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Seaweed Salad Lowers Blood Pressure

Analysis by Dr. Joseph Mercola Fact Checked

seaweed salad

Story at-a-glance -

  • Seaweed salad, also called hiyashi wakame and goma wakame, may lower blood pressure according to published research
  • Although there are many prescription drugs available to treat high blood pressure, their side effects are numerous, so new and natural treatments are encouraging
  • High blood pressure affects 1 out of 3 American adults and is responsible for 94 million deaths a year, worldwide
  • Major complications of high blood pressure include heart attack, stroke, aneurysms, eye and kidney problems, metabolic syndrome, vascular dementia and cognitive decline
  • Edible seaweed contains valuable nutrients such as iodine, potassium, calcium, iron and alginic acid, which is used in some medical treatments

Have you discovered seaweed salad? Since it has become a popular restaurant item as an appetizer or garnish in Japanese restaurants and sushi bars, some consider it the new coleslaw. Also called hiyashi wakame and goma wakame, seaweed salad is usually seasoned with sesame oil and seeds with red pepper flakes, vinegar, salt, mushrooms and seaweed-based agar agar added.1

While many people enjoy the taste of marine-derived greens, which include kelp, nori, kombu and wakame, seaweed is also one of the world's best sources of iodine.2 It has also been credited with significant health benefits such as neuroprotective,3 anti-inflammatory4 and anti-viral properties.5

Seaweed is also being studied as useful for high blood pressure6 — yes, your seaweed salad may lower your blood pressure. In an observational study in children,7 seaweed consumption was shown to lower diastolic blood pressure in boys and systolic blood pressure in girls.

As for adults, research published in the American Journal of Hypertension found that a preparation made from seaweed decreased mean blood pressure in 62 middle-aged patients with mild high blood pressure.8 An article in Marine Drugs also cited several studies linking seaweed consumption to decreased blood pressure.9 The associations are encouraging.

Seaweed Actions That May Lower Blood Pressure

High blood pressure is defined as a condition in which the long-term force of blood against artery walls is too high and may eventually cause health problems.10 Although there are many prescription drugs available to treat high blood pressure, their side effects are numerous.

That is why natural treatments such as seaweed are so important. This is how researchers writing in Marine Drugs explain the likely potential actions of seaweed compounds on high blood pressure:11

"Polyphenols have been described to act as Angiotensin-I converting enzyme (ACE) inhibitors. ACE is a zinc-containing metalloproteinase that catalyses the conversion of angiotensin I to angiotensin II, the latter is a potent vasoconstrictor involved in the pathogenesis of hypertension.

ACE also facilitates the degradation of the vasodilator bradykinin. This enzyme has a crucial role in the control of BP [blood pressure]. In consequence, its inhibition has become a major target for hypertension control …

… several polyphenolic compounds from plant extracts have been reported to inhibit ACE activity through the sequestration of the enzyme metal factor, Zn2+ ion. Similarly, phlorotannins might be found to be associated with proteins or glycoproteins, forming a complex. This complex inhibits the ACE activity, following a noncompetitive profile.

In contrast, commercial ACE inhibitors, such as captopril, show competitive inhibition. In fact, several studies have confirmed this activity for different phlorotannins, such as those present in extracts from Ecklonia cava or Ecklonia stolonifera, including phlorofucofuroeckol A, dieckol and eckol …

… In addition to E. cava and E. stolonifera, other marine algae containing phlorotannins, such as Lomentaria catenata, Lithophyllum okamurae, Ahnfeltiopsis flabelliformis and Fucus spiralis also exert potent ACE inhibitory activity."

In short, seaweed polyphenols exert effects similar to ACE inhibitor drugs, which in conventional medicine are often prescribed as a first-line treatment for high blood pressure.

High Blood Pressure Is a Modern Condition

High blood pressure is a condition fueled by lifestyle behaviors. It began to emerge in adults in higher income countries from changes in how people live, eat and work.12 Contributors to high blood pressure include:

Unhealthy diet — Processed food, trans fats and too much sugar can lead to high blood pressure over time.

Sedentary lifestyle — Lack of physical activity weakens the heart, contributing to weight gain, high stress levels and high blood pressure.13

Smoking — Cigarette smoke and second-hand smoke contribute to arterial stiffness and the chance of developing high blood pressure.14

Excessive alcohol intake — Regularly drinking excessive amounts of alcohol can significantly increase blood pressure levels.15

Stress, anxiety and depression — These conditions can cause short-term blood pressure spikes and lead to overeating and consuming too much alcohol.16,17,18

Sleep deprivation19 and chronic dehydration20 These symptoms of an overactive lifestyle can also put you at risk of high blood pressure.

Acute pain, medications and stimulating drinks — These factors can also cause high blood pressure with symptoms like dizziness or shortness of breath.21

High Blood Pressure Is a Dangerous Condition

One in 3 Americans suffers from high blood pressure, which amounts to 75 million people.22 People may not be aware that they have high blood pressure, but the condition is far from harmless. Worldwide, high blood pressure causes 9.4 million deaths each year, according to the World Health Organization.23 Here are some of the major complications of high blood pressure, according to the Mayo Clinic:24

"Heart attack or stroke. High blood pressure can cause hardening and thickening of the arteries (atherosclerosis), which can lead to a heart attack, stroke or other complications. Aneurysm. Increased blood pressure can cause your blood vessels to weaken and bulge, forming an aneurysm. If an aneurysm ruptures, it can be life-threatening.

Heart failure. To pump blood against the higher pressure in your vessels, the heart has to work harder. This causes the walls of the heart's pumping chamber to thicken (left ventricular hypertrophy). Eventually, the thickened muscle may have a hard time pumping enough blood to meet your body's needs, which can lead to heart failure.

Weakened and narrowed blood vessels in your kidneys. This can prevent these organs from functioning normally. Thickened, narrowed or torn blood vessels in the eyes. This can result in vision loss.

Metabolic syndrome. This syndrome is a cluster of disorders of your body's metabolism, including increased waist circumference; high triglycerides; low high-density lipoprotein (HDL) cholesterol, the "good" cholesterol; high blood pressure and high insulin levels. These conditions make you more likely to develop diabetes, heart disease and stroke."

Other Serious High Blood Pressure Complications

There are other serious complications increasingly linked to high blood pressure, such as dementia and cognitive decline.25 Those with high blood pressure are at risk of memory and understanding problems as well as vascular dementia, likely because of narrowed or blocked arteries that can limit blood flow to the brain.

Here is what scientists sharing their research in Advances in Experimental Medicine and Biology wrote in 2016:26

"Hypertension and dementia are two of the most prevalent and damaging diseases associated with aging. Chronic hypertension, particularly during mid-life, is a strong risk factor for late-life cognitive decline and impairment.

Hypertension is also the number one risk factor for stroke and a major contributor to the pathogenesis of vascular dementia and Alzheimer's disease.

Despite the vast epidemiologic and mechanistic evidence linking hypertension to cognitive impairment, and the positive effects of blood pressure lowering on reducing the risk of post-stroke dementia, uncertainty remains about the benefit of antihypertensive medication on other forms of dementia."

Researchers are also now exploring the links between high blood pressure and the development of breast cancer. Evidence of links exist, wrote researchers in Scientific Reports in 2017:27

"Observational studies examining the relationship between hypertension and breast cancer risk have reported conflicting findings … We included observational studies that reported relative risks (RR) with corresponding 95% confidence intervals (Cis) … We observed a statistically significant association between hypertension and increased breast cancer risk.

In the subgroup analysis, we found a positive association between hypertension and breast cancer incidence among postmenopausal women … This meta-analysis collectively suggests a significantly association between hypertension and breast cancer risk, specifically for postmenopausal hypertensive women."

Other Studies Cite Seaweed Benefits for High Blood Pressure

There is more evidence of seaweed's value in controlling high blood pressure. This is what researchers wrote in a 2009 issue of Asia Pacific Journal of Clinical Nutrition about seaweed's effect on metabolic syndrome, a condition in which high blood pressure is central:28

"Incidence of the metabolic syndrome is increasing worldwide, with notable exceptions of some Asian countries where seaweeds are commonly consumed. 13 men (mean age 47.4+/-9.9 yr) and 14 women (average age 45.6+/-12.2 yr) with at least one symptom of the metabolic syndrome were recruited in Quito Ecuador to a randomized double-blinded placebo-controlled trial.

Subjects were assigned to either Group 1 (1 m[onth] placebo, followed by 1 m[onth] 4 g/d seaweed [Undaria pinnatifida]) or Group 2 (1 m of 4 g/d seaweed, followed by 1 m of 6 g/d of seaweed).

Blood pressure, weight, waist circumference, inflammation biomarkers, and lipids were measured monthly … Consumption of 4 to 6 g/d seaweed, typical for most people in Japan, may be associated with low metabolic syndrome prevalence."

Further, even as only one part of an improved diet, seaweed has been found useful in treating high blood pressure, according to research in Current Hypertension Reviews.29

The study found that following a diet that includes traditional Japanese foods, including seaweed, green/yellow vegetables and mushrooms, supports the prevention and improvement of high blood pressure for people with readings in the high-normal range.

More Seaweed Benefits

As I noted earlier, seaweed is a good source of iodine, which is an important nutrient. In fact, kelp is credited as the largest known dietary source of iodine — capable of providing close to 2,000% of the recommended daily intake.30 Iodine helps regulate the thyroid gland to produce strong, healthy hair, skin and nails and forms the important thyroid hormones, thyroxine and triiodothyronine.

Iodine is also crucial for regulating the body's energy and brain metabolism, which are under the effect of the pituitary gland, and for formation of your skeletal framework itself. Iodine is an especially important nutrient for developing babies.

Balanced iodine during pregnancy and breastfeeding is central to the myelination process, correct formation of the baby's central nervous system and the development of a baby’s brain cells.31

Edible seaweed contains other valuable substances such as potassium, calcium, iron and alginic acid. Alginic acid naturally protects marine plants from bacteria and binds to heavy metals in humans, a process sometimes called chelation. This makes seaweed an important detoxifying food.

It is not a surprise that alginic acid is used, medically, as a chelator to remove heavy metals from blood. It is also used to make dental and prosthetic molds and in wound and burn dressing.32

Compounds containing alginic acid are also used in the treatment of patients with symptoms of gastroesophageal reflux disease (GERD) because it displaces the postprandial gastric acid pocket in people in whom GERD medications don't work.33 In fact, seaweed outperformed antacids for this purpose in some studies.34 Alginic acid is also used in weight loss.35

Clearly any new treatments for high blood pressure, especially natural ones, are good news for those affected. So, don't forget to enjoy your seaweed salad — and be sure any seaweed you consume is harvested from nonpolluted waters.