Background
Trials that attempt to increase fruit and vegetable (F/V) intake commonly rely on self-reported dietary intake data that are prone to bias. Our primary objective was to assess the magnitude of the effect of a dietary intervention on F/V consumption, using two different measures: serum carotenoids and 24-hour dietary recall. A secondary goal was to explore the use of serum carotenoid levels as an indicator of F/V consumption.
Methods
Three intervention groups in the PREMIER trial (n=554) consisted of an Advice Only control group, an Established group that received counseling on weight loss, physical activity and sodium reduction (but no advice on F/V intake), and an Established +DASH group that also received counseling on the DASH diet (with advice to increase F/V intake). Self-reported F/V consumption was measured via two 24-hour dietary recalls administered at baseline, 6- and 18-months. Serum carotenoids were collected via fasting blood samples at each time point. Linear mixed models were used to examine the relationship between intervention assignment and F/V consumption. Pearson correlation and ROC curves informed the secondary objective.
Results
Compared to the control group, F/V consumption was highest in the Established+DASH group measured by recall (2.95 servings greater, 95% CI 2.43 to 3.47) and serum carotenoids (20.51 ug/dl greater, 95% CI 12.72 to 28.29). However, only 34% (57/167) of the Established+DASH group met the recommended level of 9 servings of F/V per day at 6 months. F/V intake and serum carotenoid levels were similarly and modestly correlated across each time point, ranging from .34 to .42. ROC curves indicated poor or fair performance of carotenoids as indicators of adequate F/V consumption. The area under the curve (AUC) was .692 for 5 servings of F/V, and .697 for 9 servings.
Conclusions
The PREMIER dietary intervention was successful in increasing F/V consumption as measured by serum carotenoids or self-report, but only a minority of study participants achieved recommended levels.
Table 1.
Mean fruit and vegetable consumption over study duration, by intervention assignment
Intervention Assignment
Advice Only (n
1
=186)
Established (n=185)
Established +DASH (n=183)
p-value
2
24-Hour Recall (servings/day: mean, SD)
18 months
4.6 (2.7)
4.8 (2.5)
7.5 (3.5)
<.001
Total Carotenoid Levels
3
(ug/dl: mean, SD)
18 months
61.1 (37.0)
63.8 (38.3)
79.8 (49.2)
<.001
Total Carotenoid Levels+Lycopene, (ug/dl: mean, SD)
18 months
85.4 (41.3)
85.3 (40.1)
102.3 (51.4)
<.001
1
Sample sizes are from baseline visit
2
P-values correspond to difference in mean values across intervention groups
3
Total carotenoids defined as the sum of -carotene, -carotene, -cryptoxanthin and lutein/zeaxanthin
Intended and Unintended Consequences of a Community-Based Fresh Fruit and Vegetable Dietary Intervention on the Flathead Reservation of the Confederated Salish and Kootenai Tribes