Researchers at the Medical University of Graz in Austria said the findings may explain why conception rates fall in the winter and peak in the summer in Northern European countries.
Oliver Gillie, director of the Health Research Forum, which campaigns for better health advice on vitamin D, told the Daily Mail: "I would say to couples hoping to get pregnant to arrange a sunshine holiday, or get into the garden in the summer as often as they can...before you go down the route of expensive IVF treatment."

However, Lead author Dr Elisabeth Lerchbaum warned that although vitamin D could help to improve fertility, overexposure could lead to skin cancer.
She said: "People could either spend more time outside in the sun - or they could take vitamin D supplements, which are a safe and cheap way to increase levels."
If you would like to boost your chances of conceiving without putting yourself at risk of skin cancer, see our natural fertility-boosting tips...
Natural Ways To Boost Your Fertility
Avoid White Bread, Pasta & Rice
Although there is no direct link between refined carbohydrates and infertility, the refining process strips grains of some of the most important fertility-boosting nutrients, such as antioxidants, B vitamins and iron.
Go Organic
Modern methods of food production, involving intensive farming, rob the soil of vital nutrients, so where possible stick to organic produce. Processed foods are packed with additives and preservatives that can upset blood sugar levels and disrupt the body's hormonal balance.
Cut Down On Red Meat
Too much red meat increases the amount of ammonia in the body, which can interfere with the implantation of the egg in the uterus. Red meat can also be detrimental for men as it increases acidity and affects sperm activity; sperm perform better in alkaline conditions.
Switch To Soya Milk
The animal hormones in dairy products can affect your own hormonal balance. If you balk at the richness of soya milk and can't bear to give up your semi-skimmed, switch to organic dairy products instead as these contain lower levels of hormones.
Reduce Your Alcohol Intake
Giving up alcohol is not strictly necessary until you fall pregnant but it might be worth bearing in mind that Danish research, studying the link between alcohol consumption and fertility, found that <a href="http://www.ncbi.nlm.nih.gov/pubmed/12848646" target="_hplink">alcohol intake had a significant effect on infertility success</a> among women above the age of 30 who drank seven or more drinks a week.
Curb Caffeine
While you don't need to give up your morning coffee, caffeine does constrict the blood vessels, slowing blood flow to the uterus and potentially making it harder for an egg to grab hold. So, if you're having any trouble conceiving, or undergoing IVF treatment, you might want to go easy on the double espressos.
Get Your Five-A-Day
Aside from being packed with vitamins and minerals, fruit and vegetables are packed with antioxidants that attack free-radicals (harmful molecules that can damage the ova, sperm and reproductive organs).
Fertility-Friendly Vitamins
Zinc helps to maintain a healthy menstrual cycle as well as being vital during pregnancy to aid cell division in a developing foetus. Folic acid (Vitamin B6), together with zinc, is essential in the function of female sex hormones. Vitamin B12 is also very important as it maximises the absorption of folic acid. Taking a multi-vitamin tablet designed especially for conception is a good way to ensure you're getting enough of these valuable nutrients. Marmite is also a great source!
Going on holiday to sunnier climes could help boost your chances of having a baby, a study has revealed.
Researchers discovered that sunlight boosts fertility in men and women by increasing their l...
Going on holiday to sunnier climes could help boost your chances of having a baby, a study has revealed.
Researchers discovered that sunlight boosts fertility in men and women by increasing their l...
I'm of south-east asian origin, and discovered I was vitamin D deficient after my second miscarriage. Since then I've done a lot of research on this subject and I've found that it probably is highest on the list of suspects for my two losses. After getting vitamin D replete, I think I can safely say that all things reported in that study have been observed in me, it has increased estrogen and progesterone and has changed my cycle.
More information about all the links between vitamin D, fertility and pregnancy is on my blog
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The Huffington Post UK First Posted: 30/01/2012 17:29 Updated: 30/01/2012 17:44