Off meat arguments off balancehttp://www.abc.net.au/science/articles/2009/07/29/2639623.htm
Opinions vary about what you should or shouldn't eat, but can your well-rounded diet be unbalanced by eating meat? Dr Karl gives that theory a grilling.
By Karl S. Kruszelnicki
I have no problems with vegetarianism. In fact, I myself was a vegetarian for many years. Even today, thanks to one of my daughters being a vegetarian, I will often go for days or weeks without eating meat.
I fully acknowledge that if you want to feed a population, vegetarian diets use up fewer resources than meat diets.
And further, I fully acknowledge that a properly devised vegetarian diet can deliver real health benefits, including lower rates of obesity, heart disease and some cancers.
But I cannot agree with those who claim that humans were never meant to eat meat. Nor I cannot agree with those who reckon that meat will putrefy and rot in your gut, ultimately giving off toxins that will cause many diseases, including insanity, premature ageing, and — God help us! — enfeeblement.
Other variations of this rotting meat myth include the claim that the average American carries several kilograms of "undigested, putrefying meat" in their intestines, because they claim that we humans were not designed to eat meat.
But we have evolved to eat meat. Here's some proof.
On one hand, the teeth in our skull include both cutting incisors (as found in carnivores) and grinding molars (as found in herbivores). This combination makes us flexible omnivores.
On the other hand, the timing of what happens to food puts paid to this claim that meat does not get digested. The human gut has all the enzymes needed to digest meat.
The human gut is some 10 metres long. The food enters at your mouth where you chew it, and where your saliva adds a few digestive enzymes. Then, after transit via the oesophagus, this food ends up in the stomach.
In the stomach, the enzyme (called pepsin) attacks the proteins in meat. It breaks down the long chains of amino acids into smaller chains.
Typically, the food will stay in the stomach for between one half an hour and two and a half hours, before moving on to the next section, the small intestine. But the pepsin acting in the stomach digests only about 15 per cent of the protein.
The small intestine does most of the digestion and absorption of what we eat. It takes some two to six hours to do so.
In the small intestine, the pancreas pumps out various enzymes that break down the small chains of amino acids into even smaller chains.
The cells lining the gut have microscopic fingers on them called microvilli. The microvilli walls have enzymes anchored or embedded in the actual walls.
These enzymes start inside the body of the microvilli, and protrude through the wall of the microvilli into the hollow tube of the gut.
When you eat food, these enzymes break down the chains of amino acids into tiny chains of three and two amino acids and, sometimes, even single amino acids.
These are carried into the cells lining the gut and broken down (if necessary) into single amino acids. Then they are passed right through the cell out to the other side, and then into a vein that carries the individual amino acids to that big organ, the liver, for further processing.
So, yes, our human gut actually has all the mechanisms needed for digesting the proteins of meat.
The gut contents are then moved into the large intestine where water and some electrolytes are removed. The time taken for this transit is much greater, ranging from 14 to 80 hours.
The various transit times are affected by many factors including genetics, quantity of fibre in the diet, the size of the meals, age, gender, smoking, exercise and so on.
But in each part of the gut, the mushy contents tend to move through as a unit, similar to toothpaste being squeezed out of its container. They are thoroughly mixed in together before they eventually escape to the outside world.
Those parts of the mush that were originally meat are not separated out, and are not specially kept aside to quietly rot.
If you want your meat to do that, you need to put it to the side of your plate.