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| Journal of the New Zealand Medical Association,
26-January-2007, Vol 120 No 1248
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The price of healthy eating: cost and nutrient value
of selected regular and healthier supermarket foods in
New Zealand
Cliona Ni Mhurchu, Siddharth Ogra
Nutrition-related risk factors such as low fruit and
vegetable intake, obesity, high blood cholesterol levels, and high blood
pressure increase risk of many chronic diseases including diabetes mellitus and
cardiovascular disease.1,2 In New Zealand,
approximately 11,000 (40%) deaths per year are attributable to the joint effects
of nutrition-related risk factors.3
Nevertheless, these factors are modifiable and (if targeted) could reduce
nutrition-related mortality and
morbidity.4
Barriers to healthy eating are many and include social,
environmental, and behavioural factors.5 United
States6 (US) and
European7 research has shown that factors such
as cost and taste are of more relevance to people when making food choices than
healthy eating and weight control.
Between a quarter and a third of New Zealanders cite cost as
the major barrier associated with eating more fruit and
vegetables,8,9 and a Canadian survey found that
61% of shoppers disagreed with the statement “healthier food options cost
the same as regular ones.”10 However, few
studies to date have directly compared the relative costs of healthy and less
healthy diets and those that have produced conflicting
findings.11–13
Our objective was to use New Zealand electronic supermarket
sales data for selected commonly purchased regular and healthier food items to
estimate the difference in cost and nutrient value across food categories.
MethodsElectronic sales data on supermarket food purchases
were obtained during the Supermarket Healthy Options Project (SHOP) pilot study:
a feasibility study of strategies to promote healthier food purchases in
supermarkets. Study methods and findings have been reported
elsewhere14 but, in brief, the SHOP pilot
evaluated the viability of conducting a large randomised controlled trial to
evaluate the effects of price discounts and culturally appropriate nutrition
education on supermarket food purchases.
One of the main aims of the feasibility study was to
evaluate electronic supermarket sales data as a means to measure the effects of
interventions on food purchases. The electronic data collection system was
available in Pak ’N Save supermarkets in the Wellington region and
consisted of handheld barcode scanners enabling registered customers to scan
each item they selected from the supermarket shelf prior to purchase.
The sales data used in our analyses comprised
electronic shopping data for 882 supermarket customers (registered users of the
self-scanning system) collected over 12 months from February 2004 to January
2005. There were no personal identifiers associated with the data and customers
were identified only by a unique number. Seventy-three percent of shoppers were
female and mean (SD) age overall was 37 (11) years.
From this database, 1000 top-selling (by sales volume)
food items (excluding alcoholic beverages) were extracted, which accounted for
59% of all sales transactions. Nutrient lines were matched to each food item
using information from the mandatory nutrition information panel (NIP) on food
packaging or national food composition data15
for generic food items such as fresh fruit and vegetables. Nutrients included
were energy, protein, total fat, saturated fat, carbohydrate, sugars, and
sodium. Fibre was not included because it is not mandatory to list it on the
NIP.
Since sales of these items spanned a full year, the
recorded prices showed variance due to price promotions, seasonality effects,
and other price fluctuations. Therefore an average price per food item was
calculated over the 1-year period so as to give an accurate estimate of price
over time rather than a single snapshot.
The items were categorised into food groups based on
those used in the New Zealand Adult National Nutrition
Survey8 and covered a range of staple food
types including bread, milk, breakfast cereals, and meat. However, not all food
categories were included in our analysis. For example, categories such as
“grains and pasta” were not included as there were no healthier
alternatives (e.g. wholegrain rice, wholemeal pasta) available within our
database of 1000 top-selling items.
Other categories such as “fresh fruit” and
“eggs” were not included since they are generally healthy foods and
a comparable regular substitute food could not be easily determined. Conversely,
“biscuits”, “cakes”, “puddings”,
“pies”, and “sugar/sweets” are generally unhealthy foods
and as comparable healthier simple substitute food could not be easily
determined these foods were also excluded.
A representative sample of foods for each category was
chosen by a Dietitian (CNM). Five regular foods per category were selected from
the database to create an average shopping basket. Efforts were made to include
a wide range of brands as well as different food types within each food
category.
The New Zealand Food and Nutrition Guidelines recommend
wholegrain breads and cereals; reduced or low-fat milk or milk products; and
lean meat, poultry, or seafood.16 Foods,
drinks, and snacks low in saturated fat, salt, and sugar are also recommended.
In keeping with these guidelines, five healthier
alternatives were chosen and compiled into a healthier alternative shopping
basket for comparison. The healthier food items were chosen based on a principle
of simple substitution—i.e. as far as possible the healthier food item
chosen was essentially the same type of food in terms of use and preparation.
Our approach to identifying regular and healthier food items has been used in
other published studies.17
Price data spanning 1 year was used to determine an
average price over time for each food item. Weights for each food item were
obtained either from the product description or, where this was not possible, by
visiting the supermarket to check the weight recorded on the product packaging.
Use of product weights combined with average price provided a cost per 100 grams
of food weight. In this way, food items that differed by weight could be
standardised and a more valid cost and nutrient comparison made.
Cost per 100 grams for a food category was derived from
the mean cost of items within that category. Finally, to estimate the average
weekly household cost for the food baskets, these data were combined with
national data on weekly estimated amounts of food required for a healthy
individual.18
ResultsOur two shopping baskets contained a total of 88 food items
across 9 food categories: meat and poultry; bread; breakfast cereal; butter and
margarine; cheese; canned fish; canned fruit; milk; and soft drinks (Table
1).
Table 1. Composition of regular and healthier
shopping baskets
It was not possible to include five breakfast cereals in the
healthier basket since there were not enough healthier options available in our
database (i.e. within top-selling 1000 foods). Therefore, the number of
breakfast cereals for the healthier basket was limited to three and the average
cost reported was the mean for three cereals.
Comparison of total weekly household costs showed there was
only a marginal price difference between the regular and healthy food baskets
($90.21 vs $96.63), although the price differential (7%) marginally favoured the
regular basket (Table 2). Certain categories of food such as bread, breakfast
cereals, milk, canned fruit, and soft drinks (i.e. flavoured carbonated drinks)
showed little or no difference in cost, but other food categories showed more
substantial cost differences (Table 2).
Table 2. Difference in weekly household cost
for regular and healthier baskets*
* Food quantities based upon weekly estimated amounts of
food required for a household comprised of one adult male, one adult female, one
10-year old child, and one 5-year old child. These are based on the New Zealand
Food and Nutrition Guidelines and will meet the nutritional needs of most
healthy people. While the food categories are the same for men, women, and
children, the amounts are appropriate for each age and sex
group.18
The healthier options were more expensive for meat and
poultry (27%), butter and margarine (44%), and cheese (19%). However, healthier
options were cheaper for canned fish (10%).
Comparison of nutrient values showed that, compared with the
regular food basket, the healthy food basket contained substantially less energy
(29%), total fat (35%), saturated fat (52%), sugar (56%), and sodium (20%) than
the regular basket (Table 3).
*Listed nutrients are those required on the mandatory
Nutrition Information Panel (NIP) for foods sold in New Zealand.
DiscussionOur analyses demonstrated that there was no major difference
in overall cost between commonly purchased regular and healthier supermarket
food items—although healthier food options within certain categories of
food tended to be more expensive, namely meats, spreads, and cheese. However,
fish canned in water or brine was cheaper than fish canned in oil. Despite
modest differences in cost, the healthier food basket offered considerable
nutritional advantages being lower in energy, total and saturated fat, sugar,
and sodium contents.
These analyses were based on actual supermarket sales data
from almost 900 customers over a 12-month period. As such, they have the
advantage of reflecting what foods people buy most frequently from supermarkets.
In addition, the fact that the sales data covered an entire year allowed us to
take account of price promotions and seasonal variations in price in estimating
food costs, rather than taking a single snapshot of price.
However, limitations include the fact that the sales data
were obtained from a single supermarket in the Wellington region and were based
on food purchases made by customers who were registered to use the handheld
barcode scanner system. As such the shopping data may not reflect supermarket
food purchases at a population level. Our analyses were also based on sales data
for the 1000 top-selling supermarket food items and thus did not include food
items that were bought in lesser volumes. However, the 1000 top-selling food
items covered 59% of all sales transactions and food items with lower sales are
likely to have a lesser impact overall on population diet.
Finally, we compared the cost of food items across a limited
number of food categories. This was due to several reasons, including a lack of
healthier food options within our product sales database for some potential food
categories such as grains and pasta, and the inability to offer appropriate
simple substitutes for some food items. As such, our analyses do not reflect the
costs of a total diet but rather those of a selection of key food categories
within the overall diet.
Some of the healthier basket items might also still be
considered suboptimal in terms of an ideal “healthy” diet. For
example, some of the healthier basket cheeses were still relatively high in
total and saturated fat, and sugar-free carbonated soft drinks are generally not
considered as healthy as plain reduced-fat milk or water.
Our findings suggest that a healthier diet is not
necessarily a more expensive diet, which is contrary to popular opinion. Both
Canadian10 and New
Zealand8,9 surveys show that a substantial
proportion of consumers perceive a healthy diet to be more expensive,
particularly in relation to fruit and vegetables.
Some previous studies have found no difference in food costs
when comparing healthy and regular diets. For example, one US study assessed
dietary costs for families with children advised to follow a 20-week behaviour
modification programme emphasising increasing diet nutrient
density.19 Twenty-four-hour dietary recalls
suggested that daily dietary costs were less at 1 year compared with baseline,
although the self-reported nature of these data means that underreporting is a
possibility.
In contrast, the perception that a healthy diet is more
expensive has been supported by studies such as the UK women’s cohort
study, which analysed food frequency intake data from over 15,000 women. The
study estimated that the difference in cost between extreme ends of the healthy
diet spectrum was ₤540 per year, with fruit and vegetable expenditure
being the main contributors to the expense of a healthy
diet.11
A United States study performed a direct comparison between
the government-endorsed Thrifty Food Plan shopping basket and a healthier
alternative, and found a US$36/fortnight (i.e. US$936/year) premium on the
healthier basket, mainly due to higher costs of lean meats and whole
grains.13
Extrapolation from our weekly cost data to an annual cost
suggests that a healthier diet in New Zealand for the food categories we
examined would cost approximately NZ$334/year more than a regular diet. This
cost difference is less than that seen in the US and UK studies, although this
is probably due to the fewer food categories included in our analyses. In
particular, the fact that fresh fruit and vegetables were not included means
that the cost differential for an overall diet is likely to be underestimated.
New Zealand household expenditure data show that vegetables
and fruit comprise approximately 14% of total food
expenditure,20 which is comparable to
expenditure on meat and poultry (14%), but it is considerably greater than
proportional expenditure on other food categories included in our analyses
including bread (4%), breakfast cereals (1%), and soft drinks (2%).
In New Zealand, 17% of deaths annually have been attributed
to high blood cholesterol levels.21 Dairy
products and meat are the major sources of fat in the New Zealand
diet,8 and our per capita consumption of butter
far exceeds consumption in comparable counties such as Australia, UK, and
USA.22
Our analysis shows that healthier options within the
“butter and margarine”, “meat and poultry”, and
“cheese” categories are substantially more expensive than regular
options, findings that support those of a previous New Zealand study that found
foods with high saturated fat content were approximately 35% cheaper than their
low saturated fat equivalents.23
Energy-dense (MJ/kg) diets, such as those high in fat, cost
less than their energy-dilute counterparts,24
and it has been suggested that the association between poverty and obesity may
be mediated by the low cost of such energy-dense
foods.25 Our findings taken in conjunction with
the well-known ethnic and socioeconomic disparities in rates of cardiovascular
disease in New Zealand,26,27 suggest an urgent
need to consider the affordability of food options low in saturated fat and
energy.
In many of the food categories included in these analyses,
the price of healthier foods was shown to be broadly similar to the cost of
regular food items. Therefore, information on healthy eating should emphasise
that it is possible to make healthier food choices for many staple food items
(e.g. bread, milk, breakfast cereals) without incurring an increase in household
grocery costs. However, healthier options for some key food categories are more
expensive and thus consideration should be given to policies by which this price
differential could be minimised, particularly for low-income shoppers who are at
greater risk of nutrition-related disease and are most likely to make food
choices based solely on cost rather than health.
Fiscal policy options include:
Finally, the lack of price differential between
regular and healthier food items for many food categories offers an opportunity
for the food industry to use relatively small price promotions to decrease the
comparative cost of the healthier food items and thus increase their sales.
ConclusionsWe found that simple substitution of commonly purchased
supermarket food items can improve the nutrient profile of a shopping basket
substantially without impacting adversely on overall cost. The implications of
this finding are two-fold: firstly, the commonly held perception that a healthy
diet is an expensive diet is not necessarily true, particularly for certain
categories of food; and secondly, it is possible that relatively minor
adjustments to the cost of healthier food items could increase their sales
relative to less healthy items.
Author information: Cliona Ni Mhurchu,
Senior Research Fellow, Clinical Trials Research Unit, University of Auckland;
Siddarth Ogra, Medical Student, University of Auckland.
Acknowledgements: SG’s summer
studentship was sponsored by the Health Research Council of New Zealand, and the
SHOP feasibility study was funded by the Health Research Council of New Zealand
and the National Heart Foundation of New Zealand. We are also grateful to the
University of Auckland for providing the opportunity for SG to conduct this
research as part of their Summer Studentship programme; Alex Bormans for
assisting with extracting data from the SHOP database; Sally Hamilton for
providing the nutrient data for the food items as part of her MPH thesis
project; Yannan Jiang for assisting with some data analysis; and Foodstuffs
(Wellington) Co-operative Society Ltd for provision of the sales data.
Correspondence: Dr Cliona Ni Mhurchu,
Clinical Trials Research Unit, University of Auckland, Private Bag 92019,
Auckland. Fax: (09) 373 1710; email: c.nimhurchu@ctru.auckland.ac.nz
References:
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