Fast Glycemic Facts: The Second Meal Effect

April 21, 2007 in breakfast, diabetes, Fast Glycemic Facts, Food Science, low glycemic index


(Glucose: Wikipedia source – public domain)

If you choose to read The Glycemic Index site, you may briefly run across something called the [tag]Second Meal Effect[/tag] (SME).

As I understand it and in short, if one eats a low [tag]GI[/tag] food at one meal, there is a carry over effect to the next meal in terms of “buffering” the impact of eating [tag]sugar[/tag] during that second meal.

This has actually been known for some time. In 1982, Jenkins, Wolever, and Taylor reported this in their seminal [tag]paper[/tag] “Slow release dietary carbohydrate improves second meal tolerance” (Jenkins et al. Am J Clin Nutr 1982 35:1339–46).

This phenomenon was further explored in 1988, in a study in the American Journal of Clinical Nutrition found that eating a [tag]low GI[/tag] [tag]meal[/tag] (even mixed with other higher GI foods) at dinner improved [tag]carbohydrate[/tag] “tolerance” at the following breakfast.

“We conclude that the difference between the [tag]glycemic response[/tag]s of mixed meals at dinner can be predicted from the GI of the individual foods consumed. In addition, breakfast carbohydrate tolerance is improved when low-GI carbohydrate foods are eaten the previous evening. This provides evidence for a sustained metabolic effect of slowing the absorption of carbohydrate.” Second-meal effect: low-glycemic-index foods eaten at dinner improve subsequent breakfast glycemic response.” Second-meal effect: low-glycemic-index foods eaten at dinner improve subsequent breakfast glycemic response Wolever TWS., et al. Am J Clin Nutr 1988 48: 1041-7.”

The [tag]mechanism[/tag] for that effect has not been well understood until recently, when in 2006 Brighenti et al found:

“In conclusion, our results show that [tag]fermentable carbohydrates[/tag], independent of their effect on food GI, have the potential to improve [tag]postprandial[/tag] responses to a second meal by decreasing NEFA ([tag]nonesterified fatty acids[/tag]) competition for [tag]glucose disposal[/tag] and, to a minor extent, by affecting [tag]intestinal motility[/tag]. The potential of fermentable carbohydrates in the management of [tag]metabolic disorder[/tag]s linked to [tag]insulin resistance[/tag] may warrant further study.” Colonic fermentation of indigestible carbohydrates contributes to the second-meal effect. Brighenti et al Am J Clin Nutr 2006 83 (4): 817-822.”

This is great news because it tells us that fermentable carbohydrates, whether low, medium, or high GI, have the ability to support a better insulin response in those experiencing insulin resistance.

An apple a day …

What are “fermentable carbohydrates”? Foods that contain high-amylose starch are “slowly digested, some … starch would escape small-intestine digestion and be fermented in the colon.” (Ibid) Things like apples, broccoli, other fiber rich foods.

Its the fermentation in the colon that is important. Fiber that just goes right through you will not have this effect. The starch needs to be digested in the colon and thus some time AFTER the meal has been eaten, resulting in a longer period of sugar delivery and the minimization of a spike in [tag]blood sugar[/tag].

There are likely other effects, other mechanisms, that are yet to be discovered.

References used: