Nutrition Research
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Micronutrients
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Dietary Factors
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Food & Beverages
Summary
Nutrition can have a significant impact on blood pressure. The DASH eating plan significantly lowers blood pressure in individuals with either normal or high blood pressure. Increasing potassium intake while reducing sodium intake has also been shown to reduce blood pressure. Supplemental vitamin C lowers blood pressure in individuals with normal and high blood pressure, while supplemental riboflavin may lower blood pressure in hypertensive individuals with a certain genetic predisposition. Although the scientific evidence is less consistent for garlic, there is some indication that supplemental garlic preparations may reduce blood pressure in hypertensive individuals.
Disease Overview
Blood pressure refers to the force of blood exerted against arterial walls as the heart pumps blood.
A blood pressure reading consists of two measurements: systolic and diastolic blood pressure
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Systolic Blood Pressure (SBP) is the amount of pressure exerted against arterial walls when the heart contracts, during a heartbeat.
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Diastolic Blood Pressure (DBP) is the amount of pressure exerted against arterial walls when the heart is relaxed, between heartbeats.
When blood pressure is elevated, there is a constant, increased force stretching arteries beyond a healthy limit. This leads to a long list of negative effects, such as: tears and scarring, weak spots that rupture easily, blood clots, increased plaque buildup, and increased workload on the heart.
High blood pressure (HBP) is considered both a risk factor and a disease:
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HBP is a major risk factor for cardiovascular disease, increasing the likelihood of heart attack, stroke, heart failure, and atrial fibrillation. It is also considered a modifiable risk factor, meaning that there are things you can do to change your blood pressure.
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HBP is sometimes called the "the silent killer" because it causes damage to the cardiovascular system without obvious symptoms.
See below for specific information about nutrients and dietary factors relevant to high blood pressure.
DEFINITIONS
Artery (adj: arterial) - A muscular-walled blood vessel that carries blood away from the heart
Plaque - a deposit of fat, cholesterol, immune cells, fibrin (a clotting protein), and other substances that forms inside arterial walls
Commonly Used Treatments and Medications
The Dietary Approaches to Stop Hypertension (DASH) eating plan
In addition to the nutrients listed below, eating pattern plays a key role in blood pressure regulation. For example, adherence to the DASH eating plan — a diet rich in fruit, vegetables, and low-fat dairy while low in saturated and total fat — has been linked to significant reductions in both systolic and diastolic blood pressure.
For more information about the DASH eating plan, see the National Institutes of Health.
Antihypertensive Medications
There are many medications prescribed to lower blood pressure. The five main classes of blood pressure-lowering medication and potential nutritional interactions are listed in Table 1.
Table 1. Main Classes of Blood Pressure-lowering Medication
Class |
How Medication Lowers Blood Pressure |
Potential Interactions |
Angiotensin-converting enzyme (ACE) inhibitors |
helps the body produce less angiotensin II, a chemical that causes blood vessel constriction (narrowing) |
may lead to elevated potassium concentration in the blood |
Angiotensin II receptor blockers |
blocks the effects of angiotensin II, a chemical that causes blood vessel constriction (narrowing) |
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may lead to elevated potassium concentration in the blood;
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grapefruit juice may decrease drug availability
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Calcium channel blockers |
prevents calcium from entering the smooth muscle cells of the heart and arteries, resulting in blood vessel dilation (widening) and reduced heart rate |
grapefruit juice may increase drug availability |
Diuretics |
helps the body excrete excess sodium and water in the urine |
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may lead to reduced sodium and potassium concentrations in the blood
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potassium-sparing diuretics may lead to elevated potassium concentration in the blood
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may lead to elevated calcium concentration in the blood if taken with calcium supplements
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prolonged use may increase the loss of zinc, magnesium, and thiamin
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β-blockers |
reduces heart rate and the force of the heart’s contractions |
may lead to elevated potassium concentration in the blood |
SOURCES:
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American Heart Association
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Safety sections for specified nutrients in the Micronutrient Information Center
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Nutrition Research
DEFINITIONS
Test tube (in vitro) experiment - a research experiment performed in a test tube, culture dish, or other artificial environment outside of a living organism; in vitro is a Latin phrase meaning in glass
Animal experiment - a research experiment performed in a laboratory animal; many different animal species are studied in the laboratory, including terrestrial (land), aquatic (water), and microscopic animals
Observational study - a human research study in which no experimental intervention or treatment is applied, and participants are simply observed over time
Randomized controlled trial - a human research study in which participants are assigned by chance alone to receive either an experimental agent (the treatment group) or a placebo (the control group)
Placebo - a chemically inactive substance
Calcium
What it does
General
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Calcium is an essential mineral that is a structural component of bones and teeth, is required for proper nerve transmission and muscle contraction, and influences blood pressure.
Blood pressure-specific
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Calcium may influence blood vessel constriction and dilation (narrowing and widening) through its actions on smooth muscle cells that make up arterial walls.
What we know
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Several large, observational studies indicate that higher dietary intake of calcium is associated with lower systolic and diastolic blood pressure.
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In randomized controlled trials, supplemental calcium had no significant effect on blood pressure in normotensive individuals; a slight reduction in systolic blood pressure (-2.5 mm Hg) has been observed in hypertensive individuals.
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Research indicates that a calcium intake at the recommended level of 1,000-1,200 milligrams/day may be helpful in preventing and treating moderate hypertension.
For references and more information, see the section on hypertension in the Calcium article.
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Magnesium
What it does
General
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Magnesium is an essential mineral that serves as a structural component of the skeleton; assists in hundreds of enzymatic reactions involved in the synthesis of energy, DNA, and proteins; and is required for proper nerve conduction and muscle contraction.
Blood pressure-specific
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The way in which magnesium influences blood pressure is not clear. Magnesium may induce vascular smooth muscle cell relaxation, alter the levels of inflammatory mediators, and reduce angiotensin-induced aldosterone synthesis, all of which can lower blood pressure.
What we know
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Several large, observational studies indicate that a higher dietary intake of magnesium is associated with lower blood pressure and a reduced risk of developing hypertension.
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However, it is difficult to attribute an independent effect of magnesium on blood pressure since food that is high in magnesium (fruit, vegetables, and whole grains) is also high in other nutrients (potassium, dietary fiber) that may have a blood pressure-lowering effect.
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A pooled analysis of randomized controlled trials demonstrated a beneficial effect of magnesium supplementation in treating hypertension. An average dose of 410 milligrams (mg) of magnesium per day for 11.3 months lowered blood pressure in hypertensive individuals. However, the dose of supplemental magnesium required to lower blood pressure appears to depend on whether individuals are taking antihypertensive medications like diuretics — in untreated individuals, the required dose is higher.
DEFINITIONS
Diuretic - an agent that increases the formation of urine by the kidneys, resulting in water loss from the individuals using the diuretic
SAFETY HIGHLIGHT
The tolerable upper intake level (UL) for magnesium is 350 milligrams (mg) of supplemental magnesium per day. Because of the potential risks of high-dose magnesium supplementation, especially in the presence of impaired kidney function, supplementation with magnesium should be conducted under medical supervision.
For references and more information, see the section on the hypertension in the Magnesium article.
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Potassium
What it does
General
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Potassium is an essential mineral that helps maintain fluid and electrolyte balance, influences blood pressure, and is required for proper nerve conduction and muscle contraction.
Blood pressure-specific
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Increased potassium intake results in the increased excretion of sodium in the urine. This loss of sodium in the urine helps reduce water retention, blood volume, and blood pressure.
What we know
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Numerous observational studies demonstrate that higher dietary potassium intake is associated with lower blood pressure.
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Even more important than potassium intake alone is the ratio of potassium to sodium in the diet. Most experts recommend increasing the intake of potassium while decreasing the intake of sodium chloride (salt).
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Randomized controlled trials demonstrate that increased potassium intake, mostly in the form of potassium chloride supplementation, has a modest blood pressure lowering effect in those with normal or high blood pressure.
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Some individuals, such as those with kidney disease or those taking certain medications (Table 1), should follow the advice of their physician regarding potassium intake.
Drug interactions
Many medications are known to increase the risk of hyperkalemia (high serum potassium) and hypokalemia (low serum potassium) (Table 2).
Table 2. Medications That Increase the Risk of Abnormal Potassium Concentration in the Blood
Hyperkalemia (High Blood Potassium) |
Hypokalemia (Low Blood Potassium) |
α-blockers |
aminoglycosides |
angiotensin converting enzyme (ACE) inhibitors |
certain antibiotics |
angiotensin receptor blockers |
anti-fungal agents |
anti-infective agents |
β-adrenergic agonists |
β-blockers |
cisplatin |
digitalis |
diuretics |
heparin |
methylxanthines |
nonsteroidal anti-inflammatory agents (NSAIDs) |
mineralocorticoids |
potassium-sparing diuretics |
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For more information, see the safety section in the Potassium article. |
For references and more information, see the section on hypertension in the Potassium article.
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Riboflavin
What it does
General
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Riboflavin is a B-vitamin that helps convert food into useable energy and assists several metabolic and antioxidant enzymes.
Blood pressure-specific
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As an assistant to the enzyme MTHFR, riboflavin helps convert folate to a form required for the transformation of homocysteine to methionine.
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Riboflavin deficiency may reduce homocysteine conversion to methionine, and too much homocysteine in the blood is associated with an increased risk of hypertension.
What we know
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Individuals with a certain genetic variation (polymorphism) in MTHFR have an increased risk of developing high blood pressure.
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In hypertensive individuals with the MTHFR c.677C>T polymorphism (homozygotes), riboflavin supplementation effectively lowers both homocysteine concentration and blood pressure.
HIGHLIGHT
The MTHFR polymorphism is measured by genetic testing. In a genetic test, a small amount of blood, saliva, or tissue is used to isolate and determine an individual’s genetic information. Genetic testing is voluntary; doctors and genetic counselors can advise you on the decision to have this type of test.
Source: National Human Genome Research Institute
For references and more information, see the section on hypertension in the Riboflavin article.
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Sodium Chloride
What it does
General
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Sodium is an essential mineral that helps maintain fluid and electrolyte balance, influences blood pressure, and is required for proper nerve conduction and muscle contraction.
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The most common dietary source of sodium is salt, which is also known as sodium chloride. One teaspoon of salt contains 2.3 grams of sodium.
Blood pressure-specific
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Sodium (coupled with chloride) is the primary determinant of extracellular (outside of cells) fluid volume, including blood volume.
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The kidneys regulate blood volume by adjusting the amount of sodium and water lost into the urine; sodium retention results in water retention, and sodium excretion results in water excretion.
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Most people ingest more sodium chloride than recommended, which can result in water retention, blood volume expansion, edema (the accumulation of excess fluid in the body), and elevated blood pressure.
What we know
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Observational studies consistently demonstrate that higher sodium intake is associated with higher blood pressure.
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Many randomized controlled trials have examined the effect of dietary salt reduction on blood pressure. Even modest salt reduction (less than one teaspoon per day) decreases systolic and diastolic blood pressure in individuals with and without hypertension.
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Even more important than sodium reduction alone may be the ratio of sodium to potassium consumed in the diet. Therefore, most experts recommend decreasing the intake of sodium chloride (salt) while simultaneously increasing the intake of potassium.
HIGHLIGHT: SALT SENSITIVITY
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A measure of how your blood pressure responds to salt intake.
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Animal experiments suggest that "salt sensitivity" may be related to an impaired ability by the kidneys to excrete excess sodium.
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While certain subgroups of the population tend to have greater blood pressure changes in response to alterations in sodium intake, the genetic basis for salt sensitivity is still under investigation.
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Even without knowing if you are "salt sensitive," certain subgroups of the population are more responsive to reduced sodium intake:
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Those with hypertension
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Older individuals
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African Americans
For references and more information, see the section on hypertension in the Sodium article.
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Vitamin C
What it does
General
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Vitamin C (ascorbic acid) neutralizes a variety of reactive oxygen species and recycles important cellular antioxidants.
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Vitamin C is also a cofactor in numerous enzymatic reactions involved in the making of collagen, L-carnitine, and several neurotransmitters, and in the regulation of gene expression.
Blood pressure-specific
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The antioxidant activities of vitamin C may protect the lining of blood vessels from damage caused by oxidative stress and increase the availability of nitric oxide, a gaseous signaling molecule that helps relax arterial walls.
What we know
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Several large, observational studies found no association between vitamin C intake and hypertension.
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On the other hand, plasma vitamin C concentration has been inversely associated with blood pressure in both men and women. In other words, the higher the vitamin C status of the body, the lower the blood pressure.
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A pooled analysis of short-term randomized controlled trials indicated that vitamin C supplementation (median dose of 500 milligrams [mg]/day for a median duration of eight weeks) reduced blood pressure in both normotensive and hypertensive adults (Table 3).
Table 3. Average Reductions in Blood Pressure Following Short-term Vitamin C Supplementation
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Systolic Blood Pressure (mm Hg) |
Diastolic Blood Pressure (mm Hg) |
Normotensive |
-3.84 |
-1.48 |
Hypertensive |
-4.85 |
-1.67 |
DEFINTIONS
Reactive oxygen species (ROS) - highly unstable oxygen-containing compounds that react easily with nearby cellular structures, potentially causing damage
Antioxidants - compounds that prevent or repair the damage caused by reactive oxygen species
Oxidative stress - a situation in which the production of reactive oxygen species exceeds the ability of an organism to eliminate or neutralize them
Inverse association - a relationship between two variables in which they move in opposite directions
For references and more information, see the sections on hypertension in the Vitamin C article.
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Vitamin D
What it does
General
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Vitamin D is a fat-soluble vitamin that helps maintain calcium and phosphorus balance, promotes bone health and immune function, and influences cell growth and development.
Blood pressure-specific
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Vitamin D influences the production of renin, an enzyme that regulates blood pressure. Deficiency of vitamin D could contribute to increased activity of the renin-angiotensin system and an increased risk of hypertension.
What we know
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Higher vitamin D status has been associated with lower blood pressure.
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A pooled analysis of randomized controlled trials reported no overall effect of vitamin D supplementation on blood pressure. However, there is some evidence that vitamin D supplementation may improve blood pressure in individuals with serum 25(OH) vitamin D concentration less than 30 nanograms (ng)/mL.
For references and more information, see the sections on hypertension in the Vitamin D article: cardiovascular disease prevention and cardiovascular disease treatment.
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Coenzyme Q10
What it does
General
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Coenzyme Q10 is a compound that can be made inside the body and obtained from food and dietary supplements.
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Coenzyme Q10 helps the body convert food into useable energy and functions as an antioxidant in cell membranes.
Blood pressure-specific
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Increased oxidative stress can interfere with the production and availability of nitric oxide, a potent vasodilator. Reduced levels of nitric oxide contribute to vasoconstriction (blood vessel narrowing) and increased blood pressure.
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The antioxidant properties of coenzyme Q10 may help reduce oxidative stress, thereby increasing the availability of nitric oxide.
What we know
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Results of clinical trials examining whether coenzyme Q10 supplementation might help treat high blood pressure have been mixed.
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The effect of coenzyme Q10 on blood pressure should be examined in large, well-designed clinical trials.
DEFINITIONS
Antioxidant - a compound that prevents or repairs the damage caused by reactive oxygen species
Reactive oxygen species (ROS) - highly unstable oxygen-containing compounds that react easily with nearby cellular structures, potentially causing damage
Oxidative stress - a situation in which the production of reactive oxygen species exceeds the ability of an organism to eliminate or neutralize them
Nitric oxide - a gaseous signalling molecule; nitric oxide promotes the relaxation of arterial walls, leading to vasodilation
Vasodilator - something that widens blood vessels
For references and more information, see the section on hypertension in the Coenzyme Q10 article.
Additional reference:
Ho MJ, Li EC, Wright JM. Blood pressure lowering efficacy of coenzyme Q10 for primary hypertension. Cochrane Database Syst Rev. 2016;3:Cd007435
Garlic
What it does
General
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Garlic is a rich source of organosulfur compounds, a category of phytochemicals that give garlic its pungent smell and taste.
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These organosulfur compounds and their breakdown products may be responsible for some beneficial health effects of garlic.
Blood pressure-specific
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Test tube and animal experiments demonstrate that there are many ways by which garlic may influence blood pressure.
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The bioactive compounds provided by garlic have been shown to:
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induce the activity of antioxidant enzymes
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increase the production of hydrogen sulfide and nitric oxide, gaseous signaling molecules that relax blood vessels
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inhibit enzymes involved in vasoconstriction (blood vessel narrowing)
What we know
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Garlic preparations appear to have a blood pressure-lowering effect in hypertensive individuals. On average, garlic preparations reduced systolic blood pressure by 9.1 mm Hg and diastolic blood pressure by 3.8 mm Hg when taken for a minimum of two months.
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No serious side effects have been reported. The most common side effect is garlic odor, taste, and breath.
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Garlic should not be used in place of blood pressure-lowering medications.
HIGHLIGHT
Although the results are promising, it is cautioned that the body of scientific evidence regarding the effect of garlic on hypertension is not strong. The majority of randomized controlled trials recruited only a small number of participants, were of relatively short duration (most lasted only 12 weeks), and used different forms and doses of garlic preparations.
DRUG INTERACTIONS
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garlic may enhance the anticoagulant effects of warfarin
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garlic may reduce the bioavailability of HIV protease inhibitors
For references and more information, see the section on hypertension in the Garlic article.