What is the "glycemic index"?
Humans have a great many "feedback" mechanisms to keep our bodies functioning normally (e.g. to maintain temperature). Among those systems is the glucose-insulin feedback loop. When you eat, your digestive system eventually puts increased glucose in the bloodstream. Glucose is the fuel that runs the body, much like gasoline in a car. But, like a car, the fuel doesn’t "automatically" go into the cylinders from the gas tank, rather a precise set of operations result in the fuel injector injecting the fuel just when you want it to. You can drive a car without knowing anything about how that system works, just like you can practice CR without knowing anything about how it works! This material is a bit complicated, but I'll make it as clear as possible.
Imagine the impact of a lifetime of rapid starts and stops on your car--you are putting more total gasoline into the car and you are damaging your car in the process...it's "lifespan" will be shorter. Similarly, putting high glycemic index carbohydrates into you puts more total glucose into your system over your lifetime. It turns out that some of that glucose forms "cross-links" with proteins (called "non-enzymatic glycosylation") and that those cross-links are a prime cause of everything we think of when we think of "old people" (wrinkles, "liver" spots, stiffness, progressive stiffening of the arteries, etc.). Hence, putting more glucose into your body, results in more rapid aging other things equal (some people have genetic advantages, of course). So, you want to eat mostly low glycemic index foods.
The following is somewhat controversial, and some on-going research may soon clarify some things. The second reason many prefer low-glycemic index foods, is the relationship between glucose and insulin. As with the car, glucose doesn’t "automatically" go into the cells that use it for fuel, but rather the cells must be "opened" to enable the glucose to enter. When the feedback mechanisms of the body sense that glucose is elevated after a meal, a series of hormonal commands have the practical effect of increasing insulin in the bloodstream. It is insulin that enables the glucose to go into the various cells (muscle, fat, etc.) in the body. Insulin is, then, absolutely critical to the functioning of the body. But, with aging (and with excessive glucose intake, as CRers believe), the body gets progressively more resistant to the insulin—to do its job more insulin must be pumped out. The role of excess insulin in "causing" Type II diabetes is controversial, but some believe that too much insulin over long periods is a really bad thing. Excess insulin (hyperinsulinemia) is argued to increase body fat, mess with the balance of other hormones causing blood pressure to rise, reduce HDL (the good cholesterol), increase total cholesterol, etc. Perhaps, one of the reasons why CR extends lifespan, then, is by reducing lifetime exposure to insulin. This is all background for the "glycemic index" of foods, to which we turn.
The glycemic index is a measure, where either white bread or pure glucose is used as a reference point, of how rapidly and how much particular foods raise glucose in the body after being eaten (technically, it's the integral under the glucose concentration curve). In the context of the previous discussion, the glucose spike of a high-glycemic food will in turn create an insulin spike during which extra-normal amounts of insulin are produced (though the relationship between glucose and insulin is poorly understood, hence this is somewhat speculative). This exacerbates the problems discussed in the preceding paragraph. You may or may not feel hungry again sooner, but that is a common folk belief (e.g. hungry two hours later after Chinese food, due to the rice, if true). The "whites" (eating plain potato, white bread, or "sticky" forms of rice is almost exactly like eating pure sugar from a glucose creation perspective) and sugars already discussed tend to have high glycemic indexes (as do carrots and corn, interestingly). The glycemic index of the average of the food in the stomach determines the overall glucose spike to expect (hence, carrots and corn can go into a healthy stir-fry with lots of other vegetables, since that ameliorates their individual effects).
Eat a diet closer to what Hunter - Gatherers ate...
Curtail the "whites" (most bread, potatoes, pasta, and rice), since they don’t deliver very much nutrition per calorie, and they often have very high glycemic indexes--result in excessive insulin production, ultimately in insulin resistance and adult-onset diabetes. If you must eat grains, eat whole grains--for their better fiber, mineral, anti-oxidant, anti-cancer and cholesterol reduction benefits.
Curtail the desserts and the snacks (pies, cakes, candy, potato chips, pretzels, etc.) for they deliver almost no nutrition per calorie. Increase fruits (especially berries, like blueberries, blackberries, or strawberries) to fully or partly substitute for the desserts. Substitute tea (discourages stroke, heart attack, cancer, and neurological damage) for empty-calorie sodas.
Increase fish consumption, especially high omega-3 oil varieties (cold-water fish like tuna, salmon, etc. Eat more tree nuts, especially walnuts and almonds to replace fatty meats)
Increase vegetables of almost any type, the more variety the better, by as much as you need to enable you to feel full at the end of a meal.
The Ideal Diet...
What fats should I eat...
Information provided above was from an article called Some Non-Original Thoughts on Diet, Health, and Longevity, by Phil Graves
CW
Christopher Wiechert's Healthblogger is for educational or informational purposes only, and is not intended to diagnose or provide treatment for any condition. If you have any concerns about your own health, you should always consult with a healthcare professional.
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