MICROWAVE USE, GOOD OR BAD?

With the recent increase in electricity tariffs one of the authors of this paper’s dad (who usually isn’t very stingy) packed away the microwave with the excuse that it was going to consume too much electricity. Of course that started a little war at home, and yes, the pro-­microwave expect did win because she had a better case than he did with respect to the convenience that we enjoyed with the microwave oven. Beyond issues of electricity consumption (which some have argued is not a big problem because after factoring in how often as well as how long it takes to microwave cook food, the cost is actually cheaper compared to the cost of gas) are there other concerns of consumers about the use of microwaves that are indeed grounded by fact? Answer is yes, there are concerns and no, not all the concerns are backed by scientific evidence. One major concern that has been raised by consumers is the assertion that microwave use can cause cancer. To better distinguish between the claims that are facts and those that are fiction, it is important to understand what microwaves are and how they manage to cook food so fast.

History of microwaves – what are microwaves and how is it used in food p rocessing?

Forgive the scientific mumbo jumbo but as explained earlier it is important to understand some of the physical principles backing microwave use so as to understand what effects they may or may not have on us. So, here it goes; microwaves are similar to radio waves but move back and forth (vibrate) at a much faster rate, described as “high frequency radiowaves”. They appear between radio waves and infrared waves on the electromagnetic (EM) spectrum. Microwaves are un ionizing radiation, implying that they are not radioactive neither can they cause other substances to become radioactive; they only have the ability to vibrate fast enough to produce heat but do not disintegrate into ions. Microwaves are selective and so affect molecules which are electrically asymmetrical or polar (in other words molecules having both a positive and negative charge); like water. Microwaves therefore heat food by causing the water molecules in it to vibrate at very high frequencies (that is, energizing the water molecules to produce kinetic energy) which eventually turn to steam which heats the food. Microwave­oven energy is more penetrating than heat that emanates from a conventional oven/stove. It immediately reaches molecules about an inch or so below the surface (through the process of radiation). In contrast, regular cooking heat, and using utensils and a stove, goes through food rather slowly, moving inward from the outside by process of conduction. Microwave technology is thought to have been originally developed by the Germans during the Second World War as a radar system although it is believed that the idea behind its use in food processing (the microwave oven) was accidentally stumbled upon in 1946 by Dr. Percy Spencer who realized that a chocolate bar he had in his pocket while working with a radar unit had melted. Among other things microwaves are currently used by fixed traffic speed cameras, and for radar; which is used in burglar alarms, by aircraft, ships and weather forecasters as well as in mobile phones. In medicine microwaves are sometimes used in place of surgery eg. in prostate enlargement which if not treated could lead to cancer. In the kitchen they are used for cooking, heating and thawing/defrosting. Why do people prefer microwave cooking?

Microwave ovens have been in use for more than 50 years and it is reported that as many as 90% of American homes own or use microwave ovens. This trend is no different in Ghana as microwave ovens have become so cheap that almost every household owns one. Microwave ovens have become very useful kitchen appliances for their convenience and the fact that they do not occupy a lot of space and so can be used even in very small rooms that otherwise cannot take a gas stove.

Concerns with Microwave use; facts vrs fiction

As stated earlier, a number of concerns have been raised with microwave use, among which include the claim that microwave energy destroys nutrients and causes cancer. Well, with regards to nutrient retention, some nutrients break down when exposed to heat from all forms of cooking. Most of the concerns are especially with cooking vegetables as cooking, in addition to destroying the structure of the nutrient through the heating process, can also leach nutrients (e.g. vitamin C) into the cooking water. This water if poured away makes these nutrients go waste. Some studies have shown that the effect of using microwave energy to cook food is no more detrimental than other conventional methods of cooking. An experiment conducted by d.l.­ Fuente published in 2002 for example showed that although calcium and phosphorus levels reduced in milk heated with a microwave and a water bath, the amounts were not significantly different in both treatments. Interestingly, some other studies have shown that cooking with microwaves retain more vitamins than other cooking methods because it uses less water and less time. In studies at Cornell University, scientists looked at the effects of cooking on water­soluble vitamins in vegetables and found that spinach retained nearly all its folate (folic acid) when cooked in a microwave but lost about 77 percent when cooked on a stove. They also found that bacon cooked by microwave had significantly lower levels of the cancer­causing chemicals known as n it r osa m in es (generated especially during char­grilling of meat) than conventionally cooked bacon. Another concern with microwave energy is the phenomenon termed “erupted water phenomenon”. Because of the nature of microwaves as explained earlier, they can superheat water and other fluids without boiling them. As a result of this water heated in a microwave can explode with agitation. A genuine concern of this phenomenon is the danger of burns as there have been reports of people being scalded in the face and hands. We have personally experienced and witnessed burns from super heated water and so can identify with this concern. Yet another valid concern of microwave use is the fact that substances used in the manufacture of the plastics used for cooking (known as plasticizers) may leak into food when it is wrapped in plastic or placed in a plastic container and microwave heated. Fatty foods in particular, such as meats and cheeses cause a chemical called d iet h ylh exyl a d ip a t e to leach out of the plastic. The effects of these chemicals have been extensively studied in animals but not in humans and there have been findings that these substances have the ability to cause cancer in animals.

Based on these studies, there is therefore a limit to the amount of leakage allowed by the FDA in a plastic bowl and the maximum allowable amount is 100–1,000 times less per pound of body weight (in humans) than the amount shown to harm laboratory animals over a lifetime of use. There are therefore strict guidelines for the manufacture of plastics for use in microwave ovens. In 1992, researchers at Stanford University Medical Center found that warming breast milk in a microwave destroyed the antibodies that provide immunity to infants, and destroyed 96% of liposome activity that inhibits bacterial growth and this has generated a scare that microwave use is detrimental for infants. The destruction of some (but not all) of these nutritive factors were observed even at a low setting. The limitation of this study was that the microwave heated breast milk was compared to unheated breast milk only and not breast milk heated by other conventional methods. The fact based on research is that heating breast milk well above body temperature regardless of whatever cooking method used is unsafe for use and so these changes that were observed were due to the fact that the breast milk was heated to begin with and not the microwave energy used for the heating per se. The real concern with microwave use in Baby food is the fact that baby’s food may also be superheated without the food’s container appearing hot. This can cause burns if food is given directly to baby without allowing cooling. There may also be concerns with baby bottles not being microwave safe and so leaching out chemicals into baby’s food. There is no evidence currently to support claims of diseases in children whose feeds are microwave heated. An alleged experiment by a secondary school student known as Arielle Reynolds in Sussex demonstrated that one plant watered with microwave heated water failed to thrive compared to another that was heated by a stove and this has also been the basis on which many anti­ microwave advocators describe microwaves as hazards as they cause heated molecules to “lose their vital energy”. The “Experiment” has since not been replicated in a more controlled trial.

Microwave use and disease

There is evidence based on animal experiments to support that direct exposure to microwaves can induce oxidative stress and cognitive impairment. Human based studies on the effects of ea t in g food p r ep a r ed in a m icr owa ve are limited, well except for an alleged human study, “Comparative Study of Food Prepared Conventionally and in the Microwave Oven” reported to have been published by Raum & Zelt in 1992. It is reported that a scientist named Dr. Hertel with a group of 7 other volunteers locked themselves up in a hotel room to conduct this experiment, subjecting themselves to microwave heated food for a period of time and then testing their blood afterwards. These scientists never supplied the data to support their claims but unfortunately their work is being sited time and time again to support statements that microwave cooked food causes cancer and sterility. It must be stated categorically that microwave heated food does not become radioactive and so the food in itself is not harmful. Covering food when microwave heating therefore does not “prevent” food from getting radioactive as supposed by some advocates but only serves the purpose of preventing splatter in your microwave oven. Dir ect exp osu r e to high doses of microwaves (and not microwave heated food) may pose health risks because if of course they have the ability to cook food then they could “cook” us as well. The American food and drugs authority (FDA) has safety guidelines for the amount of microwaves that can leak from a microwave oven. Microwave ovens are therefore designed to stop producing radiation once the door is opened. On the basis of current knowledge about microwave radiation, the FDA believes that ovens that meet its standard and are used according to the manufacturer's instructions are safe for use.

Are we to throw our microwaves away? There is currently very little evidence that microwaving food or water causes any ill effects both in the short and long term. The claims that exist are presented in pseudoscientific language (not from any valid peer­reviewed research) and so make it difficult to generalize. It is however always better to be safe than sorry and YO U can make microwave cooking more “safe”. First of all, purchase microwave ovens made by reputable manufacturers and follow the manufacturer's instruction manual for recommended operating procedures and safety precautions. Use only plastic containers labeled “m icr owa ve sa fe” for microwave cooking. Do not use containers with metallic decoration or aluminum foil for microwave cooking as these can reflect microwaves and generate sparks. Plastic storage bags, plastic grocery bags and foam trays are also not advised. Brown paper bags are also not advised because they are usually manufactured from recycled paper which also contains unsafe chemicals. Do not reuse containers that came with microwave convenience foods or take­away because they might be designed for one­time use only. Always look out for the re­use sign on plastic containers. This looks like a triangle with a number in the middle. The number tells the number of times you can use the plastic for microwave cooking. The most ideal containers for microwave use are glass and ceramic dishes, Paper plates, towels, and napkins, wax and parchment paper. Do not over­ heat water or liquids as these can cause accidents. As there is very little evidence to at least test the claims of anti­microwave advocates, I would like to task Ghanaian research scientists (including us) to be interested in and conduct studies in this field to supply evidence and more conclusive information. In the mean time consumers should take personal responsibility of their health and follow appropriate practices for microwave use.

Ruthfirst Ayande and Frank Hayford Microwave Image Source: Google Images