Hemp seed protein, hydrolysate may lower BP in hypertensive adults

Adults with hypertension may derive some benefits from consuming hemp protein, as well as its bioactive peptides, suggests a study.

In particular, consumption of both hemp seed protein (HSP) and its hydrolysate-derived bioactive peptide (HSP+) has led to a reduction in 24-h systolic (SBP) and diastolic blood pressure (DBP) compared with casein. HSP+ also shows a greater lowering effect on 24-h SBP and DBP relative to HSP.

“Similar to the hypotensive effects, HSP and HSP+ reduced plasma angiotensin-converting enzyme (ACE) activity and increased renin and nitric oxide (NO) concentrations when compared with casein,” the researchers said. “However, we did not observe a difference between HSP and HSP+ in terms of their effects on plasma BP biomarkers.”

Thirty-five adults with mild hypertension (SBP between 130 and 160 mm Hg; DBP ≤110 mm Hg) were enrolled in this double-blind, randomized, crossover design trial. They were randomly assigned to varying sequences of three 6-week treatment: 50-g casein/d, 50-g HSP/d, or 45-g HSP plus 5-g HSP+/d. Each treatment was separated by a 2-week washout period.

Finally, the researchers evaluated the effects of these interventions using a linear mixed model with repeated measures.

Compared with casein, HSP consumption reduced 24-h SBP and DBP from 135.1 and 80.0 mm Hg to 133.5 and 78.9 mm Hg (p<0.0001), respectively, while HSP+ intake resulted in greater BP reduction to 128.1 mm Hg SBP and 76.0 mm Hg DBP (p<0.0001 for both). [Am J Clin Nutr 2024;120:56-65]

No differences were observed in plasma ACE activity, renin, or NO concentrations between HSP and HSP+ consumption. However, when compared with casein, these two treatments succeeded in reducing both ACE and renin activities and in increasing plasma NO concentration.

“These findings imply that the inclusion of hemp protein in the diet may potentially play a role in managing mild hypertension among adults,” the investigators said.

“It is important to note that our study primarily focused on assessing the impact of hemp protein on BP within the parameters of our trial,” they added.

Animal study

These results also support those from the study by Girgih and colleagues, who examined the BP-lowering effects of HSP or HSP+ compared with casein in an animal experiment. These researchers evaluated the preventive and treatment effects of HSP and HSP+ in rats. [Euphytica 2004;140:65-72]

“Although each treatment period was 4 weeks, their findings showed a greater hypotensive effect than our results; however, we were not anticipating similar results because animal studies usually do not translate into replications in human studies,” said the investigators of the current study. [BMJ 2007;334:163-164]

The present study has some limitations, which include the absence of a run-in period, the 2-week washout period between treatments, and the failure to observe adherence to treatment.

In addition, “the extent to which disparities in dietary intake and physical activity patterns between treatments may have modified the BP or plasma biomarker responses to the study treatments in our trial remains speculative as we did not tightly control diet or exercise in participants in this free-living trial,” the investigators said.

“Further studies will be needed to confirm the potential of HSP and its hydrolysate-derived bioactive peptides in BP reduction. Dose–response research is strongly encouraged in the future to investigate the highest dose of hemp seed bioactive peptides with the optimum hypotensive response,” they added.