With the human body there is a sweet spot for pretty much everything. Our temperature can be a problem if it is too high or too low. Likewise with pulse, blood pressure, blood sugar, and all our hormones to name just a few. Hence it makes sense that with external factors there is likely an amount which we need. Too much or too little being a problem.

As has been observed before, singer Joe Jackson was prescient in 1982 when he sang “Everything causes cancer”. The WHO has graded carcinogens by their ability to cause cancer. It is significant that this takes an account of the likelihood. Thus, a grade one carcinogen, which has a one in one billion chance of causing cancer, is in the same group as cigarette smoking where the rate is much higher.

It also does not take dosage or other circumstances into account. Thus, the sun is a grade one carcinogen as we know that excess sun exposure can cause skin cancer. However, with no sun there is no life on earth. So clearly it can’t be all bad.

Yet we are bombarded with public health messages telling us the sun is a “killer”. School children are not allowed out to play in the middle of winter without sun protection. And we also know that vitamin D deficiency is a problem for many people, as they do not get enough sun exposure having been convinced that two sunrays will create cancer!

Vitamin D is produced in the body from the inactive form with uv light exposure. One does not, of course need to spend hours in the sun to achieve adequate levels. For most people it is 10-15 minutes a few days a week. This underlines the point about quantum of exposure to a carcinogen being vitally important in addition to its actual likelihood of causing cancer.

With the human body there is a sweet spot for pretty much everything. Our temperature can be a problem if it is too high or too low. Likewise with pulse, blood pressure, blood sugar, and all our hormones to name just a few. Hence it makes sense that with external factors there is likely an amount, which we need. Too much or too little being a problem.

Various studies have looked at why rates of myopia (short sightedness) are increasing. This is particularly the case in children. The reason seems to be a lack of sun exposure. Bloomberg reports, “In the 1950s, roughly 20 to 30 percent of 20-year-olds in Hong Kong, Taiwan and South Korea suffered from myopia. Today, the shares are above 80 percent. In the U.S., the increases have been significant though a bit less dramatic. In the early 1970s, 24 percent of 25- to 34-year-olds were nearsighted. By the early 2000s, that share had almost doubled, to 44 percent”.

It adds that sales of glasses are projected to double between 2012 and 2026. There is a correlation between level of education and need for glasses. However, this is a proxy for time spent indoors. The Bloomberg report notes a summary of evidence: “There is now consistent evidence that children who spend more time outdoors are less likely to be or become myopic.”

I have no doubt this also applies to adults albeit to a lesser degree.

Think about it for a moment. For most of human history people worked outside. Our eyes are adapted to sunlight. It is only in very recent times that we have the ability to avoid the sun!

I recognise that I am a stuck record on this – but public health messages for everyone to totally avoid the sun are not helpful. As we are seeing, it is creating its own set of problems.

Human beings historically lived in the outside world. There are numerous physical and mental health benefits in getting outside. We can add better vision to that list.