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for people ages 21 years and up
Healthy Volunteers
healthy people welcome
at San Francisco, California
study started
estimated completion:



Improving diets through increased food and vegetable (F&V) consumption significantly reduces the risk of cardiovascular disease (CVD). Programs increasing the accessibility and affordability of F&Vs among low-income Americans have been hindered by the food consumption cycle associated with poverty: the tendency to over-consume calories shortly after receiving funds at the beginning of each month, draining the budget for F&V purchases, or for all food purchases, by month's end. An emerging theory about dietary behavior suggests that providing funds for food in smaller installments distributed throughout the month will smooth the consumption cycle and improve healthy eating—counteracting the tendency to respond to lump sum, once-monthly funding installments by purchasing calorie-dense foods immediately after funds are received. The theory also suggests that funds targeted toward specific healthy foods (e.g., F&Vs) will improve diets more than untargeted funds, despite the inconvenience of utilizing targeted funds. We will rigorously test both hypotheses in a real-world setting by comparing alternative approaches for delivering food purchasing vouchers. We have established and tested the infrastructure to provide vouchers accepted by numerous food sellers (e.g., supermarkets, corner shops) in low-income neighborhoods. Leveraging this infrastructure, we will conduct a randomized trial with a two-by-two factorial design, comparing $20 of vouchers valid for one month to four $5 vouchers each valid for a sequential week of the month (lump sum versus distributed funding), and comparing vouchers restricted to F&V purchases to vouchers redeemable for any food (targeted versus untargeted funding). Low-income adults (N=288) recruited through our community partners will be randomized to one of four 6-month interventions: monthly targeted, monthly untargeted, weekly targeted, or weekly untargeted vouchers. Participants will be assessed through efficient verbal 24-hour dietary recalls validated among low-literacy populations, to determine daily consumption of F&Vs and metrics of overall dietary quality at months 0, 6 and 12 (6 months after vouchers end). Additional surveys will identify moderators and mediators of dietary improvement.

Official Title

Coupons for Healthy Intake Using Variable Economic Strategies (CHIVES)


Participants for the trial will be recruited via advertisements at community sites including primary care clinics, housing assistance sites, and soup kitchens in the city of San Francisco. Recruitment materials will direct interested individuals to attend one of the study information sessions at a 'storefront' site in San Francisco for an initial screening evaluation by the study staff, and a study orientation session to detail the study purpose, procedures, and participant rights. The orientation sessions will consist of a 60-minute session at a centrally-located room. After the orientation session, participants will be invited to sign a consent form, complete the baseline assessment, and be randomized to one of the four intervention conditions in a 1:1:1:1 allocation. We will use permuted block randomization so that sample sizes in each intervention group are nearly equal. Allocation sequence will be concealed prior to assignment; staff for sequence generation, allocation concealment, and implementation will be separate.

Those agreeing to participate will sign a written consent form after the study orientation and before randomized to one of four voucher conditions, as part of our 2-by-2 study design: (1) vouchers targeted to fruits and vegetables and valid for sequential weeks of the month; (2) vouchers targeted to fruits and vegetables and valid over the entire month; (3) vouchers applicable to any food and valid for sequential weeks of the month; and (4) vouchers applicable to any food and valid over the entire month. Half of participants will receive a blue voucher valid for any food (not tobacco, alcohol, or prepared foods), while the other half will receive a green voucher valid only for qualified fruits and vegetables (fresh or frozen fruits, vegetables, or herbs without added sugars or fats, to correspond to the eligibility guidelines of existing voucher programs). All vouchers will have the same individual value ($5), but one half of participants will receive four vouchers that are each valid for the whole month (a lump sum payment of $20), while the other half will receive four vouchers that are each valid for one sequential week of the month, as labeled on the voucher (a distributed payment of $5 per week). Therefore, all intervention groups will be balanced on time and attention from study staff, as well as effort to obtain the vouchers. By having all vouchers in small increments of $5, we minimize the need for a large voucher to be spent all at once, reducing the risk of food spoilage affecting intervention effectiveness. Having all vouchers be worth the same value also simplifies processing of the voucher at the level of the food vendor. We have specifically designed the monetary amounts of the trial to be sufficient for achieving nutritional goals (the Healthy People 2020 goal of consuming 1.4 cups of fruits and vegetables per day), but not be unduly large so as to be coercive to low-income populations.

One month's supply of vouchers will be picked-up by each participant during the first week of each month. Therefore, all intervention groups will be balanced on time and attention from study staff, as well as effort to obtain the vouchers. Vouchers can be picked up by participants at multiple neighborhood community-based locations. The locations are food pantries, area public health clinics or neighbor-hood public housing project offices that served as recruitment and distribution sites during a pilot feasibility study, and will again serve as recruitment sites in the trial. The sites are open over extended business hours. Vouchers will be placed in a small sealed envelope in a lockbox at the front desk of these locations; only participant identification numbers appear on the envelope. Voucher distributors have access to the lockbox combination, and will login to our secure HIPAA-compliant Access database to record when a participant has picked up their vouchers. Picture identification will be required for pick-up, and participants will sign a pick-up sheet. Participants without a picture ID will be referred to the city hall office that provides a free city-sponsored picture ID. Participants must pick up their own vouchers, and lost vouchers will not be replaced.

To redeem vouchers, participants present the voucher to a cashier, and sign and date the voucher at the time of redemption. The cashier processes the voucher just as they processes vouchers for the Women, Infants and Children's program or manufacturer's coupons, and the vendor then submits the redeemed voucher for payment (the financial infrastructure is handled by the San Francisco General Hospital Foundation). The names of the vendors who will accept the vouchers are printed on each voucher, along with their address and business hours. All voucher rules will be reviewed with participants during the orientation session. We will continue routine meetings with the neighborhood food vendors' managers to ensure continued active participation and correct usage of the vouchers.

Following informed consent, participants will complete a baseline survey and a 24-hour dietary recall before being randomized to one of the four study conditions. The recall includes three distinct passes to obtain a participant's food intake during the previous 24 hours—a quick list, a detailed description, and a review—including foods obtained at home and away from home, and including bartered, foraged, food pantry and other non-purchased items. Participants are provided standard 2-dimensional booklets for reference to portion sizes. Our research assistants are blinded to the participant's intervention arm and skilled in guiding dietary recalls among diverse participants in a non-judgmental, comprehensive manner. The baseline recall will be conducted in person at the storefront site; subsequent recalls will be conducted over telephone. Recalls will be performed during week 1 and week 4 of the month-0 (baseline), month-6, and month-12 assessments. Two recalls each will be done during week 1 (one weekday and one weekend) and two during week 4 (one weekday and one weekend) of the assessment months. This minimizes the number of recalls required to capture intra-person variation in diet between weekdays and weekends, while simultaneously capturing the monthly consumption cycle among participants (the key hypothesized mediator for the lump sum vs. distributed voucher effect).

In addition to dietary recalls, research assistants will orally administer surveys to prevent literacy-based biases, consistent with recent Institute of Medicine recommendations. These 20-minute surveys will be conducted at months 0, 6, and 12 and will cover attitudes and preferences regarding the vouchers and fruits and vegetables generally, shopping patterns, food expenditures, household environment, and food insecurity.

Each participant will receive vouchers for a total of 6 months. The participants will then be tracked by the recruitment/retention coordinator through brief telephone contact monthly to ensure retention until they complete the month 12 survey and dietary recall (6 months after the end of the intervention), after which they are discharged from the study.

In addition to participants who receive the vouchers, we will also conduct a brief survey with managers of the ten stores who have signed memos of understanding with the City of San Francisco and San Francisco General Foundation to accept the vouchers. The managers will be given informed consent forms to consider participating in a post- intervention survey. The paper-based vendor survey will be hand-delivered to vendors' managers to assess: (i) whether managers have any difficulties with the voucher system and whether those difficulties are at the point of sale, at the point of reimbursement, and/or when answering questions to customers about the vouchers; (ii) what if any activities were used by vendors to promote fruit and vegetable purchases during the voucher trial period; (iii) what if any activities they had engaged in to sell more fruits and vegetables; and (iv) a free text entry to elicit what changes vendors would propose to the voucher system in future


Cardiovascular Diseases nutrition food security behavioral economics


You can join if…

Open to people ages 21 years and up

age ≥21 years; household income <250% of the federal poverty level;has regular access to a mobile phone; understands English sufficiently to provide informed consent; a resident of the City of San Francisco as defined by official municipal boundaries; willing to be randomized.

You CAN'T join if...

participating in a diet including any other dietary or nutrition study; currently has diagnosed cancer or congestive heart failure; planning to move in the next year.



accepting new patients
Start Date
Completion Date
Stanford University
Study Type
Last Updated
December 2016
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