Calcium

    A diet that is rich in calcium has been shown to lower blood pressure (BP), thus calcium supplementation has might also offer some benefit. The Women’s Health Initiative randomized trial randomized over 36,000 post-menopausal women to receive either placebo or calcium plus vitamin D3. Their results showed no reduction in BP over seven years and calcium plus vitamin D3 did not lower the risk of developing hypertension over the same time period.¹³ Knox and Gaster report that four out of twelve randomized controlled trials (RCTs) looked at showed a blood pressure lowering effect, a meta-analysis done showed marginal lowering, calcium supplements can cause headaches and kidney stones, and calcium might have an effect by way of a natriuresis.⁷ A recent Cochrane review by Beyer et al. found no evidence to suggest supplements of calcium & magnesium or of calcium & potassium can reduce BP.² Labarthe and Ayala report of two studies, one, a meta-analysis and the other, a prospective cohort study, that showed no effect of supplemental calcium on BP, but an additional meta-analysis found a small BP lowering effect with supplementation.⁹ It seems that from these results, calcium, whether taken alone or with vitamin D, magnesium, or potassium, does not have any effect on BP.

Fish Oil

    From results of animal and clinical studies, it is theorized that the w-3 fatty acids in fish oil have hypotensive properties through stimulation of the prostaglandins that control sodium and water excretion, cause vasodilation and inhibition of the vasoconstrictor thromboxane, regulate renin release, and decrease the response to vasopressor hormones.¹⁵ Only hypertensive patients, and not normotensive patients, may seem benefit from from oil according to two meta-analyses and one RCT found by Labarthe and Ayala.⁹ Chagan and her associates cite a meta-analysis of 31 trials that showed a significant dose-response effect with fish oil and lowering of BP, but only in hypertensive patients, not normotensive. Fish oil was also well-tolerated without any adverse events and variations in the trials did not appear to influence the results. The authors did note, however, that a wide variety of doses were used, and until a therapeutic dose range can be found, patients should only increase fish intake instead of consuming supplements.³ The amounts of change in BP seen in these analyses were small, in the range of 2-8 mmHg. Even though, fish oil might have a lowering effect in hypertensive patients, that effect is small, and a recommended dose cannot be made due to the fact of the wide variety of doses studied. More on fish oil can be found here.

Coenzyme Q10

    Patients with hypertension have been shown to have reduced levels of coenzyme Q10, also known as ubiquinone and a necessary protein in the human body. A meta-analysis, found by Nahas of twelve trials of coenzyme Q10 in a heterogenous population of study participants, showed a BP lowering effect of nearly 16 and 8 mmHg for systolic and diastolic BP, respectively. Mild gastrointestinal upset was the only reported side effect.¹⁶ Two RCTs, both placebo-controlled, studying coenzyme Q10, found by Knox and Gaster, showed significant decreases in BP as well, to the effect of a 10% decrease.⁷ From the results of this research, it looks like coenzyme Q10 has a good chance to be of benefit to hypertensive patients. However, these studies were done over a short time period and had a small number of patients. A large and longer RCT would need to be completed to show the true benefit of coenzyme Q10. More on coenzyme Q10 can be found here.

These three supplements had the most evidence for or against them in this search. Other supplements found that have been researched were vitamins D, C, and E, magnesium, L-arginine, taurine, melatonin, black currant seed oil, and chocolate. Please see references 3, 7, 13, 14, and 16, for further discussion.