Vitamin D

Vicki Koenig, MS, RD, CDN

Vitamin D might actually help us live longer. While most of us know vitamin D increases calcium absorption, research keeps confirming more benefits. A 2007 meta-analysis of 18 research studies with 57,311 people showed that those with normal vitamin D levels had decreased risk of death from life-threatening diseases like heart disease, diabetes and cancer.

Vitamin D is critical for children, teenage girls, postmenopausal women, older men, obese people and people of color. Those who live in higher latitudes with less sun exposure are known to have lower vitamin D levels.

Vitamin D’s benefits

• Increases calcium absorption while decreasing risk of osteoporosis.
• Helps with immune system responses and may lower risk of influenza.
• Helps maintain insulin levels for diabetics and prediabetics.
• Involved in blood-pressure regulation; helpful for hypertension.
• Associated with increased muscle strength and decreased falls in the elderly.

How to get enough vitamin D

The daily value (DV) for vitamin D is 400 IU. Scientists at the Vitamin D Council recommend raising this to at least 1000 IU per day for healthy people.

• Foods. The most common way to get vitamin D is with fortified foods like milk and yogurt. It’s also in catfish, salmon and shrimp.
• Get some sunshine! 10,000-20,000 IU of vitamin D is produced naturally with 20 minutes of midday sun exposure. Unfortunately, those who live north of an imaginary line running from San Francisco to Philadelphia don’t produce vitamin D from the sun between October and May. We store what we make during the summer, but can be deficient in the winter without supplementation.
• Supplements. Vitamin D3 is more potent than vitamin D2. Check with a knowledgeable MD for how much to take.

Can you get too much?

You can’t overdose from the sun. You store what you need. Sunscreen with an 8 SPF (sun protection factor) blocks >95% of vitamin D production in the skin.

Vitamin D toxicity from supplements is extremely rare, especially for Vitamin D3. The upper level of toxicity is 2000 IU, but many scientists support raising this to 10,000 IU.

Make sure you get enough vitamin D from all sources. Fortify yourself with sunshine, Stonyfield Farm yogurt and a supplement when necessary, and reap the benefits associated with optimal vitamin D intake.

For more information:

• Autier P and Gandini S. “Vitamin D Supplementation and Total Mortality..” Arch Intern Med 2007;167(16):1709-1710, 1730-1737.
• Food and Nutrition Board. Dietary Reference Intakes: Guiding Principles for Nutrition Labeling and Fortification. 1997.
• Grant WB and Holick MF. “Benefits and Requirements for Vitamin D for Optimal Health: A Review.” Alt Med Rev 2005;10(2):94-111.
• Hanley DA and Davison KS. “Vitamin D Insufficiency in North America.” J Nutr Feb 2005;135(2):332-337.
• Maalouf J et al. “Short- and Long-Term Safety of Weekly High-Dose Vitamin D₃ Supplementation in School Children.” J Clin End & Metab 2008;93(7):2693-2701.
• Vieth R et al. “Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level.” Am J Clin Nutr Feb 2001; 73(2):288–294.
• The Vitamin D Council is a concerned group of scientists who believe most humans are deficient in vitamin D.
• Wagner CL et al. “Prevention of Rickets and Vitamin D Deficiency in Infants, Children, and Adolescents.” Pediatrics Nov 2008; 122(5):1142–1152.