Vitamin D deficiency and Health Consequences
Vitamin D deficiency is now recognized as a world-wide problem with health consequences. The major cause of vitamin D deficiency is the lack of appreciation that sun exposure in moderation is the major source of vitamin D for most humans. Increased skin pigmentation markedly reduces vitamin D synthesis. Inadequate dietary intake, winter season, latitude, aging, medication and certain medical condition are also associated with increased risk of vitamin D deficiency.
In Australia, a dramatic increase in skin cancer rates resulted in the promotion of sun-safe policy to avoid exposing the skin to direct sunlight without sun protection, i.e., clothing or sunscreen. This message has resulted in a marked increase in the risk of vitamin deficiency in Australia. Studies suggest that upwards of 30–50% of children and adults worldwide are at risk of vitamin D deficiency.
Very few foods naturally contain vitamin D, which is found in small quantities in foods such as fatty fish, Liver, and eggs. Foods that are fortified with vitamin D are often inadequate to satisfy either a child’s or an adult’s vitamin D requirement.
Vitamin D deficiency can have musculoskeletal and nonskeletal consequences.
•It causes growth retardation and rickets in children and will precipitate and exacerbate osteopenia, osteoporosis, and fractures in adults, and other bone disorders
•It has been associated with proximal muscle weakness, increase in body sway, and an increased risk of falling
•It has been associated with increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases
Mild vitamin D deficiency is defined as serum 25-OHD levels in the range 25–50 nmol/L
Moderate vitamin D deficiency is defined as serum 25-OHD levels of 12.5–25 nmol/L
Severe vitamin D deficiency is defined as Serum 25-OHD levels of < 12.5 nmol/L.
A circulating level of 25-hydroxyvitamin D of >75 nmol/L, or 30 ng/mL, is required to maximize vitamin D’s beneficial effects for health. In the absence of adequate sun exposure, at least 800–1000 IU vitamin D3/day may be needed to achieve this level in children and adults. To treat moderate to severe vitamin D deficiency, supplementation with 3000-5000 IU/day for 6–12 weeks is often recommended.
Source: Am J Clin Nutr 2008;87(suppl):1080S– 6S. MJA 2005; 182 (6):281-285
Nutrition News
Vitamin D Supplementation Inhibits Age-Related Bone Loss In Older Women
New research shows that vitamin D supplementation can reverse normal age-associated bone loss in postmenopausal women, which can lead to a reduced risk of osteoporosis and other bone disorders.
Until recently, it was unknown whether improving vitamin D status (without changing calcium intake) could have a positive effect on bone turnover.
New Zealand Researchers at Massey University recently measured the effect of vitamin D supplementation on markers associated with bone turnover in women known to be vitamin D deficient <20 ng/mL.
Participants were South Asian women at least 20 years of age. The women were categorized by age and menopausal status, and then randomized to receive either 4,000IU of vitamin D or a placebo every day for 6 months.
In the women who received vitamin D supplements, average vitamin D blood levels increased from 8.4 ng/mL to 30 ng/mL. Additionally, measured bone markers either stayed the same or decreased in postmenopausal women who received vitamin D supplements, indicating a potential reduction in bone turnover. In postmenopausal women who received placebo, markers associated with bone turnover increased. In younger, premenopausal women, no significant bone turnover change was reported for either placebo or supplementation group.
This research confirms that correcting vitamin D deficiencies in older women can suppress age-related increases in bone turnover, which also helps reduce bone resorption (the process by which bone breaks down and releases its minerals, resulting in a transfer of calcium from bone into the blood).
Source : von Hurst PR et al2010. J Steroid Biochem Mol Biol. EPub ahead of print, retrieved online 6 April 2010.
Advanced Doses of Vitamin D Are Required To Achieve Optimal Vitamin D Status
Vitamin D is a fat-soluble vitamin that plays multiple roles in human health. The importance of vitamin D in calcium metabolism and bone health is well recognized but more recently, its role in cardiovascular health, immune function, glucose metabolism, and cell differentiation and proliferation have been defined.
It is well established that vitamin D deficiency leads to rickets in developing children but more current research has also linked vitamin D deficiency with osteoporosis, osteomalacia, impaired muscle function, infection, autoimmune disorders, diabetes, and some cancers in adults.
Vitamin D deficiency is now recognized as a common problem worldwide. The major cause of vitamin D deficiency is the lack of sun exposure and that very few foods provide adequate level of vitamin D.
In the latest USANA clinical study in collaboration with Linus Pauling Institute, scientists investigated the effectiveness of moderately high daily doses of vitamin D3 on increasing circulating levels of vitamin D during winter, spring, and summer seasons.
19 healthy volunteers, with average intake of vitamin D (supplements and diet) between 800-1000 IU/day, were randomly divided into either treatment or control (placebo) groups. The treatment group was given a daily supplement providing 4000 IU of vitamin D3 (by USANA Health Sciences, Inc.) during winter season. The control group received a placebo tablet. Both groups took their supplement/placebo daily for 12 weeks and circulating levels of vitamin D were measured every 4 weeks. From week 16, a subset of the treatment group went on to be supplemented with 2000 IU/day of vitamin D into the spring and summer seasons.
This study found that supplementation with an additional 4000 IU/day of vitamin D during winter increased circulating levels of vitamin D by 4 weeks to within the optimal range and maintained the for the duration of the treatment. The subset of subjects who went on to receive 2000 IU/day during the late spring and summer were able to maintain their optimal vitamin D status. The authors concludes that continuous intakes of vitamin D at advanced level are needed to obtain optimal circulating levels of vitamin D above 50ng/mL throughout the entire year.
For more information, please visit USANA Clinical Trial Bulletin on Vitamin D
A Higher dose of vitamin D reduces the risk of falls in Nursing home residents
Elderly nursing home residents have a high risk of falls and are often deficient in vitamin D. Fall-related fracture and injury is a serious problem affecting the quality of life and cost of healthcare for these elderly nursing home residents. Effective interventions to reduce falls are needed in those at high risk of falling.
To determine the effect vitamin D supplement doses on falls risk in elderly nursing home residents, 124 nursing home residents (average age 89) in a 725-bed long-term care facility were randomly assigned to receive one of four vitamin D supplement doses (200 IU, 400 IU, 600 IU, or 800 IU) or placebo daily for 5 months. Number of fallers and number of falls were assessed using facility incident tracking database.
Over the 5-month study period, the proportion of participants with falls was 44% in the placebo group (11/25), 58% (15/26) in the 200 IU group, 60% (15/25) in the 400 IU group, 60% (15/25) in the 600 IU group, and 20% (5/23) in the 800 IU group. Participants in the 800 IU group had a 72% lower adjusted-incidence rate ratio of falls than those taking placebo over the 5 months. No significant differences were observed for the adjusted fall rates compared to placebo in any of the other supplement groups.
This study indicates that nursing home residents in the highest vitamin D group (800 IU) had a lower number of fallers and a lower incidence rate of falls over 5 months than those taking lower doses. Adequate vitamin D supplementation in elderly nursing home residents could reduce the number of falls experienced by this high falls risk group.
Source: J Am Geriatr Soc 2007;55:234-239
Prevention of nonvertebral fractures with oral vitamin D
A doos-response relationship between vitamin D and fracture reduction is supported by epidemiologic data showing a significant positive trend between serum 25-hydroxvitamin D concentrations and hip bone density and lower extremity strength.
To assess the amtifracture efficacy of oral vitamin D supplementation in the elderly, a recent study performed a meta-analysis on the efficacy of oral supplemental vitamin D in preventing nonvertebral and hip fractures among older individuals (> or = 65 years). This study included 12 double-blind randomized controlled trials (RCTs) for nonvertebral fractures (n = 42279) and 8 RCTs for hip fractures (n = 40886) comparing oral vitamin D with or without calcium, with calcium, or placebo.
The meta-analysis found that antifracture efficacy increased significantly with a higher dose and higher achieved blood 25-hydroxyvitamin D levels for prevention of both non-vertebral fractures and hip fractures. The higher dose (>400IU) reduced nonvertebral fractures in community-dwelling individuals (-29%) and institutionalized older individuals (-15%), and its effect was independent of additional calcium supplementation.
CONCLUSION: Nonvertebral fracture prevention with vitamin D is dose dependent, and a higher dose should reduce fractures by at least 20% for individuals aged 65 years or older.
Source: Arch Intern Med. 2009 Mar 23;169(6):551-61