overheating foods are two different things. Microwaving food involves using electromagnetic radiation to heat items quickly and efficiently, focusing on water molecules within the food to create steam and heat from the inside out. Overheating food, on the other hand, occurs when food is exposed to high heat for too long, regardless of the method, potentially leading to nutrient loss, undesirable texture changes, and even the formation of harmful compounds. The key difference lies in the method and outcome, with microwaving being a controlled process for warming food and overheating representing an excessive heat application that diminishes food quality.

Tips for Maximizing Nutrient Retention in Microwaved Food

To maximize nutrient retention in microwaved food, consider the following tips and recommendations:

• Use Minimal Water: Use as little water as possible when microwaving vegetables. Steaming in a microwave-safe container with a lid using just a splash of water helps preserve vitamins and minerals often lost through boiling.
• Opt for Short Cooking Times: Keep cooking times as short as possible. Overcooking can lead to nutrient loss, so adjust the power settings and time to ensure food is just cooked through.
• Cover Your Food: Covering food with a microwave-safe lid or wrap helps retain moisture, cook food evenly, and preserve its nutrients. Ensure the materials used are truly microwave-safe to avoid chemical leaching.
• Stir Food Midway: When cooking larger portions or denser food, stir it halfway through the cooking process. This promotes even cooking and helps preserve nutrients throughout the dish.
• Choose Microwave-Safe Containers: Always use labeled microwave-safe containers. Glass and ceramic containers are preferable over plastics to avoid any risk of chemicals leaching into your food.

Implementing these techniques can significantly impact the nutritional quality of microwaved foods, making them not just convenient but also a healthy option.

The Bottom Line

Microwaving is a convenient and safe way to cook food, as long as you use the right vessels and follow the manufacturer’s directions. When it comes to whether it breaks down nutrients, it is true that some nutrients may be degraded when using any heating method. However, since microwaving takes a shorter time to cook and less water, it seems to result in less nutrient breakdown compared to other methods.

Frequently Asked Questions

Is it unhealthy to use a microwave, and if so, why?

Using a microwave is generally considered safe and not unhealthy. The World Health Organization states that when used according to manufacturers’ instructions, microwave ovens are reliable and safe for heating and cooking a variety of foods. The type of microwaves used in kitchen appliances does not make the food radioactive or diminish its nutritional value significantly.

Is it bad for your health to stand in front of a microwave?

Standing in front of a microwave while in operation is generally considered safe due to the stringent safety standards that microwave ovens must adhere to. These appliances are designed with shielding to prevent microwaves from leaking out, keeping exposure well below levels that could harm human health.

Do microwaves destroy enzymes in foods?

Microwaves can affect enzymes in foods, as they cause water molecules in food to vibrate, producing heat that cooks it. This process can lead to the denaturation of some enzymes, meaning they aren’t able to function. However, it’s worth noting that any cooking process, not just microwaving, can have a similar effect on enzymes due to the heat involved.

Read the original article on Eating Well.