The Impact of Vitamin D Deficiency on African Americans

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More than one-third of all Americans are vitamin D deficient, but many people may be surprised to learn that eight out of 10 African Americans are vitamin D deficient. Given the increasing role recent studies show that vitamin D may play in overall health, it is important to know your vitamin D levels and talk to your doctor about ways you can improve them.

The production of vitamin D by the body begins at the skin and is followed by other activation processes at the liver and kidney. Individuals with darker skin produce more melanin, which provides the skin with its color and the protective function of absorbing UV rays from the sun. The increased melanin, however, also reduces the ability of the skin to perform the necessary conversion to produce vitamin D, which requires direct exposure to UV rays.

Further complicating the issue is the fact that African Americans also have a high rate of lactose intolerance-the inability to digest milk products-which may lead to less consumption of dairy products, including those fortified with vitamin D. The combination of the limited ability to produce vitamin D naturally and less consumption of it in food products contribute to the higher rate of vitamin D deficiency observed in African Americans. Specifically, studies show that from puberty onward, African Americans have lower consumption of vitamin D than is recommended.

Why is vitamin D important? Many studies have found increased rates and severities of diseases associated with vitamin D deficiency in African Americans. Although it has not been shown that there is a causal relationship between vitamin D deficiency and these diseases, the association should be considered.  For example, an association has been reported between vitamin D deficiency and increased obesity and insulin resistance, which are associated with diabetes mellitus and high blood pressure. Another study has shown that some changes impacting the structure and function of small blood vessels may be influenced by vitamin D which may also impact other factors involved with regulation of blood pressure. Studies of African Americans have shown a link between vitamin D deficiencies and increased ‘end stage renal disease,' which is kidney failure requiring dialysis.

Studies also show African American women exhibit increased rates of low birth weight babies. A high rate of vitamin D deficiency during pregnancy in African Americans has been identified, and has been associated with lower birth rates and lower vitamin D levels in their newborns. Some think this might impact kidney formation and development in the babies, and potentially contribute to the increased rate of kidney failure in African Americans.

Additionally, there is an association with lower vitamin D levels and Multiple Sclerosis (MS) in African Americans, and additional studies show that African American women with low vitamin D may develop more aggressive breast cancers. Other studies indicate that vitamin D may have an impact on other cancers and on the immune system. Vitamin D deficiency may also have a greater impact on the elderly, or African Americans with existing conditions like Crohn's and celiac diseases.

The National Institutes of Health (NIH) Office of Dietary Supplements currently makes the following recommendations regarding average daily dietary intake of vitamin D. The amounts below are for maintenance of recommended levels, however, not for correction of a deficient status.  In addition, individual physicians may make different recommendations.

 

Life Stage

Recommended Amount

Upper Safe Limit

Birth to 12 months

400 IU

1,000-1500 IU

Children 1-13 years, Teens 14-18 years, Adults 19-70 years

600 IU

Children 1-8 Years: 2500-3000 IU

Children 9 years and older and adults: 4,000 IU

Adults 71 years and older

800 IU

4,000 IU

Pregnant and breastfeeding women

600 IU

4,000 IU

The NIH also recommends the following blood level of Vitamin D described in both ‘nanomoles per liter' (nmol/L) and ‘nanograms per milliliter' (ng/mL).

Low levels

Sufficient Levels

High Levels

30nmol/L (12 ng/mL

50nmol/L (20ng/mL)

125 nmol/L (50ng/mL)

High levels of Vitamin D are unlikely to result from sun exposure because the body can limit the amount of Vitamin D it produces. However, it is possible for the body to get too much Vitamin D.  It is important to note that excess Vitamin D supplementation may result in high levels possibly causing nausea, vomiting, poor appetite, constipation, weakness and weight loss with the potential to cause damage to the kidneys.

Given the health concerns associated with vitamin D deficiency, it is important to discuss your Vitamin D levels with your physician. Learning your vitamin D level can help you work with your physician to create a plan of action, which may include changes to your diet or supplements. Neither the testing nor the supplementation is costly and the risks of supplementation are low, particularly if monitored, so learning your vitamin D level is important given the impact it may have on some of these conditions.

About Dr. Cillo:

Dr. Cillo graduated from Case Western Reserve University in Cleveland Ohio with majors in Biology and English and then attended the University of Medicine and Dentistry of New Jersey (UMDNJ), New Jersey Medical School in Newark, New Jersey. She stayed at UMDNJ to complete her residency in Orthopaedic Surgery and practiced Orthopaedic Surgery for 10 years and maintains board certification in Orthopaedic Surgery. Dr. Cillo completed a Master's in Business Administration (MBA) at the University of Redlands while in practice. After building a successful consulting business within the orthopaedic industry, she worked for Medtronic Spinal and Biologics with recombinant proteins for bone healing, allograft bone grafts and implantable devices for spinal surgery. She joined Abbott in September 2007 as Medical Director for Abbott Point of Care, and currently works in Medical Affairs in Abbott's Diagnostics Division.

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