Wednesday, February 25, 2009
Eating Healthy - Part 5: Nutrition 101
Before we go on to the next food group, I thought it would be helpful to pull out my nutrition textbook and do an overview of some basic nutrition information so that you know exactly what I am referring to when I use words like "sugar" "carbohydrates" "fat" "vitamins" "anti-oxidants" etc. I think understanding the information will also help things make sense when I get into how to read product labels... A nutrient is a substance obtained from food and used in the body to promote growth, maintenance or repair. There are six classes of nutrients: water, carbohydrate, fat, protein, vitamins, and minerals. Three of these six nutrients (carbohydrate, fat, protein) provide energy to the body through metabolism. Metabolism refers to all of the chemical reactions that are going on in the body - both the buildup and breakdown of substances. Vitamins and minerals facilitate the release of energy. Water is the medium in which all of the body's processes take place. A calorie (actually the correct term is kcalorie) is a measure of the amount of energy in a food. Carbohydrates yield 4 kcalories of energy from each gram of carbs. Protein the same - 4 kcalories per gram of protein. Fat yields 9 kcalories per gram of fat. While foods may be higher in one nutrient or another, most foods contain some amount of protein, carbohydrate and fat - the exceptions would be things like white sugar (which is pure carbohydrate) or vegetable oil (which is pure fat). I think this is important to understand so that you can see why certain popular diets are unhealthy. The body needs protein, carbohydrate AND fat in an appropriate balance in order to function properly. We'll get into more of that later... So, as an example: if 1 cup of milk contains 13 g of carbohydrates (4 x 13), 8 g of protein (4 x 8) and 2.5 g of fat (9 x 2.5), then that cup of milk would contain 106.5 calories - the Nutrition label on the gallon of milk rounds it off to 100 or 110 calories, but you can see now where these numbers are coming from. (Don't ask me how they figure out how many grams of carbohydrates are in the milk. That is all done in a chemistry lab somewhere and is way beyond the scope of this post.)
-Carbohydrates are classified as single sugars (monosaccharides), double sugars (disaccharides) and complex carbohydrates (polysaccharides). Fibers are the constituents of carbohydrates that humans cannot digest. Fibers may be soluble or insoluble in water. Fibers are not a source of energy but they benefit health in many ways, so it is important to have the recommended amount in the diet (and most of us fall short).
-Fats, also called lipids or fatty acids, are classified by chain length (having to do with the length of the molecule) and saturation (having to do with whether or not the hydrogen atoms are missing on the fatty acid chain). Lipids are classified as saturated fatty acids or unsaturated fatty acids - more specifically monounsaturated fatty acids (MUFA) (one hydrogen atom missing) or polyunsaturated fatty acids (PUFA) (more than one hydrogen atom missing). Omega-3 fatty acids are a family of fatty acids in which the endmost double bond is three carbons back from the end of its carbon chain. An omega-6 fatty acid is one with its endmost double bond six carbons back from the end of its carbon chain. A "trans-fat" is an unsaturated fatty acid with a rare or unatural configuration of the hydrogen atoms around a double bond, often a product of the hydrogenation process. Hydrogenation is the process of adding hydrogen atoms to unsaturated fat to make it more solid and resistant to chemical change.
-A protein is composed of amino acids. There are 20 different amino acids and each amino acid is unique. These amino acids can bond together to form a peptide chain which folds together into a three-dimensional shape which is also called a protein molecule. You don't really need to know all of this except that some of these amino acids are marketed as supplements to those wanting to build muscle mass. You are probably also familiar with the amino acid called tryptophan - which has been blamed for the drowsiness that typically occurs after Thanksgiving turkey dinner, although it is probably not really the cause (read here).
-A free radical is a highly reactive chemical form that can cause destructive changes in nearby compounds, sometimes setting up a chain reaction. If left uncontrolled these chain reactions can damage cell structures and impair cell functions. Free radicals occur in normal metabolism but are also thought to play a role in the inflammatory process, cancer and heart disease as well as aging and other disease processes. Anti-oxidants ("against oxidation") are compounds that protect other compounds from attack by oxygen by themselves reacting with oxygen.
-Fruits and vegetables, as I stated in Part 2 and 3, are high in anti-oxidants. So, in addition to being low in calories (which will help to maintain a healthy body weight), fruits and vegetables contain vitamins and anti-oxidants (go back to this link if you are interested in the specifics), which helps to decrease inflammatory and disease processes, or in other words help to keep our bodies functioning properly so that we can be as healthy as possible and feel well. The research on anti-oxidants is that they are generally "good" but it is a very complex thing and anti-oxidants are not always beneficial - I would summarize by saying that too much of a good thing (high doses in supplements) is probably no longer a good thing. Thus, once again stressing the importance of a balanced diet. This is not surprising, since we know that we are all aging as a result of The Fall in the Garden of Eden. Our lives on this earth are limited and there is nothing, nor will there ever be anything, that can completely prevent that process.
-I know...that was a lot of biochemistry!! I essentially condensed about 5 chapters or more into this one post. But, I think you will see how understanding this makes identifying healthier food choices easier. Also, the terms "anti-oxidants," "carbs," "omega-3 fatty acids," and "trans-fats" have gotten a lot of publicity so I thought it would be helpful to explain what these terms actually mean.