Garlic may reduce blood pressure in people who have high levels, according to About.com. Studies show that, particularly with systolic blood pressure (the bottom number in the results), garlic may reduce numbers by as much as 10 mmHg.
The ingredients in garlic that contribute to reduced blood pressure include allicin, which may cause relaxation in the arteries by engaging the nitric oxide system. Research on people using between 600 and 2,400 milligrams of aged garlic extract or garlic powder in divided or single doses for as long as three months have shown signs of reduction. It's worth noting that garlic interacts unsafely with many conditions and medications, so talking to a physician is a must before starting to use garlic, advises About.com.
Another supplement that can reduce high blood pressure is omega-3 fatty acids that are present in fish oil. These acids are also found in fish as a food as well as in some plant foods. Existing research as of March 2015 indicates that this supplement can also bring minor drops in pressure. Higher doses of these fatty acids can elevate the risk of bleeding in people who take warfarin or who have bleeding disorders. As with garlic, talking to a physician is necessary before starting an omega-3 fatty acid regimen, About.com states.