Vitamin D really has been in the news a lot over the last two years and for good reason. There are plenty of posts on this blog relating to the vital importance of this nutrient for optimal health and wellbeing and I think the research will continue to expand over the next few years to come.
A recently published review paper in the Journal of the American Medical Association (1) again makes a point of stressing the importance of this vitamin. The author of the paper mentions the growing body of evidence which shows that vitamin D deficiency and insufficiency are linked to poor health outcomes for a variety of conditions – such as osteoporosis and bone fracture, muscle weakness, cancer, autoimmune disease, diabetes, schizophrenia, depression, lung dysfunction, kidney disease, and cardiovascular disease. Although there are many hundreds of medical/scientific studies now published there is still no specific recommendation for vitamin D intakes and blood levels (1). There is certainly a need for studies to clarify optimal vitamin D levels and to recommend safe supplementation limits.
This recent paper (1) also points out that low levels of vitamin D can be very common and mentions a study which found that in Americans aged between one and twenty-one 70% had deficient or insufficient vitamin D levels. A truly striking figure.
So how much vitamin D is needed?
Well, unfortunately, as the paper (1) mentions, there is still no consensus on how much vitamin D is optimal for health and wellbeing. Studies need to ascertain out how much vitamin D is needed to keep most people from becoming deficient or insufficient and also how much vitamin D can safely be taken on a daily basis. Vitamin D is a fat soluble vitamin and is stored in the body and it is possible to take too much of it.
In the UK the majority of individuals do not get enough sunlight on their skin to generate optimal vitamin D levels in their body. We are spending increasing amounts of time indoors, even in the summer months when there is more available sunlight. Unfortunately vitamin D is also difficult to obtain from dietary sources, with oily fish and egg yolk being the biggest providers. Most individuals in the UK would probably need to take a daily vitamin D supplement in order to maintain optimal levels of this vital nutrient in their blood. The paper (1) quotes the current upper limits of vitamin D intake to be 2000IU for individuals over one year old. However, there is also discussion which suggests that the safe upper limit could be raised to 5000IU per day for children and 10,000IU for adults (1). (IU stands for International Units)
Interestingly the paper also mentions the fact that it may be important for us as patients to go and ask our doctors for a test to see what levels our vitamin D is in the blood. This may be met with some resistance in the medical world but often these tests reveal that the person in question has low blood levels of vitamin D – bringing this to the attention of the medical community may actually be helpful for other individuals and to the profession as a whole (1).
Vitamin D is called the sunshine vitamin, though technically vitamin D is a hormone, as it is produced in the body when the skin is exposed to the UVB rays in sunlight (for more information on the importance of sunlight for health please visit the SUNARC centre website). In the past it was thought that spending just 10-15 minutes in the sun everyday would supply all the vitamin D that we need – However this is now estimated not to be enough and many of us in the UK do not get enough sun on our skin to generate adequate amounts of vitamin D especially in the autumn and winter months.
Evidence from the National Diet and Nutrition Surveys (NDNS) suggests that in the UK vitamin D deficiency is a real problem (2,3,4,5). The problem is made worse in the older generations since, as we age our bodies find it increasingly difficult to manufacture vitamin D.
It is probable that unless you are taking a daily vitamin D supplement you may well have low levels of vitamin D in your body. The suggested supplemental amounts vary so much, however I would not recommend supplementing more than 2000IU daily unless you are under medical supervision.
(1)Mitka M. 2009. More evidence on low vitamin D levels fuels push to revise recommended intake. JAMA. 302(23):2527-2528
(2) Finch S et at. 1998. National Diet and Nutrition Survey of People aged 65 Years and Over. London: H. M. Sationery Office.
(3) Gregory L et al. 2000. National Diet and Nutrition Survey of People aged 4-18 years. Vol 1. Report of the Diet and Nutrition Survey. London: The Stationery Office
(4) Henderson L et al. 2002. National Diet and Nutrition Survey: Adults Aged 19-64 years. Vol 1: Types and Quantities of Foods Consumed. London: The Stationery Office
(5) Hypponen E & Power C. 2007. Hypovitaminosis D in British adults age 45y: nationwide cohort study of dietary and lifestyle predictors. Am J Clin Nutr. 85:860-888.
Written by Ani Kowal
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- Experts call for a change in policy to increase daily vitamin D intakes
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- A group of researchers recommend vitamin D supplementation in pregnancy
- Calls for a re-examination of Vitamin D recommendations
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