Background
Methods
Trial design
-
Arm 1: regular online supermarket used as control condition;
-
Arm 2: information nudges;
-
Arm 3: position nudges;
-
Arm 4: information and position nudges.
Participants
Interventions
Healthy products | Unhealthy or neutral products | |||
---|---|---|---|---|
Information nudges | No intervention | Position nudges | No intervention | |
All foods and beverages (n = 9217) | n=966; 62% of all healthy products | n=604 | n=486; 6% of all unhealthy products | n=7161 |
Fruits (n=211) | Fresh, pre-cut, and frozen fruits (n=94; 61% of all healthy fruits) | Fresh fruit, canned fruits, apple sauce (n=61) | N/A | Canned fruits with added sugar, apple sauce with added sugar, fruit puree with added sugar (n=56) |
Vegetables (n=415) | Fresh, pre-cut, and frozen vegetables (n=199; 73% of all healthy vegetables) | Fresh vegetables (n=75) | N/A | Vegetables with added cream, canned vegetables (salted) (n=141) |
Breads (n=218) | Wholegrain bread (n=57; 90% of all healthy bread) | Wholegrain bread (n=6) | White and non-wholegrain brown bread (n=61; 39% of all unhealthy bread) | White and non-wholegrain brown bread (n=94) |
Bread substitutes (n=222) | Wholegrain crackers, oats, muesli (n=28; 88% of all healthy bread substitutes) | Oats, muesli (n=4) | Non-wholegrain crackers, breakfast cereals with added sugar, salt, and/or fat (n=142; 75% of all unhealthy bread substitutes) | Rice crackers, rusk, non-wholegrain crackers, breakfast cereals with added sugar, salt, and/or fat (n=48) |
Potatoes (n=105) | N/A | Fresh and/or pre-cut unprocessed potatoes (n=50) | N/A | Processed potatoes (n=55) |
Pasta and rice (n=208) | Wholegrain pasta and rice (n=28; 88% of all healthy pasta and rice) | Wholegrain pasta and rice (n=5) | Non-wholegrain pasta and rice (n=103; 59% of all unhealthy pasta and rice) | Non-wholegrain pasta and rice (n=72) |
Teas and coffees (n=361) | Tea bags (n=102; 35% of all healthy tea and coffee) | Tea bags, filtered coffee products (n=190) | N/A | Unfiltered coffee products, tea bags (added sugar) (n=69) |
Sodas, waters, and juices (n=735) | Water, flavored water (unsweetened) (n=67; 96% of all healthy beverages) | Flavored water (unsweetened) (n=3) | N/A | Sodas, energy drinks, fruit juices, lemonade (n=665) |
Cheeses (n=332) | Low-fat and low-salt cheeses (n=28; 72% of all healthy cheeses) | Low-fat and low-salt cheeses (n=11) | N/A | High-fat and/or high-salt cheeses (n=293) |
Milk and yogurt products (n=571) | Semi-skimmed and skimmed milk and yogurt products (n=111; 71% of all healthy milk and yogurt) | Soy-dairy products (unsweetened), semi-skimmed and skimmed sterilized milk, coffee milk (n=46) | N/A | Semi-skimmed and skimmed dairy products (sweetened), full-fat dairy, custard, desserts, pudding, whipped cream, pudding, cooking cream, dairy drinks, chocolate milk, soy-dairy products (sweetened), ice cream (n=414) |
Meats (n=769) | N/A | Unprocessed and low-fat meats, meat substitutes (unsalted), and eggs(n=105) | N/A | Processed and high-fat meats, and meat substitutes (salted) (n=664) |
Fish (n=140) | Fresh, frozen, canned, and breaded fish (> 70% fish) (n=87; 92% of all healthy fish) | Canned fish (n=8) | N/A | Breaded fish (< 70% fish), processed fish dishes (n=45) |
Legumes (n=135) | Canned legumes (low salt) (n=63; 94% of all healthy legumes) | Canned legumes (low salt) (n=4) | N/A | Canned legumes (high salt) (n=68) |
Nuts (n=179) | Seeds, nuts, peanuts, natural peanut butter (n=34; 67% of all healthy nuts) | Seeds, nuts, peanuts, natural peanut butter (n=17) | Nuts, peanuts (salted) (n=103; 81% of all unhealthy nuts) | Sugared peanuts, peanut butter (added salt and palm oil) (n=25) |
Fats (n=163) | Olive oils, sunflower oils, and margarines (n=68; 78% of all healthy fats) | Vegetable oils, frying oils (n=19) | Butters, baking butters (n=56; 78% of all unhealthy fats) | Frying oils, coconut oils, butters, baking butters (n=20) |
Other foods (n=2077) | N/A | N/A | N/A | Ready-to-eat meals, meal salads, pancakes, pizza, canned soup, drinking broth, seasoning products (n=2077) |
Savory snacks (n=417) | N/A | N/A | Savory snacks (n=21; 5% of all unhealthy snacks) | Salty snacks, fried snacks, chips, popcorn, bread sticks, (n=396) |
Sweet snacks (n=1255) | N/A | N/A | N/A | Cookies, candy, confectionary, chocolate, liquorice, bubblegum, water-based ice cream (n=1255) |
Alcoholic drinks (n=704) | N/A | N/A | N/A | All alcoholic drinks (n=704) |
Outcomes
Sample size
Implementation and randomization
Statistical methods
Results
Arm 1 | Arm 2 | Arm 3 | Arm 4 | |||||
---|---|---|---|---|---|---|---|---|
(n=2992) | (n=2864) | (n=2976) | (n=2943) | |||||
Females, n (%)a | 1931 | (64.5) | 1847 | (64.5) | 1989 | (66.8) | 2018 | (68.6) |
Age, mean (SD)b | 56.5 | (17.4) | 57.0 | (17.6) | 56.8 | (17.5) | 55.9 | (17.4) |
Shoppers from deprived areas, n (%) | 1503 | (50.2) | 1466 | (51.2) | 1494 | (50.2) | 1423 | (48.4) |
Total grams purchased, median (IQR) | 21,766 | (17,679) | 21,172 | (17,576) | 21,275 | (16,440) | 21,995 | (17,626) |
Shoppers within food groups, n (%) | ||||||||
Fruits | 2179 | (72.8) | 2100 | (73.3) | 2148 | (72.2) | 2120 | (72.0) |
Vegetables | 2309 | (77.2) | 2235 | (78.0) | 2324 | (78.1) | 2292 | (77.9) |
Breads | 1796 | (60.0) | 1761 | (61.5) | 1848 | (62.1) | 1811 | (61.5) |
Bread substitutes | 1038 | (34.7) | 980 | (34.2) | 1011 | (34.0) | 977 | (33.2) |
Potatoes | 1202 | (40.2) | 1114 | (38.9) | 1067 | (35.9) | 1151 | (39.1) |
Pasta and rice | 773 | (25.8) | 795 | (27.8) | 784 | (26.3) | 832 | (28.3) |
Teas and coffees | 1163 | (38.9) | 1213 | (42.4) | 1193 | (40.1) | 1148 | (39.0) |
Sodas, waters and juices | 1955 | (65.3) | 1828 | (63.8) | 1914 | (64.3) | 1939 | (65.9) |
Cheeses | 1759 | (58.8) | 1745 | (60.9) | 1739 | (58.4) | 1778 | (60.4) |
Milk and yogurt products | 2623 | (87.7) | 2493 | (87.0) | 2590 | (87.0) | 2572 | (87.4) |
Meats | 2558 | (85.5) | 2465 | (86.1) | 2556 | (85.9) | 2463 | (83.7) |
Fish | 721 | (24.1) | 660 | (23.0) | 683 | (23.0) | 701 | (23.8) |
Legumes | 520 | (17.4) | 569 | (19.9) | 537 | (18.0) | 574 | (19.5) |
Nuts | 779 | (26.0) | 805 | (28.1) | 846 | (28.4) | 846 | (28.7) |
Fats | 1502 | (50.2) | 1480 | (51.7) | 1488 | (50.0) | 1457 | (49.5) |
Other foods | 2526 | (84.4) | 2472 | (86.3) | 2552 | (85.8) | 2529 | (85.9) |
Savory snacks | 1589 | (53.1) | 1510 | (52.7) | 1603 | (53.9) | 1613 | (54.8) |
Sweet snacks | 2186 | (73.1) | 2057 | (71.8) | 2101 | (70.6) | 2098 | (71.3) |
Alcoholic drinks | 1001 | (33.5) | 1002 | (35.0) | 1112 | (37.4) | 1078 | (36.6) |