A major study of UK dietary habits has found that the food we eat contains an average of at least 49 different species each week.
Researchers used innovative algorithms to establish the number and type of unique ingredients in 6,000-plus food and drink items in the National Diet and Nutrition Survey (NDNS) nutrient databank then cross-referenced thousands of four-day food diaries.
They found an average of 29 unique species on the first day – with nine more added on day two, five on day three and four on the last day – suggesting the weekly number would top 50.
The species included different varieties of meat, seafood, fruit, vegetables, herbs and spices – with only excluding certain extracts and flavourings not counted in the score.
The peer-reviewed paper, published in Public Health Nutrition, demonstrates that this novel method can be used to make robust scientific calculations about the variety of elements that make up what we consume and provides a case study for countries that have a relatively high consumption of processed foods as part of Western-style diets
It provides important new insights into the science of diet biodiversity, which is gaining attention as a way to measure the health and climate impacts of what we eat.
Professor Baukje de Roos
And it reinforces the value of existing dietary advice, finding DSR is “significantly higher in those adhering to dietary guidelines for fruit and vegetables, fish and fibre”.
The research was carried out by a Scottish Government-funded team at the Rowett Institute, University of Aberdeen in collaboration with colleagues from the Unilever Foods Innovation Centre, Wageningen in the Netherlands – which part-funded the study - and from Robert Gordon University in Aberdeen.
Lead author Professor Baukje de Roos said: “Eating more ‘species’ is likely to improve the quality of our diets, and therefore our health.
“Our research clearly shows that sticking to existing dietary guidelines to eat five portions of fruits and vegetables a day, and at least one or two fish meals a week, is an important way to maximise the number of species we eat as part of our diet”.
A spokesperson for the Unilever Foods Innovation Centre added: “We’re proud to be part of a project that uses cutting-edge algorithms to validate dietary species richness and explore how increased diversity of species in our diets can improve nutrition and public health.”
The idea that eating a varied diet benefits health is well established but has traditionally been measured by counting food groups, rather than individual elements within them.
Now there is a growing focus on food biodiversity (different plants, animals, fungi, insects etc) – both for human and planetary health
Professor Baukje de Roos
Recent research which associated a higher DSR with lower death rates has led to suggestions it be included in public health strategies as a new metric for healthy and sustainable foods and diets. Food biodiversity and total and cause-specific mortality in 9 European countries: An analysis of a prospective cohort study - PMC
Some commercial nutrition programmes already encourage customers to consume a minimum number of different types of certain foodstuffs per week, as this may help to improve the diversity of their gut microbiome.
But, the paper notes, questions remain about how DSR can best be measured, its exact relationship with diet quality and what score is required for optimal health.
For example, whilst a higher DSR was generally associated with a small improvement in diet quality, perhaps unexpectedly the new study found that avoiding sugar and salt actually tends to be linked to a lower DSR.
DSR was also found to be higher in younger people, those with higher household incomes and those living in the least deprived areas – but with no significant variation between men and women or between people of different ethnicities.
The paper concludes: “It is essential to understand how food biodiversity is associated with dietary quality and health outcomes to justify its use as a meaningful new metric that can link diets to human and planetary health, complementing existing indicators for healthy and sustainable diets.
It goes on: “To increase DSR in UK diets in a just manner, we will need to ensure that we conserve natural biodiversity worldwide through our dietary choices and maintain the affordability of high-DSR foods and diets, which requires integration of environmental and public health policies.
“The most important strength of this study is the robust bottom-up analysis of DSR in UK diets, using four-day food intake data collected from 3,558 participants across sex, age, ethnicity and socio-economic groups over a recent period of three years.”