Adherence to Healthy and Unhealthy Plant-Based Diets and the Risk of Gout.

Importance: Plant-based diets are increasing in popularity due, in part, to their health benefits for selected cardiometabolic diseases as well as favorable environmental impact. Little is known about how such a diet is related to gout risk. Objective: To examine associations between adherence to a plant-based diet (including healthy and unhealthy versions of this diet), as well as its 18 individual food groups, and incident gout. Design, Setting, and Participants: This prospective cohort study used data from population-based cohorts of US men and women enrolled in the Health Professionals Follow-Up Study (1986-2012) and Nurses' Health Study (1984-2010). Participants were men and women free of gout at baseline. Statistical analyses were performed over March 2020 to August 2023. Exposures: An overall plant-based diet index (PDI), as well as healthy (hPDI) and unhealthy (uPDI) versions of this index that emphasize healthy and less healthy plant-based foods, respectively. These diet indices were comprised of 18 food groups, assessed using a validated semiquantitative food frequency questionnaire. Main Outcomes and Measures: Incident cases of gout that were confirmed with a supplementary questionnaire to meet the preliminary American College of Rheumatology survey criteria for gout. Cox proportional hazards regression models were used to evaluate multivariable-adjusted associations of all 3 PDIs with incident gout using quintiles (Q) of adherence. Results: Among a total of 122 679 participants (mean [SD] age, 53.8 [9.8] years among 43 703 men; mean [SD] age, 50.9 [7.2] years among 78 976 women) over 2 704 899 person-years of follow-up, 2709 participants experienced incident gout. The overall PDI was not significantly associated with gout in either cohort (Q5 vs Q1 pooled hazard ratio [HR], 1.02 [95% CI, 0.89-1.17]; P for trend = .63). In the pooled analysis, hPDI was significantly inversely associated with risk of gout (Q5 vs Q1 HR, 0.79 [95% CI, 0.69-0.91]; P for trend = .002), while the uPDI was positively associated with risk of gout (Q5 vs Q1 HR, 1.17 [95% CI, 1.03-1.33]; P for trend = .02), particularly in women (Q5 vs Q1 HR, 1.31 [95% CI, 1.05-1.62]; P for trend = .01). In analysis of individual food groups, higher intakes of certain healthy plant foods, such as whole grains (pooled HR per 1 serving/d, 0.93 [95% CI, 0.89-0.97]) and tea and coffee (pooled HR per 1 serving/d, 0.95 [95% CI, 0.92-0.97]), as well as dairy (pooled HR per 1 serving/d, 0.86 [95% CI, 0.82-0.90]), were independently associated with a lower risk of gout, while selected unhealthy plant foods, such as fruit juice (pooled HR per 1 serving/d, 1.06 [95% CI, 1.00-1.13]) and sugar-sweetened beverages (pooled HR per 1 serving/d, 1.16 [95% CI, 1.07-1.26]) were associated with increased risk of gout. Conclusions and Relevance: The findings of this prospective cohort study of PDIs and gout support current dietary recommendations to increase consumption of healthy plant foods while lowering intake of unhealthy plant foods to mitigate gout risk.

Low-Carbohydrate Diet Macronutrient Quality and Weight Change.

Importance: The associations of low-carbohydrate diets (LCDs) with long-term weight management remains unclear, and the source and quality of macronutrients within LCDs are less explored. Objectives: To prospectively examine associations between changes in LCD indices and weight change among US adults. Design, Setting, and Participants: This prospective cohort study included initially healthy participants at baseline from the Nurses' Health Study (NHS; 1986-2010), Nurses' Health Study II (NHSII; 1991-2015), and Health Professionals Follow-up Study (HPFS; 1986-2018). Data analysis was performed between November 2022 and April 2023. Exposures: Five LCD indices were examined: (1) a total LCD (TLCD) emphasizing overall lower carbohydrate intake; (2) an animal-based LCD (ALCD) that emphasized animal-sourced protein and fat; (3) a vegetable-based LCD (VLCD) that emphasized plant-sourced protein and fat; (4) a healthy LCD (HLCD) emphasizing less refined carbohydrates, more plant protein, and healthy fat; and (5) an unhealthy LCD (ULCD) emphasizing less healthful carbohydrates, more animal protein, and unhealthy fat. Main Outcomes and Measures: The outcome of interest was 4-year changes in self-reported body weight. Results: A total of 123 332 participants (mean [SD] age, 45.0 [9.7] years; 103 320 [83.8%] female) were included in this study. The median carbohydrate intake (as a percentage of energy) of the highest quintiles of TLCD score at baseline ranged from 38.3% in HPFS to 40.9% in NHSII. Mean weight gain over 4-year intervals among participants varied from 0.8 kg in the HPFS to 1.8 kg in the NHSII. After adjusting for demographics and baseline and concomitant changes of selected lifestyle factors, each 1-SD increase in TLCD score was associated with 0.06 (95% CI, 0.04-0.08) kg more weight gain over the 4-year periods. Similarly, participants gained 0.13 (95% CI, 0.11 to 0.14) kg per each 1-SD increase in ALCD score and 0.39 (95% CI, 0.37 to 0.40) kg per each 1-SD change in ULCD score. In contrast, each 1-SD increase in VLCD score was associated with 0.03 (95% CI, 0.01 to 0.04) kg less weight gain, and each 1-SD increase in HLCD score was associated with 0.36 (95% CI, 0.35 to 0.38) kg less weight gain. The associations were more pronounced among obese individuals (per 1-SD increase in HLCD score: BMI ≥30, 0.88 [95% CI, 0.80, 0.97] kg less weight gain; BMI <25, 0.23 [95% CI, 0.20, 0.26] kg less weight gain; P for interaction < .001). Conclusions and Relevance: These findings suggest that the quality of LCDs may play a critical role in modulating long-term weight change. Only LCDs that emphasized high-quality protein, fat, and carbohydrates from whole grains and other plant-based foods were associated with less weight gain.