Wednesday, November 28, 2007
C is for Carbohydrate
The role of carbohydrates in human nutrition is to supply a readily accessible and quickly utilizable form of energy. They allow your body to spare its muscles (protein) from being broken down to supply the needed fuel. We may be complex creatures, but we run on the simplest of sugars, glucose. In fact, it is the only fuel our nervous systems and brain can use.
So let's start our foray into this topic with the simplest of the carbs - sugars. Sugars come in multiple forms: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. As you can tell from the prefixes, they are made of sugar molecules ranging from one (mono) to many thousands (poly). Sugars also have the suffix '-ose', which designates them as being part of the sugar family. {For those of you who are chemistry junkies, this is the site for you.}
Monosaccharides are single sugar molecules, as I've mentioned, and the most important of these is glucose (also called dextrose). It has the chemical structure [C6(H2O)6] and exists in a ring (cyclic) formation. But there are other monosaccharides besides glucose such as fructose, xylose, galactose, and ribose.
Disaccharides are, as their name suggests, sugars comprised of two monosaccharides. They occur when the two monosaccharides join together and kick out a water (H2O) molecule in a dehydration reaction forming a glycosidic bond. Different combinations of monosaccharides come together to form different disaccharides. Glucose + Fructose = Sucrose (what we call table sugar), Glucose + Galactose = Lactose (milk sugar), and Glucose + Glucose = Maltose (malt sugar).
Oligosaccharides are sugars comprised of 4 to 8 monosaccharides (oligo means few) and are known as simple sugars. The most common are fructo-oligosaccharides which occur in vegetables (like asparagus & onions) and are short chains of fructose molecules. They are of particular interest these days because of research that proves they enhance the growth of beneficial gut bacteria - this is called a prebiotic effect. Because of this, food scientists are finding new applications where they can add oligosaccharides.
And lastly, polysaccharides are long chains (100+) of monosaccharides. Typically they are insoluble in water and are not sweet. You know some of them as starches and cellulose. There is also one which you may not be as familiar with (yet) called inulin. And like a fructo-oligosaccharide, has a prebiotic effect that aids in digestive health. Inulin belongs to a category of carbs called fructans. {For more information on inulin: click here}
So to recap - carbohydrates are the fuel our bodies run on. Sugars are the simplest forms and as you add on molecules, they become strings and those strings become chains, which makes them less soluble and less sweet. In the next post I will continue to discuss this category of carbohydrates and some of their individual details. Until next time - Stay sweet!
Friday, November 16, 2007
Talking Turkey
Monday, November 12, 2007
What's My Function?
Tuesday, November 6, 2007
A Perfect Score
Bioavailability - the degree to which a substance can be digested and utilized by the body in the amount and form in which it is present.
% Biological Value (% BV) - the proportion of absorbed protein (Nitrogen balance) that is retained in the body for maintenance and/or growth.
Casein (milk protein) = 85% Whey Protein Isolate = 98% Soy Protein Isolate = 80%
Rice Protein = 64% Whey Protein Concentrate = 95% Whole Egg = 100%
Net Protein Utilization (NPU) - the proportion of protein intake that is retained; a completely digested protein would have an equal %BV and NPU value.
Casein = 76 Whey Protein Isolate = 92 Soy Protein Isolate = 61
Rice Protein = NA Whey Protein Concentrate = 93 Whole Egg = 94
Protein Efficiency Ratio (PER) - based on the weight gain of a growing test animal (rat) divided by its protein intake over a study period (usually 10 days).
Casein = 2.9 Whey Protein Isolate = 3.5 Soy Protein Isolate = 2.1
Rice Protein = 1.3 Whey Protein Concentrate = 3.0 Whole Egg = 3.8
Protein Digestibility Corrected Amino Acid Score (PDCAAS) - a method of comparing protein quality based on the amino acid requirements of humans (a score of 1.0 = a complete protein, i.e. 100% of the essential amino acids after digestion).
Casein = 1.23 Whey Protein Isolate = 1.14 Soy Protein Isolate = 0.92
Rice Protein = 0.55 Whey Protein Concentrate = 1.0 Whole Egg = 1.19
So, does anyone really pay attention to these values? A few do, (body builders, olympic atheletes) but most of us don't. Does this have any practical applications? Can you use this info? Well sure. If you happen to like protein bars, you can use this information when looking at the nutrition panel to determine the quality of the proteins it contains. If you are a vegetarian/vegan, you can use this information to make sure you are getting a complete compliment of proteins in each meal so your body doesn't feed on itself. And you can impress people at the gym with your newly acquired expertise on this topic! Ok, maybe that's just me.
So, what's next you ask? Well, you know what a protein is and you know how to judge their quality, so how about what it is they do in the food products you purchase? In my line of work we are far more concerned with the properties different proteins exhibit and I will tell you all about it in my next post.