Food preferences A worldwide shared newsletter
Genetic and environmental influences on fruit and vegetable liking in adolescence
It is estimated that around 10% of the world’s entire health burden is attributable to sub-optimal dietary intake, with 5.7% of disability-adjusted life-years (DALY’s) lost due to diets low in fruit and vegetables1. Our food and drink preferences influence strongly what we choose to eat or drink, evidenced by the fact that preferences predict actual food intake2. Understanding the factors that shape our liking of fruit and vegetables is therefore important for public health initiatives that aim to increase intake.
Twins can establish genetic and environmental influence on fruit and vegetable liking
Twin studies are a powerful method for understanding the extent to which liking for fruit and vegetables (or any trait) is driven by genetic and environmental influence. The basis of the method is to compare resemblance in liking between identical twin pairs who share 100% of their genes, with liking between non-identical twins who share about 50% of their genes. Because both types of twins share their environments to a very similar extent, the only real difference between the two types of twins is the fact that identical twins are twice as similar genetically. Greater resemblance between liking for identical versus non-identical twins therefore indicates a genetic contribution to preferences; similar liking for both identical and non-identical pairs indicates that environmental factors shared completely by twin pairs are important (e.g. maternal gestational diet); and low similarity in liking between twin pairs suggests that factors unique to each individual twin are key (e.g. illness).
Environmental influence on liking for fruit and vegetables changes from early childhood to late adolescence
Previous studies have shown that aspects of the environment shared entirely by twin pairs play an important role in shaping liking for fruit (51% to 53%) and vegetables (35% to 51%) among young children3,4, alongside modest genetic influence (fruit: 53% to 54%; vegetables: 37% to 54%). This is not unexpected given the importance of the family environment for the eating behaviour of young children. However, the relative influence of genes and the environment can change dramatically with age, and the drivers of older teenagers’ preferences were unknown until very recently. In 2016, we explored this for the first time in a large sample of 18-19 year old twins (n=2865) from the Twins Early Development Study (TEDS), a population based British cohort of twins born in 1994-965. Preferences for 62 individual foods were selfreported, and categorised into six food groups: fruit, vegetables, meat/fish, dairy, starch food and snacks. In contrast to the study of younger children we found no influence of the shared environment on preferences for any type of food. Instead, aspects of the environment that are not shared by twin pairs (experiences unique to each individual twin, such as having different friends) exerted an important influence on liking for all of the foods (46% to 68%), alongside modest genetic influence (32% to 54%; in keeping with estimates observed for young children) (see Figure 1).
Figure 1. Proportions of variation in food preferences explained by genetic (black portion of bars) and unique environmental (grey portion of bars) influences at 18-19 years of age (n=2685).
How could genes influence preferences for fruit and vegetables?
Food preferences can vary considerably, even among people from the same cultural background, evidenced by the fact that the food preferences of twin pairs can differ. Genes play a part in explaining some of these differences, and specific genes and their pathways have been proposed. Variants in the TASR gene family (a family of bitter taste receptors) affect sensitivity towards bitter compounds6, and carriers of a variant in the TAS2R8 gene are especially sensitive to bitter tastes, and have lower liking of cruciferous vegetables7,8. Other proposed mechanisms relate more to cognitive aspects of food preferences9, such as food neophobia10 or reward circuitry11.
What environmental influences might be important?
Much more is known about the environmental influences that shape food preferences, especially for children. When it comes to vegetable liking, exposure is key. In short, we like what we know, and we eat what we like. Repeatedly offering (15 times or more) vegetables to children can increase both liking and intake over the short term12. However, research is needed to establish which strategies are effective for modifying preferences for fruit and vegetables on a wider scale (e.g. for public health initiatives).
Our findings indicate that the effects of family upbringing on liking for fruit and vegetables (and other foods) have entirely disappeared by late adolescence; replaced instead by environmental influences that are unique to each individual twin. This suggests that efforts to improve adolescent nutrition may be best targeted at the wider environment rather than the home. However, the substantial influence of the non-shared environment suggests considerable scope for modification of food preferences by environmental means. Research is needed to establish the most effective strategies for increasing liking of fruit and vegetables in this age group on a large scale.
- Lozano R, et al. Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012 Dec;380(9859):2095–128.
- Drewnowski A, Hann C. Food preferences and reported frequencies of food consumption as predictors of current diet in young women. Am J Clin Nutr. 1999 Jul 1;70(1):28–36.
- Fildes A, et al. Nature and nurture in children’s food preferences. Am J Clin Nutr. 2014 Apr 29;99(4):911–7.
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- Haworth CMA, Dale P, Plomin R. A Twin Study into the Genetic and Environmental Influences on Academic Performance in Science in nine-year-old Boys and Girls. Int J Sci Educ [Internet]. 2008 Jun;30(8):1003.
- Turner-McGrievy G, et al. Taking the bitter with the sweet: relationship of supertasting and sweet preference with metabolic syndrome and dietary intake. J Food Sci. 2013 Feb;78(2): S336-42.
- Boxer EE, Garneau NL. Rare haplotypes of the gene TAS2R38 confer bitter taste sensitivity in humans. Springerplus. 2015 Jan; 4:505.
- Dinehart ME, et al. Bitter taste markers explain variability in vegetable sweetness, bitterness, and intake. Physiol Behav. 2006 Feb 28;87(2):304–13.
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- Schoenfeld MA, et al. Functional magnetic resonance tomography correlates of taste perception in the human primary taste cortex. Neuroscience. 2004 Jan;127(2):347–53.
- Fildes A, et al. Parent-administered exposure to increase children’s vegetable acceptance: a randomized controlled trial. J Acad Nutr Diet. 2014 Jun;114(6):881–8.