So you’ve been living a healthy low-carb lifestyle ... What about that microwaved lunch?
If you happen not to own a microwave, you are most probably in the minority. It is undeniable that this aid is about as convenient in the kitchen as is an underground train network in a large city. Sometimes that keto lasagna needs to get warm quickly, while on other days, a keto mug cake prepared in two minutes is an unbeatable evening treat. Not to even mention making cheddar crisps (that go so well with the leftover guacamole) in a minute! Yes, these are only a few of the ways of using a microwave. But some people believe this method to be unhealthy.
The rumors about microwaving food not being safe have been lingering around for literally decades. While microwaving sometimes does have an impact on the flavors of the food, some people are more concerned about food losing its nutrients or even becoming unhealthy and cancerogenic if heated or cooked in a microwave. Should they really be concerned? Before we try to answer this question, let us have a quick look at how microwaves work.
Microwave heating mechanism
A microwave oven contains a generator that gives off waves of energy (similar to radio waves) at a particular frequency. These waves are called microwaves. They are, in fact, nothing exotic; They belong on a spectrum of waves, stuck between radio waves and light waves. Being invisible, they might seem scary, but why are we not afraid of radio transmissions then? Anyhow, microwaves are extremely selective, mostly affecting water molecules because they are electrically asymmetrical. These molecules start vibrating, which causes enough friction to build up the heat. Thus, the food in a microwave gets cooked from the vibrating water molecules inside it [1].
Does microwaving cause loss of nutrients?
In short: Yes, it does to some degree. However, so does any other form of heating. If we take vitamin C for example, all cooking treatments cause a significant loss of it, except steaming.
Vegetables in the microwave
Vegetables, as a source of vitamin C and other beneficial micronutrients like chlorophyll, seem to prefer steaming to any other heating method, including microwaving. If you want to keep most of the antioxidants in, choose to steam the vegetables. On the other hand, boiling vegetables can be even worse than microwaving them because nutrients leach into the boiling water [2].
Take broccoli for example. Its carotenoids, potential protectors against numerous cancers, seem to "survive" steaming or microwaving, as opposed to boiling or frying. Unfortunately, broccoli’s glucosinolates, another supposedly anti-carcinogenic substance, can lower significantly, no matter what form of heating we choose [3]. So, "Eat your greens raw" is what children reluctant to eating broccoli at the dinner table, should be hearing.
Fish in the microwave
If you want to retain as much of healthy Omega 3 fatty acids inside the fish, choose either cooking/boiling or microwaving before frying. During frying, as much as 85% of Omega 3 can be lost [4]!
We can agree with most nutritional scientists who say that the amount of time and the heat are more important for nutrient loss than the method. In fact, using a microwave means cooking food for shorter periods, thus helping to minimize nutrient loss.
Is microwaved food cancerogenic?
There is no evidence supporting the cancerogenic activity of microwaved food. Actually, we should be asking ourselves how cancerogenic is not using a microwave. Especially when it comes to meat. Namely, there is a general consensus that during cooking or frying meat, there is a production of carcinogens going on. The amount of doneness supposedly increases the risk of human cancers [5].
What to do about this? Firstly, if you don’t want to become a vegetarian, you can modify your cooking practices. Did you know that you need about the same time to reach the desired 70°C internal temperature of meat whether you fry it at 250°C or cook it at 160°C? It’s only a couple of minutes difference. Moreover, it is advisable to flip a beef patty over every minute rather than turning it over at 5 minutes [5].
What is more, a study has demonstrated that microwave pretreatment of beef patties before frying reduced production of carcinogens! The same study did not show any cancer-related mutagenic activity in microwaved meat [6].
How to ...
So, you find yourself in a rush and need to prepare something simple real quick. Or perhaps, instead of frying something in a tablespoon of butter, you just want to pour some MCT oil over your bacon and eggs. Have you tried cheddar crisps yet? Cut a slice of cheddar in triangles, place it on a sheet of parchment paper, then microwave on high for about a minute and a half. Upgrade this by powdering the cheddar with garlic or red hot chili powder. Not convinced yet? Search online for recipes for keto mug cakes. They can be quite amazing. Avocado mug cake and bulletproof coffee mug cake are just two examples you can try.
Bacon and other meats in the microwave
Experiments have demonstrated that the fatter a piece of meat contains, the more uniform the heating. Since fat is usually not uniformly distributed in a piece of meat, it is advisable to use lower power and longer cooking duration.
Moreover, the higher the fat content, the shorter the cooking time should be [1]. We can't know what type and how strong your microwave oven is, so it might take some experimenting with slices of bacon or other meat to see what works best in your case. The line between crispy and unrecognizable can be quite thin with the first couple of tries, though.
Eggs in the microwave
Using the microwave, if you take an egg out of its shell, the egg white will get heated sooner than the egg yolk. Interestingly, the egg shell is microwave-transparent, so you can cook the whole egg in the microwave.
In this case, due to the shell’s properties, the white and the yolk get cooked at similar times. Yet, it might happen that your egg explodes during microwaving. Oops. To avoid that, use low power mode and longer duration of cooking [1].
The downsides of microwaving
So far, we've more or less listed advantages of microwaving. The list could continue. For example, besides being convenient for cooking, microwaving also helps get rid of dangerous microbes and enzymes. How about the downsides? There is no doubt that some food doesn't taste all that good anymore after being microwaved. But this issue can be entirely subjective.
If you weren't living grain-free, you'd also know that microwaved bread loses all the crispiness. But so does some of the low-carb food. That happens because during microwaving, the air surrounding the food is cold, and water evaporating from food gets condensed in contact with cold air. All this condensation leads to loss of crispiness [1]. On the other hand, if you don’t want your food to dry out, put a cup of water in the microwave, together with the food to be heated.
Moreover, microwave ovens tend to heat the food unevenly. More so if the food consists of various ingredients that vary broadly in a number of water molecules. The uneven temperature of food can be quite annoying. Still, you can solve this problem to a satisfactory degree by using low to medium power and a longer duration of cooking.
Last, but not least, microwaving can actually be dangerous if you don't read the labels. Even the ones on plastic wraps and containers. Do not microwave any food that is packed inside anything that doesn't explicitly say it is microwave-safe. Plastic wraps and containers can melt (even if you don't see it happen) and release the not-so-healthy particles into your lunch.
Happy cooking! And remember: To remain healthy, do not over occupy yourself with obligations, leaving all the cooking to your microwave. Getting creative in the kitchen every now and then, using conventional ways, can be quite relaxing and fulfilling.
References
[1] Chandrasekaran, S., Ramanathan, S., & Basak, T. (2013). Microwave food processing—A review. Food Research International, 52(1), 243-261.
[2] Zhang, D., & Hamauzu, Y. (2004). Phenolics, ascorbic acid, carotenoids and antioxidant activity of broccoli and their changes during conventional and microwave cooking. Food Chemistry, 88(4), 503-509.
[3] Yuan, G. F., Sun, B., Yuan, J., & Wang, Q. M. (2009). Effects of different cooking methods on health-promoting compounds of broccoli. Journal of Zhejiang University Science B, 10(8), 580-588.
[4] Stephen, N. M., Shakila, J. R., Jeyasekaran, G., & Sukumar, D. (2010). Effect of different types of heat processing on chemical changes of tuna. Journal of Food Science and Technology, 47, 174–181.
[5] Knize, M. G., & Felton, J. S. (2005). Formation and human risk of carcinogenic heterocyclic amines formed from natural precursors in meat. Nutrition Reviews, 63(5), 158-165.
[6] Felton, J. S., Fultz, E., Dolbeare, F. A., & Knize, M. G. (1994). Reduction of heterocyclic aromatic amine mutagens/carcinogens in fried beef patties by microwave pretreatment. Food Chem. Toxicol, 32(397.9), 3.
Sakti says
Hello dear, I am looking for that kind of stuff and I appreciate your work, microwave oven cooked food is not healthy for us. I am going to make or reheat the food after reading your article, thanks for sharing this information with us.
McDonna says
Oh my goodness! THANK YOU FOR THIS POST! It has really irritated me for years the way unsubstantiated rumors grow feet and keep moving on the internet. Since the LCHF community is ahead of the curve of mainstream group-think nutritionally, it's even *more* important for us to be factual. Scrupulously factual. When lunacy is embraced and repeated, it can discredit the entire community.
My whole point is that microwaving couldn't be any worse than any other form of heat for affecting nutritional content of food. It's heat that can diminish nutritional value - not *how* it's heated.
One would think common sense could make that clear, but apparently common sense isn't always common. Lol
Thank you for breaking the info down by food categories, too! What a well researched, **well documented** post!
My Sweet Keto says
Thank you, McDonna, I highly appreciate your comment! I love digging into research and trying to sum it up in a way that virtually everyone should comprehend.
People are often afraid of processes they can not observe clearly, and don't understand, especially if such processes are not "natural". Admittedly, years ago, when I was younger, I was also kind of influenced by my family always saying that microwaving was the most unhealthy thing in the world.
And you are absolutely right: Common sense doesn't always make sense. It is merely common because the majority of people use it to make sense of the things around them by taking too many shortcuts in their train of thought and too little logic. But it is human nature. 🙂