• Question: Why do you think exposure to the sun has both benefits and risks to us and our health?

    Asked by Lucy.T6690 to Barbara, Matt, Ravinder, Sophie, Tristan on 10 Mar 2015. This question was also asked by lauren currie.
    • Photo: Barbara Shih

      Barbara Shih answered on 10 Mar 2015:

      The risk of sun exposure is more straightforward – UV would damage DNA in the skin, which leads to increased risk of skin cancers. The benifits have been controversial, the only heavily confirmed benifits is vitamin D gain. Sun exposure is the main source of vitamin D, and there are very few foods that naturally contain large amount of vitamin D. (*see note below) Vitamin D is important for bone health; lack of vitamin D in children would lead to rickets.

      Debated effects:
      1) UV raises mood. (I’m not sure how much evidence there are for this one, but I seem to remember the evidence being pretty strong).
      2) Immune modulation – immune cells responds to UV exposure. Some skin disorders, such as psoriasis, are found to be imporved with UV exposure (in fact, UV is used as a treatment). A few skin/immune disorders gets worse over winter when there is less UV.
      3) A recent study noted that exposure to UV lowers blood pressure.
      4) Lower chances of a lot of non-skin cancers. Studies looking at cancer rate over geographic regions found that although people have increased skin cancer rate near the equator (high UV), they have reduced rate of several other cancers. Some goes as far as suggesting that the strong message asking everyone to avoid the sun is actually worse for health on the whole.
      5) Some studies linked low vitamin D status to cancers/other disorders.

      It’s important to note that both 4) and 5) lead to the question if the relationship found is cause/consequence/other factors invovled. For example,people living near the equator might have less chance of non-skin cancer because they drink more water due to heat.

      It’s still a heavily debated area that requires a lot more research. Personally, I think most things are best when taken into moderation.

      *This is becoming a debated area (the plus side of doing research, you know most information before other people) – some people find that although things like red meat and eggs have very little vitamin D, they have the more metabolised form of vitamin D [25(OH)D].

    • Photo: Tristan Smith

      Tristan Smith answered on 11 Mar 2015:

      There is also a huge amount of research now that shows people that receive less hours of direct sunlight per day are at a much higher risk of getting a variety of autoimmune diseases such as multiple sclerosis and Type I diabetes, now Barbara is right in that a lot of it was done originally in relationship to the equator, as in the farther away you live the more likely. But now there is some very compelling evidence that sunlight exposure or lack of, is one of the main environmental risks for multiple sclerosis.

    • Photo: Matthew Moore

      Matthew Moore answered on 11 Mar 2015:

      That’s interesting Tristan, I didn’t know that!

      In extreme cases people can literally get rickets –a condition where the bones develop out of shape– for lack of Vitamin D from the sun. Lighter skin colour is actually thought to have evolved for just this reason. As early humans moved to climates further away from the equator (where dark skin would be an advantage) they struggled to get as much vitamin D from the sun. Lighter skin colour would have been an advantage in cooler climates therefore and also explains why a single variant (the ginger gene) could be a massive advantage and is more prevalent in Europeans, even today, than elsewhere.

      UV rays on the other hand are damaging to DNA and can break apart chromosomes even in high enough amounts! In that case lighter skin becomes a disadvantage and darker skin an advantage! As people with lighter skin have, in modern times, moved back to warmer climates the occurrence of skin cancer for example has massively increased!