Thursday October 9 2014
Carefully planning your weekly shop can help save you money
“Healthy food now costs three times as much as junk, study shows,” The Independent reports. It also reports a sharper rise in the cost of fruit and veg over the past decade compared to other types of foods.
This news story is based on research which looked at changes in the price of 94 food items in the UK in the decade from 2002 to 2012. It found that in this period foods classified as healthier (such as fruit and vegetables) were more expensive per calorie than foods high in fat or sugar. The healthy foods increased more sharply in price over time, and in 2012 were three times more expensive on average per calorie than unhealthy foods.
Prices were assessed per 1,000 calories, as this is a standard way of assessing food poverty. However, as healthier foods tend to have a much lower energy density (fewer calories per gram) than less healthy foods, this measure may not always give a realistic comparison of different food choices you might buy. For example, you would need to buy and eat around 30 cucumbers to gain around 1,000 calories, compared to about one 200g packet of ginger nut biscuits (about 20 biscuits).
Given the recent economic climate and also concerns about diet-related health conditions, this is likely to be of interest to policy makers, as well as the public. This sort of information could contribute to discussions about whether changing food pricing could motivate people to eat more healthily.
Where did the story come from?
This research was carried out by researchers at the University of Cambridge and the University of East Anglia. The study was funded by the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, the National Institute for Health Research, and the Wellcome Trust, and took place in a UK Clinical Research Collaboration centre. One of the authors was funded by the Gates Cambridge Trust.
It was published in PLOS One, which is a peer-reviewed, open access science journal, so the study is freely available online.
The UK media generally covered this study accurately.
What kind of research was this?
This was a time trend study, looking at how the costs of more and less healthy foods changed over time in the UK. They used two sources of routinely available UK government data, as they hoped their method could be a way to routinely monitor how affordability of these foods is changing over time. They say that their study is the first to use UK data to assess price trends by nutrient composition of foods.
The researchers report that diet related ill health has been estimated to cost the NHS £5.8 billion per year – more than smoking, alcohol, or physical inactivity. Although consuming healthier foods is linked to better health outcomes, many people in the UK do not meet healthy eating recommendations. The researchers describe one survey which found that 39% of people rated price as the most important factor in their food choice compared to just 9% who considered a food’s healthiness to be most important.
So if healthier food is more expensive, this could be a significant barrier to people eating more healthily.
What did the researchers do?
The researchers selected 94 foods and drinks and classified them as “more healthy” or “less healthy” based on their calorie and nutrient contents. They identified their costs from 2002 to 2012, and compared the prices of the “more healthy” and “less healthy” foods over time to see how they differed.
Foods and drinks were chosen from UK Consumer Price Index (CPI), which the government uses to track the prices of commonly bought and used goods and services every quarter to measure inflation. The researchers used only those foods and drinks which remained in the survey between 2002 and 2012, and that did not include an element of service (for example a meal in a pub). They also excluded non-calorie containing foods such as tea bags, coffee and mineral water. This left them with 94 foods and drinks, and they obtained an average cost for each item for each year.
The researchers also obtained weight of the items where this was reported in CPI, or estimated the weight based on information on prices for similar items online, or for items with varying weights (such as individual fruit) by using the US Department of Agriculture’s National Nutrient Database standard reference weights.
The nutrient contents of the items was obtained using the UK Department of Health’s National Diet and Nutrition Survey. This survey includes detailed nutritional information on the foods eaten by 1,491 adults. The researchers identified the best match or matches to each of their 94 items from the survey. In some cases there were multiple similar items – for example, if the CPI item was a potato, the survey could contain nutritional information on boiled, baked, and fried potatoes. In these cases the researchers took the average nutritional values. The weight and nutritional information per weight data allowed researchers to calculate costs of each item per 1,000 kilocalories (kcal).
Foods were classified into categories in the Eatwell Plate:
- bread, rice, potatoes and pasta
- fruit and vegetables
- milk and dairy foods
- meat, fish, eggs, beans and other sources of protein
food and drinks high in fat and /or sugar
The researchers also used a Department of Health tool which assigns an overall score to foods based on their level of nutrients per 100g, which allows classification of foods as “more healthy” or “less healthy” based on their score.
The researchers used statistical tests to see if the prices of the “more healthy” and “less healthy” foods, or different Eatwell categories differed over time.
What were the results of the study?
Average prices for both more and less healthy food rose by 35% between 2002 and 2012, from £3.87 per 1,000kcal to £5.21 per 1,000kcal.
Price per 1,000kcal was always highest for fruit and veg, lowest for starchy foods (bread, rice, potatoes and pasta), and second lowest for foods and drinks high in fat and/or sugar. The price of starchy foods per 1,000kcal stayed roughly the same between 2002 and 2012, while the other groups showed price rises. Each of the food categories, with the exception of fruit and veg, contained both foods classified as more healthy and some as less healthy.
Healthier foods increased in price per 1,000kcal more rapidly than less healthy foods. Healthier foods increased in price by an average of 17 pence per 1,000kcal per year while less healthy foods rose seven pence per 1,000kcal per year.
In 2012 the average price of more healthy foods was about three times higher – £7.49 for 1,000kcal compared to £2.50 for 1,000kcal of less healthy foods.
How did the researchers interpret the results?
The researchers concluded that “Since 2002, more healthy foods and beverages have been consistently more expensive than less healthy ones, with a growing gap between them.” They say that this trend may worsen social inequalities in health, and affect the population’s health as a whole. They also suggest that the findings support routinely monitoring food prices to inform possible economic policy responses.
The current study has found that the price of food per calorie in the UK between 2002 and 2012 was consistently higher for healthier food than for less healthy food. The suggestion is that this may affect people’s food choices, and therefore their long term health.
The method the researchers used took advantage of routinely available government data on food prices and nutritional content. This means it would not require collection of new data to keep track of healthy and unhealthy food prices per calorie.
There are some limitations to the findings, which the authors themselves discuss, including the small number of foods and drinks they assessed, as they were restricted to using those listed in the UK Consumer Price Index between 2002 and 2012. However, the index includes commonly bought items.
They assessed price per calorie, rather than price per unit weight, as this is the way international organisations assess food poverty. Also dietary recommendations are given in terms of calories rather than weight of food. However, one of the reasons for less healthy foods to be classed as less healthy is that they have high levels of calories per gram. So it is perhaps not surprising that less healthy food tends to costs less per calorie than more healthy foods such as fruit and veg, which tend to have fewer calories per gram. Building on this research to estimate the price of healthy and unhealthy diets as a whole, or also presenting prices per weight could help in giving an idea of the practical day to day impact of these differences.
This study has added another layer to the information available about food prices in the UK, linking it to nutritional value. Given the recent economic climate and also concerns about diet-related health conditions, this is likely to be of interest to both the public and policy makers.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.