I got to say, out of all the classes I have taken in college over the years, Nutrition has intrigued more than most. Perhaps it is because nutrition is such an integral part of our lives, and something most of us know little about. After years of trying this diet, or that diet, and reading book after book about various diets that only briefly touch on the science of nutrition, I feel like I only scratched the surface in understanding how our bodies process nutrients. I am realizing that to maintain a healthy balance in your body, and to correct health problems based on diet, it helps tremendously to understand how complex the chemical interactions within your body really are, and how we can manipulate those interactions to a positive outcome.
In the textbook Understanding Nutrition by Whitney, in chapter 5 lipids (fats) are discussed, and particularly phospholipids. Phospholipids are like typical triglycerides (fats), except a third of the molecule has been replaced with a phosphate molecule and a choline molecule. We all know how oil and water don't mix right? Well this is like saying, "We all know how lipids and water don't mix." The word lipids is a scientific synonym for fat. The lipids don't mix well with water by themselves, but when they are changed into a phospholipid via the replacement of part of the molecule with a phosphate and choline molecule they suddenly can mix well with water. Substances that can bind with fat molecules and water molecules are called emulsifiers. An example of a food that has a high level of phospholipids, or emulsifiers, is eggs.
Soon as I read this I realized this is why so many baking recipes use egg in them. Eggs act as an emulsifier, and binds the lipid based ingredients to the hydrolyzed ingredients, helping create structures in food like bread. The emulsifier binds the nutritional starch and gluten together creating pockets that trap released gases in the bread as it bakes and rises. I remember trying to skimp out on eggs when baking a few times and the results were dramatic, and now I know why.
Another personal ah-ha moment happened in the same chapter when I read about how cholesterol, a sterol lipid, is processed in the digestive system and blood. There is a lot of confusion about how to decrease cholesterol in the blood, with some people believing that if they simply eat less cholesterol in their diet it will significantly decrease the levels of cholesterol in their blood.
Most people consume around 200-300 mg of cholesterol daily in their diet, however the liver manufactures between 800 to 1500 mg of cholesterol regardless of what you eat. So you can see how the ratio of 5:1 favors the liver production over the diet when it comes to what really causes cholesterol. Before we get mad at our livers for betraying us we need to understand that the body needs cholesterol to repair and build cells, among other things, but too much cholesterol in the blood can lead to plaque buildup in our arteries, leading to dysfunction of the blood stream, and eventually death.
Ok, back to the 5:1 ratio of production of cholesterol. 20% of your cholesterol coming from your diet is still 20% though, and if you want to limit cholesterol in your diet there is a smart way to do it. If you eat raw vegetables and fruits, the plant sterols within them enter the digestive system and block some of the cholesterol you consumed from entering your blood stream, thus lowering the levels of cholesterol in your blood. Once again, you shouldn't expect more than a 10-15% decrease, but it's worth considering if you have high levels of cholesterol in your blood.
The reason the plant sterols interfere with cholesterol absorption is that the plant sterols are similar in structure to the cholesterol sterols, and when your digestive system attempts to break down the cholesterol and transfer it to the blood stream, the plant sterols cut in line and prevent some of the cholesterol sterols from being absorbed.
Another plan of attack to lower cholesterol is consuming foods with soluble fiber. Soluble fiber is found in fruits, beans, and whole grains. Soluble fiber chemically binds with bile that is released into your small intestine, and takes the bile all the way through the digestive system and out the body. Why is this important? Well, remember how earlier I said the liver produces five times more cholesterol than what people typically consume? Cholesterol is used by the liver to create bile. If you are eating food that absorbs bile and forces your liver to make more bile than it normally would, the liver will consume more of the cholesterol reserves it has access to in the blood stream, thus decreasing the levels of cholesterol circulating in your blood.
It seems our bodies were built to consume considerable amounts of fruits and vegetables, and not built that well to consume large amounts of foods that have a lot of cholesterol, such as meats, eggs, seafood, poultry, and dairy products. Everything in moderation right? Well, except for fiber and plants! Actually, you CAN eat too much fiber and should be careful not to over do it. Fiber can bind with dietary minerals you need as well, and can also stress your digestive system if you eat too much. 40 grams of fiber per day is a good goal to have.