Vitamin D is essential for the maintenance of normal bone and muscle function, and may be important for proper functioning of the cardiovascular and immune systems. It is the 'sunshine vitamin' because most of the natural vitamin D in our body is made in the skin following exposure to ultraviolet radiation from the sun. Unfortunately, there is a pandemic of vitamin D insufficiency around the world, and those of us living in sunny Los Angeles are not immune from the problem.
Overall in the U.S., more than a third of the otherwise healthy young adult population have low vitamin D levels. Part of the reason is that we have done an excellent job of heeding the advice of dermatologists to avoid excessive sun exposure by covering our arms with long-sleeved garments, wearing wide-brimmed caps, and smearing on copious quantities of high SPF sunscreens. So, as we attempt to avoid skin cancers, we have increased our risk for developing vitamin D deficiency.
Elderly individuals, who may be housebound, are at high risk for the deficiency. Hispanic and African-American individuals are at higher risk than Caucasians because of the effect of skin pigmentation from melanin, which is protective against skin cancer and photoaging, but also blocks efficient vitamin D production.
Vitamin D deficiency is associated with osteopenia or osteoporosis, bone pain if the deficiency is severe, muscle weakness and aches, and increased risk of falls. Low levels of vitamin D in the blood have been associated with an increased risk of cardiovascular disease, autoimmune diseases, some cancers and depression, but a cause-and-effect relationship has not been established.
For many of us, dietary sources of vitamin D are inadequate to overcome diminished skin production of the vitamin. Natural food sources of vitamin D include fatty fish, such as salmon, mackerel and herring, fish liver oils and egg yolks, while many foods, including milk, margarine, yogurts, breads and cereals are fortified with extra vitamin D. However, the levels of the vitamin in the fortified foods are in the range of 100 IU per serving or less.
The current recommended daily allowances for vitamin D are 200 IU per day for individuals under 50 years, 400 IU a day between ages 50 and 70, and 600 IU a day for people older than 70. Unfortunately, these levels are now considered to be too low by most experts. Many physicians, including me, are recommending that patients take 1000 to 2000 IU a day, preferably in the form of vitamin D3 which is more potent than D2. These amounts usually raise the blood levels into the normal range and generally are not associated with toxic levels of the vitamin, which can result headache, nausea and vomiting. This means that most people will have to supplement their dietary and sun-induced vitamin D sources with extra vitamin D, either combined with a calcium supplement or taken as a separate tablet. Indeed, vitamin D and calcium supplementation has been shown to reduce falls and fractures and may improve cognitive function and depression.
LA's sunny reputation is here to stay. As Angelenos, we should enjoy it, continue to protect ourselves from the skin aging and cancer-causing radiation through covering up and using sunscreen, and taking a vitamin D supplement.