Sincerely, Joshua M. Yelon
Spring B, Chiodo J, Harden M, Bourgeois MJ, Mason JD, Lutherer L. Department of Psychology, UHS, Chicago Medical School, IL 60064.
J Clin Psychiatry 1989 May;50 Suppl:27-33
The authors studied whether the fatiguing effects of eating lunch are greater for carbohydrate-rich meals than for other meals, and related the time course of behavioral change to plasma glucose, insulin, and amino acids. On different occasions, in counterbalanced order, normal women (N = 7) fasted overnight, ate a standard breakfast, and at lunch either continued to fast or ate a high-carbohydrate, low-protein meal; a hedonically similar meal containing both carbohydrate and protein; or a high-protein, low-carbohydrate meal. Meals were isocaloric and equated for fat content. Only the carbohydrate meal significantly increased fatigue, which could not be attributed to hypoglycemia because plasma glucose remained elevated. Fatigue began approximately, when the carbohydrate meal elevated the plasma tryptophan ratio but ended even though the ratio remained elevated. Fatigue after a high-carbohydrate lunch could not be explained by reactive hypoglycemia or sweet taste, and could partially be explained by the hypothesis that fatigue parallels an elevation of the tryptophan ratio.
Comments: It's already known that big meals loaded with carbs make you sleepy. They wanted to know why. They figured that maybe the meal would mess with your blood sugar, and when the blood sugar dropped, you'd be ``low on fuel'', making you tired. That turned out not to be the case. Instead, when they were checking the people's blood, they found a rise in the amount of tryptophan in the blood --- tryptophan is a tranquilizer. So, in all likelihood, carb-rich meals make you tired because they create the tranquilizer tryptophan. That's all it says. Now, I'm going to add one conclusion of my own. You can get addicted to most tranquilizers. So, it seems inevitable that you can get addicted to carbs. When addicted people are stressed out, they reach for the valium, the miltowns... and maybe the carbs?
White PJ, Cybulski KA, Primus R, Johnson DF, Collier GH, Wagner GC. Rutgers, State University of New Jersey, New Brunswick 08903.
Physiol Behav 1988;43(1):73-77
It has been hypothesized that the serotonergic system is involved in the regulation of carbohydrate and/or protein intake. Tests of this hypothesis using added dietary tryptophan and diets varying in the ratio of carbohydrate/protein resulted in depressed intakes of high carbohydrate/low protein diets, elevated intakes of low carbohydrate/high protein diets, and a reduction of total caloric intake. The present studies gave rats increased options for adjusting to added tryptophan by providing them with separate sources of protein, carbohydrate, and fat. The results showed the expected decrease in carbohydrate intake, but also increases in fat intake and, to a lesser extent, protein intake. Total caloric intake was conserved. Hypothalamic concentrations of serotonin and 5-hydroxyindole acetic acid indicated increased activity of the serotonergic system. These results lend support to serotonin's involvement in nutrient selection, in that carbohydrate consumption decreased in response to tryptophan loading, but indicate that other nutrients may also be affected. Given the option of altering fat intake, the animals maintained a constant caloric intake despite the reduction of carbohydrate consumption.
Comments: They gave some rats a bowl of carbs, a bowl of fat, and a bowl of protein. The rats headed straight for the bowl of carbs. Then, they gave the rats some tryptophan, which is a tranquilizer. After the tryptophan, the rats changed their minds: they moved over to the fat and protein bowls. They didn't eat any faster, they just changed their minds about which bowl they liked. That's all it says. Now, I'm going to add some opinions of my own. Remember that carbs are a tranquilizer. (See the other articles on this subject). Maybe the rats are stressed (heck, they're in a cage), and they want to relax. So they go grab some carbs. But, if you give 'em tryptophan first, they become really relaxed, they don't feel stressed anymore, and they don't want another tranquilizer. Could be?
Fullerton DT, Getto CJ, Swift WJ, Carlson IH
Brain Res Bull 1985 Jun;14(6):673-680
There is evidence that endogenous opiates are involved in the control of feeding in experimental animals. Several types of experimental obesity are associated with increased opiate production and/or increased numbers and sensitivity of opiate receptors. Research with experimental animals suggests that nutrients, particularly sugar, have an effect on feeding behavior that is mediated by opiates. For instance, the obesity-producing effect of a palatable diet in rodents is blocked by opiate antagonists. Stress induced feeding in rodents leads to preferential sucrose ingestion and is blocked by opiate antagonists and beta-endorphin. The effect of nutrients on the endogenous opiate system of humans is less clear. Clinical experience suggest that carbohydrates (sugar in particular) play a role in binge eating and obesity. Many binge eaters preferentially eat sweets during a binge. Many obese individuals consume more than half of their total daily calories as carbohydrates. Sweet snacking is a frequent behavior at times of stress. Recent evidence suggests that sugar can lead to increased beta-endorphin production in obese subjects.
Comments: (I'm going to take some liberties with this one). Sugar makes your brain release beta endorphin, a chemical with effects like valium. When people are under stress, they binge on carbs, especially sugar. One might speculate that this is essentially the same thing as taking valium for stress, except it makes you fat too. Rats do the same thing: when under stress, rats choose carbs, especially sugar. If you give the rats opium, they lose interest in the carbs. One might speculate that they've already got their opium fix for the day, and aren't interested in taking more.