What is Vitamin D?
Vitamin D is important for good overall health and strong and healthy bones. It’s also an important factor in making sure your muscles, heart, lungs and brain work well and that your body can fight infection.
Your body can make its own vitamin D from sunlight. You can also get vitamin D from supplements and a very small amount comes from a few foods you eat.
The vitamin D that you get in your skin from sunlight, and the vitamin D from supplements, has to be changed by your body a number of times before it can be used. Once it’s ready, your body uses it to manage the amount of calcium in your blood, bones and gut and to help cells all over your body to communicate properly
What does Vitamin D do?
Vitamins are chemicals that are needed by your body for good health. They are vital for everyone and ensure that your body works well, is able to fight illness and heal well.
The link between vitamin D and strong healthy bones was made many years ago when doctorsrealized that sunlight, which allows you to produce vitamin D, or taking cod liver oil, which containsvitamin D, helped to prevent a bone condition called rickets in children. Today, vitamin D is seen as a vital part of good health and it’s important not just for the health of your bones. Recent research is now showing that vitamin D may be important in preventing and treating a number of serious long term health problems.
Vitamin D isn’t like most other vitamins. Your body can make its own vitamin D when you expose your skin to sunlight. But your body can’t make other vitamins. You need to get other vitamins from the foods you eat. For example, you need to get vitamin C from fruits and vegetables.
Also what makes vitamin D unique compared to other vitamins, is that when your body gets its vitamin D, it turns vitamin D into a hormone. This hormone is sometimes called “activated vitamin D” or “calcitriol.”
Getting the right amount of vitamin D doesn’t depend on the foods you eat. To get enough vitamin Dyou need to expose your skin tsunlight regularly and you may also need to take supplements. This makes getting the right amount a little more complex compared to other vitamins and minerals. Vitamin D is very important for strong bones. Calcium and phosphorus are essential for developing the structure and strength of your bones, and you need vitamin D to absorb these minerals. Even if you eat foods that contain a lot of calcium and phosphorus, without enough vitamin D, you can’t absorb them into your body. Vitamin D is important for general good health, and researchers now are discovering that vitamin D may be important for many other reasons outside of good bone health. Some of the functions of the body that vitamin D helps with include:
• Immune system, which helps you to fight infection
• Muscle function• Cardiovascular function, for a healthy heart and circulation
• Respiratory system –for healthy lungs and airways
• Brain development
• Anti-cancer effects
Doctors are still working to fully understand how vitamin D works within your body and how it affectsyour overall health.If your body doesn’t get enough vitamin D to keep it healthy, this is called vitamin D deficiency. Severe vitamin D deficiency can sometimes cause a condition called rickets in children and a condition called osteomalacia in adults. Both of these conditions cause soft, thin, and brittle bones.
A lack of vitamin D has also been linked to some other conditions such as cancer, asthma, type-II diabetes, high blood pressure, depression, Alzheimer’s and autoimmune diseases like multiple sclerosis, Crohn’s and type-I diabetes.
Your body gets vitamin D mainly from sunlight, though very small amounts can also be found in a few foods. You can also get vitamin D by taking supplements
Why is vitamin D important?
A significant proportion of the UK population have low vitamin D levels, which has resulted in a rising number of reported cases of rickets in children and osteomalacia in adults. This is of particular concern for all pregnant and breastfeeding women, young children, older people, black and ethnic minority groups, and those at risk of inadequate sunshine exposure. Pregnant women especially need to ensure their own requirement for vitamin D is met and to build adequate fetal stores for early infancy.
Vitamin D deficiency impairs the absorption of dietary calcium and phosphorus, which can give rise to bone deformities in children, and bone pain and tenderness as a result of osteomalacia in adults.1
It is essential that everyone, especially those people most at risk, are aware of the implications of vitamin D deficiency and most importantly what they can do to prevent it.
1 Update on Vitamin D: Position statement by the Scientific Advisory Committee on Nutrition, 2007
How does Vitamin D work?
Vitamin D mainly comes from your skin when it is exposed to sunlight. After that, your body goes through a number of chemical processes to change it so that your body can use it. When your skin is exposed to the sun, it produces vitamin D and sends it to your liver. If you take supplements or eat foods that contain vitamin D, your gut also sends the vitamin D to your liver.
From here, your liver changes it to a substance called 25(OH)D. When your doctor talks about your vitamin D levels, he means the amount of 25(OH)D you have in your blood. This chemical is sent all over your body where different tissues, including your kidney, turn it into activated vitamin D. This activated vitamin D is now ready to perform its duties. From here, it gets a little complicated, but you can think of activated vitamin D working in two ways:Manages calcium in your blood, bones and gut Helps cells all over your body to communicate properly As you can see, vitamin D goes a long way from its original form from the skin, supplement or food.
But without vitamin D, your body can’t perform at its best.
Who is most at risk of vitamin D deficiency?
All pregnant and breastfeeding women, especially teenagers and young women, are particularly at risk of vitamin D deficiency.
• Young children under 5 years of age.
• All people aged 65 years and over.
• People who are not exposed to much sun, for example those who cover their skin for cultural
reasons, who are housebound or confined indoors for long periods.
• People from ethnic minorities who have darker skin, because their bodies are not able to
produce as much vitamin D. Clinical deficiency has been most reported among children of AfricanCaribbean and South Asian origin.
How do we get vitamin D?
From the sun
Our body creates most of our vitamin D from modest exposure to direct UVB sunlight. Regular, short periods of UVB exposure without sunscreen during the summer months are enough for most people.
However, some groups (refer to Who is most at risk of vitamin D defi ciency?) may not be able to get enough vitamin D in this way. In addition, those living at above 52° N latitude (the UK is at a latitude
of 50–60° N) may not get enough vitamin D during the winter months.
IMPORTANT – everybody should be aware that the longer they stay in the sun, especially for prolonged unprotected periods, the greater the risk of skin cancer. So it’s wise to stay covered up and
use sunscreen (with a high UVB factor) for the majority of the time spent outside. Remember to always cover up or protect the skin before it starts to turn red or burn.
Food in the diet can also contribute to vitamin D levels, but the average daily intake is just 2–4μg, and it is difficult to obtain enough vitamin D from diet alone. Vitamin D can be found naturally in oily fish (such as salmon, mackerel and sardines), eggs and meat.
Manufacturers also have to add it to all margarine and infant formula milk. Other manufacturers add it voluntarily to some breakfast cereals, soya products, some dairy products, powdered milks and
low-fat spreads; however, this is often a minimal amount.
Breastfed babies get their vitamin D from their mother’s breastmilk, which is one reason why it is important for pregnant and breastfeeding mothers to have adequate vitamin D levels of their own.
Infant formula milk is fortified with vitamin D, so formula-fed infants get their vitamin D in this way.
The time of year and time of day
When the sun’s rays enter the Earth’s atmosphere at too much of an angle, the atmosphere blocksthe UVB part of the rays, so your skin can’t produce vitamin D. This happens during the early and later parts of the day and during most of the day during the winter season.
The closer to midday you expose your skin, the better this angle and the more vitamin D is produced. A good rule of thumb is if your shadow is longer than you are tall, you’re not making much vitamin D. In winter, you’ll notice that your shadow is longer than you for most of the day, while in summer, your shadow is much shorter for a good part of the middle of the day.
Where you live
The equator is an imaginary line on the Earth’s surface halfway between the North Pole and South Pole, which divides the Earth into the Northern Hemisphere and Southern Hemisphere. The further away you are from the equator, the more of an angle the sun will hit the atmosphere at, and the less UVB there will be available for you to produce vitamin D, particularly during the winter time. In the summer, when the Earth rotates, the angle improves and more UVB reaches the places far away from the equator, allowing you to produce vitamin D outside of winter months.
For example, in the southern United States, in places like Florida, your body can produce vitamin D most of the year, while in more northern places, like New York City or Boston, you can’t produce much vitamin D from November through March. If you live even further north, like in Edmonton, Canada, you can’t produce vitamin D from October through April. These times are even longer (by a month or two) if you’re skin type is darker.