I get my microwave popcorn at the ready as I weigh up the evidence for and
against the domestic electromagnetic oven…
Few other pieces of kitchen kit remain as distrusted as the microwave oven.
Despite being a common fixture in homes and businesses across the UK (and a saviour of the mid week meal for many), a huge cross section of the population still consider the microwave a demon device – blamed for zapping nutrients out of food and letting toxic chemicals in. Other more fanciful studies have suggested microwaves can change the structure of our blood, immune and digestive systems – and pump out near nuclear levels of “brain-damaging” radiation.
So what’s the real truth behind some of the more overheated claims?
Nourish or nuke?
Let’s start with the nuking nutrients theory. Only two studies have linked microwaves with depleting nutrients in food: the first suggesting one minute of microwaving could destroy the cancer-fighting compounds in garlic (while this took 45 minutes in a conventional oven), and the second, published in 2003 by the Journal of the Science of food and Agriculture, concluding that broccoli lost 97 percent of its flavonoid antioxidants after a blast in the microwave.
However, what the studies don’t highlight is that all forms of cooking reduce nutrient value, not just microwaving – and in fact, other studies have shown that microwaving is among one of the best methods for cooking vegetables because of its speed and the lack of water used in the process. Boiling by comparison is considered the worst for nutrient depletion due to the fact water-soluble vitamins tend to leach into the water. Indeed, in the 2003 study, the researchers added water to the broccoli bowl before microwaving it – so it could be said the water, not the microwave was to blame for the nutrient loss.
“I have never seen any evidence that microwaves ‘zap’ nutrients,” says Dr David Franklin, head of Engineering at Portsmouth University. “Heating and cooking food will generally take some nutrients out of food, vitamin C being an obvious example, but cooking food quickly without much water will tend to preserve more nutrients – and microwave cooking meets these conditions reasonably well.”
Of course, the very words we associate with microwave cooking – ‘nuking’, ’zapping’ and ‘radiation’ – all conjure up the idea that they are death rays. But while they do leak a certain level of radiation, what’s important is the type and amount. Unlike ionizing radiation, given off by radioactive gases, nuclear disasters or procedures like radiotherapy – which has been shown to change the DNA make up of cells and, at high levels, cause serious illness – microwaves produce non-ionising radiation. This type of radiation can move things around inside a cell but don’t have enough energy to damage it.
While the non-ionising, ultraviolet lights of sun beds have been shown to be carcinogenic, it’s thought the levels produced by microwaves during short cooking intervals are too small to be harmful. What’s more, the amount of non-ionising radiation reduces the further you move away from the oven. Coupled with the fact all ovens have protective door covers, and the risk is further lowered.
In 1997, Peter Valberg, from the Harvard School of Public Health, conducted a review of all the epidemiological studies into the incidence and distribution of cancer in relation to microwave radiation exposure and found very little evidence to support a causal relationship. But could microwaves leak radiation into our foods instead? One 2002, Swedish study suggested the food contaminant ‘acrylamide’ was formed in potatoes when heated in a microwave to 100C. However, while this might sound like a good reason to ditch your microwave, in reality this chemical is produced naturally in food that is fried or grilled at high temperatures too.
The Food Standards Authority (FSA) suggest that given the uncertainties in exposure, “it is not possible to draw any definitive conclusions about the cancer risks of acrylamide in food”, but it is funding several new research projects into the chemical. So, should we all expect to experience radiation poisoning from our microwaves anytime soon? It seems unlikely.
“I have not seen anything yet that has been regarded as conclusive on this subject,” affirms Dr David Franklin. “A microwave oven that is in good working order should produce negligible leakage of radiation. I have tested many over the years and have not found a problem with one yet.”
Another area of concern has been about Bisphenol A or BPA, used widely in plastic manufacturing, leaching into microwaved foods via plastic trays and containers. Some studies have claimed a link between it and several cancers, including breast cancer, however, independent studies have shown that, even when consumed at high levels, BPA is rapidly absorbed, detoxified, and eliminated from our bodies. In a 2015 European FSA evaluation, experts concluded “BPA poses no health risk to consumers of any age group (including unborn children, infants and adolescents) at current exposure levels”.
“And any plastic that’s suitable for microwaving will say it’s suitable for microwaving,” adds Dr Kirsten Brandt, senior lecturer at the School of Agriculture, Food and Rural Development at the University of Newcastle. “And this means it has been specifically designed so it won’t deteriorate under heat.”
That said, while the studies have looked at BPA, the jury is till out on whether there could still be other unknown toxic chemicals in BPA-safe plastics. Brandt suggests common sense should prevail.
“You just need to take sensible precautions,” she adds. “You wouldn’t wrap something in clingfilm and put it in the oven, so don’t do it in a microwave. If in doubt, take it off the plastic tray and put it on a glass or ceramic plate.”
But could microwaves be killing us softly in another way – through our increasing reliance on convenience food? Brandt doesn’t think so.
“While nutrients will have degraded in ready meals due to their long shelf life, they score better than tinned food overall. Tinned food has to heated to 121C for 20 minutes to kill any bacteria and can sit around for 12 months before being eaten, meaning very few nutrients survive.”
“In fact, microwaves have helped people eat better on the whole by allowing us to use up leftovers and waste less food,” adds Brandt. “And for many people, it’s the only time they cook a fresh meal. If the microwave hadn’t come along, there would have been something else to replace it, and we could have all ended up eating pot noodles.”
FIVE FAIL-SAFE MICROWAVING TIPS
1. Preserve more nutrients in vegetables by covering them tightly so they steam in their own juices – reducing the cooking time – and scrub rather than peel (the most nutritious part can often end up in the compost).
2. Always keep 30cm between you and your microwave when it’s on as non- ionising radiation decreases rapidly with distance.
3. Make sure your oven is in good repair. If you’ve had it for more than 10 years, or the door doesn’t close properly, consider getting a new one.
4. If you’re worried about ‘acrylamide’, cook things for shorter bursts, or always cook starchy food (i.e. potatoes, bread) in a conventional oven until slightly golden.
5. If you must use plastic or clingfilm, at least ensure it says ‘microwave safe’ on the packaging.
First published in Natural Health (http://www.naturalhealthmagazine.co.uk/)