New research challenges the idea that healthy eating is simply a matter of willpower, finding that genetics may help explain why some people find it easier than others to maintain healthy dietary habits.
An international study of middle-aged and older twins has found that genetic differences contribute to how much fruit and vegetables people consume, highlighting the complex mix of biological, social and environmental factors that shape our diets.
The study, published in Behavior Genetics, examined 5,789 twins aged 45 to 90 from four international community-based studies.
Researchers found that fruit consumption was estimated to be 25% heritable and vegetable consumption 17% heritable - meaning genetic differences accounted for approximately one-quarter of the variation between individuals in fruit intake and around one-sixth for vegetables.
Lead author and Post Doctoral Research Fellow at UNSW Sydney’s Centre for Healthy Brain Ageing (CHeBA), Dr Annabel Matison, said the findings challenge the idea that healthy eating is purely a matter of choice or self-discipline.
“Dietary behaviour is far more complex than people think,” Dr Matison said.
“Genetics is one of many factors that may contribute to what we eat, alongside food availability, culture, cost, personal preferences and our individual life experiences.
“But genetic influence is not genetic destiny. If fruit intake was 25% heritable, around 75% of the variation was attributable to non-genetic influences, and for vegetables that proportion was even greater.
“The important message is that healthy eating is not simply about willpower.”
Looking beyond the link between diet and depression
Previous research has associated higher fruit and vegetable consumption with fewer depressive symptoms. This study took a different approach, using twins to investigate the extent to which genetic and environmental factors contribute to differences in both diet and depressive symptoms.
It also explored whether fruit and vegetable intake and depressive symptoms share common genetic influences.
“An association alone cannot tell us whether eating more fruit and vegetables reduces the risk of depression, whether people experiencing depression are less likely to maintain a healthy diet, or whether both are influenced by common genetic or environmental factors,” Dr Matison said.
“Understanding what sits behind these relationships can help us identify the most effective targets for prevention and intervention.”
The researchers also found a positive genetic correlation between fruit and vegetable intake, suggesting some of the genetic factors influencing fruit consumption may also influence vegetable consumption.
“One possible explanation is that genetic differences affecting taste and smell perception may influence willingness to consume both fruits and vegetables, although our study was not designed to identify the specific mechanisms involved,” Dr Matison said.
The study found no detectable shared family environmental influence on fruit and vegetable intake or depressive symptoms in mid- to later life. Instead, individual-specific experiences accounted for a much larger proportion of the variation.
Healthy choices don't happen in a vacuum
Dr Karen Mather, Leader of CHeBA’s Genomics & Epigenomics Group, said the research highlights the complexity behind behaviours often viewed primarily as personal choices.
“Genetics does not dictate what ends up on our plate, but it can be one piece of a much larger puzzle,” Dr Mather said.
“This research helps move us away from the idea that everyone begins from exactly the same starting point when it comes to maintaining a healthy diet.
“There is no single ‘fruit gene’ or ‘vegetable gene’. Rather, differences across many genes may collectively contribute to dietary behaviour, alongside the substantial influence of our individual environments and experiences.
“Recognising that complexity is important. Making healthy food accessible, affordable and appealing remains critical, regardless of someone’s genetic background.”
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Heidi Douglass
