I have just popped my morning vitamin D pill, one of the few chemical additions to my super healthy diet. In the past, I used to think my body just makes vitamin D as it is exposed to light, just any light, whatever light. My body just makes it because it needs it.

I was forced to abandon this misguided preconception a few years ago after I got my vitamin D levels tested due to increased hair loss.

It was mid-July, I just returned from holiday in Greece and my vitamin D levels were way below what is considered optimal.

My trichologist (the hair doctor) associated my low vitamin D levels with my hair loss (which was only a part of the problem in my case), but clearly, being low in vitamin D in the long term is not great.

Here are a few headlines from latest research linking low vitamin D levels to various conditions:

A recent study by American researchers found that breast cancer sufferers with low levels of vitamin D have lower chances of survival than those with higher levels of vitamin D

“We found that women with the highest levels of vitamin D had about a 30 per cent better likelihood of survival than women with the lowest levels of vitamin D,” said Lawrence H. Kushi, research scientist with the Kaiser Permanente Northern California Division.

The study involved 1,666 women.

A study by Danish researchers published in late October found that children of mothers who took Vitamin D supplements during pregnancy had lower incidence of ADHD (hyperactivity) at two and a half years of age than those whose mothers did not supplement.

“And for every 10 nmol/L increase in the vitamin D concentration in umbilical blood, the risk of a being among the 10 per cent highest score on the ADHD symptom scale fell by 11 per cent,” explained one of the study’s initiators, Professor Niels Bilenberg.

1,233 children were involved in the study, which included measuring vitamin D levels in umbilical blood and mothers completing a questionnaire measuring early signs of ADHD.

Another American study published this month found a link between Vitamin D insufficiency and an increased risk of asthma. This study also found that 68 per cent of the children involved in the study and 70 per cent of adults had levels of vitamin D that were lower than what’s usually considered adequate for healthy people (30 nanograms per milliliter). The study involved 25,000 adults and 9,700 children who completed the US national health survey.

A Norwegian study recently found lower levels of vitamin D also in patients with depression and schizophrenia.

Why should you care? Well, because if you live somewhere like the UK, central and northern Europe and if you spend most of your days indoors and wearing sunscreen, then chances are you are low in vitamin D as well.

In fact, all of my friends living in the UK who ever got tested had insufficient levels of vitamin D.

For your skin to make vitamin D, it needs direct exposure to UVB radiation, one of the types of radiation deliberately blocked by sunscreen.

Interestingly enough, the darker your skin, the more direct exposure to UVB on bare skin you need. While myself, a green-eyed, freckled, fair skinned creature may be able to produce enough vitamin D in 15 minutes in direct sun, someone who traces his or her ancestry to Africa may need two hours to do the same.

On the other hand, fair-skinned aging-conscious creatures like myself are usually concerned about sun damage and barely ever leave the house without sunscreen in the summer months. And with sunscreen on, UVB has a hard time to reach your skin’s surface thus no production of vitamin D takes place.

In winter, there is not enough UVB to produce enough vitamin D even if you spend the day naked outdoors, which is why the UK advisory committee for nutrition recommends everyone over the age of 10 to take 10mcg of vitamin D if not every day, then at least in winter.

You can get some vitamin D from food such as oily fish and egg yolks but the scientific consensus seems to be that it is not enough. (As my hair doctor told me, even if you stuff yourself with oily fish three times a day, it’s nowhere near to what your skin can produce in ten minutes in the Sun.)

There have been studies reporting risks of taking vitamin D but that usually refers to very high doses – something like 40,000 international units (IU). If you stay at around 1,000 IU or even a bit lower, you shall be safe.

The number one problem linked to low levels of vitamin D is of course osteoporosis and loss of bone density. Loss of bone density is typical for old age but some studies done a couple of years ago on astronauts suggest that we may not necessarily have to lose bone mass as we get older. The key is (yes of course) vitamin D paired with sufficient exercise that keeps telling the bones to keep renewing themselves.

While vitamin D is clearly not a panacea, used in conjunction with other health-enhancing measures, such as intense exercise and an overall healthy diet, it can definitely make a difference.