Methodological considerations in a pilot study on the effects of a berry enriched smoothie on children’s performance in school

Figures & data

Table 1. Number of participants divided by gender and grade in study groups A and B for trial periods 1 and 2, respectively.

		Period 1			Period 2
		Male	Female	Total	Male	Female	Total
Group A	Grade 4	30	38	68	30	39	69
	Grade 5	21	18	39	17	22	39
Group B	Grade 4	23	39	62	26	39	65
	Grade 5	23	24	47	24	24	48
	Total	97	119	216	97	124	221

Table 2. Description of the cross-over design.

	1	2	3	4	5	6	7
Week	Period 1		Washout			Period 2
Group A	Active smoothie					Control beverage
Average consumption (g)	173					246
Group B	Control beverage					Active smoothie
Average consumption (g)	248					136
d2 test*	Test 1	Test 2				Test 3	Test 4

*The first and third tests were carried out one school day before the periods of beverage consumption; the second and fourth tests were carried out on the last day of beverage consumption.

Table 3. List of ingredients in the active smoothie and control beverage.

Active smoothie	Content (%)	Control beverage	Content (%)
Pear juice	40.2	Water	80.0
Apple juice	13.1	Invert sugar. 73° Brix	12.4
Apple purée	10.1	Apple juice. 12.5° Brix	5.0
Strawberry purée	10.1	Pear juice concentrate. 70° Brix	2.2
Blackcurrant purée	6.5	Citric acid	0.3
Pear purée	6.5	Pear aroma	0.05
Carrot purée	6.5
Elderberry purée	3.9
Spinach, chopped and frozen	2.0
Oat oil	1.0

Table 4. Analysed nutritional content and quality parameters of the active smoothie and the control beverage.

Nutrient and quality parameters	Active smoothie	Control beverage
Water (g/100g)	89.0	89.5
Crude protein (g/100g)	0.34
Carbohydrates (g/100g)	10.3	10.5
Energy (kcal/kJ per 100g)	43/181	43/179
Fructose (g/100g)	5.31	3.77
Glucose (g/100g)	2.21	3.36
Sucrose (g/100g)	0.09	3.51
Total sugars (g/100g)	7.61	10.64
Vitamin E (alpha-tocopherol, mg/100g)	0.36	-
Vitamin C (mg/100g)	-	-
Beta-carotene (μg/100g)	421	-
Total phenol content (mg gallic acid/100 mL)	86.6	9.4
Total anthocyanin content (mg cyanidin-3- glucoside/100 mL)	19.1	-
Potassium (mg/L)	1700	340
Phosphorus (mg/L)	180	27
Calcium (mg/L)	120	110
Magnesium (mg/L)	75	25
Sulphur (mg/L)	55	20
Sodium (mg/L)	30	56
Boron (mg/L)	1.2	0.58
Iron (mg/L)	1.2	0.43
pH	3.7	3.0
Soluble dry matter (°Brix)	11.8	11.8
Titratable acid (g citric acid/100 mL)	0.52	0.41

Table 5. Change in processing speed (processed number of targets, PTO) following consumption of the active smoothie and the control beverage.

	Active smoothie			Control beverage
Statistica	Start	End	Change	Start	End	Change	Change Active – Control
N	226	220	210	232	217	214	192
Missing	10	16	26	4	19	22	44
Mean	147.5	165.7	19.4	144.8	167.1	22.8	−2.98
Std	40.3	44.0	18.8	33.9	40.2	24.1	27.1
P-value^1	NA	NA	0.000	NA	NA	0.000	0.459
95% CI LL	142.17	159.87	16.89	140.45	161.74	19.55	−6.83
95% CI UL	152.75	171.55	21.99	149.21	172.49	26.04	0.87

a Wilcoxon signed rank test. 2-sided p-value.

Table 6. Change in concentration performance (CP) following consumption of the active smoothie and the control beverage.

	Active smoothie			Control beverage
Statistica	Start	End	Change	Start	End	Change	Change Active – Control
N	226	220	210	232	217	214	192
Missing	10	16	26	4	19	22	44
Mean	129.4	147.6	19.2	127.4	147.4	20.0	−1.0
Std	39.8	42.9	17.5	33.1	37.3	18.7	26.0
P-value^a	NA	NA	0.000	NA	NA	0.000	0.938
95% CI LL	39.90	34.64	−8.67	38.93	37.51	−3.97	−11.87
95% CI UL	54.54	48.80	−1.11	52.68	53.05	5.97	1.65

a Wilcoxon signed rank test. 2-sided p-value.

Table 7. Change in error percentage (EP) following consumption of the active smoothie and the control beverage.

	Active smoothie			Control beverage
Statistica	Start	End	Change	Start	End	Change	Change Active – Control
N	226	220	210	232	217	214	192
Missing	10	16	26	4	19	22	44
Mean	47.2	41.7	−4.9	45.8	45.3	1.0	−5.1
Std	55.8	53.3	27.8	53.2	58.1	36.9	47.5
P-value^3	NA	NA	0.014	NA	NA	0.202	0.915
95% CI LL	39.90	34.64	−8.67	38.93	37.51	−3.97	−11.87
95% CI UL	54.54	48.80	−1.11	52.68	53.05	5.97	1.65

a Wilcoxon signed rank test. 2-sided p-value.