Dietary Habits, Food Preferences, Food Selection, Healthy Diet, Nutrition, Sustainability
Conditions
Keywords
food choices, climate, dietary substitutions, diet
Brief summary
The study aims to determine whether viewing health or climate labels (or both) and receiving recommendations for healthier or more climate-friendly swaps (or both) in an online grocery store environment improves the healthfulness and reduces the carbon footprint of consumers' food and beverage purchases compared to shopping as usual without swap recommendations. The online store will record participants' food selections. Participants will also be asked to complete survey measures.
Detailed description
Participants will complete an online between-subjects randomized experiment. The experiment will involve three study visits. In the first study visit, participants will complete an online grocery store shopping task without intervention. Participants will be given a budget of $50 and asked to shop as they normally would. The store will record participants' food selections. After completing the shopping task, participants will complete an online survey. Approximately one week later, participants will complete a second study visit with the same instructions. They will be randomized to 1 of 4 conditions (1) health only, 2) climate only, 3) combined health and climate, 4) control. In the health only condition, participants will view labels with nutrition grades and may be directed to swap their selections for healthier items. In the climate only condition, participants will view labels with climate grades and may be directed to swap their selections for more climate-friendly (lower-carbon-footprint) items. In the combined health and climate condition, participants will view labels with health and climate grades and may be directed to swap their selections for healthier or more climate-friendly items. In the control group, participants will not view any labels or swaps. The store will record participants' selections. After completing the shopping task, participants will complete an online survey. In the third study visit, the participants will maintain their assigned group and will be asked to repeat the same tasks as in the second visit.
Interventions
BEHAVIORALHealth swaps
Participants will view "health grade" labels on all products in the online grocery store indicating their healthfulness as estimated by United Kingdom Ofcom Nutrient Profiling Model scores. The health score labels will mimic Nutri-Score labels, a labeling system used in some European countries, showing a color-coded grade of "A" (green) through "F" (red) on each product. Products with "A" and "B" labels will meet the United Kingdom's cutoff for products that can be marketed to children and "C", "D" and "F" labels products are less healthy than this cutoff (based on tertiles of Ofcom scores within each food group). When participants attempt to add a less healthy product to their cart (e.g., "C," "D" or "F" health label), the store will automatically suggest a healthier product from the same category (e.g., with a "A" or "B" health label).
BEHAVIORALClimate swaps
Participants will view "climate grade" labels on all products indicating their climate impact. The climate impact is calculated as the greenhouse gas emissions associated with producing the product in carbon dioxide equivalents (CO2-eq) per 100g (i.e., "carbon footprint"). Labels will be applied based on quintiles of carbon footprints in each food group. When participants attempt to add a high-climate-impact product to their cart (e.g., with a "C," "D," or "F" climate label), the store will automatically offer them swaps to more climate-friendly products (e.g., with a "A" or "B" climate label).
BEHAVIORALCombined health and climate swaps
Participants will view both the health and climate grade labels on all products in the online grocery store. When participants attempt to select a product with a "C," "D," or "F" label on either dimension to their cart, the store will automatically offer them swaps to products that offer improvement over the original food on at least 1 dimension (health or climate-friendliness) and were at least as good or better on the other dimension, with the additional guardrail that the store never suggests products with a "C," "D" or "F" label on either dimension.
BEHAVIORALControl
Participants will not view any extra labels or be offered any swaps in the online grocery store.
Sponsors
Stanford University
National Heart, Lung, and Blood Institute (NHLBI)
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
* Aged 18 years or older * Reside in the United States * Able to complete a survey in English * Have internet access to complete the 3 online study visits
Exclusion criteria
* Under the age of 18 * Reside outside of the United States * Unable to complete a survey in English * Do not have internet access to complete the 3 online study visits
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Healthfulness of Product Selection | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will asses healthfulness of participants' selections as the average Ofcom Nutrient Profiling Model score of the products the participants select in the shopping task. The score ranges from 0 to 100, where higher scores are healthier. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Carbon Footprint of Participants' Grocery Store Selections | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess the carbon footprint of participants' selections, operationalized as the average carbon footprint (in CO2-equivalents) of the products the participants select in the shopping task. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, the non-missing value was used. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Calorie Density of Participants' Grocery Selections | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess the average calorie density of participants' grocery selections, calculated as the average kcal per 100g of the selected products. Higher values will indicate higher calorie density. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Sugar Density of Participants' Grocery Selections | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess the average sugar density of participants' grocery selections, calculated as the average grams of sugar per 100g of the selected products. Higher values will indicate higher sugar density. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Sodium Density of Participants' Grocery Selections | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess the average sodium density of participants' grocery selections, calculated as the average milligrams of sodium per 100g of the selected products. Higher values will indicate higher sodium density. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Saturated Fat Density of Participants' Grocery Selections | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess the average saturated fat density of participants' grocery selections, calculated as the average grams of saturated fat per 100g of the selected products. Higher values will indicate higher saturated fat density. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Fiber Density of Participants' Grocery Selections | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess the average fiber density of participants' grocery selections, calculated as the average grams of fiber per 100g of the selected products. Higher values will indicate higher fiber density. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Protein Density of Participants' Grocery Selections | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess the average protein density of participants' grocery selections, calculated as the average grams of protein per 100g of the selected products. Higher values will indicate higher protein density. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Total Spending on Participants' Grocery Selections | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess the total amount participants spent on their grocery selections in United States dollars. Higher values will indicate greater spending. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Thinking About Health | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess thinking about health using 1 item: "We are interested in how you selected products while you were grocery shopping. When you selected foods, how much did you think about each of the following characteristics? ... health." Response options range from "Not at all" (1) to "A great deal" (5). Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Thinking About Climate Impact | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess thinking about climate impact using 1 item: "We are interested in how you selected products while you were grocery shopping. When you selected foods, how much did you think about each of the following characteristics? ... climate impact." Response options range from "Not at all" (1) to "A great deal" (5). Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Thinking About Taste | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess thinking about taste using 1 item: "We are interested in how you selected products while you were grocery shopping. When you selected foods, how much did you think about each of the following characteristics? ... taste." Response options range from "Not at all" (1) to "A great deal" (5). Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Negative Emotional Reactions While Shopping | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess negative emotional reactions using 3 items: "While you were shopping, how much did you feel…" "worried", "guilty," "ashamed"? Response options range from "Not at all" (1) to "Extremely" (5). The investigators will average the 3 items; higher average scores indicate stronger negative emotional reactions. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Positive Emotional Reactions While Shopping | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess positive emotional reactions using 3 items: "While you were shopping, how much did you feel…" "inspired", "proud," "reassured"? Response options range from "Not at all" (1) to "Extremely" (5). The investigators will average the 3 items; higher average scores indicate stronger positive emotional reactions. Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Injunctive Norms to Buy Healthy Foods | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess injunctive norms to buy healthy foods with 1 item: "People who are important to me think I should buy healthy foods." Response options range from "Strongly disagree" (1) to "Strongly agree" (5). Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Descriptive Norms to Buy Healthy Foods | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess descriptive norms to buy healthy foods with 1 item: "Most shoppers buy healthy foods when they are shopping for groceries." Response options range from "Strongly disagree" (1) to "Strongly agree" (5). Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Injunctive Norms to Buy Foods With Low Climate Impact | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess injunctive norms to buy foods with low climate impact with 1 item: "People who are important to me think I should buy foods with low climate impact." Response options range from "Strongly disagree" (1) to "Strongly agree" (5). Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
| Descriptive Norms to Buy Foods With Low Climate Impact | 1-week follow-up (visit 2), and 2-week follow-up (visit 3) | The study will assess descriptive norms to buy foods with lower climate impact with 1 item: "Most shoppers buy foods with low climate impact when they are shopping for groceries." Response options range from "Strongly disagree" (1) to "Strongly agree" (5). Outcome values were calculated as each participant's mean across visits 2 and 3. If participants had missing data at one of these visits, data from the non-missing visit was used. |
Countries
United States
Contacts
PRINCIPAL_INVESTIGATORAnna H. Grummon, PhD
Stanford School of Medicine
Baseline characteristics
| Characteristic | — |
|---|---|
| Age, Categorical <=18 years | 0 Participants |
| Age, Categorical >=65 years | 25 Participants |
| Age, Categorical Between 18 and 65 years | 1176 Participants |
| Age, Continuous | 31.5 years STANDARD_DEVIATION 12.2 |
| Ethnicity (NIH/OMB) Hispanic or Latino | 27 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 273 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 0 Participants |
| Household Income $0 to $49,999 | 95 Participants |
| Household Income $100,000 to $149,999 | 62 Participants |
| Household Income $150,000 or more | 31 Participants |
| Household Income $50,000 to $99,999 | 108 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 1 Participants |
| Race (NIH/OMB) Asian | 11 Participants |
| Race (NIH/OMB) Black or African American | 89 Participants |
| Race (NIH/OMB) More than one race | 8 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 2 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 8 Participants |
| Race (NIH/OMB) White | 713 Participants |
| Region of Enrollment United States | 1201 Participants |
| Sex/Gender, Customized Man | 141 Participants |
| Sex/Gender, Customized Unknown or other | 2 Participants |
| Sex/Gender, Customized Woman | 157 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk | EG004 affected / at risk |
|---|---|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 300 | 0 / 301 | 0 / 300 | 0 / 300 | 0 / 1,201 |
| other Total, other adverse events | 0 / 300 | 0 / 301 | 0 / 300 | 0 / 300 | 0 / 1,201 |
| serious Total, serious adverse events | 0 / 300 | 0 / 301 | 0 / 300 | 0 / 300 | 0 / 1,201 |
Outcome results
None listed