Vitamin D Supplementation

 

Registered Dietitian Recommendation: All breastfed infants should be supplemented with 400 IU Vitamin D daily. Supplements are to begin within the first weeks of life and no later than two months of age. All formula fed infants should likewise be supplemented if intake is less than 1 liter of Vitamin D fortified formula (7). Supplementation is to continue throughout the lifespan when dietary intake does not meet RDAs for age (400 IU 0-12 months; 600 IU 1-70 yr; 800 IU >70 yr) at latitudes higher than 33 degrees or when exposure to direct sunlight is restricted (3,5,6). Institutionalized and home bound elderly should be supplemented at 800 IU. Supplements should not exceed the RDA unless directed by a physician in instances with noted deficiency (6).

Vitamin D is a hot topic within current research, with suggested associations between adequate levels in the blood and prevention of cancer and autoimmune diseases such as Multiple Sclerosis and Diabetes (1,5,6,7). While it would be inaccurate to suppose that Vitamin D is the sole cause or cure of a specific disease, Vitamin D's benefits should be appreciated and care should be taken to obtain adequate dietary intake and/or exposure to the sun.
Listed below are the known and suspected benefits of adequate Vitamin D levels in the blood:
Known roles/benefits of Vitamin D in the Body:

1. Bone formation and maintenance (1,5,6,7)
2. Reduced risk of bone fractures particularly in the elderly (5)
3. Decreased risk of falls and increased lower extremity function (5)
4. Increased oral health (5)
5. Calcium regulation in the blood (1,5,6)
6. Cell specialization and regulation of cell growth/multiplication (1,5,6)
7. Decreased risk of Colorectal cancers (5)

Possible health benefits currently under investigation:

1. Decreased blood pressure (1,5,6)
2. Autoimmune protection against disease such as Multiple Sclerosis, Diabetes, Arthritis (1,5,6,7)
3. Increased immunity (1,5) and possible reduction in infectious diseases (6,7)
4. Increased insulin sensitivity (1,5,6)
5. Prevention of various cancers (6,7)

The number one source of Vitamin D is sunlight (1,2,6,7), which produces the vitamin within the skin according to need (1). As a protective feature, Vitamin D synthesis via the sun is inactivated within the human body when levels are adequate thus preventing toxicity from that route (1,6). Dark skin further aids in this protection by decreasing the rate of the sun's synthesis of vitamin D in populations characteristically located in parts of the world receiving more direct sunlight. Therefore, when someone of a darker skin tone moves to a higher latitude of increased distance from the equator (either North or South) they need 3-10 times more exposure to sunlight to synthesize adequate levels of Vitamin D (2,5, 6,7). During the winter months all populations in higher latitudes are at greater risk for deficiency as direct sunlight exposure decreases (5). Additional risk for deficiency arises as more time is spent indoors and sunscreen or other protective measures are utilized to decrease direct sunlight exposure during the summer. Of interest, sunscreen with a SPF of 30 will decrease Vitamin D synthesis from the sun by 95% (6). Risk factors other than limited sun exposure and dark skin, include obesity (4,5,6), residence at latitudes greater than 33 degrees (5,6) exclusively breastfed infants (7) and age (5,6).
Maintenance of Vitamin D via dietary intake is also becoming more difficult as consumption of natural sources such as milk and fatty fish (herring, salmon, tuna, sardines) is decreasing. Additional natural dietary sources include beef, egg yolks, cheese, butter and liver. Fortified sources may include yogurt, cheese, margarine, orange juice, bread and cereal depending on the manufacturer (1). When dietary intake fails to meet age specific Recommended Dietary Allowances (RDA) of 400 IU (0-12 mo), 600 IU (1-70 yr), 800 IU (>70 yr) at latitudes greater than 33 degrees or when exposure to direct sunlight is restricted (3,6) supplementation should be initiated to decrease risk of deficiency. It should be noted, that breast milk is not a good source of vitamin D with levels between 25-78 IU regardless of maternal supplementation. Therefore, exclusively breastfed infants should be supplemented with Vitamin D (7). Supplements should not exceed the RDA unless directed by a physician in instances with noted deficiency (6). In correlation with Vitamin D's role in bone health, deficiency is characterized by improper bone development in infants and children identified as Rickets and decreased bone density in adults known as osteomalacia (1,6).

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References:

1. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. 5th ed. Belmont, CA: Wadsworth Cengage Learning; 2009.
2. Weishaar T, Vergili JM. Vitamin D status is a Biological Determinant of Health Disparities. J Acad Nutr Diet. 2013; 113 (5): 643-651.
3. Institute of Medicine Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press; 2011.
4. Au LE, Rogers GT, Hariss SS, Dwyer JT, et al. Associations of vitamin D Intake with 25-Hydroxyvitamin D in overweight and Racially/Ethnically Diverse US Children. J Acad Nutr Diet. 2013; Article in Press. Accessed September 2, 2013.
5. Bischoff-Ferrari HA, Giovannucci E, Willett WC, Dietrich T, DawsonHughes B. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr. 2006;84(1):18-28.
6. Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: An Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(7):1911-1930.
7. Wagner CL, Greer FR. Prevention of Rickets and Vitamin D Deficiency in Infants, Children and Adolescents. Pediatrics. 2008; 112: 1142.