From the article: "...the grain figure doesn't even include the two hundred pounds of potatoes Americans ate every year in the early 20th century."
Table 4 of the original report gives more detailed numbers. In the period 1909-1919, grains, potatoes and sweeteners together contributed 54.4% of American calories. In 2004, it was down to 43%.
In terms of GI, the Glycemic Index, sure they are. However, the more important measure it GL, the Glycemic Load, which is basically the GI multiplied with the average amount.
For example, even though a cherry has much higher GI than a potato, you eat more sugar/carbohydrates in one potato than in one cherry, so a potato has higher GL and thus higher insulin response.
How many people would think to compare a single cherry to a single potato though? Most people would think in terms of roughly equal mass (x grams of cherries vs. y grams of potatoes where x is approx. y).
A potato is basically sugar, as far as digestion is concerned.
The "complex carb" and glycemic index thing is pretty well nonsense. A carb is a carb. The only question is whether you have a properly functioning metabolism and insulin sensitivity. They call a screwed up insulin sensitivity "metabolic syndrome". If you've developed one, typically through many years of poor eating, you need to cut out starch, because your fat cells and pancreas can't handle it properly. If you're thin, well then the glycemic index thing is useless. Your pancreas and fat cells work fine.
A carb is a not a carb. Sucrose is composed of equal parts glucose and fructose, while starch is pure glucose. Fructose and glucose are two different 'carbs' and handled much differently by the body.
You posted my exact reaction. Having read Gary Taubes' book and seen film interviews with him on the subject, I don't once recall him focusing solely on grains.
