It’s that time of year when those of us living in the northern hemisphere start experiencing cooler temperatures and a little less sunshine. Sunlight is our main source of vitamin D and is produced when UVB rays come into contact with with our skin. Cholesterol in the skin is responsible for the conversion of these rays into vitamin D. Vitamin D is a fat soluble vitamin and has the properties of both a vitamin and a hormone. Technically, it’s not really a vitamin at all, but a prohormone or hormone precursor.
The summer months in the northern hemisphere are an optimal time for us to obtain vitamin D. If you’re in Florida, congratulations! You can produce vitamin D pretty much year round. For those of us in Southern Canada/Northern US, peak times of sun exposure are from April to October between the hours of 11am to 3pm. Those further north, like in Edmonton, Alberta will experience peak vitamin D synthesis between May to September. The more skin you have exposed (think shorts and t-shirt or bikinis), the more vitamin D your body will be able to produce. It’s also important to note that wearing sunscreen blocks the production of vitamin D.
The colour of your skin is also a major factor when it comes to producing vitamin D. Our skin contains a substance called melanin which affects how light or dark our skin colour is. Those with more melanin have darker skin tones. Melanin prevents UVB rays from permeating the skin, blocking the production of vitamin D. Those with pale skin (less melanin) require about 10 to 20 minutes of sun exposure during peak times to make 10,000 IU of vitamin D. For those with darker skin (more melanin) it can take up to 2 hours. The Vitamin D Council has an excellent chart describing varying skin types and exposure requirements.
So why is Vitamin D so important?
- required for calcium and phosphorus absorption which is essential for the health of your bones and teeth as well as helping prevent fractures
- reduces inflammation
- regulates your heartbeat
- prevents osteoporosis and osteopenia
- decreases risk of osteoarthritis
- enhances the immune system
- helps prevent autoimmune diseases like multiple sclerosis and rheumatoid arthritis
- necessary for normal blood clotting
- required for healthy thyroid function
- reduces incidence of dental cavities
- supports brain health
- prevents and treats depression
- reduces incidence of type 2 diabetes by improving insulin sensitivity
Who’s at risk of developing a deficiency?
There are a number of factors that can put us at risk for vitamin D deficiency. As discussed, our geographical location, the amount of melanin in our skin, time spent indoors and wearing sunscreen reduce our ability to make adequate vitamin D.
- the elderly are at risk due to loss of skin elasticity making it more difficult to produce vitamin D
- breastfed infants – if the mothers vitamin D level are insufficient, the infant will not receive adequate levels through breast milk
- Alcoholics – due to impaired absorption of nutrients
- Obesity – because vitamin D is fat-soluble, it can get trapped in adipose tissue, preventing it from being utilized by the body
Best Dietary Sources
You can obtain vitamin D by enjoying these foods each week. Ensure these animal sources are grass-fed/pastured and have had optimal exposure to the sun.
- liver and other organ meats
- grass fed butter and ghee
- wild salmon, mackerel, herring, oysters, shrimp and crab
- fermented cod liver oil (rich in both vitamin A and D)
There are many products on the market that are fortified with vitamin D, but many of these are heavily processed as well as being potential allergens and/or gut irritants like cereals, dairy and soy products.
Unfortunately, obtaining adequate vitamin D from food alone may not get you to levels required for optimal health.
The Vitamin D Council recommends that infants receive 1000 IU per day. Children should get 1000 IU per 25 lbs of body weight per day and adults should get 5000 IU per day.
If you choose to go with a supplement, look for vitamin D3 which is a more bio-available form. Liquid forms are available and and are usually derived from lanolin (found in sheep wool) and mixed with a medium chain triglyceride like coconut oil. Before reaching for the supplement, it’s important to have your vitamin D [25(OH)D] levels tested. It is recommended that levels be tested every 3-6 months and can be obtained through a blood test with your physician.