Sunday, September 27, 2009

GI Tractate

This is just some basic stuff. The glycemic index tells how fast a given food turns into bloodsugar, on a scale of 0 to 100. Lower is slower, which is better. It's like octane for fuel. Higher is hotter. The raw score however doesn't tell us much of practical value. How much after all of the food, or fuel, do we have? No info. GI tells you about how fast a carb turns into bloodsugar, whether a gram or a pound, not about how much of that carb -- how many calories -- you've eaten.

So the practical approach involves glycemic load, which calculates the bloodsugar effect of a carb serving you actually might use. Honey, for example, has a fairly low glycemic index, but if you eat a bowl of it, not so much -- the load would be very high indeed. The index is an unchanged absolute, a constant; the load varies with appetite. Glycemic load then takes into account serving sizes, the same way gallons count when we talk about fuel. In thinking about miles per gallon, both miles and gallons matter. Each GL point corresponds to the body's response to one gram of glucose. A typical diet includes about a hundred GL points each day, ranging between 60 and 180. Lower is better. A score under 10 is low, between 10 and 20 is moderate, and over 20 is high, bad.

Spaghetti has a GL value of 21 (GI of about 50). Brown rice 16 (≈ 70), white rice 30 (≈ 75). You can see that rice white or brown looks pretty much the same from a GI POV, but it's twice as bad in its actual effect, for amounts you are likely to eat. A "serving." Carrots, grapes, 7 (and both about 45). A donut, 17 (≈ 75). Do you eat just one donut? Three donuts is a GL of 50, and the GI is still 17.

Raisins 28 (≈ 65). Strawberries 1 (≈ 40). Brocolli, califlower, peppers, nuts -- zero.

Here is an index for GL values. This is a site that gives GI values. This is a site that lists too many values for GI and GL. Just more foods than I've ever even heard of. This is that same info, in spreadsheet form. I don't know nothing about no spreadsheet, but some people seem to think it's useful. They're crazy of course, but it takes a village. Which reminds me that somewhere in Kenya, a village is missing its idiot.


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