Your Ultimate Guide to Vitamin D
Your Ultimate Guide to Vitamin D (produced in conjunction with nutri advanced)
Vitamin D is your ultimate vitamin. Not only is it an important nutrient for healthy bones, but more and more research is linking deficiency of this fat-soluble vitamin to a wide range of health problems, including some of the most common chronic conditions of modern times. It’s a worrying fact that the majority of the UK population is deficient in vitamin D, and recent government guidelines recommend that most people take a vitamin D supplement to support their health.
What does vitamin D do?
Vitamin D contributes to numerous biological functions in the body, including
-Normal function of the immune system
-Maintenance of normal muscle function
-Maintenance of normal bones
-Normal utilisation of calcium and phosphorous
Where does vitamin D come from?
What many people don’t realise is that very few foods naturally contain vitamin D. Wild, oily fish is by far the best dietary source, followed by fortified milk and egg yolks, but you certainly cannot rely on food to provide you with optimal amounts of vitamin D on a daily basis. In fact, the major source (80-100%) of vitamin D is actually sunshine. Vitamin D is primarily manufactured in the skin on contact with the sun’s UVB rays
Vitamin D deficiency
So why are we so deficient? The simple answer is that we don’t get as much sun as we used to. Millions of years ago, our ancestors would have spent most of the day working and travelling outside, with plenty of regular bare skin exposure to sunlight. Over the years, we have put on clothes and both work and play inside; we travel in cars and live in cities where buildings block the sun. In addition, skin cancer scares have further reduced sun exposure for all ages, and especially for babies and younger children who are advised to completely avoid full sun exposure. The recommended liberal use of high factor sunscreen, whilst needed to protect against skin cancer, has an unfortunate downside as it blocks the skin’s vitamin D production process. Before the sun scare, 90% of human vitamin D stores came from skin production not dietary sources. Now, when you look at how lifestyles have evolved to cut out the sun’s contact with our skin, it’s easy to see why low vitamin D has become such a significant public health concern.
Groups at higher risk of deficiency
✓ Pregnant women, breastfed babies and all children under the age of five
✓ Increasing age – The body’s ability to make use of vitamin D falls by at least half between the ages of 20 – 80 years. Elderly people are at high risk of deficiency
✓ Limited time outside - Anyone frail or housebound, hospitalised or in a care home and spending minimal time outdoors
✓ Obesity - Obese children and adults may need at least 2 to 3 times more vitamin D for their age group to satisfy their body’s vitamin D requirements
✓ Underweight – Low body fat puts people at higher risk of deficiency
✓ Skin tone – The paler your skin, the easier it is for you to make vitamin D. People with darker skin, including African & Asian populations, have in-built sun protection and require at least 3-5 times longer sun exposure.
✓ Extent of skin covering – Those whose skin is always covered for religious, or any other reasons
✓ Liberal use of sunscreen - Sunscreen blocks UVB rays and reduces vitamin D production in the skin
✓ Where you live - The further away from the equator you live, the more challenging it is for your skin to make vitamin D
✓ Time of year - Vitamin D production in the skin drops significantly between Oct – March.
✓ Genetic factors - There are single nucleotide polymorphisms (SNPs) within the vitamin D metabolism pathway which are known to modify vitamin D status.
Vitamin D safety
Historically there have been concerns about vitamin D toxicity, however it is now well established that toxicity is extremely rare and associated with very high, long-term supplemental doses. Doses of 10,000 iu daily have been used for up to 5 months with no adverse effects and studies suggest that only when more than 10,000 iu of vitamin D is ingested daily for several months to several years will vitamin D intoxication occur.
Vitamin D toxicity is defined by a 25(OH)D level >150 ng/mL, and associated with hypercalcemia and hyperphosphatemia. Toxicity does not occur with sunlight exposure.
Vitamin D dosage calculator
Leading vitamin D experts use the following equation to calculate how many IU (international units) of vitamin D are needed to achieve your desired blood vitamin D levels.
(Target vitamin D level- current vitamin D level in ng/ml multiplied (body weight in kg/70) multiplied by 10,000
Here’s a worked example
Target vitamin D level = 70ng/ml
Current vitamin D level=29ng/ml
(50-29) x (80/70) x 10,000 = 240,000IU
Spread over 60 days, you would need 4000 IU of vitamin D per day to achieve a vitamin D level of 50ng/ml
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