Vitamin D-a-day to keep the doctor away
October is the time of year in the UK when Public Health Guidelines recommends you get vitamin D from the diet/supplementation because the sun exposure during winter isn’t enough. Vitamin D is a unique nutrient: it acts as a pro-hormone and the requirement for vitamin D can be met by both endogenous synthesis from sunlight and by dietary sources. Most people think of Vitamin D as important for bone health but it actually controls expression of over 1000 processes in the body. Importantly it is a powerful manipulator of the immune response, collaborating with vitamin A to immune optimiser our immune system. In fact, many of our immune cells contain vitamin D receptors, enabling them to directly respond to this vitamin. And these immunologic cells are all are capable of synthesising the active vitamin D metabolite which affects their behaviour.
Vitamin D has been used (unknowingly) to treat infections such as tuberculosis for generations before the advent of effective antibiotics. Tuberculosis patients were sent to sanatoriums where treatment included exposure to sunlight which was thought to directly kill the tuberculosis. Not just for the Wold Economic Forum, Davos in Switzerland with its climate and above average hours of sunshine was at one time a hub renowned for its Tuberculosis healing properties & high-class medical sanitariums. This has evolved into the home of world-class research on respiratory disease today. Cod liver oil, a rich source of vitamin D has also been employed as am ‘old wives’ treatment for tuberculosis as well as for general increased protection from infections.
Autoimmune diseases arise when your immune system is confused or overly stressed and begins attacking your own tissues instead of outside pathogens. Vitamin D prevents this by promoting regulatory T cells, which are responsible for accurately differentiating between outside invaders and our own “self” cells. Vitamin D essentially makes your immune system smarter, teaching it to not attack itself and preventing the development of an autoimmune disease. There are a number of studies demonstrating higher rates of autoimmune disease, as well as a greater rate of autoimmune disease progression, among people with Vitamin D deficiency. Although these data do not prove a causal relationship between vitamin D and autoimmune diseases, they warrant further investigation into whether at-risk individuals and patients could benefit from vitamin D supplementation.
Am I deficient?
In addition to the changing season, several other factors can alter vitamin D status; Sunscreen use can also – UVB radiation is required to elicit vitamin D synthesis. Skin pigmentation – Melanin, the pigment found in skin, serves as a natural sunscreen, so your ability to make vitamin D can vary depending on skin tone. Age – As we age our body becomes less efficient at producing vitamin D from sun exposure. Body fat – Since vitamin D is fat soluble, the higher the body fat, the lower the bioavailability. A higher concentration of body fat prevents the vitamin D from being released into the blood stream. It may also be partially genetic as certain Single Nucleotide Polymorphisms in vitamin D-related genes appear to modify our vitamin D status and disease risk.
Oily fish – such as salmon, sardines, herring, mackerel, as well as red meat (in particular organ meats such as liver) and egg yolks are also food sources of vitamin D. Mushrooms are high in vitamin D, especially if they have been in contact with UVB radiation (i.e. sunlight! Top tip - pop them on a sunny windowsill to encourage them to churn out more vitamin D). It’s not only vitamin D that make mushrooms an immune nourishing powerhouse. They possess a wide array of nutrients including copper, potassium, B vitamins and are one of the highest source of two antioxidants called ergothioneine and glutathione that help fight unruly inflammation, protect from infection and bolster general health - so a great addition to your diet over the winter months. Get adventurous and try some of the more functional varieties such as shitake, miatake and rishi which appear to pack the biggest immunity punch.
Like a 3-legged stool, vitamin D can only do its job with the cooperation of vitamin A and Vitamin K. Lesser known vitamin K has somewhat languished in obscurity, but works as an important cofactor to maximise the effects of A & D. Vitamin A is supplied primarily by foods of animal origin such as dairy products, fish and liver, or plant-based beta-carotene rich fruits and vegetables, normally orange or dark green in colour (think carrots, pumpkin, winter squash, dark green leafy vegetables and apricots). Vitamin K is primarily found in dark leafy vegetables and is particularly enriched in Natto, a fermented Soy. Remember these vitamins are all fat soluble so eat them with a healthy fat such as extra virgin olive oil. Supplementing vitamin D without enough magnesium can induce further magnesium depletion, so magnesium should go hand-in-hand with vitamin D.mFortunately all these nutrients are found in many delicious, everyday foods that go well together: dark leafy greens, nuts, tofu, and brown rice are all powerhouse sources for magnesium and vitamin K, while eggs, fish, dairy, fortified foods, and mushrooms all have vitamin D. Don’t forget that magnesium can be bolstered topically too.
Although we know that vitamin D deficiency is prevalent in autoimmune disease and there is a correlation of deficiency with more active infection - there is still much to be learned. Although a recent meta-analyses reinforce the finding that 10–20 µg per day of vitamin D can reduce all-cause mortality and cancer mortality in middle-aged and older people. A subsequent systematic review of meta-analyses and randomised trials in Sept 2018 showed no new evidence that supplementation could have an effect on most non-skeletal conditions, including cardiovascular disease, adiposity, glucose metabolism, mood disorders, muscular function, tuberculosis, and colorectal cancer, or on maternal and perinatal conditions. This has led some to suggest that low vitamin D status is a consequence, rather than a cause, of ill health (ie, reverse causality). However the 2018 Lancet study did show that vitamin D supplementation helps to prevent common upper respiratory tract infections and asthma exacerbation’s.
Confused? I don’t blame you.
We still don’t have a clear picture of all the various ways vitamin D contributes to our overall well-being at different life stages. There are several possible reasons why most meta-analyses and trials published so far do not provide a concordant view on the effectiveness of vitamin D supplementation for bone health & non-skeletal outcomes, including too small trials, too low vitamin D doses, type of administration (monthly bolus vs. daily) & too short duration of interventions, especially for chronic diseases. Often clinical trial participants are already vitamin D replete which may obscure effects on deficient subjects. No doubt there is much more to be learned about vitamin D. The hypotheses on its protective role against chronic inflammation are not necessarily contradictory because inflammation, innate immunity, and adaptive immunity have complex interactions, and the multiple roles of vitamin D within these systems are still unknown.
Make sure you check the current guidelines in your area such as the NHS in the UK. Generally speaking “optimal” levels of vitamin D are often reported as serum levels between 30-80 ng/ml with Vitamin D insufficiency reported as <30 ng/ml and deficiency as <20 ng/ml. But it can be difficult to determine how much vitamin D supplementation is needed to obtain the ‘sweet spot’ For these reasons, you should routinely get your vitamin D levels tested and aim to include vitamin D (with vitamin A & K) containing foods into your diet.