Food choices and diet costs:
An economic analysis
Adam Drewnowski, PhD
Director, Center for Public Health Nutrition
Director, NIH Roadmap Center for Obesity Research
Professor of Epidemiology and Medicine
School of Public Health and Community Medicine
University of Washington
Poverty and Obesity: Disparities in Diet and Health.
ECOR Interdisciplinary Forum, Seattle, WA, March 2, 2007
Disparities in diet and health:
A new focus on money and time
Some basic points:
•
•
•
•
Energy-dense foods cost less
Nutrient-rich foods cost more
Healthier diets cost more per MJ
There are inequities in food access
• Consumer food choices are driven by
• Taste, cost, convenience,
health, variety
Consumers care about food costs
Some health professionals do not
Are healthy diets available to all?
The Harvard SPH Food Pyramid
Is this the perfect diet…
………or is it economic elitism?
Taste, cost, convenience = sugar + fat
Energy
Grains,
Taste
density
Sugar/fat
Sugar/fat
Grains,
Cost
Sugar/fat
Obesity
Food
choices
Grains,
Time/Convenience
Sugar/fat
Variety
Health
Obesity
First question
Do energy-dense foods cost less?
•
•
•
•
Energy density defined as MJ/kg
Energy cost defined as $/MJ (€/MJ)
Energy and nutrients from databases
Mean national food prices in France
Energy density (MJ/kg) depends on the
water content of foods
40
Energy density (MJ/kg)
oil
Fats
30
Sw eets
Grains
Vegetables
Fruit
Meat
Dairy
butter
20
grains
meats
10
fruit
Potato chips
vegetables
0
0
10
20
30
40
50
60
w ater content (g/100g)
70
80
90
100
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
600
spreads
400
Log scale!
200
0
0.01
0.1
1
10
Energy cost (Euros/1000kcal)
100
1000
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
600
sugar
400
desserts
200
soft drinks
0
0.01
0.1
1
10
Energy cost (Euros/1000kcal)
100
1000
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
600
grains
sugar
400
bread
desserts
200
pasta
soft drinks
0
0.01
0.1
1
10
Energy cost (Euros/1000kcal)
100
1000
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
600
grains
sugar
cheese
400
desserts
200
pasta
yogurt
milk
0
0.01
0.1
1
10
Energy cost (Euros/1000kcal)
100
1000
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
600
grains
sugar
cheese
400
desserts
meat
200
pasta
milk
0
0.01
0.1
1
10
Energy cost (Euros/1000kcal)
100
1000
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
600
grains
sugar
cheese
400
foie gras
desserts
meat
200
pasta
fish/shellfish
milk
0
0.01
0.1
1
10
Energy cost (Euros/1000kcal)
100
1000
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
600
grains
sugar
cheese
400
desserts
meat
200
pasta
fish/shellfish
milk
0
0.01
0.1
vegetables
1
10
Energy cost (Euros/1000kcal)
100
1000
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
nuts
600
grains
sugar
cheese
400
fruit
desserts
200
pasta
fish/shellfish
milk
0
0.01
0.1
vegetables
1
10
Energy cost (Euros/1000kcal)
100
1000
Energy density (kcal/100g) and energy cost
(Euros/1000kcal) – INCA study
1000
oil
Energy density (kcal/100g)
800
butter
nuts
600
grains
sugar
cheese
400
Wine/alcohol
fruit
desserts
200
pasta
fish/shellfish
milk
0
0.01
0.1
vegetables
1
10
Energy cost (Euros/1000kcal)
100
1000
Disparity in food costs:
Are “junk” foods simply cheaper?
1000
oil
Energy density (kcal/100g)
800
600
400
butter
Low energy density
High satiating power
Antioxidants
Phytochemicals
Fiber
CLA
Vitamins
Minerals
High glycemic Index
High glycemic load
Hydrogenated fats
Trans fatty acids
Added sugars
Added fats
Energysugar
dense foodsgrains
Empty calories
Minimal nutritional value
desserts
fruit
fish
200
soda
0
0.01
0.1
vegetables
1
10
Energy cost (Euros/1000kcal)
100
1000
Second question
Are energy-rich foods nutrient-poor?
• Energy-dense foods cost less
• Grains, fats, oils are more affordable
• Energy-dense foods taste better
• Palatability = energy density
• Are low-cost, energy-dense foods low in
key nutrients?
We need to create a nutrient density
score for foods:
•
Nutrient Density Score is the ratio between the
amount of nutrients in a food and the energy that the
food provides
NDS = (NAS/ED) * 100
•
Nutrient Adequacy Score is based on percent DVs
for N key nutrients as provided by 100 g of food
NAS = (Σ
Σ (Nutrienti/DVi) * 100)/N
•
Nutrient-to-price ratio NPR = NAS/price per 100g
Work by Darmon, Drewnowski, Monsivais
Yes – energy dense foods have lower
Nutrient Density Scores (NDS/100kcal)
900
Fats/oils
Energy Density (kcal/100g)
800
700
600
500
400
300
sugar
200
100
F+V
0
0.1
10
Nutrient Density Score/100 kcal
Darmon, Darmon, Maillot, Drewnowski JADA 2005
1000
Higher nutrient-density (per 100g) usually
means higher cost (also per 100g)
Nutrient Adequacy Score/100g
1000
100
10
1
All foods
0.1
0.01
0.1
1
Price (Euros/100g)
Darmon, Darmon, Maillot, Drewnowski JADA 2005
F+V
10
NNR scores for vegetables and fruit
40
vegetables
fruit
Energy density (MJ/kg)
cantaloupe
mango
30
potato chips
tangerines
strawberries
20
fried potatoes
raisins
10
applesauce
grape juice
grapefruit
kiwi
spinach
romaine
broccoli
tomato
OJ
potatoes
avocado
canned pears
blueberries
0
10
100
Nutrient Density Score (NNR version)
1000
Third question:
Do energy-dense diets cost less?
•
•
•
•
•
French INCA study conducted by AFSSA
Sample of 1,985 adults; 7-day food diaries
National prices for 650 foods
Diet costs measured in €/d
Energy cost measured in €/10MJ
At each intake quintile,
higher energy density = lower cost (€/wk)
100
Diet cost (Euros/week)
90
80
70
60
50
EI1
40
30
20
10
0
0
INCA data
2
4
6
Energy density (KJ/g)
8
10
At each intake quintile,
higher energy density = lower cost (€/wk)
100
Diet cost (Euros/week)
90
80
70
60
50
EI2
40
EI1
30
20
10
0
0
INCA data
2
4
6
Energy density (KJ/g)
8
10
At each intake quintile,
higher energy density = lower cost (€/wk)
100
Diet cost (Euros/week)
90
80
70
60
EI3
50
EI2
40
EI1
30
20
10
0
0
INCA data
2
4
6
Energy density (KJ/g)
8
10
At each intake quintile,
higher energy density = lower cost (€/wk)
100
Diet cost (Euros/week)
90
80
70
EI4
60
EI3
50
EI2
40
EI1
30
20
10
0
0
INCA data
2
4
6
Energy density (KJ/g)
8
10
At each intake quintile,
higher energy density = lower cost (€/wk)
100
Diet cost (Euros/week)
90
80
EI5
70
EI4
60
EI3
50
EI2
40
EI1
30
20
10
0
0
INCA data
2
4
6
Energy density (KJ/g)
8
10
Spend less = Eat more
Are obesity and poverty linked by the low cost of energydense foods that are both palatable and convenient?
Drewnowski & Specter, Am J Clin Nutr 2004;79:62004;79:6-16
The Energy Density curve
Drewnowski and Specter AJCN 2004:79:6-16
2 5
Sugar
fat
Low quality
High quality
Energy
density
Food energy
Food energy
requirement
0
Food costs (log)
The paradox – it is possible to spend less and get more
But the calories will be refined grains, added sugar and fat
As dietary ED increases –
so do total energy intakes
10
Energy density (KJ/g)
9
8
7
6
5
4
3
2
1
0
0
INCA data
20
40
60
80
100
Energy intake (MJ/week)
120
140
160
Last question:
What happens when you stratify
diets by energy cost?
Food expenditures can be a proxy for SES
An epidemiological dogma falls
The unshakeable relationship
between nutrients and calories
disappears
A principle of nutritional epidemiology
• “Intakes of virtually all nutrients are
positively correlated with total caloric intake”
• “People who consume more total food have
higher nutrient intakes”
• “Nutrient intakes are biologically important in
relation to caloric intakes”
• Hence the need to correct for energy in
epidemiologic studies
•Willett and Stampfer in Nutritional Epidemiology, 2nd Ed, OUP 1998
The INCA (1998) data set
•
•
•
•
•
•
INCA is a nationally representative study of 1,985
French adults
Dietary intakes based on 7-day diet records.
More than 850 foods in the nutrient database
Mean national food prices supplied by the French
government (INSEE); by market research agencies
(SECODIP), as well as Paris websites
Diet costs estimated by multiplying unit price for
each item by portion size and summing over all
foods consumed by that person
That is the estimated cost of the diet – assuming
that all foods are purchased and prepared at home
Low-cost diets:
Spend less – but eat more
Quartiles of energy cost (€/10MJ)
P Anova
Q1 (4.9)
Q2 (5.9)
Q3 (6.9)
Q4 (9.0)
0.0001
Energy Density (MJ/kg)
6.4
6.1
6.0
5.7
0.0001
Energy Intake (MJ/d)
9.4
9.0
8.7
8.2
0.0001
Vitamin C (mg/day)
65
79
85
96
0.0001
Vitamin D (µ
µg/day)
2.2
2.4
2.8
2.9
0.0001
Vitamin E (mg/day)
6.9
7.2
7.5
8.0
0.0001
ß-Carotene (mg/day)
2287
2824
2908
2969
0.0001
Folates (µ
µg/day)
237
255
277
290
0.0001
Andrieu,
Andrieu, Darmon,
Darmon, Drewnowski, EJCN, 2006
Low cost diets:
more energy, fewer nutrients
Referent diet
Vitamin C
% of Q1
140
Vitamin D
ß Carotene
Folates
Vit E
120
100
Energy Intake
Energy Density
80
Q1
4.9 €/10MJ
4.5 €/d
Q2
5.9 €/10MJ
5.3 €/d
Q3
6.9 €/10MJ
6.0 €/d
Q4
9.0 €/10MJ
7.4 €/d
Val-de-Marne: Contribution of food groups to
diet energy and to diet cost
(Drewnowski & Darmon, AJCN, 2005)
50
% diet cost
% dietary energy
40
30
20
10
0
Meat/Fish
F+V
Dairy
Grains
Sugar
Fats/oils
The energy/price hierarchy is such that the lowest-cost food
groups contribute the most to energy intakes
Final question:
What about food prices in Seattle?
• We collected food prices in 2004 and 2006
•
•
•
•
•
Same supermarkets, same foods, same
package sizes
The foods were divided by energy density
Low ED = vegetables and fruit
High ED = grains, sugars and fats
Manuscript (Monsivais et al.) submitted to
JADA
Energy density (kcal/100g) and energy cost ($/1000kcal) –
Seattle 2006 Supermarket prices
10
oil
Energy density (kcal/100g)
8
butter
nuts
6
sugar
grains
cheese
4
fruit
desserts
2
pasta
fish/shellfish
milk
0
0.01
0.1
vegetables
1
10
Energy cost ($/1000kcal)
100
1000
The rising cost of low-energydensity foods
Fruits and vegetables
Fats and sweets
2004-2006 Price Inflation (%)
30
20
]
*
]
10
]
]
0
]
-10
1
2
3
Quintiles of Energy Density
Monsivais et al. submitted
4
5
Access to healthy foods
Affordability
• Energy-dense foods are cheaper
• Accessibiity
• Energy-dense foods are closer
• Convenience
•
• Fast foods take less time to prepare
What can you get for $100/week for a family of 4.
The USDA Thrifty Food Plan: 1999
40
Energy density (MJ/kg)
oil
shortening
zucchini squash
green peppers
margarine
30
mayonnaise
lettuce
fresh tomatoes
crackers
20
sugar
white bread
cheese
ground beef
10
beans
eggs
potatoesmilk
koolAid
0
10
100
1000
Energy cost (log cents/10MJ)
10000
100000
Is obesity an economic issue?
A challenge for public health nutrition
Less expensive
More expensive
• High-fat energy-dense foods are often the
cheapest options for the consumer
•Editorial, The Lancet January 31, 2004
• If a meal of grilled chicken, broccoli and fresh
fruit costs more and is less convenient than a
burger and fries, the battle against obesity
will be lost
•Editorial, The Lancet January 31, 2004
Food choices and diet costs:
An economic analysis
Adam Drewnowski, PhD
Director, Center for Public Health Nutrition
Director, NIH Roadmap Center for Obesity Research
Professor of Epidemiology and Medicine
School of Public Health and Community Medicine
University of Washington
Poverty and Obesity: Disparities in Diet and Health.
ECOR Interdisciplinary Forum, Seattle, WA, March 2, 2007