Are you getting enough vitamin D?
17 June 2011
You may have heard about the importance of vitamin D in bone health – and especially in relation to its ability to ward off the childhood bone disease rickets.
But did you know that vitamin D, (which strictly speaking is really a hormone), is involved in the expression of more than 1,000 genes? This means it acts on cells in every organ of the body and has extremely far-reaching effects on our health. Here are just some of the things it does:
- Regulates calcium balance for bone health, nerve transmission and to make sure that calcium does not end up in our arteries.
- Controls cell proliferation and differentiation, which reduces the risk of cancer
- Enables our immune system to be more ‘tolerant’, which may reduce the risk of allergies and auto-immune diseases
- Helps to control microbes, by producing antibiotic substances, such as cathelicidin
- Improves insulin secretion, which may be helpful in people at risk of diabetes
- Regulates the action of renin, which is important in controlling blood pressure
- Helps with balanced neurotransmitter synthesis, important in memory, mood and cognition.
Vitamin D status is measured by looking at serum levels of 25-hydroxyvitamin D (25(OH)D3). ‘Normal’ reference ranges vary but in the UK they are about 40-140nmol/L. However, in my clinical experience, many people who get their serum levels measured are only at the bottom end of this range.
Moreover, many doctors and scientists believe that 40nmol/L is far too low for health and that the absolute minimum for health is 75nmol/L (Gillie, 2006, 2011). Some experts even believe that we should be going as high as 100-150nmol/L in order to reduce the risk of cancer and other chronic diseases (Heaney 2011, Baggerly 2011, Zittermann 2003).
The worldwide average serum level is estimated to be 54nmol/L, which is considered insufficient for optimal health (Haggenau 2009). ‘All studies, in virtually all nations, irrespective of latitude, show that the majority of the world’s population has inadequate vitamin D status’ (Heaney 2011).
Why are we so low in vitamin D? Well, it is hard to get what we need from food. In the UK, the only significant source is oily fish. Most of our vitamin D comes from the sun. But there is a problem: many people in the UK never get what they need from sunlight alone because sunlight’s ability to help us produce vitamin D is hampered by the season (it only works in the summer), the latitude (the UK is pretty far north), time of day (needs to be between 11am and 3pm), cloud cover (complete cloud cover reduces vit D synthesis by 50%), smog/pollution (most of us live in cities), skin melanin content (the darker skinned you are, the less vitamin D you’ll get from the sun) and sunscreen (SPF of 8 and above). And remember that the vitamin D UVB rays cannot penetrate glass.
Even in summer, when vitamin D is most available, it is estimated that 45% English have <40nmol/L (deficient) and that 75% fail to reach the ‘optimal’ level of 75nmol/L. Levels are worse in winter; and worse in Scotland (twice as likely as Southern English to have low serum levels of vitamin D) (Gillie, 2006, 2011).
This situation is worrying some experts to the extent that they are calling for vitamin D deficiency to be classified as a major ‘lifestyle’ risk, like smoking, alcohol, obesity and being sedentary (Gillie, 2006, 2011).
And indeed, vitamin D insufficiency has been implicated in many different diseases, such as osteoporosis, cancer, rheumatoid arthritis, psoriasis, muscle weakness and falls, cognitive disorders, seasonal affective disorder, cardiovascular disease, type 2 diabetes, respiratory tract infections, periodontal disease, multiple sclerosis and chron’s disease (Zhang and Naughton 2010, Holick 2008, Hewison 2010, Grant 2011, Vitamin D Council 2011).
Toxicity has been a concern in the past but recent studies have indicated that we would need to supplement extraordinarily high doses to ever get into the toxic range. For example, a 2007 paper showed that up to 10,000IU/day is safe and a 2011 study indicated that even doses of 40,000IU/day is unlikely to be toxic (Hathcock et al 2007, Garland et al 2011).
7 major UK health charities, including Cancer Research UK and Diabetes UK, have now developed a new joint position statement on vitamin D and sun exposure: ‘Enjoying the sun safely, while taking care not to burn, can help to provide the benefits of vitamin D without unduly raising the risk of skin cancer.’
So, try and get some sun in the middle of the day, every day, without burning. And get your vitamin D levels checked in a blood test, either through your GP or via a nutritional therapist. If your levels are low, ask your health adviser whether you would benefit from taking a vitamin D supplement in order to get your serum levels up to a healthy status.
© Lorraine Nicolle 2011.
Baggerly C and Garland C (2011). Vitamin D and breast cancer prevention. Presentation at The Vitamin D Experts’ Forum, London. April 2011.
Garland C, French C, Baggerly L, Heaney R (2011). Vitamin D supplement doses and serum 25(OH)D in the range associated with cancer prevention. Cancer Research. 31:617-22.
Gillie O (2006). A new government policy is needed for sunlight and vitamin D. British J Dermatology. 154:1052-1061.
Gillie O (2011). Sunlight Robbery: the failure of UK policy on vitamin D: In search of evidence-based public health policy. Presented at the Vitamin D Experts’ Forum, London, April 2011.
Hagenau T, Vest R, Gissel TN et al (2009). Global vitamin D levels in relation to age, gender, skin pigmentation and latitude: and ecologic meta-regression analysis. Osteoporos Int. 20(1):133-40.
Heaney R (2011). Vit D: What it does and how much we need. Presentation at Vitamin D and Breast Cancer Symposium 23 March 2011. Available from: http://www.grassrootshealth.net/media/download/heaney_vit_d_deficiency1110.pdf
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Holick MF (2008). The vitamin D deficiency pandemic and consequences for nonskeletal health: mechanisms of action. Mol Aspects Med. 29(6):361-8.
Vitamin D Council (2011). Health Conditions. Available from: http://www.vitamindcouncil.org/health-conditions/. [Accessed 9 June 2011]
Zhang R, Naughton D (2010). Vitamin D in health and disease: current perspectives. Nutr J. 9(65).
Zitterman A (2003). Vitamin D in preventive medicine: are we ignoring the evidence? Br J Nutr. 89:552-72.
© 2011 Lorraine Nicolle