Development and validation of a food frequency questionnaire for Japanese athletes (FFQJA)

Table 1 Number of selected items and the cumulative contribution to total nutrient intake from selected food items

	Number of items contributing up to 90% cumulative contribution*	Stepwise multiple regression analysis
		Number of items explaining more than 90% of variance*²	Cumulative R² for 66 items*³	Cumulative R² for 62 items*⁴
Energy	36	12	0.990	0.980
Protein	29	12	0.995	0.955
Fat	22	11	0.988	0.982
Carbohydrate	29	9	0.990	0.980
Calcium (Ca)	34	16	0.992	0.943
Iron (Fe)	39	19	0.979	0.867
Retinol*⁵	17	3	0.999	0.998
Vitamin B₁	28	3	0.998	0.450
Vitamin B₂	30	6	0.991	0.665
Vitamin C	16	3	0.999	0.942
Dietary fiber	27	16	0.975	0.849

*Number of food items to reach cumulative percentage contribution of 90% from 103 foods/food groups
*² Number of food items selected by stepwise multiple regression analysis explaining more than 90% of variance from 103 foods/food groups
*³ 66 items were all foods/food groups selected by contribution to 90% cumulative contribution and multiple regression analysis, excluding sugar, sauces, soy sauce, stock, and other seasonings (sweet sake, ketchup, and spices), and including nuts, honey or maple syrup, bread stuffed with meat or vegetables, sponge cake or steamed bread, rice crackers, chips, and alcoholic drinks
*⁴ 62 items were only basic items asked about in the food frequency questionnaire. Supplements, minor cereals, sesame, and soymilk were excluded from the list of 66 items
*⁵ Retinol was calculated as retinol activity equivalents

ISSN: 1550-2783