CARBOHYDRATE AND THE GLYCEMIC INDEX
Biologic Importance
This class of foodstuffs, whether starch or table sugar, has the common
physiologic property of being digested or converted to glucose. Reduced
availability is seldom selective to the extent as with protein. Rather,
therefore, the focus is in the opposite direction. In this context, epidemi-
ologic studies have shown that fat intake has decreased from 42% to
about 34% over the last three decades. Even so, overweight has increased
in children and adults, suggesting that other dietary factors may have an
equally important role in body weight regulation.
1
Central to this latter
disturbance is the concept of the glycemic index, which shifts the focus
on digestion rate away simply from saccharide chain length to a
classification based on handling of isoenergetic consumption, in terms of
the incremental area under the response curve. Here the type, dietary
composition, structure, and method of preparation are all integrated with
metabolic events to explain and provide a mechanism for preventing and
treating overweight, diabetes, and cardiovascular disease.
2
Thus the
hypothesis that a calorie is not a calorie requires rethinking, and has
practical relevance in that the optimum amount of ingested carbohydrate
designed to lower insulin response, improve access to stored fuels,
decrease hunger, and promote weight loss is found when abundant
quantities of vegetables, fruits, and legumes counterbalance moderate
amounts of meat and less refined grain products, potato, and concentrated
sugar. Pragmatically, one cannot help but recognize the close resem-
blance of this recommendation to what was consumed by our human
ancestors over the last several thousand years. Neither is this understand-
ing irrelevant in contemporary considerations of wasting. Thus, when the
nonendocrine disorders are excluded, profound hypercatabolism is seen,
with sepsis, cancer, and, of major consideration, in chronic inflammatory
processes, such as acquired human immune deficiency syndrome. Energy
wasting is explained with inappropriate use of substrates, their futile
cycling, and uncoupling of enzymatic events, with the interesting obser-
vation that these are pathophysiologic epiphenomenon rather than cause
in such clinical prototypes, and anorexia has a different explanation from
critical reduction in supply.
3
It would be invidious in considering this
Dis Mon 2004;50:107-113.
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doi:10.1016/j.disamonth.2004.02.011
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