Monday, July 7, 2008
Laying down the lines
This is not, by any means, a complete summary of what we know about food and nutrition, nor is it meant to be. For the most part, I am merely defining what I mean when I refer to, say, carbohydrates, because going by what I've seen floating around on the Internet, there are some confused souls, to be sure.
With that in mind:
There are five basic food groups--carbohydrates, proteins, lipids (fats), vitamins, and minerals. (I did consider adding alcohol, but decided against it for expediency)
Not what you were expecting, were you?
The food pyramid that the USDA devised is still valid, for the most part, as a guide for what to eat to stay healthy. But from a nutritional point of view--the view your cells have of that apple you've eaten--all foods are made of these five things, but in different proportions.
I say "for the most part" because, in my opinion (and the opinion of just about everybody else in the world who doesn't drink 3 glasses of milk a day or eat meat) the milk and protein recommendations are still grossly exaggerated. But we'll see what the science has to say about that later.
Carbohydrates are, in a nutshell, sugars. At the molecular level, sugars look like rings--some have five links, some have six. And the most amazing thing is, depending on where they join together--which link of one sugar is joined to a link of another--they can take on different properties. Some are readily assimilated into the body. Others are wholly undigestible (fiber). Some soak up water--the starch that thickens sauces relies on this property.
Proteins are comprised of amino acids, linked together like a set of magnetic dumbbells. It is not the actual linkage that is important, though--it's what's attached to the handle of the dumbbell that makes a protein what it is (the side chain). The side chains play an important role in how the protein gets metabolized.
Lipids are the fats and cholesterol--the greasy bits. They are, essentially, long strings of carbon molecules. Carbon-carbon bonds are some of the strongest in nature, meaning that there is a great deal of energy stored in them. This makes lipids a valuable source of energy.
The most amazing thing about carbohydrates, lipids, and proteins is that the body can convert one to the other. A few steps, a few atoms added here or there, and voila--you have fat from sugar, sugar from protein, protein from sugar. These three groups comprise the main sources of energy for the body.
Vitamins are organic molecules that aid in the function of our body. Unlike the three listed above, they are not a major source of energy--rather, they are like the starter block of the wood fire--they get the fire started, but contribute little to the actual burn. But once the fire is out, and you need a new one, if you don't have enough starter, you might not be able to get it lit.
Minerals are inorganic substances (substances that come from the earth, and are not manufactured by living things). They have a diverse role in the body, too complex to cover here, but suffice it to say that it is amazing that trace amounts of a salt or metal can make the difference between sickness and health. Most minerals are only needed in trace amounts in the average diet of an average person in good health.
If you'd like to learn more about nutrition, you can start here. As I said above, the point of this is not to explain how these are integrated into a seamless picture of metabolism. The point of this is to lay out what I mean when I later say "vitamin" or the like.