Vitamin D – Sun or Supplements?

Daniel Roytas - Clinical Nutritionist and Naturopath, MHSc(N u t),BHSc (N a t), D i p. R M , MANTA

Bayleaf Wellness

Vitamin D is well known for its beneficial effects on the nervous, musculoskeletal, immune and endocrine systems. In fact, individuals with a healthy vitamin D status have lower rates of depression, osteoporosis, infection and diabetes compared to those who are deficient. Many Australian’s take a vitamin D supplement for these purported health effects, however is supplementation really the best way to achieve an optimal vitamin D status?


The major source of vitamin D is from exposure to ultra-violet B (UV-B) light from the sun. How can it be, that despite living on the sunniest continent on Earth, approximately 25% of Australian’s are vitamin D deficient?The most common factor associated with vitamin D deficiency is insufficient sun exposure, however there are a number of other contributing factors including inflammatory conditions, chronic disease, being overweight or obese, ageing and deteriorating health. In 1988, the ‘sun smart’ public health initiative was implemented in an attempt to reduce the rates of skin cancer. This program encouraged people to stay out of the sun, and to slip on a shirt, slop on sunscreen and slap on a hat in the event they did venture outdoors. The initiative was quite successful, achieving a 50% reduction in people getting sun burnt since its inception, however is it possible it worked too well?


Many Australian’s are now too afraid of venturing out in to the sun for fear of getting skin cancer and as a result, they are becoming deficient in vitamin D. By strictly adhering to the ‘slip, slop, slap’ recommendations, when these people do venture out, it is relatively difficult to achieve a meaningful increase in vitamin D status. Hence, some researchers have called for modifications to the ‘sun smart’ guidelines be made, recommending people to get more sun exposure, to reduce the risk of vitamin D deficiency.


Sun exposure is a double-edged sword, too much and you get burnt, too little and you risk becoming deficient in vitamin D. Getting sun burnt doubles your risk of melanoma, however, regular non-burning sun exposure is actually associated with a reduced risk of melanoma. In fact, it is well established that people who work outdoors actually have a lower incidence of melanoma compared to people who work indoors. This suggests that a certain amount of sun exposure may actually be protective against melanoma, whereas too much or not enough sun, increases your risk.


In order to maintain a healthy vitamin D status (>50 nmol/L), it is recommended that people get sensible levels of sun exposure. This involves exposing 15% of the bare skin (arms and hands) to the sun for just seven minutes outside of the hours of 10 am – 3 pm in Summer and between 7 – 40 minutes at midday during Winter. The body has a remarkable capacity to produce vitamin D from sun exposure. A whole body minimum erythema dose (faint skin redness) from sun exposure, can generate 10 000 – 25 000 IU of vitamin D per day.


To put that in to perspective, you would need to take the equivalent of 10 – 25 vitamin D capsules (1000 IU per capsule) to achieve the same dose. This may eventually prove problematic long term because using high doses (20 000 IU per day) of supplemental vitamin D might cause toxicity. Sun exposure on the other hand, cannot cause vitamin D toxicity, because the body has an inbuilt mechanism that stops creating vitamin D when it has sufficient levels.


Many people are under the assumption that they can compensate their lack of sun exposure with a vitamin D supplement. It is easy to forget that the sun regulates a number of biological effects that are above and beyond that of vitamin D. In fact, sunlight is said to have effects over multiple signaling molecules that are independent of vitamin D. For example, our skin plays a major role in controlling homeostasis of the entire body through a highly complex relationship with the nervous, endocrine and immune systems. In order for this mechanism to function normally, the skin must be activated by UV light from the sun. The sun also regulates our internal body clock (circadian rhythm) by activating receptors in the back of the eye, which then influences the hypothalamic-pituitary-adrenal axis (HPA axis).


Probably the most important effects of sun exposure are those that are not yet completely understood. For example, sun exposure has been shown to significantly reduce the risk of diseases such as breast cancer, colorectal cancer, prostate cancer, hypertension, cardiovascular disease, metabolic syndrome, multiple sclerosis, Alzheimer’s disease, autism, asthma, type 1 diabetes, type 2 diabetes, and myopia. Conversely, oral vitamin D supplementation has not been associated with reductions in these diseases. This suggests that sun exposure has beneficial effects above and beyond that of vitamin D. Other authors have also highlighted the fact that there are beneficial effects induced by sun exposure other than vitamin D17.


So what does all of this mean?


It means that it is preferable for people to get sensible amounts of sun exposure, rather than taking a vitamin D supplement to maintain a healthy vitamin D status. It has been stated that a low serum vitamin D test result may be “a proxy for and not a mediator of the beneficial effects of sun exposure”. In other words, nothing beats the real thing. Getting outside, in the fresh air and getting some sensible sun exposure is good for you. A vitamin D supplement cannot be a complete substitute. It is worthwhile to note that UV-B radiation does not penetrate glass, so exposure to sunshine indoors through an office window is unable to increase vitamin D levels.


Is it time to re-think our fear of the sun?


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