Diets high in carbohydrate calories increase the risks for obesity, high blood pressure, heart disease, and even cancer.
Many of the health risks are related to the ease with which a carbohydrate is digested and absorbed. This is reflected in a food’s glycemic index - the higher the glycemic index, the more rapid the rise in the blood sugar after eating.
All carbohydrates are built up from single sugar molecules. Simple carbohydrates (table sugar for example) is composed of just two single sugar molecules (one glucose and one fructose). Complex carbohydrates are made from longer chains of multiple sugar molecules.
To be absorbed from the small intestine, all carbohydrates must first be broken down (digested) into single sugar molecules. Some complex carbohydrates are easily digested (wheat flour for instance) while others are not (fruit and vegetable fiber).
A food’s glycemic index is higher if it contains processed carbohydrates. In processed grains the outer bran and inner germ layer (which tend to bind its sugar molecules and retard their absorption) are removed from the original kernel of grain. The result? A more rapid spike in blood sugar levels than after eating a less-processed grain.
Table sugar is easily digested, readily absorbed into the bloodstream has a high glycemic index. As a result, these carbohydrate molecules are often absorbed faster than they can be used in normal metabolism. The excess are converted into fat (triglycerides) and stored for future needs. This fat is the most likely culprit behind the health risks of high carbohydrate diets.
Another negative aspect to high glycemic foods is their potential to cause “reactive hypoglycemia” (low blood sugar). The rapid spike in blood sugar levels immediately after eating stimulates the release of insulin from the pancreas. Insulin is needed to move blood sugar into many tissues. But the sugar from these foods is so quickly and efficiently absorbed that the insulin is often still working when there is no more sugar being absorbed. This leads to an equally sudden drop in blood glucose levels and symptoms of fatigue and hunger.
Complex carbohydrates or starches are more slowly broken down by digestive enzymes and in turn more slowly absorbed. The rate of rise of the blood sugar after eating starches is less (their glycemic index is lower) and is spread over a longer period of time. The blood sugar spike is less severe, less insulin is released, sugar calories are absorbed over a longer period of time, and the body now has more time to use them as part of normal metabolism. As a result hypoglycemia is less of a problem.
Fiber is also a complex carbohydrate, but the sugar molecules are linked in a way that resists digestion. As a result they pass relatively unchanged into the colon. Fiber has a glycemic index of zero.
This poor absorption explains fiber’s health benefits. Once it reaches the colon, resident bacteria (the microbiome) which have the enzymes necessary to digest it, produce numerous small molecules in the process which can be absorbed and have proven health benefits.
The following are a few ideas and conclusions to improve your (and your family’s) daily diet.
First, limit your daily carbohydrate calories to no more than 50% of the daily total daily. The only exception is for those on a regular exercise program. As active muscles use glucose directly as fuel, any carbohydrate drinks and snacks that replace these exercise calories can be added to your daily total.
Second, minimize simple sugars. Get rid of the sugar bowl on the table, take pre sweetened cereals and sugar-ed drinks out of the cupboard, and limit processed food which are often high in added sugars.
Finally, take advantage of the health benefits of more slowly absorbed complex carbohydrates. Have an extra serving of vegetables instead of a piece of bread or a double serving of potatoes.
And for an added health bonus, add a tablespoon of minimally digested flax fiber to your morning routine to keep the microbiome healthy.
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Notes:
- The physical form of a carbohydrate affects glycemic index - wheat in Spaghetti vs wheat in bread. https://nutritionfacts.org/video/which-is-a-better-breakfast-cereal-or-oatmeal/
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