We’re all sick of the seemingly endless winter and there is growing evidence the grey days are making us physically ill.
Sunshine is essential to produce vitamin D, an important nutrient for bone health and keeping diseases like rickets at bay.
But scientists believe vitamin D deficiency is a key factor in a huge range of health problems, from heart disease and cancer, to diabetes and dementia.
Everyone in the UK is in danger of vitamin D deficiency for at least three months during winter.
And if you live north of Birmingham, the angle of the sun means you won’t manufacture it for at least five months of the year.
Even with the start of British Summertime on Sunday, the warmer, sunnier days are yet to arrive.
Dr Oliver Gillie, founder of the Health Research Forum, says recent weather patterns mean many of us will be dangerously low on this vitamin.
“Vitamin D deficiency is a major problem because of our climate and because this past summer was so bad for sunshine, there was little chance to build up reserves to last us through this winter.
“Sunbathing can increase a person’s gain in vitamin D substantially during the summer putting him or her in the best condition to avoid chronic disease, but that has been impossible.”
An international authority on vitamin D deficiency, Dr Robert Moy, agrees: “An awful summer increases the risk of deficiency, which is reckoned to contribute to a whole range of conditions such as cancer, heart disease and autoimmune diseases like multiple sclerosis.
“What is not really known is at what sort of level these risks increase but we probably ought to be supplementing our intake for six months of the year, from October to March.”
Those most at risk are the over-65s, pregnant and breast-feeding women, children under five, people with darker skin and anyone who wears clothing that covers their skin or spends a lot of time indoors — as most of us now do.
The Department of Health recommends at-risk adults have a daily top-up of 10mcg – try Boots Vitamin D supplement (£2.19 for 90).
All children under five can take a daily supplement of 7-8.5mcg, unless they drink formula milk, which is fortified with vitamin D, such as the Cow & Gate Growing Up Milk range.
Evidence of the importance of vitamin D is compelling.
A Danish study of 10,000 people last year found low levels increased the risk of dying from heart disease by 81%, while US Department of Health researchers reported that high levels cut the risk of stroke by 11%.
A Canadian study of 1,200 women found those who regularly took a vitamin D supplement cut their cancer risk by 60%.
There was also evidence of protection against breast, lung and bowel cancer — the three most deadly forms, which claim 62,400 lives in the UK annually.
Type 1 diabetes, rheumatoid arthritis and Parkinson’s disease are some of the health problems linked to low levels.
Patterns of disease also point to the importance of vitamin D. Multiple sclerosis, a degenerative neurological condition which affects 100,000 people in the UK, is much more common in northern climates, where lack of sunlight means vitamin D deficiency is common.
In England and Wales it is estimated that MS affects about one in 1,000 people, but in Scotland it is twice that and in Orkney, one of the most northerly parts of the UK, four in 1,000 people have MS — the highest incidence in the world.
So why does lack of vitamin D spell danger to our health?
An important clue was identified by Danish researchers who discovered that vitamin D arms and triggers T cells — the foot soldiers of our immune system, which destroy viruses, bacteria and other threats.
Prof Carsten Geisler, of the Department of International Health, Immunology and Microbiology at the University of Copenhagen, Denmark, says: “If the T cells cannot find enough vitamin D, they won’t even begin to mobilise.”
We asked City Assays, a laboratory based at Sandwell & West Birmingham Hospitals NHS Trust, to test blood samples from five people to see what impact the weather has had. The results are shocking.
A safe level is at least 50nmol/L but two were so deficient (under 15nmol/L) they risked serious health problems.
Case study 1: Fran Smith
Risk factor: None
Vitamin D reading: 25.2 deficient
Fran Smith, 32, a part-time buyer for an IT company, from Burnaston, Derby
Fran eats a healthy diet and occasionally takes a multivitamin tablet.
She spends a lot of time outside and had a fortnight’s sunshine holiday in the Canaries in November.
She wore a high-factor sunscreen and spent some time in the shade with her 16-month-old son Finlay.
Dr Moy says: “Being outdoorsy in this country is irrelevant for half the year but a winter holiday is a good way of boosting your levels when sunshine is rare at home.
"And wearing sunscreen is always vital to prevent skin cancer. A supplement is the only way to ensure your levels are safe.”
Fran says: “I was very surprised by the results. We are a fairly outdoorsy family so I always thought it didn’t apply to us.
"Having been in the sun on holiday I thought my levels would be fine.”
Case study 2: Ishaq Khan
Risk factor: Darker skin
Vitamin D reading: 32.1 deficient
Ishaq Khan, 19, a train supervisor, from Rotherham, South Yorks
Ishaq doesn’t spend much time in the sun, and being of Pakistani origin, he is at higher risk of deficiency because people with darker skin do not produce as much vitamin D from sunlight compared with those who have pale complexions.
Dr Moy says: “Even though he says he is quite light-skinned, being of Asian origin, Ishaq is an at-risk group and needs to take a supplement.
"Getting more sun exposure during the summer will help, but he will never get enough from sun and diet alone.”
Ishaq says: “I was surprised by the results. I thought I was young, it couldn’t be that bad.
"I will definitely be getting out in the sun more and do things outdoors, rather than just sitting at home on the laptop.
"I will also start taking a vitamin D supplement.”
Case study 3: Julie Hainsworth
Risk factor: Avoids the sun and takes regular medication
Vitamin D reading: 13.4 severely deficient
Full-time mum-of-four Julie Hainsworth, 30, from Leeds
Julie avoids the sun, so is unlikely to build reserves during summer.
In 2011, she was diagnosed with lupus, an autoimmune condition characterised by inflammation of the joints, skin and organs.
Lupus patients with low vitamin D are also likely to have the most severe symptoms.
Julie is at even greater risk because to control her lupus she takes medication that makes her sensitive to the sun and steroids that are thought to deplete vitamin D.
Dr Moy says: “Having to avoid the sun makes it all the more important that Julie takes a vitamin D supplement, and it would not hurt to take extra calcium, too.
"Being severely deficient increases her risk of a number of problems, not least with her bones.”
Julie says: “I recently had my vitamin D checked at the hospital and it was still low. I had no idea it could be so important.
"My GP has now prescribed me with vitamin D.”
Case study 4: Chris Scott
Risk factor: Has a poor diet and prefers to stay indoors
Vitamin D reading: 10.9 severely deficient
Chris Scott, 30, unemployed
Julie’s partner Chris spends a lot of time indoors and the family’s last sunshine holiday was two years ago.
At 6ft 1in and 18st 9lb, he has a BMI of 34 and being overweight increases his risk of deficiency. He also eats few vitamin D-rich food.
Dr Moy explains: “Because vitamin D is fat soluble it gets stuck in the fat and therefore blood levels will be lower.
"Chris will benefit from losing weight. Being so deficient he is at high risk of osteomalacia — the adult form of rickets”.
Chris says: “I used to eat a lot of takeaways and drink between four and six litres of cola a week and at the moment, I am overweight.
"The results have shocked me into taking action. I’m now taking up jogging, will eat fewer calories and use a high-dose vitamin D spray.”
Case study 5: Paige Hainsworth
Risk factor: Under five
Vitamin D reading: 34.1 insufficient
Julie’s daughter Paige Hainsworth, four
Paige spends a lot of time in the sun during summer but living in Yorkshire means it is impossible to make vitamin D from October to March.
The youngster had the highest levels of those tested, but was still short of the ideal minimum of 50nmol/L.
A survey by the Feeding for Life Foundation, a panel of child health experts, found that 66% of parents have never been told of the need to top up vitamin D.
Dr Moy says: “Paige should take a daily supplement of 7.5mcg of vitamin D, as recommended by the Chief Medical Officer.
“The shortfall in vitamin D in young children is worrying and the impact is already being seen in hospitals and GP surgeries, with the return of rickets and other deficiency diseases.”
Julie says: “Paige loves playing in the sun and I am not one for putting sun cream on them at the drop of a hat.
"I have four children and no one has ever said anything about them needing supplements but Paige is now receiving free vitamin D supplements through the Government’s Healthy Start scheme.”
Top up your Vitamin D levels
? Oily fish such as mackerel and herring are the best dietary sources of vitamin D.
? Eggs can also deliver a useful top-up as recent Department of Health tests revealed they contain 70% more vitamin D than they did 30 years ago.
? Some breakfast cereals, yoghurts, spreads and juice have added vitamin D. But the British Dietetic Association warns: “Even a healthy, well-balanced diet is unlikely to provide enough.”
? On average, food provides about 10% of our intake. Supplements are recommended, however, poor digestion can reduce the effectiveness of vitamin D tablets and drops, and a spray is recommended. A spray such as BetterYou DLux 1000 oral vitamin D spray (Holland and Barrett and independent pharmacies, £7.29) is effective. Tests showed more than a third of it is absorbed immediately into the bloodstream.
? Free vitamin D supplements are available for at-risk women and children under five who are eligible for the Government’s Healthy Start scheme.