To account for differences in serving size, we used the standard of 50 g for each product as 1 serving. We used 50 g (about 1.7 oz) to help compare the different foods and between foods within the same group. Additionally, 50 g is close to 1 serving for most foods in these groups; it is about the size of a typical granola bar, three-quarters to 2 cups of cereal, 10 to 12 crackers, and 15 to 25 chips. We determined the GL for each product by multiplying the number of available carbohydrates (total carbohydrate – dietary fiber) by the product’s glycemic index/100. In general, GL is categorized as low (≤ 10), medium (11-19), or high (≥ 20).
We applied the Altman Rule to categorize each product as meeting or not meeting the rule. We compared the proportion of foods meeting the Altman Rule, stratified by GL and by specific foods, and used chi-square to determine if differences were statistically significant. These data were collected and analyzed in the summer of 2019.
RESULTS
There were 1235 foods (342 breakfast cereals, 305 chips, 379 crackers, and 209 granola bars) used for this analysis. There is a significant relationship between the GL of foods and the Altman Rule in that most low-GL (68%), almost half of medium-GL (48%), and only a few high-GL foods (7%) met the rule (P < .001) (TABLE 1). There was also a significant relationship between “meeting the Altman Rule” and GL within each food type (P < .001) (TABLE 2).
The medium-GL foods were the second largest category of foods we calculated; thus we further broke them into binary categories of low-medium GL (values 11-14) and high-medium GL (values 15-19) to explore the results of the Altman Rule. About half of the foods in medium-GL category met the Altman Rule. About eighty-five percent of the foods with low-medium GL passed the Altman Rule, while only 39% of the foods with high-medium GL did.
Foods that met the rule were more likely to be low GL and foods that did not pass the rule were more likely high GL. Within the medium-GL category, foods that met the rule were more likely to be low-medium GL.
Continue to: The findings within food categories...