BACKGROUND Policies to reduce red meat intake are important for mitigating climate change and improving public health. We tested the impact of taxes and warning labels on red meat purchases in the United States. The main study question was, will taxes and warning labels reduce red meat purchases? METHODS AND FINDINGS We recruited 3,518 US adults to participate in a shopping task in a naturalistic online grocery store from October 18, 2021 to October 28, 2021. Participants were randomized to one of 4 conditions: control (no tax or warning labels, n = 887), warning labels (health and environmental warning labels appeared next to products containing red meat, n = 891), tax (products containing red meat were subject to a 30% price increase, n = 874), or combined warning labels + tax (n = 866). We used fractional probit and Poisson regression models to assess the co-primary outcomes, percent, and count of red meat purchases, and linear regression to assess the secondary outcomes of nutrients purchased. Most participants identified as women, consumed red meat 2 or more times per week, and reported doing all of their household's grocery shopping. The warning, tax, and combined conditions led to lower percent of red meat-containing items purchased, with 39% (95% confidence interval (CI) [38%, 40%]) of control participants' purchases containing red meat, compared to 36% (95% CI [35%, 37%], p = 0.001) of warning participants, 34% (95% CI [33%, 35%], p < 0.001) of tax participants, and 31% (95% CI [30%, 32%], p < 0.001) of combined participants. A similar pattern was observed for count of red meat items. Compared to the control, the combined condition reduced calories purchased (-312.0 kcals, 95% CI [-590.3 kcals, -33.6 kcals], p = 0.027), while the tax (-10.4 g, 95% CI [-18.2 g, -2.5 g], p = 0.01) and combined (-12.8 g, 95% CI [-20.7 g, -4.9 g], p = 0.001) conditions reduced saturated fat purchases; no condition affected sodium purchases. Warning labels decreased the perceived healthfulness and environmental sustainability of red meat, while taxes increased perceived cost. The main limitations were that the study differed in sociodemographic characteristics from the US population, and only about 30% to 40% of the US population shops for groceries online. CONCLUSIONS Warning labels and taxes reduced red meat purchases in a naturalistic online grocery store. Trial Registration: http://www.clinicaltrials.gov/ NCT04716010.

中文翻译：

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税收和警告标签对美国消费者购买红肉的影响：一项随机对照试验。

背景技术减少红肉摄入量的政策对于缓解气候变化和改善公众健康非常重要。我们测试了税收和警告标签对美国红肉购买的影响。主要研究问题是，税收和警告标签会减少红肉的购买吗？方法和结果我们招募了 3,518 名美国成年人，于 2021 年 10 月 18 日至 2021 年 10 月 28 日期间在一家自然主义在线杂货店参与购物任务。参与者被随机分配到 4 个条件之一：控制（无税收或警告标签，n = 887)、警告标签（健康和环境警告标签出现在含有红肉的产品旁边，n = 891）、税收（含有红肉的产品价格上涨 30%，n = 874），或组合警告标签 + 税收（n = 866）。我们使用分数概率和泊松回归模型来评估购买红肉的共同主要结果、百分比和数量，并使用线性回归来评估购买的营养素的次要结果。大多数参与者都是女性，每周食用红肉两次或以上，并表示自己负责全家的杂货购物。警告、税收和综合条件导致购买的含红肉食品的百分比较低，与对照组相比，对照组参与者购买的含红肉食品的比例为 39%（95% 置信区间 (CI) [38%, 40%]）。 36% (95% CI [35%, 37%], p = 0.001) 的警告参与者，34% (95% CI [33%, 35%], p < 0.001) 的税务参与者，以及 31% (95%)合并参与者的 CI [30%, 32%], p < 0.001)。红肉项目的计数也观察到类似的模式。与对照组相比，综合条件下购买的卡路里减少了（-312.0 kcals，95% CI [-590.3 kcals，-33.6 kcals]，p = 0.027），而税收（-10.4 g，95% CI [-18.2 g， -2.5 g]，p = 0.01）和组合（-12.8 g，95% CI [-20.7 g，-4.9 g]，p = 0.001）条件减少了饱和脂肪的购买；没有任何情况影响钠的购买。警告标签降低了人们对红肉的健康性和环境可持续性的认知，而税收则增加了人们对红肉的成本的认知。主要局限性在于该研究的社会人口特征与美国人口不同，并且只有约 30% 至 40% 的美国人口在网上购买杂货。结论 警告标签和税收减少了自然主义在线杂货店的红肉购买量。试验注册：http://www.clinicaltrials.gov/NCT04716010。