Plant-based diets and blood pressure: How to boost the positive link

Plant-based diets are associated with a lower risk of cardiovascular diseases​ and the 2015 Dietary Guidelines Advisory Committee report recommends shifting to a plant-based diet and limiting intake from animal sources in order to maintain a healthy blood pressure but this diet label can be interpreted in many ways especially from one country to another.

The current study points out that previous investigations have considered all plant foods healthy—even those associated with adverse health effects including refined grains and sugar-sweetened beverages. 

The team of international researchers conducted a study using the INTERnational study on MAcro/micronutrients and blood Pressure (INTERMAP) to discover how three different types of plant-based diet impacted blood pressure, in order to discover applicability across populations with diverse dietary patterns.

The three diets studies were: overall plant-based diet index (PDI), healthy PDI (hPDI) including foods such as whole grains, fruits, vegetables, nuts, legumes, vegetable oils and tea/coffee and low in fruit juices, sugar-sweetened beverages, refined grains, potatoes and sweets and desserts and animal foods.

They conclude that, in addition to current guidelines, the nutritional quality of the foods is as important as limiting animal-based components. Specifically, their findings indicate that refined grains, sugar-sweetened beverages and high meat consumption are linked with higher blood pressure while a diet with a lower animal consumption and high in vegetables and whole grains is linked to lower blood pressure (BP).

The report adds: "Most participants in the present study were omnivorous (consume animal and plant foods). This suggests that for health benefits, a healthy plant-based diet does not have to be vegan or vegetarian; however, fewer animal-based foods should be consumed. ​

"Our results show that eating one serving of whole grains and four servings of vegetables, while limiting total meat intake to 100 g per day was associated with a systolic BP lower by around 4 mm Hg. ​

"To our knowledge, this is the first study that investigated the influence of healthiness on the association between plant-based diets and BP."​

They suggest the BP-lowering effects could be due, not only to the low animal-based content, but also the various arrays of nutrients and micronutrients present in vegetables and whole grains, including dietary fibre​, potassium​, calcium​ and unsaturated fatty acids may improve vascular endothelial function​.

Methodology

The team used cross-sectional data including 4,680 men and women aged 40–59 in Japan, China, the United Kingdom, and the United States.

PDI, hPDI and uPDI were modified according to country-specific dietary guidelines for use across populations with diverse dietary patterns. The team categorised all reported foods into 18 food groups according to Satija ​et al​​. Country-specific cut-offs were based on recommended intakes of the US Dietary Guidelines for Western participants​ and the Chinese Dietary Guidelines for East Asian participants​.

During four visits, participants provided 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 (physical activity, smoking, medical history, special diet, medication, contraceptives, alcohol).

The results revealed that consumption of hPDI was linked with lower BP while consumption of an uPDI was linked with higher blood pressure. However, significant associations between hPDI with BP were attenuated with separate adjustment for vegetables and whole grains and associations between uPDI and BP were attenuated after adjustment for refined grains, sugar-sweetened beverages, and meat.

Overall, plant-based diets rich in vegetables and whole grains and limited in refined grains, sugar-sweetened beverages, and total meat appeared to contribute to lower BP. 

Further results

Results also showed that participants with high hPDI scores were older, mostly women, more educated, mostly omnivorous and less likely to smoke; with higher urinary excretion of potassium and lower urinary excretion of sodium while participants with high uPDI scores were younger, mostly men, less educated and more likely to smoke.

The nutrient composition of the score in Western and East Asian participants showed higher hPDI scores were lower in trans-fatty acids and dietary cholesterol, and higher in dietary beta-carotene, calcium, iron, magnesium, phosphorus, potassium, retinol, vitamin E, vitamin A, vitamin C compared with lower hPDI scores.

Source: BMJ Nutrition, Prevention & Health​

Aljuraiban G, Chan Q, et al

"Association between plant-based diets and blood pressure in the INTERMAP study"​

doi: 10.1136/bmjnph-2020-000077