In February 2020 researchers from Japan published their review on the potential benefits of garlic and other dietary supplements for the management of hypertension. The control of hypertension is extremely important so as to prevent cardiovascular disease and many types of medications are available to treat it. When blood pressure cannot be controlled with one drug, treatment with multiple anti-hypertensive agents, is given. Most individuals think that their anti-hypertensive medication successfully controls their blood pressure but a study in 2013 found that the prescribed anti-hypertensive medication successfully controlled blood pressure levels in only 33% of individuals. Despite an initial fall in the incidence of uncontrolled hypertension in the USA, a study published in 2017 showed that although there has been an improvement since 2010 uncontrolled hypertension still remains a global problem. There has therefore been a growing awareness of complementary and alternative approaches in the prevention and treatment of cardiovascular disease. According to a 2012 survey, natural products in the form of dietary supplements is the most popular approach. Although a large variety of dietary supplements are used worldwide, only a few supplements have been investigated extensively for their effectiveness, safety and potential interactions with other medicines and dietary supplements. In addition, there may be differences in ingredients, raw material used, the manufacturing process, etc, which may be the reason for conflicting results in different studies.
However, despite this multiple studies have shown that the following dietary supplements may significantly reduce blood pressure levels without severe side effects:
CoQ10 is a potent antioxidant and many studies have shown that a higher level of CoQ10 in the blood is associated with a reduced risk of cardiovascular disease, including hypertension. In fact one study involving individuals with high blood pressure showed that CoQ10 supplementation for a 10-week period reduced the systolic blood pressure level by 17.8 mmHg and the diastolic blood pressure by 12.0 mmHg. Another study involving individuals with hypertension and coronary artery disease showed that CoQ10 supplementation for 8 weeks not only significantly reduced blood pressure levels and heart rate, but that the levels of antioxidants in the blood, such as vitamins A and E, were also significantly increased. In addition, several studies have shown that those individuals taking CoQ10 have been able to reduce the dosage or the number of anti-hypertensive drugs they were taking. Studies involving CoQ10 treatment have produced few adverse effects and minimal drug interactions. However, it should be noted that CoQ10 may increase the risk of bleeding in patients taking blood thinning agents.
A review of 29 studies revealed that vitamin C supplementation for 8 weeks reduced the systolic blood pressure levels by an average of 3.8 mmHg and diastolic blood pressure levels by 1.5 mmHg. Of note, one study reported that taking vitamin C at the same time as amlodipine, provided additional benefits, such as a lower systolic blood pressure and a higher level of superoxide dismutase in the blood. Superoxide dismutase promotes the breakdown of free radicals and supplements of this substance are used to treat and prevent a number of health problems and diseases. Studies have also shown that the side-effects of vitamin C appeared to be relatively minor.
Fish oil contains long-chain and polyunsaturated omega-3 fatty acids, such as eicosapentaenoic acid and docosahexaenoic acid. A higher consumption of fish oil or omega-3 polyunsaturated fatty acids is associated with a reduced mortality from cardiovascular disease. The majority of studies involving individuals with hypertension have shown that fish oil supplementation produces a modest, but significant reduction in both systolic and diastolic blood pressure levels but the results were dependent on the treatment period and on the type of individual, ie with or without increased blood pressure levels (fish oil supplementation had no effect on blood pressure in individuals with normal blood pressure levels). Currently it does not appear that any studies have been undertaken that report adverse effects following fish oil supplementation.
Ginseng (Korean red ginseng, American ginseng)
Ginseng has been reported to produce a beneficial effect in atherosclerosis and cardiovascular disease, as well as hypertension. One study showed that 3 hours after taking Korean red ginseng (Panax Ginseng) 400 mg, the systolic blood pressure level reduced by 5.7 mmHg and the diastolic level by 5.1 mmHg. Another study showed that an extract of American ginseng (Panax quinquefolius) 3 g for 12 weeks, significantly reduced systolic blood pressure levels by 11.7% and arterial stiffness by 5.3% in individuals with hypertension and diabetes type 2. However, other studies found that ginseng had no effect on either arterial stiffness or blood pressure in subjects with hypertension. It may be that these inconsistent results are due to different concentrations in the active ingredients in the gingseng used, the individuals studied as well as measurement methods. Studies looking at the safety of ginseng have shown that it has a good safety profile with no specific adverse events.
Garlic (Kwai garlic powder, Garlic homogenate diet, Aged garlic extract)
Studies undertaken on the effect of garlic on blood pressure levels have shown inconsistent results. However, the most recently published studies suggest that garlic may be effective in individuals with hypertension and slightly elevated cholesterol levels. There are over 10 studies which show that Kwai garlic powder in doses ranging from 600 to 900 mg/day significantly reduces blood pressure levels in individuals with hypertension but not in individuals with normal blood pressure. The most consistent effects have been observed in studies using aged garlic extract, which has been shown to significantly reduce blood pressure in patients with uncontrolled hypertension. Interestingly, the aged garlic extract also reduced arterial stiffness, decreased inflammation and improved gut microbiota. The majority of studies have shown that garlic supplements are very safe with only a few studies reporting adverse events, eg unpleasant smelling breath, body odour and mild gastrointestinal disturbances. However, these side-effects have generally been seen in studies using raw garlic and are improved with the use of aged garlic extract.
Gut microbial richness and diversity have been shown to be significantly reduced in individuals with hypertension. An increasing number of studies have shown that the use of probiotics can lead to a moderate or significant reduction in blood pressure, and that this is also associated with an improvement in gut microbiota. One study has shown that consuming a drink containing Lactobacillus plantarum for 6 weeks can lead to a significant reduction in systolic blood pressure, leptin, fibrinogen and interleukin-6 (an inflammatory marker) in healthy individuals. In addition, several studies involving individuals with hypertension have shown that milk fermented with bacteria, specifically the Lactobacillus species, can significantly decrease blood pressure. One study showed that consuming fermented milk products containing Lactobacillus casei at least 3 times a week considerably reduced the incidence of hypertension over a 5-year follow-up period. It has also been shown that probiotics can improve lipid levels, reduce blood glucose levels in addition to reducing blood pressure levels. Todate, no studies have been identified which report side-effects from using probiotics.
Whilst some studies appear to show some supplementation can reduce blood pressure levels, larger and longer term studies are required to determine the substantial benefits and risks associated with the use of these dietary supplements.
Matsutomo T. Potential benefits of garlic and other dietary supplements for the management of hypertension. Exp Ther Med. 2020 Feb;19(2):1479-1484