Nutrition Research

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

  • Systolic Blood Pressure (SBP) is the amount of pressure exerted against arterial walls when the heart contracts, during a heartbeat.
  • 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:

  • 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.
  • 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)
  • may lead to elevated potassium concentration in the blood;
  • grapefruit juice may decrease drug availability
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
  • may lead to reduced sodium and potassium concentrations in the blood
  • potassium-sparing diuretics may lead to elevated potassium concentration in the blood
  • may lead to elevated calcium concentration in the blood if taken with calcium supplements
  • prolonged use may increase the loss of zinc, magnesium, and thiamin
β-blockers reduces heart rate and the force of the heart’s contractions may lead to elevated potassium concentration in the blood

SOURCES:

  1. American Heart Association
  2. Safety sections for specified nutrients in the Micronutrient Information Center

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

  • 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

  • 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
  • Several large, observational studies indicate that higher dietary intake of calcium is associated with lower systolic and diastolic blood pressure.
  • 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.
  • 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.  

Calcium Flashcard. Main Functions: 1) structural component of bones and teeth, 2) regulates nerve transmission and muscle contraction, 3) helps maintain a healthy blood pressure, and 4) helps maintain acid-base balance in the blood. Good Sources: dairy (yogurt, milk, cheese), plain yogurt, 8 ounces or 1 cup = 415 mg; sardines (canned) 1 can or 3.75 ounces = 351 mg; green leafy vegetables (kale, bok choy), collard greens (cooked), one-half cup = 300 mg; mg= milligrams. Daily Recommendation: 1,000 mg for men 19-70 years, 1,200 mg for men 71+ years; 1,000 mg for women 19-50 years, 1,200 mg for women 51+ years. Special Notes: 1) Many Americans do not consume enough calcium. Just 3 servings of dairy per day would meet the recommendation. For those who don't consume dairy, calcium-fortified juices, cereals, and milk alternatives are a good substitute. 2) To maximize absorption from supplements, take no more than 500 mg at a time.

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Magnesium

What it does

General

  • 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

  • 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
  • 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.
  • 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.
  • 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.
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.

Magnesium Flashcard. Main Functions: 1) Structural component of bones and teeth, 2) Regulates nerve transmission and muscle contraction, and 3) Assists in hundreds of essential cellular reactions. Good Sources: Whole Grains (wheat, oats, barley), brown rice, cooked, 1 cup = 86 mg; Green Leafy Vegetables (Swiss chard, spinach), spinach (boiled), 1 cup = 157 mg; Nuts (hazelnuts, cashews), almonds, 1 ounce or 23 almonds = 77 mg. Daily Recommendation: 400 mg for men 19-30 years, 420 mg for men 31 years and older; 310 mg for women 19-30 years, 320 mg for women 31 years and older. Special Notes: 1) Most people consume too little magnesium. 2) The Tolerable Upper Intake Level (UL) for magnesium is 350 mg/day from supplements. The UL does not apply to naturally occurring magnesium from food.

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Potassium

What it does

General

  • 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

  • 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
  • Numerous observational studies demonstrate that higher dietary potassium intake is associated with lower blood pressure.
  • 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).
  • 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.
  • 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 β-adrenergic agonists
angiotensin converting enzyme (ACE) inhibitors  bronchodilators
angiotensin receptor blockers decongestants
anti-infective agents diuretics
β-blockers high-dose glucocorticoids
digitalis mineralocorticoids
heparin tocolytic (labor suppressing) agents
nonsteroidal anti-inflammatory agents (NSAIDs)  
potassium-sparing diuretics  
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

Potassium Flashcard. Main Functions: (1) maintains fluid and electrolyte balance, (2) Required for proper nerve conduction and muscle contraction, and (3) Influences blood volumen and blood pressure. Good Sources: Fruit (prunes, banana, orange juice); prunes (dried plums), one-half cup, 637 mg; banana, 1 medium, 422 mg; Vegetables (potato, tomato, artichoke), potato with skin, 1 medium, 926 mg. Daily Recommendation. 4,700 mg for adults. Special Notes: (1) Potassium and sodium work together. A diet high in potassium and low in sodium helps maintain a lower blood pressure. (2) Fruit, vegetables, and legumes are naturally high in potassium and low in sodium. (3) Most people consume too little potassium. In addition to fruit and vegetables, nuts and beans also provide potassium.

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Riboflavin

What it does

General

  • Riboflavin is a B-vitamin that helps convert food into useable energy and assists several metabolic and antioxidant enzymes.

Blood Pressure-specific

  • As an assistant to the enzyme MTHFR, riboflavin helps convert folate to a form required for the transformation of homocysteine to methionine.
  • 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
  • Individuals with a certain genetic variation (polymorphism) in MTHFR may have an increased risk of developing high blood pressure.
  • In hypertensive individuals with the MTHFR c.677C>T polymorphism (homozygotes), riboflavin supplementation 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

Riboflavin (vitamin B2) Flashcard. Main Functions. (1) helps convert food into useable energy, and (2) assists several antioxidant enzymes. Good Sources. Dairy Products (milk, yogurt, cheese), milk (nonfat), 8 ounces, 0.45 mg; Meat (chicken, beef, fish), salmon, 3 ounces, 0.13 mg; Egg (1 large), 0.26 mg. A 3-ounce serving of meat or fish is about the size of a deck of cards. Daily Recommendation. 1.3 mg for men, 1.1 mg for women. Special Notes. (1) riboflavin is easily destroyed upon exposure to light. (2) Low-dose riboflavin supplementation may lower blood pressure in individuals with a genetic mutation in MTHFR, and enzyme involved in folate metabolism.

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Sodium Chloride

What it does

General

  • 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.
  • 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

  • Sodium (coupled with chloride) is the primary determinant of extracellular (outside of cells) fluid volume, including blood volume.
  • 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.
  • 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
  • Observational studies consistently demonstrate that higher sodium intake is associated with higher blood pressure.
  • 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.
  • 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
  • A measure of how your blood pressure responds to salt intake.  
  • Animal experiments suggest that "salt sensitivity" may be related to an impaired ability by the kidneys to excrete excess sodium.
  • 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.
  • Even without knowing if you are "salt sensitive," certain subgroups of the population are more responsive to reduced sodium intake:
    • Those with hypertension
    • Older individuals
    • African Americans

For references and more information, see the section on hypertension in the Sodium article

Sodium Flashcard. Main Functions: (1) Maintains fluid and electrolyte balance. (2) Required for proper nerve conduction and muscle contraction. (3) Influences blood volume and blood pressure. Good Sources: Most dietary sodium comes from processed and restaurant food. Processed Foods (canned foods, lunch meat, potato chips), chicken noodle soup, canned, 1 cup, 789 mg; ham, minced, 3 ounces, 1,059 mg. Table Salt (sodium chloride): table salt, 1 teaspoon, 2,325 mg. Daily Recommendation: 1,500 mg for adults 19-50 years, 1,300 mg for adults 51-70 years, and 1,200 mg for adults 71 years and older. Special Notes: Most people consume too much sodium! (1) Diets low in sodium and high in potassium reduce fluid retention and favorably affect blood pressure. (a) Consuming 1,200 mg of sodium per day or less is associated with significant blood pressure reduction. (b) Fruit, vegetables, and legumes are naturally low in sodium and high in potassium.

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Vitamin C

What it does

General

  • Vitamin C (ascorbic acid) neutralizes a variety of reactive oxygen species and recycles important cellular antioxidants, augments the functional activity of immune cells, and helps make collagen, L-carnitine, and several neurotransmitters.

Blood Pressure-specific

  • 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
  • Several large, observational studies found no association between vitamin C intake and hypertension.
  • 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 one’s blood pressure.
  • A pooled analysis of short-term randomized controlled trials indicated that vitamin C supplementation at a dose of 500 milligrams (mg)/day for a 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
  Systolic Blood Pressure (mm Hg) Diastolic Blood Pressure (mm Hg)
Normotensive -3.84 -1.48
Hypertensive -4.85 -1.67
DEFINTIONS
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
Reactive oxygen species (ROS) - highly unstable oxygen-containing compounds that react easily with nearby cellular structures, potentially causing damage
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: cardiovascular disease prevention and cardiovascular disease treatment.

Vitamin C (ascorbic acid) Flashcard. Main Functions: 1) Antioxidant defense, 2) Enhances immune function, 3) Needed to make collagen, carnitine, and the neurotransmitters serotonin and norepinephrine. Good Sources: Fruit, 1 medium-sized kiwifruit = 90 mg; strawberries, 1 cup whole, 85 mg; Vegetables (broccoli, kale, tomatoes), sweet red pepper (one-half cup, chopped) = 95 mg. Daily Recommendation is 400 mg for all adults. Special Notes: 1) Heat destroys vitamin C. Try to eat fresh foods and cook by steaming, microwaving, or stir-frying. 2) Vitamin C in food is identical to vitamin C in supplements. 3) The Daily Recommendation listed is specific to the LPI based on extensive review of the scientific evidence. The Institute of Medicine's Recommended Dietary Allowance (RDA) is 90 mg/day for men and 75 mg/day for women.

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Vitamin D

What it does

General

  • 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

  • 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
  • Higher vitamin D status has been associated with lower blood pressure.
  • 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.

Vitamin D (calciferol) Flashcard. Main Functions: 1) Facilitates absorption of calcium and phosphorus, 2) Promotes bone health, 3) Required for proper immune function, and 4) Influences cell growth and development. Good Sources: Fatty Fish (salmon, mackerel, sardines), pink canned salmon, 3 ounces = 465 IU or 11.6 micrograms; Canned mackerel, 3 ounces = 211 IU for 5.3 micrograms; Fortified food, low-fat milk, vitamin D fortified, 8 ounces = 98 IU or 2.5 micrograms. Daily Recommendation: 600-1,000 IU (15-25 micrograms) for chldren and adolesents (4-18 years), because vitamin D is scarcely found in food, it may be necessary to take supplements. 2,000 IU or 50 micrograms for all adults, this amount applies to supplemental vitamin D, which is recommended in addition to vitamin D from a mixed diet. Special Notes: 1) The Daily Recommendation listed is specific to the LPI based on extensive review of the scientific evidence. The Institute of Medicine's Recommended Dietary Allowance (RDA) is 600 IU (15 micrograms)/day for males and females who are 4-70 years old, and 800 IU (20 micrograms)/day for all adults over 70. 2) Vitamin D is considered a "Nutrient of Public Health Concern" because underconsumption is linked to adverse health outcomes. 3) More than 90% of Americans do not meet the dietary requirement for vitamin D. 4) our bodies make vitamin D upon skin exposure to UVB radiation from the sun. Darker skin color, northern latitude, and older age impede the amount of vitamin D produced.

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Coenzyme Q10

What it does

General

  • Coenzyme Q10 is a compound that can be made inside the body and obtained from food and dietary supplements.
  • Coenzyme Q10 helps the body convert food into useable energy and functions as an antioxidant in cell membranes.

Blood pressure-specific

  • 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.
  • The antioxidant properties of coenzyme Q10 may help reduce oxidative stress, thereby increasing the availability of nitric oxide.
What we know
  • A significant deficiency of coenzyme Q10 has been detected in patients with hypertension.
  • Coenzyme Q10 supplementation added to conventional medical therapy results in moderate blood pressure decreases in hypertensive individuals. 
  • The effective dose of coenzyme Q10 supplementation varies from person to person but appears to be approximately 100 to 120 milligrams (mg) per day.
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.

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Garlic

What it does

General

  • Garlic is a rich source of organosulfur compounds, a category of phytochemicals that give garlic its pungent smell and taste.
  • These organosulfur compounds and their breakdown products may be responsible for some beneficial health effects of garlic.

Blood Pressure-specific

  • Test tube and animal experiments demonstrate that there are many ways by which garlic may influence blood pressure.
  • The bioactive compounds provided by garlic have been shown to:
    • induce the activity of antioxidant enzymes
    • increase the production of hydrogen sulfide and nitric oxide, gaseous signaling molecules that relax blood vessels
    • inhibit enzymes involved in vasoconstriction (blood vessel narrowing)
What we know
  • 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.
  • No serious side effects have been reported. The most common side effect is garlic odor, taste, and breath.
  • 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
  • garlic may enhance the anticoagulant effects of warfarin
  • garlic may reduce the bioavailability of HIV protease inhibitors

For references and more information, see the section on hypertension in the Garlic article.  

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