Wednesday October 24 2007
What you eat may not be up to you
Your preferred choice of foods is all controlled by your genes, reported The Daily Telegraph. A study has found that “preferences for certain foods over others is inherited through the genes rather than what your parents forced you to eat as a child”, the newspaper said. The taste preferences of more than 3,000 sets of twins both identical (with the same genetic make-up) and non-identical were examined to see whether food preferences could be down to “nature or nurture”. The results “could mean that the Government's promotion of fruit and vegetables in the five-a-day campaign will have limited success – because diet is less about choice and more about genetics”, the Telegraph said.
This study suggests that some of our preference for food may be genetic, however there are many other social and environmental factors that can have an effect on the foods we eat, it may not all be "in the genes".
Where did the story come from?
This research was carried out by Birgit Teucher and colleagues of Institute of Food Research, Norwich Research Park; School of Medicine, University of East Anglia; and Twin Research and Genetic Epidemiology Unit, Kings College London. Funding was provided by The Wellcome Trust, Chronic Diseases Research Foundation, and Cancer Prevention Trust. It was published in the peer-reviewed medical journal Twin Research and Human Genetics.
What kind of scientific study was this?
This is a cross-sectional study in twins where the researchers have looked at the responses to food questionnaires to investigate the effects that genetic and environmental factors may have upon food choice.
The researchers selected 3,262 female twins between the ages of 18 and 79 years from the Twins UK Registry. All of the twins completed questionnaires between 1996 and 2000; in addition to questions on lifestyle, there were questions about food frequency. The questionnaire included questions about 131 food types that were placed into groups according to nutrient content; the amount of each food consumed was determined by the number of servings per week.
Statistical analyses were used to look at the patterns of food consumption and to compare this between identical and non-identical twins. Both identical and non-identical twins largely share their environment, at least early in life, but identical twins share the same DNA, while non-identical twins are no more similar than any other sibling pair. Therefore, if identical twins are more alike than non-identical twins in particular characteristics (in the case of this study – their food preferences), researchers can conclude that this increased similarity is likely to result from their shared genetic make-up rather than environment.
What were the results of the study?
The researchers examined data for 498 identical and 1,133 non-identical female twin pairs. They found there to be patterns in the types of food that people ate, which could be grouped broadly into frequent consumption of fruit and vegetables, traditional English food (e.g. meat, potatoes, pies), low fat diet food, low meat diets (e.g. white fish, beans, fish) or one that included drinking a large amount of alcohol.
They found that identical twins were more likely to fall into the same preferred eating group than non-identical twins, which suggests that there is a genetic component to food preference. When they looked at specific food types there found that the consumption of garlic, coffee, red meat and fruit and vegetables had the strongest genetic contribution.
What interpretations did the researchers draw from these results?
The researchers conclude that “genetic factors have an important influence in determining food choice and dietary habits in Western populations.”
What does the NHS Knowledge Service make of this study?
This study suggests that there is a possibility of a genetic link to food preference. However, some points to bear in mind are:
- Although there seems to be a pattern for increased similarity in food preference amongst identical twins, there is the possibility that this is not just related purely to genetic factors. For example, identical twins may sometimes dress alike, and share common interests but these could be contributed to by “environmental” effects, such as others’ expectation of them behaving similarly, as well as genetic effects.
- The study has considered many food types. It relies on the participants’ accurate recall of the food that they ate for the average week over the past year, which is unlikely to remain consistent over time. The authors themselves state that food questionnaires “may not reflect lifetime dietary habits”.
- This study examined only female twins, therefore we cannot generalise these findings to males. It is also in a Western population, and may not apply to people with other ethnic backgrounds.
This study suggests that some of our preference for food may be genetic, but we should not discredit the considerable effect that social and environmental factors can have on the foods we eat.
Sir Muir Gray adds...
Genes and the environment interact on all aspects of life and food preferences are no different. However, the fact that diet often changes when people move from one country to another suggests that in this case at least the social environment is more important; people learn what to eat rather than being programmed.