Every so often, I hear someone confuse
‘radiation’ and ‘radioactivity.’ These are two wildly different concepts, but
they’re usually conflated in an attempt to convince someone that, say,
microwaving food is unhealthy, because it uses radiation to heat the food –
“How can that be healthy?” Fortunately, I do not deal in emotional appeals to
fear, but rather to the facts at hand.
Radioactivity, as we all know, is the
process by which an unstable atomic nucleus loses energy by emitting radiation,
by way of alpha, beta or gamma radiation. So what is radiation? Simply the
emission or transfer of energy in the form of waves or particles. Alpha and
Beta radiation, as you might recall, are particles that are radiated, while
Gamma radiation is electromagnetic radiation with high energy. This is what is
known as ionizing radiation – radiation with high enough energy to free
electrons from atoms and molecules, and thus ionizing them – allowing different
chemical reactions to occur.
So what about microwaves, then? Well, not
all radiation that occurs occur due to radioactivity – and not all radiation is
ionizing radiation. Simply put, food is ALWAYS cooked via radiation – thermal
radiation! Microwaves are in fact a form of electromagnetic radiation of a
lower frequency than thermal radiation just above the radio frequencies and
below visible light frequencies. The wavelength of microwaves are between 1mm
and 33cm.
How does it work, then? Well, food is
heated by passing the non-ionizing microwave radiation through it. In
consumer-grade ovens, this is typically electromagnetic waves at a wavelength
of 12.2 centimetres, while industrial microwave ovens operates at 32.8
centimetres. During this process, water, fat and the rest of the food substances
absorb this energy via the dielectric effect. In essence, water molecules are
electric dipoles, with a partial positive and partial negative end. As these
waves pass through them, they try to align with it, and as the microwaves
alternate, this causes the water molecules to rotate. These rotating water
molecules vibrate, putting other molecules in motion and causing them to
vibrate as well. This molecular vibration is commonly referred to as ‘heat’.
A common misconception is that microwaves
heat food from the inside out – this, however, is not the case. Microwaves face
the same issue as normal thermal radiation in penetrating dense materials, and
thus also cook from the outside in. The penetration depth varies depending on
the material, but generally it only penetrates for about 1cm in meats and
vegetables, to about 2 to 5cm in water and bread.
So what does this all mean for our food?
Well, oddly enough scientists have found almost the opposite of what you’d
expect – microwaved food is HEALTHIER! In terms of carcinogens, microwaved food
contains a lot less heterocyclic amines, which are usually found in meats after
grilling or braaing, and less is created when meats are cooked at less than 100
degrees Celsius or with a shorter cooking time. In fact, if meat is precooked
in the microwave before they’re grilled, it could reduce HCA’s between 3 and 9
times in the final product.
This result is also found with polyaromatic
hydrocarbons as well as nitrosamines, two other carcinogens. So microwave cooking tends to produce less
carcinogens, but what about other nutritional effects? Well, studies showed
that in terms of proteins, the nutritional value remains much the same. In
vitamins and minerals, however, there again appears a distinct advantage. Due
to shorter cooking times, and the fact that vitamins and minerals are absorbed
by water when cooking, microwaved food retained much more of vitamins B & C
compared to traditional cooking, as well as more phosphorus and potassium.
Clearly, the drive by some to demonize microwaves
simply due to fear of association with ‘radiation’ is ill-founded and are not
backed up by scientific studies, and show that it might actually be healthier.
True, microwave cooking does have some dangers, and I would not, for example
recommend microwaving eggs, due to pressure build up in the shell. Microwave
ovens usually go ‘ding’ when there’s stuff to eat, but in this case, it’s not
pretty when they blow, and you’ll have to clean up for quite some time.
Of course, it’s not just microwaves that
get people up in arms. There’s also ‘Irradiated food!’ If you’ve read this far,
you’ll probably realise what comes next – it’s not dangerous either. In fact,
it could be said that it’s helping world hunger. In this case, however, when
they talk about irradiation, they’re not talking about non-ionizing radiation.
Oh no, this is actual ionizing radiation.
Food is passed through a food irradiation
machine that blasts it with energetic particles or waves, causing collisions
with particles and breaking chemical bonds – specifically, those of cells and
targeting DNA and RNA, limiting cell division and limiting reproduction. Why is
this done? Why, to kill microorganisms, kill invasive pests and to delay or
eliminate sprouting – effectively preserving food much longer, and allowing
food to travel much further, allowing you to have a wider variety of food on
your table. Even in this case, the radiation is carefully measured, and does
not make the food radioactive – after all, exposing food to light does not make
food emit light, does it?
So next time someone tells you that
microwaving food with radiation makes it radioactive, ask them why they do not
glow in the dark, as they’re irradiated daily with visible light. As for you,
you can continued to heat or cook food safely in your microwave, and eat food
with an irradiated label on it, safe and secure in the knowledge that you’ll be
healthier, less prone to cancer, and potentially getting greater amounts of
vitamins and minerals, without having to worry about the pseudo-scientific
mumbo-jumbo that everyone keeps trying to peddle to you.
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