TempoLife › Features › Nutrition myths, checked › microwaving-destroys-nutrients
Microwaving destroys the nutrients in food.
Every cooking method costs some nutrients. Microwaving usually costs the fewest, because nutrient loss tracks heat, time and water — and a microwave uses less of all three.
Verdict: Falsemicrowavenutrient losscooking methodsradiation
The claim, as people state it
“Microwaving destroys the nutrients in food.”
What is actually known
Microwave ovens heat food by making water molecules rotate. They are non-ionising: they cannot alter atoms, they do not make food radioactive, and the only thing arriving in the food is heat. On that point there is no scientific disagreement at all.
Nutrient loss during cooking is driven by three things: how hot, how long, and how much water the food sits in. Water-soluble vitamins — C and the B group — leach into cooking water and are poured down the sink. Microwaving typically wins on all three variables, which is why it repeatedly performs as well as or better than boiling for vitamin retention in vegetables.
The comparison below is computed from real database rows for the same vegetable prepared three ways. The database carries macronutrients and fibre, not vitamin C, so no vitamin C figure is invented here; the vitamin point is stated in words and the numbers shown are the ones that actually exist.
It is also worth noting what does not change with any cooking method at all. Minerals do not degrade with heat — calcium, iron, potassium and zinc are elements, and no oven destroys an element. They can be lost by leaching into water you then pour away, which is the same mechanism as the vitamins, and which is again the one microwaving mostly avoids. Protein, fat and carbohydrate are likewise essentially unchanged in quantity; cooking alters their structure and often makes them easier to digest rather than scarcer.
Why the myth persists
Because "radiation" is a word that does two jobs, and most people meet it first in the context of the dangerous kind. A widely circulated experiment about a plant watered with microwaved water — a school project, never replicated — has been repeating on the internet for two decades and continues to be cited as though it were research.
The arithmetic
Green beans are one of the few foods carried in the database in several preparations at once, so the comparison can be made from real rows rather than asserted.
| Green beans, per 100 g | kcal | Protein (g) | Carbs (g) | Fibre (g) |
|---|---|---|---|---|
| Raw | 35 | 1.9 | 7.9 | 3.2 |
| Boiled | 35 | 1.9 | 7.9 | 3.2 |
| Microwaved | 33 | 2.3 | 6.4 | 3.4 |
| Frozen | 33 | 1.8 | 7.5 | 2.6 |
One honest note before reading anything into that table: the raw and boiled rows for green beans carry identical values in this database, so they are not two independent measurements and no conclusion should be drawn from the difference between them. The comparison worth reading here is the microwaved row against the others.
The microwaved row carries 0.4 g more protein per 100 g than the boiled row and 0.2 g more fibre. Whatever else is true, "microwaving destroys the nutrients" is not what these numbers say — and the mechanism is unglamorous: less water to leach into, less time to leach for.
The database carries energy, macronutrients, fibre, sugar, saturated fat and salt. It does not carry vitamin C, which is the nutrient the myth is really about, so no vitamin C number is printed here. The vitamin argument is made in words above, where it belongs, rather than with a figure this repository does not have.
Every figure in this section was computed when this page loaded, from 5 237 food rows and 31 exercise rows already in this repository. Nothing in it is stored as prose.
The honest nuance
Uneven heating is a genuine microwave problem, and it matters for food safety rather than nutrients. Cold spots can survive in reheated rice, meat and infant food, so stir, rotate and let food stand.
Some containers are a real issue. Certain plastics are not intended for microwave use and can degrade; glass and ceramic sidestep the question entirely.
General information, not a diagnosis and not medical advice. Anything touching a condition you have, a medicine you take or a test result belongs with your own clinician, who has information no web page does.
Frequently asked questions
Does microwaving make food radioactive?
No. Microwaves are non-ionising and stop the instant the oven does. There is nothing left in the food but heat.
Which cooking method keeps the most nutrients?
For vegetables, steaming and microwaving with minimal water are consistently at the top. Prolonged boiling in a lot of water is consistently at the bottom.
Source: USDA FoodData Central (SR Legacy) via the TempoLife food database; MET values from the 2011 Compendium of Physical Activities · checked 2026-09-02
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