Opinion: A varied diet can prevent diabetes – but can you afford it?
In a study of over 25,000 adults with detailed information about their eating habits, people with a greater diversity of foods in their diet showed a 30% lower risk of developing type 2 diabetes over a ten-year period. Unfortunately, the diets with more variety were 18% more expensive than the less-varied ones.
A healthy diet is critical for preventing and managing type 2 diabetes. Type 2 diabetes affects around 415m adults globally; a figure that is expected to rise to 643m by 2040, mostly in low- and middle-income countries. So governments should support their citizen's ability to eat well.
For several decades now, governments have recommended that people eat a varied diet. Global five-a-day campaigns stress the consumption of a variety of fruits and vegetables. The theory goes that consuming a variety of foods ensures that a person receives all the necessary vitamins, minerals and phytochemicals that are needed for the body to function and stay healthy. But, what do we really mean by a varied diet and what is its relationship with diabetes?
A varied diet is a healthier diet
Although dietary guidelines have for a long time recommended eating a variety of foods, scientists are not sure exactly what it is about eating a varied diet that might promote health. There has been research on how the variety of foods relate to the nutritional quality of a person's diet, but little is known about whether the diversity of the diet is related to risk of chronic diseases such as type 2 diabetes.
For example, there are no studies on whether a diet containing foods from all five food groups reduces a person's risk of type 2 diabetes. We also don't know whether the variety of foods within each of the five food groups is important for health.
People's diets vary in terms of the different food groups. For example, one person's diet might consist mainly of meat and grains while another person's might contain dairy, vegetables and fruit. Diets also vary in the variety of foods within each food group. We were interested in analysing whether the recommendation to consume a wide range of different foods within each food group would have an impact on the risk of developing diabetes.
To do this, we used data collected from middle and older-aged British adults who reported their lifestyles, including their eating habits, when they entered the study and were followed for about ten years. We found that people who routinely ate from all five food groups had a 30% lower risk of type 2 diabetes than people who only ate three food groups or fewer. Also, people eating the widest variety of fruits and vegetables and dairy products also greatly reduced their risk of diabetes compared with people who had a less varied diet. These results could not be explained by other potential risk factors, such as body weight, occupation, income and education, as we took these factors into account in our analysis.
The bill, please
Research shows that healthy eating is expensive. The price gap between more and less healthy foods is growing in the UK and higher food costs may prevent people from eating a healthier diet, particularly those on low incomes. But what about a more varied diet? Is that more expensive, too?
Most epidemiological studies don't have information about consumer food costs, but our study did because we linked the dietary data to retail food prices. We found that diets containing all five food groups were on average 18% more costly than diets containing three food groups or fewer. And diets with more variety within each of the five food groups were more costly than diets that contained less variety within each food group.
So, while diverse diets may help prevent chronic diseases, health policymakers will need to acknowledge that the adoption of more varied diets, particularly those containing the most variety of vegetables and fruits, may be substantially more costly and may worsen existing socioeconomic inequalities in diet.
What government can do
Financial incentives can improve food choices and some local authorities are experimenting with taxes on unhealthy foods, including on sugar-sweetened beverages. These are a good start, but financial approaches are no silver bullet.
Tweaking food prices may just be fiddling around the edges if governments don't also deal with systemic issues such as agricultural policies that are out-of-sync with the dietary priorities most governments advocate. And our neighbourhood environments, supermarket shelves and portion sizes may be promoting overconsumption of primarily processed, energy-dense foods.
The government, the private sector and civil society need to bring policy coherence across the food system, including agriculture, business and health. Easy, affordable access to a varied diet will benefit everyone's health now and in the future.