By Jeremy Appleton, ND, CNS
Long gone are the days when vitamin D was something you took only to enhance calcium supplementation for bone strength. While it remains true that vitamin D and calcium have important interactions in the body, evidence from peer-reviewed medical journals continues to mount in support of a much greater role of vitamin D in maintaining health and longevity than was previously known.
Vitamin D is a part of the endocrine system and is critical to the integrity of many vital physiologic processes and for bone strength. Although the scientific community has raised the recommendations for optimal vitamin D levels, intakes of vitamin D much larger than those currently recommended may be needed.
Important for Kids
It is well-known that prolonged and severe vitamin D deficiency leads to rickets in children. Several recent studies have examined the adequacy of vitamin D status in children and adolescents and have reported teens in particular have low vitamin D levels during the winter.
Vitamin D is sometimes called the “sunshine vitamin” because the body makes the vitamin after being exposed to ultraviolet rays from the sun. In most cases, 10-15 minutes of sunshine three times a week is sufficient to produce the body’s requirement of vitamin D. However, if you use sunscreen with a sun protection factor (SPF) of 8 or more, this can interfere with vitamin D synthesis.
The Daily Reference Intake of Vitamin D for adults under 50 years is just 400 IU per day. Individual needs may vary depending on a person’s age, gender, and other factors (such as pregnancy). In general, people over 50 years need slightly higher amounts of vitamin D than younger persons. According to the National Osteoporosis Foundation, adults under age 50 need 400 to 800 IU (International Units) of vitamin D daily. Menopausal women and adults over the age of 50 are advised to get 800 to 1,000 IU of vitamin D daily. In addition to sun exposure, vitamin D can be obtained from fortified milk, egg yolks, saltwater fish, liver and dietary supplements. Vitamin D is safe when taken in appropriate amounts. Although, the Institute of Medicine has set the tolerable upper limit at 2000 IU, this recommendation is no longer considered to be up-to-date or reflective of the vitamin’s growing importance and recognition of safety.
Safety and Vitamin D
Toxicity of vitamin D is rare. The exact long-term safe dose of vitamin D is not known, but amounts up to 10,000 IU per day in healthy adults are believed to be safe. Total-body sun exposure easily provides the equivalent of 10,000 IU vitamin D per day, suggesting that this is a physiologic limit. Except in those with conditions causing hypersensitivity, there is no evidence in the medical literature of adverse effects of vitamin D with intakes of less than 40,000 IU per day.Reversal of vitamin D deficiency in an otherwise healthy person can be readily accomplished, usually with 2,000-7,000 IU vitamin D per day.
Pittas AG, Lau J, Hu FB, Dawson-Hughes B. The role of vitamin D and calcium in type 2 diabetes. A systematic review and meta-analysis. J Clin Endocrinol Metab 2007 Jun;92(6):2017-29. Epub 2007 Mar 27.