By Jessica Patella, ND abstracted from “A 16-Week Randomized Clinical Trial of 2000 International Units Daily Vitamin D3 Supplementation in Black Youth: 15-Hydroxyvitamin D, Adiposity, and Arterial Stiffness.” in the July 21, 2010 publication of the Journal of Clinical Endocrine Metabolism.
Key words: vitamin D3, adiposity, arterial stiffness, adolescence
The current National Institutes of Health’s recommended daily adequate intake for vitamin D is 200 IU per day (1). In 2008, the American Academy of Pediatrics recommended that intakes for children and adolescent populations be increased to 400 IU per day (1). Yet, is 400 IU per day enough? Recent research suggests that 2000 IU per day may be needed to achieve optimal vitamin D status, especially in those at higher risk of deficiency (2). Those at higher risk have darker skin, wear concealing clothing (a barrier to producing vitamin D from sunshine) or live in areas farthest from the equator (3).
Recent research included 44 black adolescents (14-18 years old) in Augusta, Georgia (approximately 33 degrees North latitude) who had normal blood pressure and were not taking any medications or supplements (2). The participants were divided into two groups: one receiving 400 IU per day of vitamin D3 (21 participants) and the second group receiving 2000 IU per day of vitamin D3 (23 participants). The trial lasted 16 weeks and participants met with researchers every 4 weeks to assess their compliance in taking the vitamin D3 capsules.
Plasma levels of vitamin D (25(OH)D) were drawn at baseline (start of study), week 4, week 8 and week 16. Based on previous research, serum 25(OH)D was defined as vitamin D deficiency if less than 50 nmol/L, vitamin D insufficiency between 50-75 nmol/L and vitamin D sufficiency if above 75 nmol/L (2). The average baseline level of 25(OH)D for all participants was 33.4 nmol/L, indicating a deficient status in black youth (2).
After 16 weeks of vitamin D3 supplementation, plasma 25(OH)D levels were significantly higher in the 2000 IU group (85.7 +/- 30.3 nmol/L) compared to the 400 IU group (59.8 +/- 18.2 nmol/L; P<0.001). Overall in the 2000 IU group, 56.5% reached sufficient levels of vitamin D, 39.1% reached insufficient levels and 4.4% remained deficient. In the 400 IU group, 23.5% reached sufficient levels of vitamin D, 15.5% reached insufficient levels, and 61% remained deficient in vitamin D (2).
Deficient levels of plasma vitamin D have been associated with cardiovascular risk factors (2). Atherosclerosis begins in adolescence, which results in arterial stiffness (4). At baseline and post-test, pulse wave velocity (PWV*) was tested to determine if vitamin D supplementation improved arterial stiffness. Of the 44 subjects, 35 were able to complete the PWV. In the 2000 IU per day group (n=18), the carotid-femoral (aortic) PWV significantly decreased from baseline (5.41 +/- 0.73 m/sec) to posttest (5.33 +/- 0.79 m/sec; P=0.01), showing improvement in arterial stiffness. In the 400 IU per day group (n=17), the PWV significantly increased from baseline (5.38 +/- 0.53 m/sec) to post-test (5.71 +/- 0.75 m/sec; P=0.01), showing possible increased arterial stiffness.
In conclusion, 2000 IU per day of vitamin D3 may help achieve optimal vitamin D status and the higher dosage needs to be considered in black youth. Higher levels of vitamin D3 also could improve arterial stiffness in young adults. Further research needs to be conducted with more participants to continue learning about the correlation between vitamin D and arterial heath, as well as the appropriate optimal adequate intake.
*PWV is a test used to calculate arterial stiffness.
About the Author: Jessica Patella, ND, is the founder of Sarasota Natural Health LLC and specializes in homeopathic medicine. She offers a holistic approach to health, inspiring and empowering her clients to lead lives of optimal health and wellness. To learn more, visit www.sarasotanaturalhealth.com
1. Dietary Supplement Fact Sheet: Vitamin D. National Institute of Health. http://ods.od.nih.gov/factsheets/vitamind.asp
2. Dong Y, et al. A 16-Week Randomized Clinical Trial of 2000 International Units Daily Vitamin D3 Supplementation in Black Youth: 15-Hydroxyvitamin D, Adiposity, and Arterial Stiffness. Doi: 10.1210/jc.2010-0606
3. Dijkstra SH, et al. High prevalence of vitamin D deficiency in newborn infants of high-risk mothers. Arch Dis Child 2007;92: 750-753
4. Berenson GS, et al. Association between multiple cardiovascular risk factors and atherosclerosis in children and young adults. The Bogalusa Heart Study. N Eng J Med 338:1650-1656.