Wed 18 Feb 2004
It’s that time of year – the weather is cold and miserable and there seems to be no end to winter.
But, according to scientists, the shorter days and freezing temperatures may have more than a mere psychological effect on the nation’s health.
In winter time the body finds it harder to absorb Vitamin D – produced naturally through daylight. And while this useful vitamin is often overlooked, it can help protect us against a variety of illnesses and complaints.
According to a recent study carried out at Harvard University, women who take Vitamin D supplements are 40% less likely to develop multiple sclerosis, an autoimmune disease.
A lack of the vitamin can lead to osteoporosis, brittle bones, faintness and mood swings, while past research has suggested that taking it may even protect against heart disease and diabetes.
Found naturally in foods such as tuna fish and cod liver oil, it can also be obtained through multi-vitamins.
But although studies are still being carried out into Vitamin D, there is still much confusion about how to prevent a deficiency and who is most at risk.
Dr Ray Rice, a food scientist at The Fish Foundation, says: “Research is still going on into the effect of Vitamin D on the body. There is currently no recommended dietary allowance for adults so it is difficult to judge how much a person actually needs.
“Certainly the best source of Vitamin D is sunlight. Although supplements can help those believed to be at risk from a Vitamin D deficiency, most people can produce the right amount of the vitamin even during the winter.”
So what is the truth about Vitamin D?
What is Vitamin D?
Vitamin D is a fat-soluble vitamin which helps the body absorb calcium, helping to form and maintain strong bones. It is found in food – in particular fatty fish and cod liver oil – but can also be produced by the body through exposure to ultra-violet rays from the sun.
How much Vitamin D do we need?
Although there is no official Recommended Dietary Allowance (RDA) for Vitamin D, experts estimate that the average adult requires around 40 micrograms a day.
What are the main food sources of Vitamin D?
Although fatty fish, such as tuna and cod liver oil, is the most Vitamin D rich food, some of the vitamin can be obtained through dairy produce, cereals and bread. In the United States, milk is fortified with 20 micrograms of Vitamin D per half pint – around 50% of the estimated amount an adult would require per day. In Britain, the best source of Vitamin D is through multi vitamins or dietary supplements.
What are the health benefits of Vitamin D?
It has long been established that Vitamin D helps maintain strong bones and prevents bone loss as we age. There is also evidence that a higher calcium and Vitamin D intake can reduce the risk of colon cancer and aid those suffering from Alzheimer’s Disease. This is because adults with Alzheimer’s Disease have an increased risk of hip fractures due to the housebound nature of the disease. A recent report from Harvard University also found that women who take Vitamin D supplements were 40% less likely to develop Multiple Sclerosis.
What problems are associated with a Vitamin D deficiency?
Bones may become brittle, soft or misshapen. It can cause rickets in children and osteo-related problems in adults such as arthritis or osteoporosis.
Who may need extra Vitamin D to prevent a deficiency?
People aged over 55 are most at risk from developing a deficiency. This is because the outer layer of the skin becomes thicker as we age, making it more difficult for the body to absorb ultra-violet rays from the sun. In addition people suffering from conditions such as Crohn’s Disease, liver disease and cystic fibrosis may also find it difficult to produce Vitamin D, while individuals employed in occupations that prevent exposure to the sun, the housebound and women who cover their bodies for religious reasons are also at risk.
Can you consume too much Vitamin D?
Yes. Vitamin D toxicity can cause nausea, vomiting, poor appetite, constipation, fatigue, weakness and weight loss. It can also raise blood levels of calcium, causing heart rhythm abnormalities, anxiety and confusion. However, you are unlikely to consume too much Vitamin D through diet unless you regularly consume large quantities of cod liver oil. Women are advised not to take Vitamin D supplements during pregnancy or when they are breast-feeding.
VITAMIN D – COMMON MYTHS
Too much Vitamin D gives you skin cancer
Not true. Over-exposure to the ultra-violet rays of the sun, which helps the body produce Vitamin D, should be avoided to prevent the risk of skin cancer. However the body does not need strong sunshine to produce Vitamin D and limited exposure of 10-15 minutes a day is sufficient. Sunscreens of factor eight and above, which block UV rays, should still be used for extended periods in the sun to prevent damage to the skin.
Babies and children do not need Vitamin D
Not true. This myth may be linked to the fact that pregnant and breast-feeding women are currently advised not to take supplements when pregnant. However, a study in the US showed that prior to milk fortification in the 1930s, rickets was a major public health problem affecting up to one in five children. Vitamin D supplements are often recommended for exclusively breast-fed babies because human milk may not contain adequate levels.
Exercise produces Vitamin D
Not true. Until the 1950s it was believed that sports such as tennis and Badminton could aid the body’s production of the vitamin. Although any exercise can aid muscular development and maintain bone mass, it will not affect the body’s ability to produce Vitamin D.
VITAMIN D – FACTS AND FIGURES
In the UK, 6% of men and 10% of women aged over 65 are currently believed to be suffering from a Vitamin D deficiency
The average adult receives 35% of their dietary intake of Vitamin D from cereals, 20% from oily fish, 20% from fats and bread and 25% from supplements and other sources.
A sample of 1,275 children aged 11-14-years-old in 2000 found that levels of Vitamin D in the body were on average 25% lower between April and June than between July and Sept, when the children were exposed to increased daylight.
People living in northern latitudes, for example in Norway or some US States such as Alaska, are most at risk from Vitamin D deficiency. In Boston, between the months of November and February, the average amount of daily sunshine is insufficient to produce the required amount of Vitamin D in the body.
(Figures taken from National Diet Nutritional Survey, 2000)
Copyright © 2004, The Scotsman