The science behind food
Science guru Dr Karl Kruszelnicki looks at why people get ice-cream headaches, whether vodka has calories and how the Girl Guides have killed more people than al Qaeda in his new book, Brain Food.
WHY DO WE CRY OVER ONIONS?
"The answer is very simple," says Dr Karl, "because onions do not have legs; because plants do not have legs.
"If plants had legs and you did something bad to them, like attack them, they would run away or they'd fight you back.
"But they don't have legs which means they have to fight some other way, so they use chemical warfare."
Dr Karl says when we cut onions they emit a chemical that floats through the air and lands on our eyes, making us cry.
His suggestion for combating this? Wear swimming goggles.
WHY DO WE GET ICE-CREAM HEADACHES?
"The answer is, we don't know," says Dr Karl, who is a qualified medical doctor.
One theory, he says, is that when ice-cream hits the back of the throat it sends sensations to a part of the brain. This section of the brain also gets sensations, he says, from the meninges (the system of membranes that envelopes the central nervous system), or the coverings of the brain that are involved in headaches.
Another theory, Dr Karl adds, is that we get ice-cream headaches due to the sudden burst of coldness, which affects blood vessels.
What makes Dr Karl believe that neither of these theories fully explain the reaction is that research shows a small number of people feel pain associated with ice-cream in the middle of their shoulder blades.
SHAKEN OR STIRRED?
The science behind the James Bond-style 'shaken not stirred' martini, Dr Karl says, was a joke theory put out in an issue of the British Medical Journal.
"They did find there were extra antioxidants if you shook but didn't stir the martini," says Dr Karl, who adds that some people argue you're meant to do it the opposite way (that is, stirred not shaken).
On a slightly different note, Dr Karl believes a small amount of alcohol each day, does in fact, have health benefits.
DOES VODKA HAVE CALORIES?
Still on alcohol, Dr Karl debunks a popular myth about vodka not having any calories.
It's a misconception, he says.
"Vodka has slightly more calories than carbohydrates and protein and slightly fewer than fat," he explains.
HOW BAD ARE HAMBURGERS?
We've all heard about how bad hamburgers are from those world-dominating fast-food chains, but just how bad is a simple beef or pork pattie?
A well-cooked hamburger can be healthy, says Dr Karl, depending on where you buy it.
He says in America, 70 per cent of all antibiotics are given to stock animals such as cattle and sheep that aren't, in fact, unhealthy. Over time, he says, bacteria mutate and become resistant to antibiotics and this is the meat we're putting in our bodies.
Of course, he concedes, this includes all cheap meat, not just hamburger patties.
IS OUR FOOD HEALTHY?
Food has dropped in nutritional value, says Dr Karl, who admits he's not an expert in food per se.
"If you compare an apple from 1940 with an apple of today it actually has one third of the amount of iron," he says.
That's right across the food pyramid, too.
"What's happening is we've got these high-speed growing techniques, all the fertilisers, and as a result plants don't get a chance to put their roots down deeply enough."
A consequence of that, says Dr Karl, is that we suffer by eating foods without all of their nutrients.
A FOOD TO AVOID
If there is one food we should all steer clear of, Dr Karl says it's trans fats.
Trans fats are trans fatty acids (TFAs), which are likely to be found in commercially-produced fats such as margarine and fats used in pastry dough.
Dr Karl says the good thing about trans fats for the food industry is they can be easily manipulated to be as fluid as water or as solid as candle wax.
The disadvantage, he says, is they do "really bad things" to the heart's blood vessels.
He says they are in most processed foods with any sort of fat.
"According to a headline in the New York Times," Dr Karl says, "the Girl Guides of America have killed more Americans than al Qaeda ever has because the Girl Guides raise money by doing Girl-Guide cookies.
"They sell trans fats, which do all sorts of bad things to blood vessels and kill people."