Repeatability and relative validity of a quantitative food-frequency questionnaire among French adults

Figures & data

Table 1. Food items, categorized into major food categories, included in the food frequency questionnaire

Major food categories	Food items
Fruit and vegetables	Raw vegetables
	Cooked vegetables
	Dried fruits
	Fruits
Proteins	Red meats
	White meats
	High-fat delicatessen, e.g. foie gras
	Low-fat delicatessen, e.g. ham
	Offal
	Eggs
	Fatty fish
	Semi fatty fish
	Lean fish
	Seafood
Cereals, grains, and potatoes	Bread (mostly white)
	Bread (mostly whole grain)
	Beans and other pulses
	Cereals, pasta, and rice
	Cold breakfast cereals
	Potatoes
Dairy	Cheese
	Creamy desserts and ice creams
	Other dairy products
	Soya milk
Oils and fat	Butter
	Margarine
	Sour cream
	Sunflower seed oil
	Colza oil
	Olive oil
	Corn oil
	Grape seed oil
	Groundnut oil
	Oil blend rich in omega 3
	Soya oil
	Walnut oil
Prepared foods	Cooked dishes
	French fries
	Fried & reconstituted products
	Pizza and other savory tarts
Beverages	Wine
	Other alcoholic beverages
	Coffee and tea
	Water
	Sugar sweetened beverages
Sugary foods	Chocolate
	Jam, marmalade, and honey
	Cakes and pastries
	Sugar
Condiments	Salt

Table 2. Age^§, body mass index (BMI)^§, gender, and place of residence of the subjects included in the repeatability and validation study

	Repeatability (n=54)	Validation (n=100)
Age (year)	37.1 (14.0)	37.5 (13.9)
BMI (kg/m2)	23.0 (3.5)	22.8 (3.1)
Gender (%)
Men	24	29
Women	76	71
Place of residence (%)
North-West	4	88
South-West	88	5
East	8	7

^§Expressed as mean (SD).

Table 3. Repeatability of the food frequency questionnaire (FFQ) shown by mean (SD) daily estimates of nutrients and Pearson correlation between the crude and energy-adjusted estimations derived from the first and second FFQs (n=54)

	Daily intakes			Pearson correlation coefficient
	FFQ1	FFQ2	FFQ2 (% FFQ1)	Crude	Energy-adjusted
Energy, kcal^$	1,814 (497)	1,721 (526)*	95	0.78	–
Protein, g	80.3 (24.4)	78.9 (27.6)	98	0.80	0.79
Carbohydrate, g	189 (53)	171 (55)*	91	0.67	0.70
Fat, g	77.9 (30.9)	76.4 (33.8)	98	0.81	0.71
MUFA, g	31.6 (14.7)	31.8 (17.0)	101	0.78	0.74
PUFA, g^§	12.2 (7.1)	12.3 (8.3)	101	0.84	0.76
SFA, g	27.3 (10.7)	25.8 (11.2)	95	0.83	0.67
Cholesterol, mg	261 (116)	265 (122)	101	0.87	0.85
Fiber, g	22.1 (7.0)	19.4 (7.1)*	88	0.62	0.59
Vitamin A, µg^§	417 (368)	421 (416)	101	0.86	0.76
Thiamine, mg^§	1.3 (0.4)	1.3 (0.5)	96	0.77	0.77
Riboflavin, mg^§	1.9 (0.8)	1.7 (0.8)*	93	0.89	0.87
Niacin, mg^§	18.8 (6.6)	18.6 (7.6)	99	0.82	0.79
Pantothenic acid, mg^§	6.0 (2.2)	5.6 (2.2)*	93	0.86	0.83
Pyridoxine, mg	2.0 (0.7)	1.9 (0.7)	95	0.85	0.83
Folic acid, µg	357 (122)	316 (115)*	88	0.77	0.78
Cobalamin, µg^§	5.1 (3.1)	5.2 (3.5)	103	0.90	0.89
Vitamin C, mg	165 (71.2)	140 (59.6)*	85	0.67	0.68
Vitamin D, µg^§	2.8 (1.9)	3.1 (2.5)	111	0.80	0.68
Vitamin E, mg^§	12.7 (6.8)	11.9 (7.0)	94	0.83	0.79
Calcium, mg^§	710 (319)	648 (345)*	91	0.83	0.80
Iron, mg	13.5 (4.2)	12.6 (4.3)*	93	0.84	0.83
Magnesium, mg	278 (78.7)	255 (80.9)*	92	0.80	0.80
Zinc, mg	10.1 (3.1)	9.6 (3.1)	95	0.80	0.79
Selenium, µg	51.6 (20.2)	52.3 (23.8)	101	0.85	0.84
Phosphorus, mg	1,222 (366)	1,175 (407)	96	0.82	0.80
Manganese, mg	3.4 (1.0)	2.9 (1.1)*	86	0.72	0.72
Potassium, mg	3,046 (894)	2,812 (897)*	92	0.74	0.73
Iodine, µg	111 (44)	107 (49)	96	0.81	0.76
Copper, mg^§	1.6 (0.7)	1.4 (0.7)*	89	0.85	0.84
Sodium, mg	2,342 (722)	2,230 (709)	95	0.68	0.67

^$Daily intakes are expressed as mean (SD).

^§Nutrient intakes were transformed (log₁₀) to improve normality.

*p<0.05 FFQ2 compared to FFQ1 (paired t-test).

Table 4. Validation of the food frequency questionnaire (FFQ) shown by mean (SD) daily estimates of nutrients and Pearson correlation between crude and energy-adjusted estimations derived from the 7-day dietary record (7-DR) and the FFQ (n=100)

	Daily intake			Pearson correlation coefficient
	7-DR	FFQ	FFQ (% 7-DR)	Crude	Energy-adjusted
Energy, kcal	1,571 (368)^$	1,558 (445)	99	0.77	–
Protein, g^§	68.5 (15.2)	68.2 (18.5)	100	0.72	0.69
Carbohydrate, g	166 (43)	160 (51)	96	0.76	0.75
Fat, g	64.7 (20.4)	66.2 (23.9)	102	0.75	0.62
MUFA, g^§	24.6 (8.9)	26 (10.5)	106	0.78	0.72
PUFA, g^§	8.7 (4.5)	9.1 (5.1)	105	0.75	0.58
SFA, g	24.6 (8.7)	24.9 (9.8)	101	0.68	0.60
Cholesterol, mg	247 (90)	249 (106)	101	0.57	0.48
Fiber, g^§	14.5 (5.3)	19.1 (7.6)*	132	0.73	0.71
Vitamin A, µg^§	366 (462)	386 (455)*	106	0.57	0.19
Thiamine, mg	1 (0.3)	1.1 (0.4)*	110	0.54	0.50
Riboflavin, mg	1.4 (0.5)	1.6 (0.5)*	114	0.71	0.72
Niacin, mg^§	14.7 (4.2)	15.5 (4.9)	105	0.57	0.49
Pantothenic acid, mg	4.2 (1.2)	5.1 (1.6)*	121	0.60	0.56
Pyridoxine, mg	1.4 (0.4)	1.7 (0.5)*	121	0.61	0.59
Folic acid, µg	234 (81)	315 (110)*	134	0.59	0.63
Cobalamin, µg^§	4.9 (5)	4.5 (2.8)	92	0.80	0.46
Vitamin C, mg^§	84.8 (42)	147.7 (69)*	174	0.42	0.56
Vitamin D, µg^§	2.5 (1.5)	2.9 (1.8)*	116	0.55	0.50
Vitamin E, mg^§	8.8 (5.4)	10.1 (5.2)*	115	0.75	0.57
Calcium, mg	644 (202)	636 (218)	99	0.65	0.65
Iron, mg	9.9 (3)	11.7 (3.6)*	118	0.58	0.51
Magnesium, mg	216 (54)	240 (69)*	111	0.67	0.67
Zinc, mg	7.3 (2.1)	8.5 (2.5)*	116	0.60	0.44
Selenium, µg^§	39.8 (18.6)	44.2 (14.2)*	111	0.54	0.50
Phosphorus, mg	1,051 (244)	1,064 (285)	101	0.68	0.60
Manganese, mg	2 (0.8)	2.8 (1.0)*	140	0.56	0.48
Potassium, mg	2,483 (636)	2,702 (811)*	109	0.64	0.64
Iodine, µg	101 (45)	102 (31)	101	0.45	0.55
Copper, mg^§	1 (0.5)	1.3 (0.5)*	130	0.36	0.19
Sodium, mg	2,006 (610)	2,057 (765)	103	0.71	0.56

^$Daily intakes are expressed as mean (SD).

^§Nutrient intakes were transformed (log₁₀) to improve normality.

*p<0.05 FFQ compared to 7-DR (paired t-test).

Table 5. Cross-classification of daily energy-adjusted nutrient intake derived from the food frequency questionnaire (FFQ) and the 7-day dietary record (7-DR), expressed as percentage of subjects classified in the same, same and adjacent, or extreme quintiles (n=100)

Nutrient (unit/day)	Same quintile	Same and adjacent quintile	Extreme quintiles
	% of subjects
Protein, g^§	39	80	0
Carbohydrate, g	44	80	0
Fat, g	39	75	1
MUFA, g^§	41	77	0
PUFA, g^§	33	78	3
SFA, g	39	72	1
Cholesterol, mg	38	72	4
Fiber, g^§	40	83	0
Vitamin A, µg^§	25	59	5
Thiamine, mg	35	74	1
Riboflavin, mg	36	78	0
Niacin, mg^§	27	67	1
Pantothenic acid, mg	37	73	4
Pyridoxine, mg	40	75	2
Folic acid, µg	42	74	2
Cobalamin, µg^§	39	72	4
Vitamin C, mg^§	31	73	2
Vitamin D, µg^§	31	69	5
Vitamin E, mg^§	40	77	3
Calcium, mg	34	75	1
Iron, mg	35	68	1
Magnesium, mg	36	79	0
Zinc, mg	41	65	0
Selenium, µg^§	27	65	1
Phosphorus, mg	33	77	1
Manganese, mg	39	73	2
Potassium, mg	38	81	0
Iodine, µg	39	75	1
Copper, mg^§	30	68	6
Sodium, mg	40	73	0

^§Nutrient intakes were transformed (log₁₀) to improve normality.

Fig. 1.  Bland–Altman plots representing the difference in the daily intake of energy-adjusted macronutrients and micronutrients intake derived from the food frequency questionnaire (FFQ) and the 7-day dietary record (7-DR) plotted against the corresponding mean energy-adjusted daily intakes derived from the two methods. Solid lines represent mean difference, and dashed lines show lower and upper 95% limits of agreement (mean±1.96 SD).