For years, you’ve heard how important the “sunshine vitamin” is to bone health, especially when taken with calcium. But D also keeps your immune system humming, heart ticking and muscles strong. It may even prevent cancer. A government advisory panel tripled its recommended daily allowance (RDA) from 200 to 600 international units (IU) late in 2010. But some of the nation’s leading scientists say this higher RDA is still too low. About 70% of whites, 90% of Hispanics and 97% of blacks in the U.S. have insufficient levels of D in their blood, according to a 2009 University of Colorado report published in the Archives of Internal Medicine. Vitamin D deficiency harms more than your bone strength. It may lead to bigger health problems, such as Crohn’s disease, lupus, diabetes and heart disease. Vitamin D influences more than 200 genes – many of which are associated witha variety of diseases. Here’s how vitamin D affects your health:
Cancer: Adequate vitamin D levels are linked with a reduced risk of breast, colon, and prostate cancers. Low levels are associated with a 30%-50% higher risk, as well as an increased risk of dying from the disease.
Heart disease: A variety of studies have found a strong link between vitamin D deficiency and cardiovascular risk factors, according to a 2010 research review published in Current Opinions in Cardiology.
Diabetes: Low vitamin D levels are linked to poor disease control in people with diabetes, according to a 2010 study by Johns Hopkins School of Medicine in Baltimore, Md. The researchers suggested that the vitamin plays an active role in regulating insulin-producing cells. Insufficient levels were also related to larger amounts of deep abdominal fat surrounding the internal organs, or visceral fat, which may promote development of insulin resistance and hypertension.
Autoimmune Disorders: The 2010 Oxford study found that many of the genes vitamin D appears to influence are associated with autoimmune conditions, such as multiple sclerosis, Crohn’s disease, rheumatoid arthritis and lupus. And in a 2011 University of Cincinnati study, patients with autoimmune interstitial lung disease were more likely to have reduced lung function if their blood levels of the vitamin were low.
Infection: The vitamin also supports a strong immune system, says Bruce Hollis, Ph.D., professor of biochemistry at the Medical University of South Carolina in Charleston. People with low vitamin D levels are 40% more likely to catch a cold or the flu, according to a 2009 University of Colorado study. If your vitamin D status is insufficient, your early [immune] attack against pathogens could be greatly compromised.
Muscle strength: Vitamin D also could help your workouts. Low levels are linked to decreased muscle strength and an accumulation of fat in muscle tissue.
Bone health: Because it helps the body absorb calcium, vitamin D is hugely important in preventing osteoporosis (bone loss) and fractures.
Why we’re deficient in Vitamin DOne reason for widespread vitamin D deficiency is our modern lifestyle. Researchers believe that humans evolved to absorb vitamin D from the sun. When we’re exposed to bright ultraviolet-B light, an early form is produced in the skin. The liver, kidneys and other tissues then metabolize it into more active forms. But use of more effective sunscreens, spending more time indoors and living in areas with limited sun in winter have reduced our UV exposure, working against the body’s natural vitamin D metabolism. Even living in a sunny climate is no guarantee that you’re getting enough.
How much do you need?
The IOM’s new RDA, which calls for 600 IU daily for people age 1-70 and 800 IU over 70, is a big boost from the previous RDA of 200 IU. (An IU, or “International Unit,” equals .025 micrograms.) Their recommendations were largely based on bone health.The IOM recommendations are intended to prevent vitamin D deficiency, which they define as less than 20 nanograms per milliliter (ng/mL) of blood. (You can get a blood test at your doctor’s office to find out your current levels.)
How to get your DDespite the ongoing controversy, everyone agrees we need at least 600 IU per day, either through food, supplements or sun exposure. Sunlight is the most efficient way to absorb the vitamin. But it’s not the safest because it increases the risk of skin cancer. In summer, less than 30 minutes of sun exposure delivers 10,000-20,000 IU to light-skinned people. Those with darker skin may need 2-5 times as much. After you reach a natural limit of around 10,000 IU, it begins to degrade in the skin. Your daily multivitamin may contain anything from 100-1,000 IU. High vitamin D foods such as fish or fortified milk can add 50-600 IU per serving. (See Top Foods for Vitamin D.) For every 1,000 IU taken daily, you can increase blood vitamin-D levels another 10 ng/mL in 3-4 months. D3 (cholecalciferol) supplements are considered the most effective at raising vitamin D levels. But because D3 comes from animal sources (often lanolin from sheep’s wool), vegetarians favor D2, which is produced from plants. (See The Forms of Vitamin D.) Extremely high levels can cause adverse health effects, and that a daily intake above 10,000 IU per day could lead to kidney and tissue damage.
Cancer: Adequate vitamin D levels are linked with a reduced risk of breast, colon, and prostate cancers. Low levels are associated with a 30%-50% higher risk, as well as an increased risk of dying from the disease.
Heart disease: A variety of studies have found a strong link between vitamin D deficiency and cardiovascular risk factors, according to a 2010 research review published in Current Opinions in Cardiology.
Diabetes: Low vitamin D levels are linked to poor disease control in people with diabetes, according to a 2010 study by Johns Hopkins School of Medicine in Baltimore, Md. The researchers suggested that the vitamin plays an active role in regulating insulin-producing cells. Insufficient levels were also related to larger amounts of deep abdominal fat surrounding the internal organs, or visceral fat, which may promote development of insulin resistance and hypertension.
Autoimmune Disorders: The 2010 Oxford study found that many of the genes vitamin D appears to influence are associated with autoimmune conditions, such as multiple sclerosis, Crohn’s disease, rheumatoid arthritis and lupus. And in a 2011 University of Cincinnati study, patients with autoimmune interstitial lung disease were more likely to have reduced lung function if their blood levels of the vitamin were low.
Infection: The vitamin also supports a strong immune system, says Bruce Hollis, Ph.D., professor of biochemistry at the Medical University of South Carolina in Charleston. People with low vitamin D levels are 40% more likely to catch a cold or the flu, according to a 2009 University of Colorado study. If your vitamin D status is insufficient, your early [immune] attack against pathogens could be greatly compromised.
Muscle strength: Vitamin D also could help your workouts. Low levels are linked to decreased muscle strength and an accumulation of fat in muscle tissue.
Bone health: Because it helps the body absorb calcium, vitamin D is hugely important in preventing osteoporosis (bone loss) and fractures.
Why we’re deficient in Vitamin DOne reason for widespread vitamin D deficiency is our modern lifestyle. Researchers believe that humans evolved to absorb vitamin D from the sun. When we’re exposed to bright ultraviolet-B light, an early form is produced in the skin. The liver, kidneys and other tissues then metabolize it into more active forms. But use of more effective sunscreens, spending more time indoors and living in areas with limited sun in winter have reduced our UV exposure, working against the body’s natural vitamin D metabolism. Even living in a sunny climate is no guarantee that you’re getting enough.
How much do you need?
The IOM’s new RDA, which calls for 600 IU daily for people age 1-70 and 800 IU over 70, is a big boost from the previous RDA of 200 IU. (An IU, or “International Unit,” equals .025 micrograms.) Their recommendations were largely based on bone health.The IOM recommendations are intended to prevent vitamin D deficiency, which they define as less than 20 nanograms per milliliter (ng/mL) of blood. (You can get a blood test at your doctor’s office to find out your current levels.)
How to get your DDespite the ongoing controversy, everyone agrees we need at least 600 IU per day, either through food, supplements or sun exposure. Sunlight is the most efficient way to absorb the vitamin. But it’s not the safest because it increases the risk of skin cancer. In summer, less than 30 minutes of sun exposure delivers 10,000-20,000 IU to light-skinned people. Those with darker skin may need 2-5 times as much. After you reach a natural limit of around 10,000 IU, it begins to degrade in the skin. Your daily multivitamin may contain anything from 100-1,000 IU. High vitamin D foods such as fish or fortified milk can add 50-600 IU per serving. (See Top Foods for Vitamin D.) For every 1,000 IU taken daily, you can increase blood vitamin-D levels another 10 ng/mL in 3-4 months. D3 (cholecalciferol) supplements are considered the most effective at raising vitamin D levels. But because D3 comes from animal sources (often lanolin from sheep’s wool), vegetarians favor D2, which is produced from plants. (See The Forms of Vitamin D.) Extremely high levels can cause adverse health effects, and that a daily intake above 10,000 IU per day could lead to kidney and tissue damage.
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