Sunshine and sea, makes Vitamin D
What is Vitamin D and how do we get it?
Cholecalciferol (D3) is a hormone precursor made in the skin in the presence of sunlight (UVB). This appears to be a nifty evolutionary adaptation from our dark skinned, equatorial dwelling ancestors. However these days adequate sun exposure is influenced by factors such as skin colour, latitude, time of year, wearing sunscreen and environmental pollution – not just actual time spent outside with your skin uncovered. While there are other forms of Vitamin D, some potentially toxic, D3 is the form made in our body and also obtained nutritionally from oily fish (especially herrings, salmon, sardines and mackerel), egg yolks (some questions are raised how current farming techniques may effect that) and offal, such as liver. In Australia all margarine is fortified, sometimes with D2. Milk is often sited as a good source of Vitamin D but it is not a natural source. In the Northern Hemisphere milk has long been fortified to add the D in, while in Australia only some brands supplement their range.
If you have absolutely no sun exposure, recent research suggests you may need up to a whopping 5,000 international units (IU)/125 micrograms* of Vitamin D a day. There are large groups in the community who are particularly vulnerable to Vitamin D deficiency such as – dark skinned people, veiled women (eg: some Muslims), those in institutions (eg hospitals and nursing homes) and your typical workaholic who is in the office all day. Interestingly, breast milk is very low in Vitamin D, so exclusively breast fed babies are at risk of deficiency especially if they spend no time uncovered in the sun. Screening for Vitamin D status in pregnancy is not routine in all hospitals in Australia yet but you can always request your obstetrician check your levels as this deficiency can also be passed onto your baby.
Evidence now show’s that Australians have an alarmingly high incidence of Vitamin D deficiency. Historically there has been no RDI’s (recommended daily intake) given in this country because of our latitude and abundant ultra violet light. However a 2002 study of women in Geelong which looked at dietary intake of Vitamin D and casual sun exposure recommended a rethink of that policy. The study used 5-10 micrograms a day as their marker for adequate Vitamin D, which is significantly less than the 25 micrograms researchers at the Vitamin D council (link above) advise. 80% of dark skinned women in the Geelong study were found to be Vitamin D deficient.
A position statement published in the Medical Journal of Australia in 2005 goes into more detail as to the issues surrounding the increasing rates of Vitamin D in Australia. It concludes that all Australians are more likely to be deficient than not and claims the successful public health “Slip, Slop, Slap” campaign is one of the contributing causes. The paper suggests a daily supplementation of 400 IU, increased to 5,000 IU a day for up to 3 months in cases of deficiency.
What role does Vitamin D play in our body?
The image of a bow legged, slum dwelling child has always been the poster boy for the well known Vitamin D deficiency disease, rickets. D3 regulates calcium and phosphorous levels. Without adequate Vitamin D, it makes no real difference how much dietary or supplemental calcium you have; you still won’t make strong bones. The Health Trip show last year on healthy bones explains this vital role further.
However the latest research into Vitamin D deficiency is painting a much broader picture. Being low in D3 has now been strongly implicated in diabetes, heart disease, hypertension, multiple sclerosis, rheumatoid arthritis, preeclampsia, colon (and possibly most forms of) cancer, metabolic syndrome, autism, and depression. A meta-analysis of 63 published reports showed that intake of an additional 1,000 international units (IU) (or 25 micrograms) of vitamin D daily reduced an individual’s colon cancer risk by 50%, and breast and ovarian cancer risks by 30%.
A caller on today’s show with Multiple Sclerosis, mentioned he’d only just been tested for Vitamin D despite it being 8 years since his initial diagnosis and has found to be lacking. The D3-MS connection has been well document in reputable scientific and medical journals for over a decade, describing the link as compelling. A further literature review could suggest that even when neurologists are supplementing D3 with a maximum dose of 1,000 IU/day it may not be enough, with 4,000 IU being a more effective dose.
Other causes of D3 deficiency beyond diet and sunshine
While high concentration of pigmentation in the skin is an obvious deterrent for D3 production there are other causes of inadequate Vitamin D absorption and utilization in the body.
These include: conditions that effect fat absorption (Vitamin D is a fat soluble vitamin) e.g.: Crohns disease, pancreatic enzyme deficiencies, cystic fibrosis, uncontrolled coeliac disease, liver dysfunction and surgery to the stomach or bowel. Kidney disease, obesity and parathyroid dysfunction may also effect your Vitamin D utilization. Drugs including rifampicin and perhaps multiple anticonvulsant drug therapy can also be a culprit.
How do you know if you are deficient in Vitamin D?
Historically, bone health was considered to be the yardstick with a diagnosis of osteoporosis or osteomalacia triggering a blood test for Vitamin D levels. But a greater understanding of D3 deficiency is exposing a variety of other common symptoms such as musculo-skeletal pain, fatigue and gum disease. Many people with a D3 deficiency are either asymptomatic of misdiagnosed with conditions such as fibromyalgia, arthritis or chronic fatigue syndrome.
What is more harmful – too much or too little Vitamin D?
Nutritional dosage has always been a contentious issue in the worlds of orthodox and complementary medicine. The MJA position paper called for a rethink on the conventional laissez-fair attitude towards minimum intake of Vitamin D in Australia. While there have not been any recorded cases of Vitamin D toxicity from sun exposure, the issue with supplementation can be problematic with any fat soluble vitamin. Vitamin D has a half-life in the body of 20-29 days, therefore there are valid concerns of accumulation causing toxicity. The US Dietary Reference intake sets an upper limit of 50 micrograms (2,000 IU) a day, however the Nutrition Desk Reference states, “The threshold for toxicity is 500 to 600 micrograms [vitamin D] per kilogram body weight per day.” This would mean a 70kg person would have a minimum toxicity at 35,000 micrograms a day. Furthermore the 2005 MJA position paper calling for a rethink on Vitamin D included a dosage of 300,000 IU intramuscularly, twice a year, for those with extreme deficiencies. Confusing, isn’t it? What is apparent is that with current lifestyles existing RDI for Vitamin D, where they do exist, appear to be grossly inadequate, particularly in the role of cancer prevention.
The melanoma paradox
So you’d like to get a little UV exposure but don’t want to risk melanoma, can you get Vitamin D from the sun safely? Well here comes the paradox. Various studies are now showing a certain amount of unblocked sun exposure may actually increase your chances of surviving melanoma. Increasingly, the assumption that developing a melanoma is all about sunlight is being overturned. For example, a Queensland study concluded over a decade ago that “No measures of acute or chronic exposure to solar UV radiation were associated with childhood melanoma”. Dr Ralph Moss’s newsletter on Vitamin D and Cancer: A Dermatologist’s Dilemma also makes interesting reading.
As UV levels vary dramatically due to location and season, it is important to understand just how much Vitamin D you can synthesize from the sun, where you live. Sun Exposure index for Australia and New Zealand published in the MJA article suggest that for those living in Melbourne, safe sun exposure, with no “slip, slop, slapping” for a fair skinned person to be 6-8 minutes at 10am – 2pm in December and January, rising to 32-52 minutes a day in winter.
NB: Despite early reports that sunscreen use does not compromise your Vitamin D synthesis, blocking UVB penetration of the skin conclusively inhibits our ability to make D3. For example a sunscreen with a SPF rating as low as 8, stops 95% of skin’s ability to synthesize Vitamin D. Perhaps with the current evidence it is time to re-evaluate when we need to use sunscreen? Research is also exploring the paradox connecting sun block use increasing your chances sunburn.
Keep watching this space. New research is being published all the time and D3 is certainly a hot topic. While there appears to be no clear agreement on how much and even in what form of, Vitamin D we need – wider screening for deficiency even in this sunburnt country is called for. Safe sun exposure, more oily fish, egg yolks from healthy chooks and even some supplementation should certainly be considered by most Australians.
* Reseach on Vit D often flips between IU’s and micrograms. To convert IUs of vitamin D into micrograms: multiply the number of IUs by 0.025. The result is the number of micrograms in the food. To convert micrograms to IUs: multiply the number of micrograms by 40. The result is the number of IUs in the food.
Lots of interesting links on this subject can be found at the Vitamin D Council