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Using portion size to increase fruit and vegetable intake in children
Eating habits are established during early childhood. It therefore is crucial to promote consumption of healthy foods, such as Fruits and Vegetables (F&V), early in life. Despite the high nutritional value of F&V, cross-sectional studies show that many children in the United States do not meet the national dietary recommendations for these foods. It is estimated that fewer than ten percent of US children who are between four and eight years of age consume the recommended number of servings of F&V daily1.
F&V not only provide essential nutrients for children, but they are also believed to play an important role in the regulation of Energy intake. F&V have a high water and fiber content but are low in energy density (calories per gram). These properties have been shown to enhance fullness in adults, but few studies have assessed these effects in children. Given the inadequate consumption patterns of F&V in many children, it is crucial to identify dietary strategies that can be used by parents and caregivers to increase children’s intake of F&V.
Increasing the portion size of fruit and vegetable side dishes
The portion size of foods has been identified as a strong determinant of energy intake in both children and adults2, 3. Studies have shown that when served larger portions of food, children as young as two years of age ate more. Many of the earlier studies have focused on changing the portion size of energy-dense entrées such as pasta dishes. Few studies, however, have focused on changing portion size of more healthy foods, such as F&V. Therefore, it is important to determine if portion size can be used strategically to promote intake of healthy foods.
The aim of a recent study in Philadelphia was to test the effects of doubling the portion size of F&V side dishes at a meal on children’s intake4. Boys and girls between five and six years of age were served dinner once a week for two weeks. Each dinner consisted of pasta with tomato sauce, three F&V side dishes (broccoli, carrots, applesauce), and milk. The portion size of the F&V side dishes was doubled between visits, while the size of the pasta remained the same. Children could eat as much or as little as they desired.
The results of the study showed that doubling the portion size of the F&V side dishes led to a 43% increase in children’s intake of the fruit side dish, which corresponded to approximately one third of a serving of applesauce. Children’s intake of the vegetable side dishes, however, remained unaffected by the portion size changes in this study. Interestingly, when served the large portions of F&V, children spontaneously ate less pasta despite the fact that the portion size of the pasta did not change. It is possible that the increased consumption of the fruit side dish when large portions were served may have displaced intake of the main entrée.
With respect to children’s vegetable intake, which remained similar between portion size conditions, it is possible that the preparation method of the two vegetables may have influenced children’s intake (both vegetables were served plain with no added butter or seasoning). Findings from a similar study by Fisher and colleagues5, which showed greater intakes of vegetables when larger portions were served, suggest that adding small amounts of fat or a dip to vegetables can enhance children’s liking of the vegetables which in turn may promote intake. Another study showed that doubling the portion size of a single vegetable (carrots with a dip) served as a first course increased carrot intake in children by 47%6.
These findings suggest that increasing the portion size of healthy foods, such as F&V, at a meal can be an effective strategy to promote children’s intake of these foods while displacing consumption of more energy-dense entrées. Parents and foodservice providers at schools and daycare settings should be encouraged to use these strategies to promote F&V consumption among children.
New Investigator Research Grant The Obesity Society and NIH K01DK078601
- Guenther PM et al. J Am Diet Assoc 2006; 106: 1371-1379.
- Fisher JO & Kral TV. Physiol Behav 2008; 94: 39-47.
- Rolls BJ. Nutr Today 2003; 38: 42-53.
- Kral TV et al. Obesity 2010; 18: 521-527.
- Mathias KC et al. Obesity, 2009, p S90.
- Spill MK et al. Am J Clin Nutr, in press.