Vitamin D, health, and sunlight
Do you find yourself seeking out the sun in winter? Wonder why you feel so much better when the weather is good? Turns out there is a scientific reason, and it's not just about vitamin D!!
For years low vit D levels have been linked to many diseases, including autoimmune disease, allergies, cancers, cognitive decline, heart disease and even shorter life expectancy. Yet trials routinely supplementing vit D have had disappointing results in these areas - a massive placebo RCT published in the NEJM in 2019 showed no reduction in cancer or heart disease risk.
Yet as people become more sun conscious and spend more time indoors (especially with our harsh NZ sun) , low vitamin D levels are increasingly common - so much so that routine supplementation is recommended in many people
Interestingly though, scientists now believe that the suns benefits extend far beyond vitamin D - and that low vit D is a MARKER of lack of sun, rather than a primary cause of disease in itself (outside of significant vit D deficiency)
When skin is exposed to sun, the body produces nitric oxide - a molecule that:
✔️dilates blood vessels
✔️reduces blood pressure
✔️induces euphoria and wellbeing
✔️ improves blood flow and oxygen delivery to tissues
✔️ improves insulin sensitivity
Fun fact - nitric oxide is also produced when you eat fruit and veges and may be part of why these are also so beneficial!
Sun exposure also triggers the release of serotonin and endorphins (happy hormones)
Adequate sun exposure is linked to :
✔️reduced rates of diabetes
✔️lower risk of high blood pressure, heart disease, and blood clots
✔️lower rates of many cancers
✔️improved mental health
✔️lower rates of autoimmune disease
✔️lower mortality (up to 50% in one study)
An article in J Intern Med even found sun avoidance had a similar effect on life expectancy as smoking 😧
Skin cancer risk is the main (and valid) logic behind avoiding sun, yet there is also evidence that regular limited SAFE exposure may lower risk of melanoma (isolated episodes of sunburn can significantly increase risk in contrast).
Sensible sun exposure may actually be far more useful than we think - a bonus for anyone who loves the outdoors!!
We obviously do NOT advise using sunbeds, getting sunburnt, or not using sunscreen. But you can get out in the sun without burning, especially in winter - and doing this in nature, and getting exercise at the same time, has so many added benefits!
So how much do vitamin D supplements ACTUALLY help??
Vitamin D is both a vitamin and a hormone - it's found in foods, but most of it is made from sunlight on SKIN.
Vitamin D is needed in:
✔️metabolism of calcium and phosphate
✔️ control of cell growth (ie cancer)
✔️ immune function
✔️insulin production
✔️ blood pressure regulation
✔️ bone and muscle strength
Extreme deficiency leads to rickets in children, and osteomalacia in adults (soft brittle bones), as well as muscle weakness
Risk factors for deficiency include
✔️people with darker skin and the elderly (reduced ability to make vitamin d from sun)
✔️ those who cover up from the sun/spend little time outside
✔️people with kidney disease /inflammatory bowel disease/ malabsorption.
✔️some people also have genetic variations that affect their ability to metabolise and transport vit D
✔️people who are obese are also far more likely to be deficient, as vit D is stored in fat cells, meaning the body cannot use it
Vit d deficiency has been linked to higher rates of
✔️ allergy
✔️autoimmune disease
✔️ cancers
✔️ heart disease
✔️ dementia
✔️ falls
✔️ poor immunity
✔️ parkinsons disease
✔️ diabetes (type 1 and 2)
✔️ premature death
Yet the evidence on whether supplementing vitamin d protects against these diseases is mixed as we've just mentioned
Diseases where vitamin d supplements MAY help:
✔️ allergic disease (ie eczema, asthma)
✔️ reducing risk of MS
✔️ inflammatory bowel disease
✔️ coronavirus
✔️ respiratory infections (daily dosing only, monthly dosing had little effect)
✔️ reducing risk of diabetes (type 1,2 and gestational)
✔️ parkinsons disease
✔️ cognitive decline (only if deficiency present)
✔️ reducing cancer deaths (in people with known cancers)
✔️ reducing falls and fracture risk in elderly
✔️ improving bone strength
Diseases where supplements do NOT appear to help :
✔️ heart disease
✔️ high blood pressure
✔️ prevention of lupus and rheumatoid arthritis
✔️ treatment of MS
✔️cancer prevention
Confused much?!
The bottom line is that since vitamin D is likely to be a marker for getting enough time outdoors and safe sun exposure, if you are able to get enough through these measures, then it's the best way to do so.
If you have risk factors for low vit D, struggle to get outdoors and get safe sun exposure, or have a confirmed deficiency, then supplementing is recommended.
https://www.thelancet.com/.../PIIS2213-8587(13.../fulltext
https://www.nejm.org/doi/full/10.1056/NEJMoa1809944
https://www.nejm.org/doi/full/10.1056/NEJMoa1809944
https://scitechdaily.com/vitamin-d-deficiency-strongly.../
https://www.medicalnewstoday.com/.../benefits-of-sunlight....