This is the time of year when sunlight is in very short supply. As I sit at my desk with my bright light therapy lamp shining in my face, I asked myself what’s the difference between getting vitamin D3 via sunlight as opposed to getting it via diet and supplementation…(yeah, this is going to be another ‘bee in my bonnet’ blog).
When our skin is exposed to sunlight, it produces endorphins, promotes feelings of wellbeing, and was used in the early 1900’s to treat Tuberculosis. UVB radiation is converted, via a complex chemical reaction, into Vitamin D3. The epidermis (the outer layer of the skin) absorbs this radiation and makes vitamin D3 in the cells of the skin. This process takes about 8 hours before its ready to leave the skin and travel into the body. 20-30 minutes of sunlight exposure daily is enough.
Vitamin D3 is essential for skeletal health, muscle function and the immune system…ever noticed how we’re more susceptible to illness in the winter? It’s not just the change in temperature.
Deficiency of this vitamin contributes to a range of health issues not limited to bone pathologies, autoimmune disorders, chronic illness, type II diabetes, cardiovascular disease, and depression and increased symptoms of SAD. There is a high prevalence of vitamin D3 deficiency in the UK.
Absorption can be affected by;
- Altitude (higher altitude, increased UVB absorption = more vitamin D3)
- Skin pigmentation (lighter skin pigmentation = increased absorption), as mankind emigrated further from the equator, scientists believe skin pigmentation lightened to allow for greater vitamin D absorption.
- Sunscreen can inhibit UVB radiation absorption by up to 98%. Australia was so good at covering up with sunscreen that 40% of the population experienced vitamin D deficiency but had a positive impact on lower skin cancer rates.
- Air pollution (also absorbs UVB radiation)
- It’s also affected by glass and plastic (which, you guessed it, also absorbs UVB radiation)
- Season & Latitude – in Boston (USA), during the months of November to February, little vitamin D3 can be produced in the skin, Boston is 42° N latitude. Higher latitudes such as Canada (52° N) and Norway 60° N can’t produce any significant Vitamin D3 for 6-months of the year. Were about 51-52° N latitude in Gloucester, UK
- Time of day – Between 12-2pm are the best time to get sunlight for Vit D3 absorption
- Age decreases the ability of the skin to produce vitamin D3.
So, is getting vitamin D3 through diet and supplementation the answer in the winter?
Ingested vitamin D3 takes a different pathway, literally and chemically. We don’t get a huge amount of vitamin D3 through diet and we likely cant get enough from diet alone. Foods containing vitamin D3 include egg (yolks), liver and fish liver oil, red meat, oily fish – such as salmon, sardines, mackerel, trout. Foods with added vitamin D3 include fat spreads, some fortified cereals and plant-based milks.
Vitamin D3 supplementation is highly recommended year long. Sunlight derived vitamin D3 lasts 2-3 times longer than oral vitamin D3, but in higher latitudes, that’s not an option 5-6 months of the year.
Thanks for reading.