Natural Beta-Blockers: Do They Really Work?

A beta-blocker is a class of drugs that blocks the stress hormones epinephrine (adrenaline) and norepinephrine (noradrenaline) from binding to specific receptors (beta receptors) in the following places in your body:

• Heart
• Lung
• Skeletal muscle

This action then blocks the effects of epinephrine and norepinephrine. This decreases the following:

• Heart rate
• Heart muscle contraction
• Blood pressure
• Oxygen demand by the heart

Due to the therapeutic effects that result from blocking epinephrine and norepinephrine, beta-blockers are used for the following medical conditions: 

• Hypertension (high blood pressure)
• Angina (chest pain)
• Heart failure
• Post–myocardial infarction (post-heart attack)
• Atrial fibrillation/flutter (irregular heart rhythm)
• Migraine headache prevention
• Essential tremor
• Performance anxiety
• Glaucoma (increased eye pressure)
• Hyperthyroidism (overactive thyroid)
• Portal hypertension (increased pressure of the portal vein in the liver)

Some nutritional supplements, like the following, have beta-blocker effects:

• Magnesium
• L-arginine
• Potassium
• Omega-3 fatty acids

Herbal supplements, such as hawthorn, garlic, and red yeast rice, also serve as natural beta-blockers. 

This article discusses some nutritional and herbal supplements that act as natural beta-blockers as well as their dosage and safety concerns. 

Natural Beta-Blocker Nutrients

Magnesium

An analysis of studies showed that magnesium supplementation in people with normal and high blood pressure decreased both:

• Systolic blood pressure: The amount of pressure blood exerts against your arterial wall when your heart muscle contracts (the top, or first, number in a blood pressure reading)
• Diastolic blood pressure: The amount of pressure blood exerts against your arterial wall when your heart muscle relaxes (the bottom, or second, number in a blood pressure reading) 

The blood pressure–lowering effect of magnesium is due to its ability to relax the blood vessels and smooth muscles.

Magnesium deficiency is known to cause a type of irregular heart rhythm called ventricular arrhythmia. This condition increases the risk of sudden cardiac death (SCD), a life-threatening condition in which the heart stops pumping blood.

Besides acting as an antihypertensive agent (a drug to lower blood pressure), similar to beta-blockers, magnesium also acts as an antiarrhythmic agent (an agent that prevents or treats irregular heart rhythm) by serving as a natural calcium blocker.

Magnesium shows potential protective effects against SCD. A study of 7,887 subjects revealed a higher risk among those with low blood levels. However, limitations include the inability to assess magnesium levels just before an SCD event, preventing baseline level comparisons, or identifying sudden drops. 

According to the American Heart Association guideline, magnesium may be considered for treating a type of irregular heart rhythm called torsades de pointes associated with long-QT interval (causes abnormal electrical conduction in the heart).

Another similarity between beta-blockers and magnesium is that both play a role in congestive heart failure. Magnesium supplementation plus medical treatment in people with severe congestive heart failure (classified as NYHA or New York Heart Association IV) increased survival rate and improved clinical symptoms and quality of life.

Beta-blockers are used off-label to prevent migraine headaches. Likewise, magnesium supplementation has been shown to reduce the frequency of migraine attacks based on a study of 81 people aged 18 to 65 years with migraine. Besides preventive use, magnesium in the form of intravenous (IV) magnesium sulfate that is given by injection through the vein is used to treat migraine headaches. 

Dosage

In general, the recommended dietary allowances (RDA) for magnesium are as follows:

• 19–30 years (male): 400 milligrams (mg)
• 19–30 years (female): 310 mg
• 31–50 years (male): 420 mg
• 31–50 years (female): 320 mg
• 51 years and older (male): 420 mg
• 51 years and older (female): 320 mg

Magnesium supplements are available in two different salt forms, as follows:

• Inorganic salts: Magnesium oxide, chloride, or sulfate
• Organic salts: Magnesium bisglycinate, citrate, malate, pidolate, taurate, gluconate, glycinate, orotate, or aspartate

The organic salt form of magnesium is preferred due to higher absorption.

Listed below are some of the dosing regimens of magnesium used in clinical trials for various medical conditions:

• High blood pressure: The doses of elemental magnesium used in clinical trials ranged from 120 to 973 milligrams (mg) by mouth per day and the duration of therapy ranged from three to 24 weeks.
• Irregular heart rhythm post-heart attack: Magnesium sulfate given intravenously, that is, given by injection into the vein at a dose of 8 millimoles (mmol) over five minutes followed by 65 mmol over 24 hours within 24 hours of a suspected heart attack.
• Congestive heart failure: Magnesium orotate 2,610 mg three times a day
• Migraine headaches: The preventative dose is 600 mg of magnesium (trimagnesium dicitrate) by mouth daily for 12 weeks.The treatment dose is  1,000 mg of magnesium sulfate given intravenously over an infusion time of 15 to 20 minutes.

Food Sources of Magnesium

Foods rich in magnesium include green leafy vegetables, legumes, nuts, seeds, and fiber-rich foods.

Listed below are the magnesium content of selected foods:

• Pumpkin seeds, roasted, 1 ounce: 156 mg per serving
• Chia seeds, 1 ounce: 111 mg per serving
• Almonds, dry roasted, 1 ounce: 80 mg per serving
• Spinach, boiled, 4 ounces: 78 mg per serving
• Cashews, dry roasted, 1 ounce: 74 mg per serving
• Black beans, cooked, 4 ounces: 60 mg per serving

Side Effects

Too much magnesium from dietary supplements or medications can cause diarrhea, nausea, and stomach cramping. The forms of magnesium most commonly associated with diarrhea are magnesium carbonate, chloride, gluconate, and oxide.

Precautions

The risk of magnesium toxicity increases with poor kidney function or kidney failure. Symptoms of magnesium toxicity include the following:

• Extreme hypotension (low blood pressure)
• Nausea
• Vomiting
• Facial flushing
• Retention of urine
• Ileus (lack of intestinal movement)
• Depression
• Fatigue
• Muscle weakness
• Difficulty breathing
• Irregular heartbeat
• Cardiac arrest

Caution should be taken in people with poor kidney function due to an increased risk of heart block or high magnesium levels.

Interactions

Magnesium interacts with the following drugs:

• Bisphosphonates: Magnesium supplements can decrease the absorption of bisphosphonate drugs, such as Fosamax (alendronate), used for osteoporosis (decreased bone mineral density and bone mass). As such, the two should be separated by at least two hours. 
• Antibiotics: Magnesium supplements can decrease the absorption of certain antibiotics, such as Vibramycin (doxycycline), Cipro (ciprofloxacin), levofloxacin, and Zithromax (azithromycin). These antibiotics should be taken at least two hours before or four to six hours after magnesium-containing products to avoid the interaction. 
• Diuretics (water pills): Diuretics, which remove excess fluid from the body, such as Lasix (furosemide), Bumex (bumetanide), and Microzide (hydrochlorothiazide), can increase the loss of magnesium in the urine. 
• Proton pump inhibitors (PPIs): Taking acid-suppressing drugs such as Prilosec (omeprazole), Protonix (pantoprazole), Nexium (esomeprazole), and Prevacid (lansoprazole) for more than a year can cause low magnesium levels. It is essential to get your magnesium levels checked before starting and while taking acid-suppressing drugs.

Certain drugs can lower magnesium levels by various mechanisms, including:

• Shift of magnesium into cells: Insulin therapy, epinephrine, theophylline (medication used for asthma and chronic obstructive pulmonary disease), Glucophage (metformin)
• Loss of magnesium via the gastrointestinal tract: Laxative abuse, antibiotics, anti-cancer agents, metformin, PPIs, Veltassa (patiromer)
• Increased magnesium loss in the urine: Anticancer drugs (carboplatin, cisplatin), calcineurin inhibitors (cyclosporine, tacrolimus), antibiotics (aminoglycosides, amphotericin B, pentamidine, foscarnet), diuretics (thiazides, furosemide), digoxin, theophylline

Using magnesium at the same time with the following drugs may increase magnesium levels in the blood:

• Glucagon
• Calcitonin
• Potassium-sparing diuretics
• Doxercalciferol (a vitamin D analog)
  

L-Arginine

An analysis of a collection of studies showed that L-arginine supplementation lowered systolic and diastolic blood pressure in adults. However, the findings suggest that L-arginine is less effective at decreasing blood pressure when taken by mouth for more than 24 days. Therefore, further research is needed to investigate the effects of long-term L-arginine supplementation on blood pressure.  

The blood-pressure-lowering effect of L-arginine is due to its ability to increase nitric oxide (NO) formation. Nitric oxide widens and relaxes the blood vessels.

Dosage

For high blood pressure, the daily dose of L-arginine in studies ranged from 2 to 30 grams (g), taken from four to 180 days. It is suggested that consuming low doses of L-arginine (i.e., less than or equal to 9 g per day) for a short period (i.e., less than or equal to 24 days) is more effective than consuming higher doses for longer durations.

Food Sources of L-Arginine

L-arginine is an amino acid (a building block of protein) that can be obtained from dietary sources or produced inside the body.

It can be found in the following food sources: 

• Seafood
• Nuts
• Seeds
• Soy protein isolate
• Watermelon
• Red meat
• Poultry
• Dairy

Side Effects

Side effects reported with the use of L-arginine include the following:

• Increased stool frequency
• Stomach pain
• Abdominal bloating
• Diarrhea
• Asthenia (weakness, fatigue)
• Skin rash
• Eosinophilia (an increase in eosinophil, a type of white blood cell, count)
• Low blood pressure 

Precautions

Caution should be taken in the following cases: 

• Pregnancy: L-arginine is possibly safe when taken by mouth for a short period during pregnancy. It is unclear if it is safe to use for the long term during pregnancy.  
• Breastfeeding: It is best to avoid use because it is unclear if L-arginine is safe to use when breastfeeding.
• Children: L-arginine is possibly safe in children when taken by mouth, used in toothpaste, or inhaled.
• Guanidinoacetate methyltransferase deficiency (GAMT): A deficiency in such an enzyme causes an inability to convert arginine into creatine, an amino acid that supports muscle performance.
• Recent heart attack: Due to the increased risk of death, especially in people of advanced age, L-arginine should be avoided for those who recently have had a heart attack.
• Kidney disease: L-arginine has caused high potassium levels in people with kidney disease. High potassium levels increase the risk of irregular heartbeat.
• Surgery: L-arginine should be stopped at least two weeks before a scheduled surgery due to its ability to interfere with blood pressure control.

Interactions

L-arginine interacts with the following medications:

• Blood pressure–lowering drugs: Taking L-arginine with blood pressure-lowering drugs might cause blood pressure to drop too low.
• Herbs and supplements that lower blood pressure: Examples of supplements that lower blood pressure include andrographis, casein peptides, niacin, and stinging nettle.
• Viagra (sildenafil): Taking sildenafil with L-arginine might cause blood pressure to drop too low.
• Blood sugar–lowering drugs: Taking L-arginine with blood-sugar-lowering drugs might cause blood sugar levels to drop too low.
• Herbs and supplements that lower blood sugar: Examples of supplements that lower blood sugar levels include aloe, bitter melon, cassia cinnamon, chromium, and prickly pear cactus. 
• Blood-thinning drugs: L-arginine might slow blood clotting, thereby increasing the risk of bruising and bleeding when used with blood thinners.
• Herbs and supplements that slow blood clotting: Examples of supplements that slow blood clotting include garlic, ginger, ginkgo, nattokinase, and Panax ginseng. 
• Water pills (potassium-sparing diuretics): Certain water pills, such as potassium-sparing diuretics, can increase potassium levels. Since L-arginine can also increase potassium levels, combining the two can cause potassium levels to rise too high. 
• Testosterone: Although L-arginine might increase testosterone levels, it is unclear if such an increase poses a significant concern. Caution should still be taken if you use testosterone. 
  

Potassium

A review of a group of studies suggested that long-term (at least four weeks) moderate supplementation with potassium reduced blood pressure, especially in people who had:

• Untreated high blood pressure
• High sodium intake (at least 4 g per day)
• A low potassium intake (less than 3,500 mg per day) at baseline

However, the study was limited in that the influence of genetic, environmental, and lifestyle factors could not be assessed.

Despite evidence showing that potassium decreases blood pressure, in people with high blood pressure treated with a blood pressure–lowering drug, it is advised not to exceed the potassium intake levels if potassium intake is high at baseline. Paradoxically, high doses of potassium may result in a higher level of blood pressure in this case.

Dosage

Forms of potassium used in clinical studies include potassium chloride, citrate, carbonate, aspartate, and/or glucuronate; doses generally ranged from 1,167–4,667 mg per day.

The duration of potassium supplementation ranged between eight and 12 weeks.

Food Sources of Potassium

The World Health Organization (WHO) recommends a daily potassium intake of around 3,500 mg in adults and children.  

Potassium is found in many fruits, vegetables, and legumes. Meats, poultry, yogurt, and nuts are also sources of potassium.

Listed below are the  potassium content of selected foods in milligrams (mg) per serving:

• Apricots, dried, 4 ounces: 755 mg
• Squash, acorn, mashed, 1 cup: 644 mg
• Prunes, dried, 4 ounces: 635 mg
• Raisins, 4 ounces: 618 mg
• Potato, baked, 1 medium: 610 mg
• Banana, 1 medium: 422 mg
• Spinach, raw, 2 cups: 334 mg
• Chicken breast, boneless, grilled, 3 ounces: 332 mg
• Yogurt, fruit variety, nonfat, 6 ounces: 330 mg
• Beef, top sirloin, grilled, 3 ounces: 315 mg
• Cashew nuts, 1 ounce: 187 mg

Precautions

Caution should be taken in people with the following conditions:

• Chronic kidney disease
• Type 1 diabetes
• Congestive heart failure
• Adrenal insufficiency
• Liver disease

While potassium causes upset stomach, vomiting, and diarrhea, symptoms of too much potassium can have the following effects:

• Muscle weakness
• Paralysis
• Burning, burning, and prickling sensation in arms or legs
• Irregular heart rate

Interactions

Potassium interacts with some medications, such as the following:

• Angiotensin converting enzyme (ACE) inhibitors, such as Lotensin (benazepril) and Prinivil (lisinopril), and angiotensin receptor blockers (ARBs), like Cozaar (losartan), decrease potassium excretion by the kidney, which increases potassium levels.
• Potassium-sparing diuretics, such as Midamor (amiloride) and Aldactone (spironolactone), also reduce potassium excretion in the urine and increase potassium levels.
• Water pills, such as loop diuretics, including Lasix (furosemide) and Bumex (bumetanide), and thiazide diuretics, such as Microzide (hydrochlorothiazide) and Diuril (chlorothiazide), increase potassium loss in the urine.

It is essential to check your potassium levels if you take the above medications, especially if you have impaired kidney function.

Omega-3 Fatty Acids

An analysis of a group of studies showed that omega-3 fatty acid supplementation consisting of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) reduced blood pressure. However, one of the limitations of the studies was the various methods of blood pressure measurement (automatic vs. manual).

The results from the study suggested that omega-3 fatty acids had a larger reduction in systolic blood pressure in people with high blood pressure and high cholesterol compared to those without such conditions.

Dosage

For blood pressure control, the optimal daily dose of omega-3 fatty acid is 3 g.

Food Sources of Omega-3 Fatty Acids

Listed below are the DHA and EPA contents of selected foods in grams per serving:

• Salmon, Atlantic, wild, cooked, 3 ounces (DHA: 1.22, EPA: 0.35)
• Herring, Atlantic, cooked, 3 ounces (DHA: 0.94, EPA: 0.77)
• Mackerel, Atlantic, cooked, 3 ounces (DHA: 0.59, EPA: 0.43)
• Trout, rainbow, wild, cooked, 3 ounces (DHA: 0.44, EPA: 0.40)
• Sea bass, cooked, 3 ounces (DHA: 0.47, EPA: 0.18)

Precautions

Common and mild side effects of omega-3 supplements include the following:

• Unpleasant taste
• Bad breath
• Heartburn
• Nausea
• Stomach discomfort
• Diarrhea
• Headache

Although the FDA concluded that dietary supplements providing no more than 5 g per day of EPA and DHA are safe, caution should still be taken in people with certain medical conditions. 

In people at high risk of heart disease, the intake of 4 g per day of omega-3 supplements for several years increased the risk of atrial fibrillation, a type of irregular heartbeat.

High doses of DHA and/or EPA (900 mg/day of EPA plus 600 mg/day DHA or more for several weeks) reduce immune function due to suppression of inflammatory responses.

Doses of 2–15 grams per day of EPA and/or DHA reduce blood clotting and increase bleeding time.

Interactions

The following include interactions with omega-3 fatty acids:

Blood-thinning medications: High doses of fish oil slow clotting times, thereby increasing the risk of bleeding. Therefore, caution should be taken with blood thinners, such as Jantoven (warfarin), Eliquis (apixaban), and Xarelto (rivaroxaban). 

Herbs and supplements that slow blood clotting: Taking omega-3s with herbs or supplements that slow blood clotting may have additive effects. Examples of supplements that slow blood clotting include garlic, ginger, ginkgo, nattokinase, and Panax ginseng. 

Natural Beta-Blocker Herbs

Hawthorn

Several clinical studies showed that hawthorn improved the typical symptoms of heart failure, such as the following:

• Reduced exercise tolerance
• Shortness of breath upon exertion
• Weakness
• Fatigue
• Irregular heart rate

Moreover, the German Commission E approved the use of extracts of hawthorn leaf with flowers for people with New York Heart Association (NYHA) class 2 symptoms.

A systematic review suggested that hawthorn reduced blood pressure in people with mild hypertension when given for at least 12 weeks. However, more rigorous studies are needed to confirm the result.

Dosage

In the heart failure study, the recommended daily dose of hawthorn extract is 160–900 mg.  

In the high blood pressure study, specifically stage 1 hypertension, the dose of hawthorn is 450 mg twice daily for 12 weeks.

Precautions

Side effects of hawthorn include the following: 

• Dizziness 
• Nausea
• Digestive symptoms
• Irregular heart rate
• Headache
• Migraine

No serious safety problems have been reported in most studies looking at the effect of hawthorn on heart failure. However, one study showed that people taking hawthorn were more likely than their counterparts to have worsening heart failure.

The safety of hawthorn use during pregnancy or breastfeeding is unknown.

Interactions

Hawthorn increases the effects of heart medications, such as Lanoxin (digoxin), a drug used to treat heart failure and atrial fibrillation (AFib). Please consult with your healthcare provider before starting hawthorn.

Hawthorn extract may also interact with anticoagulants (blood thinners) and antihypertensives (blood pressure-lowering drugs).

Garlic

A review of a group of studies showed that garlic supplements lower blood pressure in people with high blood pressure. However, larger and longer-term studies are needed to clarify the result due to inconsistent findings among the studies.

Dosage

In the setting of high blood pressure, a clinical trial used garlic supplements in doses ranging from 600–900 mg per day.

Precautions

Mild side effects of garlic include burping, flatulence, and reflux.

Interactions

Garlic may increase the effects of blood-thinning medications, such as warfarin, and reduce the efficacy of antiretroviral therapy, such as protease inhibitors.

Red Yeast Rice

In a Japanese clinical trial consisting of people with mild dyslipidemia (abnormal cholesterol levels), red yeast rice reduced not only low-density lipoprotein (LDL) cholesterol("bad cholesterol") but also blood pressure. However, further studies with larger sample sizes are needed.

Dosage

A clinical study used low-dose red yeast rice (200 mg/day) containing 2 mg of monacolin K for eight weeks.

Precautions

Monacolin K is structurally identical to Mevacor (lovastatin). So, red yeast rice containing monacolin K has side effects similar to statin drugs, including muscle, kidney, and liver damage. Other side effects include diarrhea, nausea, and stomach pain.

A review of a collection of clinical trials suggested that red yeast rice products with varying levels of monacolin K were safe. However, the European Food Safety Authority (EFSA) concluded that monacolin K in red yeast rice could lead to severe side effects.

Caution should be taken with red yeast rice products as some contain a toxic contaminant called citrinin that can damage the kidneys.

Red yeast rice should be avoided during pregnancy and breastfeeding due to a lack of safety studies.

Interactions

Red yeast rice products can have similar types of drug interactions as statin drugs. As such, speak with your healthcare provider before adding red yeast rice to your regimen.

Other Considerations for Blood Pressure Health

Lifestyle modifications, such as the following, are important for maintaining blood pressure health:

• Movement or exercise
• Stress reduction
• Reduced alcohol consumption
• Mediterranean diet (a mainly plant-based diet stressing healthy fats like olive oil, nuts and beans, and lean protein, while limiting dairy and red meat)
• DASH (Dietary Approach to Stop Hypertension) diet (a diet stressing heart-healthy foods)
• Hydration
• Screening

Summary

Nutritional and herbal supplements considered natural beta-blockers include the following:

• Magnesium
• L-arginine
• Potassium
• Omega-3 fatty acids
• Hawthorn
• Garlic
• Red yeast rice

These primarily mimic the blood-pressure-lowering effect of beta-blocker drugs.

However, such natural beta-blockers should be used with caution if you have certain medical conditions or take certain prescription drugs or supplements due to potential additive effects.