Abstract
Background Plant-based diets are associated with a lower risk of cardiovascular diseases; however, little is known how the healthiness of the diet may be associated with blood pressure (BP). We aimed to modify three plant -based diet indices: overall plant-based diet index (PDI), healthy PDI (hPDI), and unhealthy PDI (uPDI) according to country-specific dietary guidelines to enable use across populations with diverse dietary patterns – and assessed their associations with BP. Design We used cross-sectional data including 4,680 men and women ages 40-59y in Japan, China, the United Kingdom, and the United States from the INTERnational study on MAcro/micronutrients and blood Pressure (INTERMAP). During four visits, eight BP measurements, and four 24-h dietary recalls were collected. Multivariable regression coefficients were estimated, pooled, weighted, and adjusted extensively for lifestyle/dietary confounders. Results Modified PDI was not associated with BP. Consumption of hPDI higher by 1SD was inversely associated with systolic (-0.82 mm Hg;95% CI:-1.32,-0.49) and diastolic BP (-0.49 mm Hg; 95% CI:-0.91,-0.28). In contrast, consumption of an uPDI was directly associated with systolic (0.77 mm Hg;95% CI:0.30,1.20). Significant associations between hPDI with BP were attenuated with separate adjustment for vegetables and whole grains; associations between uPDI and BP were attenuated after adjustment for refined grains, sugar-sweetened beverages, and meat. Conclusion An hPDI is associated with lower BP while a uPDI is adversely related to BP. Plant-based diets rich in vegetables and whole grains and limited in refined grains, sugar-sweetened beverages, and total meat may contribute to these associations. In addition to current guidelines, the nutritional quality of consumed plant foods is as important as limiting animal-based components.
Generated Summary
This cross-sectional study, part of the INTERMAP study, investigated the association between plant-based diets and blood pressure (BP) in a diverse population across Japan, China, the United Kingdom, and the United States. The research aimed to modify three plant-based diet indices: the overall plant-based diet index (PDI), healthy PDI (hPDI), and unhealthy PDI (uPDI), according to country-specific dietary guidelines to facilitate their use across various populations with distinct dietary patterns. The study involved cross-sectional data from 4,680 men and women aged 40-59 years, focusing on eight BP measurements and four 24-hour dietary recalls. The primary methodology involved estimating multivariable regression coefficients, pooled, weighted, and adjusted extensively for lifestyle and dietary confounders. The research sought to determine how different plant-based diet indices correlated with BP levels and identify the specific food groups influencing these associations. The findings underscore the importance of dietary quality within plant-based diets, providing insights into how diet can affect BP and contribute to cardiovascular health.
Key Findings & Statistics
- Modified PDI was not associated with BP.
- Consumption of hPDI higher by 1 SD was inversely associated with systolic (-0.82 mm Hg; 95% CI: -1.32, -0.49) and diastolic BP (-0.49 mm Hg; 95% CI: -0.91, -0.28).
- Consumption of uPDI was directly associated with systolic (0.77 mm Hg; 95% CI: 0.30, 1.20).
- The partial correlation between hPDI and uPDI was -0.3, while the correlation of overall PDI with hPDI was 0.6 and with uPDI was -0.2.
- Reliability estimates for PDI, hPDI and uPDI for East Asian participants were 65%, 65% and 66%, respectively, and for Western participants 69%, 67% and 67%, respectively.
- A six-point higher score of eating a PDI was not associated with BP after adjusting for lifestyle and dietary factors (model 2; table 1).
- A six-point higher score of an hPDI, however, was associated with a -0.82 mm Hg lower systolic BP (95% CI: −1.32 to −0.49) and a -0.49mm Hg lower diastolic BP (95% CI: -0.91 to 0.28) after adjustment for lifestyle and dietary factors.
- A six-point higher uPDI score was associated with +0.77mm Hg higher systolic BP (95% CI: 0.30 to 1.20).
- For diastolic BP, uPDI score higher by 1SD was associated with a higher diastolic BP in Western participants only (0.48mm Hg; 95% CI: 0.14 to 0.93).
- In subcohorts, associations of hPDI and uPDI with systolic BP were consistent with main findings.
- Consumption of an hPDI, with a one standard deviation increase in the score, was associated with a reduction in systolic blood pressure of -0.82 mm Hg (95% CI: -1.32 to -0.49) and a reduction in diastolic blood pressure of -0.49 mm Hg (95% CI: -0.91 to -0.28).
- A higher score of an unhealthy plant-based diet (uPDI) was associated with an increase in systolic blood pressure of 0.77 mm Hg (95% CI: 0.30 to 1.20).
- The reliability estimates for the plant-based diet indices (PDI, hPDI, and uPDI) ranged from 65% to 69% across the different populations.
- Higher hPDI scores were associated with lower systolic and diastolic BP, with the most significant reductions observed in Western participants.
- A six-point higher score on the hPDI was associated with a decrease of -0.82 mm Hg in systolic BP (95% CI: -1.32 to -0.49) and a decrease of -0.49 mm Hg in diastolic BP (95% CI: -0.91 to -0.28).
- Conversely, a higher score on the uPDI was associated with an increase in systolic BP by 0.77 mm Hg (95% CI: 0.30 to 1.20).
- The study showed a correlation of -0.3 between hPDI and uPDI scores, indicating a degree of inverse relationship between the two indices.
Other Important Findings
- An hPDI is associated with lower BP while a uPDI is adversely related to BP.
- Plant-based diets rich in vegetables and whole grains and limited in refined grains, sugar-sweetened beverages, and total meat may contribute to these associations.
- In addition to current guidelines, the nutritional quality of consumed plant foods is as important as limiting animal-based components.
- Higher adherence to a high quality plant-based diet, but not an overall plant-based diet, was inversely associated with systolic and diastolic BP.
- A higher score of an unhealthy plant-based diet was directly associated with systolic BP.
- Intakes of vegetables and whole grains explained the inverse associations of a healthy plant-based diet with BP, while intakes of refined grains, sugar-sweetened beverages, and total meat contributed to the direct associations of an unhealthy plant-based diet with BP.
- Significant associations between hPDI with BP were attenuated with separate adjustment for vegetables and whole grains; associations between uPDI and BP were attenuated after adjustment for refined grains, sugar-sweetened beverages, and meat.
- The inverse associations of hPDI with BP were independent of BMI and urinary excretion of sodium and potassium.
- The associations of uPDI with BP were independent of BMI and urinary excretion of sodium and potassium.
- The PDI, hPDI, and uPDI were modified according to country-specific dietary guidelines to enable use across populations with diverse dietary patterns.
- The study used detailed multipass 24-hour dietary recalls and 24-hour urinary excretion data.
- The study included 4,680 participants (2,359 men and 2,321 women) from Japan, China, the United Kingdom, and the United States.
- The INTERMAP study initially surveyed 4,895 adults.
- The remaining six food groups were consumed in low amounts (nuts, fish or shellfish, fruit juice, whole grains, dairy products and sugar-sweetened beverages).
- The maximum score for all scores is 54 and the minimum score is 12.
- Reliability estimates for PDI, hPDI and uPDI for East Asian participants were 65%, 65% and 66%, respectively, and for Western participants 69%, 67% and 67%, respectively.
- We detected no evidence of potential effect modification by age, sex, smoking, ethnic group, physical activity, BMI or family history of CHD.
- Additionally, no cross-country heterogeneity was detected.
- In these subcohorts, associations of hPDI and uPDI with systolic BP were consistent with main findings.
- The remaining six food groups were consumed in low amounts (nuts, fish or shellfish, fruit juice, whole grains, dairy products and sugar-sweetened beverages) and scores were assigned based on consumed (score=1) or not consumed (score=0) to ensure comparability across the various population samples.
Limitations Noted in the Document
- The study’s cross-sectional design limits the ability to establish long-term causality.
- Residual confounding, particularly from inaccurate measurement of physical activity and reporting bias in dietary recalls, may exist.
- The study used standardized food groups, which might not fully capture the nuances of specific food groups known to be beneficial for BP, such as dark chocolate or low-fat dairy.
Conclusion
The study concludes that adherence to a high-quality plant-based diet, as measured by the hPDI, is inversely associated with both systolic and diastolic BP. Conversely, an unhealthy plant-based diet, reflected in a higher uPDI score, is directly associated with systolic BP. The findings emphasize that the nutritional quality of plant-based foods, particularly the intake of vegetables and whole grains, is crucial for these beneficial associations. In contrast, the consumption of refined grains, sugar-sweetened beverages, and total meat may undermine the positive effects of plant-based diets on blood pressure. The study suggests that focusing on the quality of plant-based diets, rather than solely limiting animal-based foods, is key to maintaining healthy blood pressure levels. This research highlights the importance of considering the healthiness of plant-based diets and the potential for promoting cardiovascular health through dietary choices. The authors emphasize that the findings support the concept that the nutritional quality of plant foods is as important as the limitation of animal-based foods in maintaining healthy blood pressure. The study’s results provide further insights into the relationship between dietary patterns and cardiovascular health, emphasizing the importance of well-planned plant-based diets. The observed relationships between hPDI and BP were largely independent of BMI and urinary sodium and potassium excretion, indicating that the diet itself plays a significant role in influencing blood pressure levels. These findings underscore the importance of promoting dietary patterns that emphasize high-quality plant foods to support cardiovascular health, with the recommendation that guidelines should emphasize the nutritional quality of the plant foods consumed.