Article Tags: seasonal health | prevention | health education | integrative medicine | Nutrition
In the grey and rainy days of winter we get less sun exposure and this can affect our levels of vitamin D.
We need vitamin D to build and maintain healthy bones because unless sufficient vitamin D is present your body cannot absorb calcium, which the main component of bone. Vitamin D also regulates many other cellular functions. Its anti-inflammatory, antioxidant and neuroprotective properties support immune health, muscle function and brain cell activity. There also appear to be beneficial effects of vitamin D supplements with autoimmune disease.
Sunshine and vitamin D synthesis
When skin is exposed to ultraviolet B (UVB) radiation from the sun, it converts cholesterol into vitamin D3.
Factors that influence this process: Why some people are low in D
- exposure time of day, season and geographical location (latitude, altitude)
- Amount of body exposed
- air pollution
- skin pigmentation
- sunscreen use
- aging
- sun passing through glass
How much sun exposure is needed
Most people can produce enough vitamin D from sunlight from late March or early April to the end of September. To get enough vitamin D, you can try exposing your face, arms, hands, and legs to the sun for 5–30 minutes, either daily or at least twice a week. People with darker skin may need more time in the sun.
During the winter when living above and below approximately 33° latitude (San Diego, Fort Worth, Charleston) very little if any vitamin D3 can be produced in the skin from sun exposure. People who live farther north or south cannot make any vitamin D in their skin for half the year. Living in Boston, no vitamin D can be produced from November thru February.
Risks of too much sun exposure
Of course, too much exposure to the sun’s UV radiation can cause skin and eye damage, sunburn, and skin cancer. To protect your skin, you can use sunscreen with a sun protection factor (SPF) of 15 or higher.
Other sources of vitamin D
Vit. D requirements can be satisfied by eating vitamin D rich foods like oily fish, liver, egg yolks, mushrooms, salmon, sardines and Vit. D fortified foods.
You can also take vitamin D supplements, which are recommended for people with certain medical conditions, darker skin tones, or fat absorption issues.
How much is enough?
Adults 18-70 – 600IU (15 mcg)
Older than 70 – 800 IU (20mcg)
Considered safe from 1000-2000IU. Upper limit 4000 IU.
Vitamin D supplements – when to take
Best time to take is in the morning. Evening intake could reduce melatonin synthesis since D regulates melatonin production. Low levels of D contribute to poor sleep.
Excess D = toxicity that leads to high calcium levels (vomiting, muscle weakness, dehydration and kidney stones). Severe toxicity causes kidney failure, irregular heartbeat
This is unlikely to result from food or sun exposure, more likely from extra high doses of D supplements.
Vitamin D Deficiency and Diseases
Autoimmune diseases. Vitamin D deficiency increases risk for autoimmune diseases including MS, lupus, type 1 diabetes.
Low levels also increase the risk of heart disease, infectious diseases, type 2 diabetes and schizophrenia.
Cancer risk includes ovarian and breast, prostate, and digestive system.
Vit D deficiency causes rickets in children and exacerbates osteoporosis in adults. Lower in utero exposure (low maternal intake of vitamin D during pregnancy) increases risk of the baby developing diabetes.