Carbohydrates 101: Why Not All Starches are Created Equal, Part Four
My goodness! Can you believe how complex carbohydrates are?! (note to self: must work on corny nutrition jokes) But seriously, we now understand the basics of carbohydrates, that food labels are our saving grace when selecting not only breads but all foods, and oligosaccharides are truly the bomb. In this next section we will discuss why not all starches are created equal and how you can change your health by selecting the right carbs!
What are Complex Carbohydrates (AKA Starches)?
As previously discussed, starches are the most common digestible polysaccharide (long complex chains of simple sugars) in plants. It is the major glycemic carbohydrate in foods; meaning that the type of polysaccharide will determine the amount of glucose in the blood post consumption. Its nutritional property is related to its rate and extent of digestion and absorption in the small intestine.
Naturally, starch contains amylose and amylopectin. Starches that are relatively high in amylose content tend to be more resistant to digestion than starches with higher amylopectin content. So considering this, starches can be broken down into three categories:
- Rapidly digestible starch (RDS)-It is digested and absorbed in small intestine leading to a rapid elevation of blood sugar. RDS have a high glycemic index and have the tendency for subsequent episodes of hypoglycemia (low blood glucose and therefore the urge to eat again). Food types include:
- White Potatoes, cooked
- Instant Rice, cooked
- Corn Flakes
- Some fruits are considered high glycemic foods, but when looking at their glycemic load they are low. (refer to glycemic index post)
- Slowly digestible starch (SDS)- It is much more cumbersome to breakdown in the small intestines, and it can take up two hours before the starch is broken down into its smaller sugar units. SDS have a lower glycemic index. Food types include:
- Barley, cooked
- Bulgar wheat, cooked
- Brown Rice, cooked
- Quinoa, cooked
- Resistant starches (RS)- It is not digested in the small intestine but is fermented by bacteria in the colon. This can produce short chain fatty acids, like butyrate, that are beneficial to colon health. Food types include:
- Banana, raw, slightly green
- Oats, rolled (uncooked)
- White Beans (cooked)
- Green Peas, frozen (cooked)
- Lentils (cooked)
- Cold Potato (uncooked)
- Oatmeal (cooked)
Why Knowing your Starches Can Save Your Life:
The rising prevalence of obesity, not only in adults but also in kids and teenagers, is one of the most important public health problems in the United States. Two-thirds of Americans and an estimated 2.3 billion people worldwide are either overweight (BMI 25-29.9 kg/m2) or obese (≥ 30 kg/m2). If those statistics don’t startle you then maybe these from the CDC will…
- Childhood obesity has more than doubled in children and quadrupled in adolescents in the past 30 years.
- The percentage of children aged 6–11 years in the United States who were obese increased from 7% in 1980 to nearly 18% in 2012. Similarly, the percentage of adolescents aged 12–19 years who were obese increased from 5% to nearly 21% over the same period.
- In 2012, more than one third of children and adolescents were overweight or obese.
A recent review article published in Nutrients (2011), addressed this concern. They looked at the relationship between different types of dietary carbohydrates and appetite regulation, body weight, and body composition throughout the scientific literature. They found that intake of starchy foods, especially those containing slowly-digestible and resistant starches are beneficial to maintain body weight, regulate appetite, and lower the insulin response. Whereas, rapidly digestible carbohydrates pose potential detrimental effects on the body. This research supports the intake of whole grains, legumes, andvegetables.
When you’re shopping for any whole-grain product, look at the ingredient label and make sure the whole grain is at or near the top of the list. Each serving should contain at least 2 or 3 grams of fiber. Once again make sure the label says “100 percent whole wheat”, “whole oats”, or “whole-grain barley”. Terms like “multigrain” and “wheat” just don’t cut it. Watch out for additives, enriched flour, degerminated (in cornmeal), bran, wheat germ, or added salt!
Figure 1: Carbohydrate classification and their main role after meal consumption. Please refer to reference #1 for the original article.
- Aller, EEJG., Abete, I, Astrip, A, Martinez, JA, and van Baak, MA. Starches, Sugars and Obesity. Nutrients. 2001: 3, 341-369.
- Ogden CL, Carroll MD, Kit BK, Flegal KM. Prevalence of childhood and adult obesity in the United States, 2011-2012. Journal of the American Medical Association 2014;311(8):806-814.
- National Center for Health Statistics. Health, United States, 2011: With Special Features on Socioeconomic Status and Health. Hyattsville, MD; U.S. Department of Health and Human Services; 2012.
- Zeng H, Lazarova DL. Obesity-related colon cancer: dietary factors and their mechanisms of anticancer action. Clinical and Experimental Pharmacology and Physiology. 2011:1-20.