Postprandial hyperglycemia is an important therapeutic target for optimizing glycemic
control and for mitigating the proatherogenic vascular environment characteristic
of type 2 diabetes. Existing evidence indicates that the quantity and type of carbohydrate
consumed influence blood glucose levels and that the total amount of carbohydrate
consumed is the primary predictor of glycemic response (1). Previous studies have
shown that premeal ingestion of whey protein, as well as altering the macronutrient
composition of a meal, reduces postmeal glucose levels (2–4). There are limited data,
however, regarding the effect of food order on postprandial glycemia in patients with
type 2 diabetes (5). In this pilot study, we sought to examine the effect of food
order, using a typical Western meal, incorporating vegetables, protein, and carbohydrate,
on postprandial glucose and insulin excursions in overweight/obese adults with type
2 diabetes.
A total of 11 subjects (6 female, 5 male) with metformin-treated type 2 diabetes were
studied using a within-subject crossover design. The average (mean ± SD) age and BMI
were 54 ± 9 years and 32.9 ± 5 kg/m2, respectively. The average duration of diabetes
was 4.8 ± 2.4 years and the mean HbA1c was 6.5 ± 0.7%.
After a 12-h overnight fast, subjects consumed an isocaloric meal (628 kcal: 55 g
protein, 68 g carbohydrate, and 16 g fat) with the same composition on 2 separate
days, 1 week apart. During the first visit, the food order was carbohydrate (ciabatta
bread and orange juice), followed 15 min later by protein (skinless grilled chicken
breast) and vegetables (lettuce and tomato salad with low-fat Italian vinaigrette
and steamed broccoli with butter); the food order was reversed a week later. Blood
was sampled for glucose and insulin measurements at baseline (just before meal ingestion)
and 30, 60, and 120 min after the start of the meal.
The mean postmeal glucose levels were decreased by 28.6% (P = 0.001), 36.7% (P = 0.001),
and 16.8% (P = 0.03) at 30, 60, and 120 min, respectively, and the incremental area
under the curve (iAUC0–120) was 73% lower (2,001 ± 376.9 vs. 7,545 ± 804.4 mg/dL ×
120 min, P = 0.001) when vegetables and protein were consumed first, before carbohydrate,
compared with the reverse food order (Table 1). Postprandial insulin levels at 60
and 120 min and the iAUC0–120 were also significantly lower when protein and vegetables
were consumed first.
Table 1
Glucose and insulin levels/iAUC for various time points/intervals during the two visits
Time (min)
Carbohydrates first
Carbohydrates last
P
c
Change (%)
Blood glucose (mg/dL)
a
0
106.7 ± 5.3
107.3 ± 6.3
0.752
0.5
30
156.8 ± 8.2
112.0 ± 5.8
0.001
−28.6
60
199.4 ± 12.2
125.6 ± 6.9
0.001
−37.0
120
169.2 ± 13.8
140.8 ± 7.7
0.030
−16.8
Serum insulin (µIU/mL)
a
0
18.8 ± 2.4
16.3 ± 1.4
0.154
−13.6
30
62.4 ± 8.6
42.9 ± 9.7
0.083
−31.2
60
125.4 ± 20.1
63.2 ± 11.0
0.002
−49.6
120
152.0 ± 31.7
90.9 ± 16.6
0.014
−40.2
Glucose iAUC (mg/dL × min)
b
0–30
751.4 ± 71.0
90.0 ± 26.8
0.001
−88.0
0–60
3,396.8 ± 606.9
444.2 ± 103.8
0.001
−86.9
0–120
7,545.0 ± 804.4
2,001.5 ± 376.9
0.001
−73.5
Insulin iAUC (µIU/mL × min)
b
0–30
657.5 ± 131.8
399.5 ± 132.6
0.102
−39.2
0–60
2,908.5 ± 432.0
1,510.5 ± 407.4
0.002
−48.1
0–120
10,097.9 ± 1,646.9
5,202.8 ± 1,061.6
0.002
−48.5
Data are means ± SEM, n = 11.
a
Blood samples were collected immediately before the meal (t = 0 min) and at 30, 60,
and 120 min after the start of the meal.
b
Intervals were measured in minutes from the start of the meal.
c
P values were calculated using the Wilcoxon matched-pairs signed rank test.
In this pilot study, we demonstrated that the temporal sequence of carbohydrate ingestion
during a meal has a significant impact on postprandial glucose and insulin excursions.
The magnitude of the effect of food order on glucose levels is comparable to that
observed with pharmacological agents that preferentially target postprandial glucose.
Moreover, the reduced insulin excursions observed in this experimental setting suggest
that this meal pattern may improve insulin sensitivity. A limitation of the study
is that we analyzed glucose and insulin responses up to 120 min following meal ingestion,
as this study was designed to test postprandial glucose levels as practically measured
by patients with type 2 diabetes. Further studies with longer follow-up to delineate
the full impact, including delayed effects and the mechanisms underlying the glycemic
effect of food order, are indicated.
In contrast to conventional nutritional counseling in diabetes, which is largely restrictive
and focuses on “how much” and “what not to eat,” this pilot study suggests that improvement
in glycemia may be achieved by optimal timing of carbohydrate ingestion during a meal.