Does low calcium cause high blood pressure

Abstract

Hypertension affects millions of Americans. Twenty-five years ago, researchers observed that calcium might be inversely related to the development and severity of hypertension. Consequently, several epidemiological, animal, and clinical studies have addressed this potential correlation. Dietary deficiencies or altered calcium metabolism can result in low serum calcium levels. Disturbances in calcium metabolism include increased urinary calcium excretion and abundance of calcium-regulating hormones such as parathyroid hormone and calcitriol. These hormones cause decreases in bone mineral content and increase intracellular calcium in vascular smooth muscle. Increased [Ca2+]i produces contraction and therefore vasoconstriction. Low calcium levels and elevated PTH and calcitriol may also affect blood pressure control by the central and peripheral nervous systems by stimulating the release of norepinephrine (a potent vasoconstrictor) and increasing its post-synaptic effect. Calcium supplementation and/or increased dietary calcium have been used to increase calcium intake. Not all studies have shown a definite inverse correlation between calcium intake and hypertension, however certain patient groups (pregnant women, salt-sensitive hypertensives) clearly benefit from increased calcium intake. Calcium interacts with other nutrients (sodium, potassium, magnesium) in affecting blood pressure. Due to its probable beneficial effects on hypertension, osteoporosis, and other diseases, RDA intake for calcium should be strongly encouraged.

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It's usually best to get calcium, magnesium, and potassium from food. Are you getting enough?

A healthy, balanced diet plays a major role in blood pressure control. And you should consume some specific minerals on a regular basis for good blood pressure management: calcium, magnesium, and potassium. But do most of us get enough of these? "If you're eating a healthy diet, you probably have nothing to worry about. But people eating a diet of processed and canned foods or taking certain medications might not be getting enough of these micronutrients," says Dr. Randall Zusman, director of the Division of Hypertension at the Massachusetts General Hospital Heart Center.

Images: Thinkstock 1/2 cup canned white beans: 595 milligrams (mg) of potassium, 67 mg of magnesium, and 96 mg calcium.

3 ounces of cooked halibut: 490 mg of potassium, and 91 mg of magnesium.

1/2 cup cooked spinach: 419 mg potassium, 78 mg of magnesium, and 146 mg of calcium.

Potassium

Normal body levels of potassium are important for muscle function, including relaxing the walls of the blood vessels. This lowers blood pressure and protects against muscle cramping. Normal potassium levels also are important for the conduction of electrical signals in the nervous system and in the heart. This protects against an irregular heartbeat.

Potassium is found naturally in many foods, such as prunes, apricots, sweet potatoes, and lima beans. But food may not be enough to keep up your potassium levels if you take a diuretic for high blood pressure such as hydrochlorothiazide (Esidrix, HydroDiuril). These drugs cause potassium to leave your body in the urine, thereby lowering your body's potassium levels. "I'd say at least a third of patients on diuretics for heart failure or high blood pressure or edema don't get enough potassium from their diets. In those cases, we do use supplements," says Dr. Zusman. Don't try a supplement on your own. Too much potassium, like too little, can lead to dangerous irregular heart rhythms.

The Recommended Dietary Allowance (RDA) of potassium is 4.7 grams per day for both men and women ages 51 and older.

Magnesium

Magnesium helps regulate hundreds of body systems, including blood pressure, blood sugar, and muscle and nerve function. We need magnesium to help blood vessels relax, and for energy production, and bone development. Just like potassium, too much magnesium can be lost in urine due to diuretic use, leading to low magnesium levels.

The National Institutes of Health (NIH) reports that most older adults in the U.S. don't get the proper amount of magnesium in their diets, although extreme magnesium deficiency is very rare. It's best to get the mineral from food, especially dark, leafy green vegetables, unrefined grains, and legumes. The RDA of magnesium is 420 milligrams (mg) per day for men ages 50 and older; 320 mg/day for women ages 50 and older.

Too much magnesium from a supplement or from magnesium-containing drugs such as laxatives may cause diarrhea. There are no known adverse effects of magnesium intake from food.

Calcium

Calcium is important for healthy blood pressure because it helps blood vessels tighten and relax when they need to. It's also crucial for healthy bones and the release of hormones and enzymes we need for most body functions. We consume it naturally in dairy products, fish (such as canned salmon and sardines), and dark, leafy greens.

The RDA of calcium for men ages 51 and older is between 1,000 and 1,200 mg per day. For women ages 51 and older it's 1,200 mg per day. However, many experts believe that these levels are set too high and some studies suggest an association between calcium supplements and higher risk of heart disease.

"It's been controversial, so most of us advise our patients to get their calcium from food rather than from supplement pills," says Dr. Zusman. If it's not possible to get enough calcium from food, talk with your doctor if you think you may need a calcium supplement.  

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