Sunday, June 13, 2010

Nutrition Series: The Basics - Carbohydrates


Hi guys, over the next few months, I will be going through a nutrition series that will hopefully cover much of the important stuff in nutrition. I will be basing the format on Mat Lalonde's lecture, explaining it, and adding to/modifying it where needed. We'll begin with the basics, going over the fundamentals of nutritional science, and next we'll get into two theories of nutrition: the fat hypothesis and the carbohydrate hypothesis. Let's get started!

THE BASICS - CARBOHYDRATES

There are two basic categories of nutrients: macronutrients, and micronutrients. Macronutrients are further categorized into carbohydrate, protein, and fat and are what our body derives energy from. Micronutrients are what we know as vitamins and minerals and do not supply any calories.
Essential nutrients are substances which are required by for normal body functioning, but which can not be synthesized by the body at all, or in sufficient amounts, and thus must be obtained from the diet. Essential nutrients include: vitamins, minerals, essential fatty acids, and essential amino acids. Oxygen and water are also required.
Non-essential nutrients are those that are not required to obtain through diet, but that may have significant impact on health status. Carbohydrates, dietary fiber, and phytochemicals fit into this category. There is no such thing as an essential carbohydrate, the body can synthesize carbohydrates as needed in the body through a process called gluconeogenesis(this will be discussed in a later post). Dietary fiber may be beneficial in the digestive process, and phytochemicals are being increasingly looked at for treating various ailments and for their other health benefits.
Carbohydrates are what we commonly refer to as sugars and are generally divided into 4 categories: Monosaccharides, Disaccharides, Oligosaccharides, and Polysaccharides.
A monosaccharide is a single isolated carbohydrate molecule, that is not linked to any other carbohydrate. They are often referred to as simple sugars. Examples include: glucose, fructose, galactose, xylose, and ribose. 
A disaccharide is two carbohydrate molecules linked by a glycosidic bond. Some common examples are sucrose(glucose+fructose; also known as table sugar), lactose (glucose+galactose; found in milk), and maltose (glucose+glucose; commonly formed when brewing alcohol).
Oligosaccharides generally contain anywhere from 3 to 9 carbohydrate molecules, though the exact number at which it should be called a polysaccharide really doesn’t matter. Oligosaccharides can only be partially digested by humans, and play a role in maintaining gut flora, which is why they are commonly used as prebiotics. The two common oligosaccharides used as prebiotics are: fructooligosaccharides (FOS) and inulin. FOS are found in various vegetables and fruits, but is found in highest concentrations in the Jerusalem artichoke. Inulin is found in many of the same plants as FOS, but is not found in fruit to a large extent.
Polysaccharides are chains of carbohydrate molecules composed of 10 or more monosaccharides. Common examples include storage forms such as starches and glycogen, as well as structural forms like cellulose (aka insoluble fiber). Starch is composed of long chains of glucose molecules, and are the found in all plants, albeit with radically varying degrees of carbohydrate density. Glycogen is the storage form of carbohydrate in animals, and is stored mainly in the liver and muscles, and to a very small extent, in the kidneys.

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