Hypertension and Vitamin D

Vitamin D, sometimes called "the sun vitamin" because our bodies use sun exposure to manufacture vitamin D, might prevent the development of hypertension. Vitamin D is also sometimes recommended as a treatment for hypertension that has already developed, though research evidence for this use is not strong. This vitamin D does have many other potential health benefits, and most people are deficient, so it may be worth taking as a supplement and/or making sure you get modest sun exposure (about 15 minutes per day of legs and arms exposed to the sun).

A common blood test can help you and your healthcare provider know your vitamin D status. If you are elderly, spend most of your time indoors, have darker skin, and/or live in northern latitudes, you are more likely to be vitamin D deficient.

Vitamin D plays a number of roles in the body, some of which are just now being discovered and confirmed. Its exact role in preventing or treating hypertension is not immediately clear. One possibility is that vitamin D helps enhance our body's levels of calcium, helping prevent calcium deficiency, which has been linked to the development of hypertension.^29,30,58 (See the article on Calcium and Hypertension for more information.)

Read more details about Vitamin D.

According to several studies, getting adequate vitamin D may help prevent the development of hypertension.^45-49

Research does not yet convincingly show that vitamin D can treat hypertension once it has developed. For instance, in an extremely large randomized, placebo-controlled trial involving 36,282 postmenopausal women, 1,000 mg of calcium plus 400 IU of vitamin D given daily did not significantly reduce blood pressure over a 7 year period in women with or without hypertension.¹³⁹

Although vitamin D is found in some foods, the best source is sun exposure (about 15 minutes per day of arms and legs exposed to the sun) and supplements.

Vitamin D is typically taken at doses between the Recommended Daily Allowance (RDA) and the Upper Level Intake (UL), the upper limit of what is considered safe. (See below.) Therapeutic doses are usually closer to the UL. These recommendations were updated in 2010 by the Institute of Medicine, and they vary for people of different ages and pregnancy/lactation status. Many health experts now recommended that people who are vitamin D deficient take daily doses closer to the UL, because lower doses might not correct a deficiency.

The Institute of Medicine's updated (November 2010) recommendations for daily intake of vitamin D⁴⁴ are as follows. The first number is the Recommended Dietary Allowance (RDA), and the second number is the Upper Intake Level (UL), the highest daily dose that is considered safe:

• Children and Infants:
  • 0-6 months: no RDA/1,000 IU
  • 6-12 months: no RDA/1,500 IU
  • 1-3 years: 600 IU/2,500 IU
  • 4-8 years: 600 IU/3,000 IU
  • 9-18 years: 600 IU/4,000 IU

• Adults:
  • 19-70 years: 600 IU/4,000 IU
  • 71 years and older: 800 IU/4,000 IU

• Pregnant/lactating women:
  • 14-50 years: 600 IU/4,000 IU

Vitamin D is a fat-soluble vitamin, which means that your body can store it in your tissues. If you wish to take higher doses of of vitamin D intake, it is recommended that you consult with a physician or other qualified health professional, such as a naturopathic doctor (see Side Effects & Warnings for more information).

• Naturopathic doctor
• Nutritionist or dietitian
• Physician, especially an integrative MD
• Chiropractor

Safety Issues

When taken at recommended dosages, vitamin D appears to be safe. However, when used at considerable excess, vitamin D can build up in the body and cause toxic symptoms. At an intake level of about 40,000 IU daily (about 100 times the recommended daily intake) vitamin D can cause dangerous elevations in blood calcium levels. ¹ Doses five times higher than this were consumed by a few individuals due to a manufacturing error; the resulting toxicity was severe and may have caused death in one individual. ² However, short of these vastly excessive dosages, it is not clear at what level vitamin D becomes toxic.

According to updated recommendations from the Institute of Medicine,⁴⁴ the safe upper limits (UL) for vitamin D daily intake are as follows:

• Children and Infants:
  • 0-6 months: 1,000 IU
  • 6-12 months: 1,500 IU
  • 1-3 years: 2,500 IU
  • 4-8 years: 3,000 IU
  • 9-18 years: 4,000 IU

• Adults:
  • 19-70 years: 4,000 IU
  • 71 years and older: 4,000 IU

• Pregnant/lactating women:
  • 14-50 years: 4,000 IU

There is no disagreement that people with sarcoidosis or hyperparathyroidism should never take vitamin D without first consulting a physician.

Taking vitamin D and calcium supplements might interfere with some of the effects of drugs in the calcium-channel blocker family. ³ It is very important that you consult your physician before trying this combination.

The combination of calcium, vitamin D, and thiazide diuretics could potentially lead to excessive calcium levels in the body. ⁴ If you are taking thiazide diuretics, you should consult with a physician about the right doses of vitamin D and calcium for you.

Interactions You Should Know About

• You may need extra vitamin D if you are taking antiseizure drugs, such as:
  • Phenobarbital
  • Primidone (Mysoline)
  • Valproic acid (Depakene)
  • Phenytoin (Dilantin)
  • Corticosteroids
  • Cimetidine (Tagamet)
  • Heparin
  • Isoniazid (INH)
  • Rifampin

• If you are taking calcium-channel blockers , do not take high-dose vitamin D (with calcium) except under physician supervision.

• If you are taking thiazide diuretics , do not take calcium and vitamin D supplements unless under a doctor's supervision.

1. Klontz KC, Acheson DW. Dietary supplement-induced vitamin D intoxication. N Engl J Med. 357(3):308-9.
2. Klontz KC, Acheson DW. Dietary supplement-induced vitamin D intoxication. N Engl J Med. 357(3):308-9.
3. Bar-Or D, Gasiel Y. Calcium and calciferol antagonise effect of verapamil in atrial fibrillation. Br Med J (Clin Res Ed). 282(6276):1585-6.
4. Riis B, Christiansen C. Actions of thiazide on vitamin D metabolism: a controlled therapeutic trial in normal women early in the postmenopause. Metabolism. 34(5):421-4.

29. Cappuccio FP, Elliott P, Allender PS, et al. Epidemiologic association between dietary calcium intake and blood pressure: a meta-analysis of published data. Am J Epidemiol. 1995;142:935-945.
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44. Institute of Medicine. Report Brief: Dietary Reference Intakes for Calcium and Vitamin D. Released November 30, 2010. Accessed at the IOM Web site: http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D/Report-Brief.aspx?page=1
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49. O'Connell TD, Simpson RU. 1,25-dihydroxyvitamin D3 and cardiac muscle structure and function. In: Crass MF II, Avioli LV, eds. Calcium-Regulating Hormones and Cardiovascular Function. Boca Raton, FL: CRC Press; 1995:191-211.
58. Porsti I, Makynen H. Dietary calcium intake: effects on central blood pressure control. Semin Nephrol. 1995;15:550-563.
139. Margolis KL, Ray RM, Van Horn L, et al. Effect of calcium and vitamin D supplementation on blood pressure: the Women's Health Initiative Randomized Trial. Hypertension. 2008;52:847-855.