A new study shows that Spirulina, a type of algae, may help lower blood pressure—especially in people with high blood pressure or other heart-related risks. Researchers looked at 29 clinical trials and found that Spirulina was the most effective algae for reducing blood pressure. People who took at least 3 grams per day for 12 weeks saw the biggest improvements.

The results showed Spirulina lowered the top number (systolic) of blood pressure by about 5 points and the bottom number (diastolic) by over 3 points. The benefits were strongest in older adults and those who already had high blood pressure. Other types of algae, like kelp, didn’t show much effect, and algae powders worked better than pills or extracts.

Experts say adding Spirulina to your diet could be a simple, natural way to support healthy blood pressure—especially if you’re at risk. Just be careful not to overdo it with seaweed-based products, which can be high in heavy metals or iodine.