In 2010, at the time of writing my obesity book, the US did not have a “Dietary Reference Intake” for vitamin D. Instead, the US had an “Adequate Intake” suggestion – they thought that 400IU (10mcg) would be adequate.
This was revised in 2011 when the US decided that the Recommended Dietary Allowance (RDA) for everyone from the age of 1 to 69 should be 600IU (15mcg) and 800IU (20mcg) for those aged 70 and over. (This post doesn’t discuss the different forms and sources of vitamin D, but this is an added complication.)
The Dietary Reference Values 1991 book is still the UK ‘bible’ for recommended nutrient intakes. This has no vitamin D targets for anyone aged 4 to 64, unless pregnant or breastfeeding – then it’s 10mcg per day. Over 65’s are also advised to have 10mcg daily.
The official European position still seems to be that of the early 1990s. This leads to this 1993 document (page 143), which confirms the lack of targets for those aged 4 to 64, as set out in the UK Dietary reference values book (1991).
On the same “European Food Information Council” site, a “mini guide” from June 2006 suggests that “European Union Recommended Daily Amounts for Nutritional Labelling of Food Products” for vitamin D should be 5 µg (that’s 5mcg).
I have no idea why the US originally only saw fit to suggest an adequate intake until 2011, or why the RDA is now 15mcg. I have no idea why the UK still doesn’t consider vitamin D to be a vital nutrient with a daily requirement. I have no idea why the recommendations for vitamin D differ from 0mcg to 15mcg for UK to US populations. This is clearly not robust, or scientific.
What I do know is:
1) Vitamin D is utterly vital for human health
Vitamin D is critical for the absorption of calcium and phosphorus. Deficiency in vitamin D can lead to tooth decay, muscular weakness and a softening of the bones (rickets), which can cause bone fractures or poor healing of fractures. Enter “vitamin D” into pubmed and over 65,000 academic articles will be listed. Vitamin D is increasingly being studied as a critical factor in the most serious human health conditions, not least heart disease, cancer and diabetes.
Vitamin D is found naturally in oily fish (for example herring, halibut, catfish, salmon, mackerel and sardines), eggs and dairy products and unnaturally in fortified breakfast cereals. (You never need junk cereals to get vitamin D – take a supplement if you don’t want to consume vitamin D naturally for some reason).
2) The average person is not getting enough vitamin D
Average male intake from diet alone for adult males in the US ranged from 5.1mcg for 19-30 year old males to 5.6mcg for males ≥ 70 years old. Average female intake from diet alone for adult females in the US ranged from 3.6mcg for 19-30 year old females to 4.5mcg for females ≥ 70 years old.
The article reported that 37% of the US population take vitamin D supplements, and this increased the intake to 6.9mcg for 19-30 year old males and 8.8mcg for males ≥ 70 years old and to 5.0mcg for 19-30 year old females and 10mcg for females ≥ 70 years old.
The lowest intake, diet alone for 19-30 year old females was less than a quarter of the US RDA; even the highest intake – women over 70 years old taking supplements – was two thirds of the intake recommended.
b) The UK data is provided annually by the UK Family Food Survey. The most recent report at the time of writing this blog is the 2013 Family Food Survey. This reported that the UK average intake of vitamin D from all food and drink was approximately 3mcg for each of the five years from 2009-2013 (Table 3.7 UK average energy and nutrient intakes from all food and drink 2009-2013). This is one fifth of the US recommended daily intake.
What the data tells us
Public health officials in the US and UK should be issuing emergency notices that vitamin D deficiency is a serious health risk to citizens. Populations should be advised to consume more foods naturally rich in vitamin D – oily fish, eggs and dairy products. Oh, but those just happen to be the fat rich foods that fat phobic public health advisors tell people to avoid! Even when oily fish is recommended, it is rarely more than twice a week. Yet we need approximately 220g of sardines (with bones) every day to meet the RDA of 15mcg of vitamin D. Vegetarians would need to eat 39 medium eggs each day (2,455 calories) to get 15mcg of vitamin D.
The other urgent piece of health advice needed is – sunbathe! We need to be exposed to the sun – without sunBLOCK – for a safe number of minutes (depends on skin type, location, time of the year etc) as regularly as possible to build up our vitamin D reserves. Being a fat soluble vitamin (along with A, E and K), vitamin D can be stored by the body. A good build up during summer months will help for annual health, but we should be rolling up our sleeves and trousers to expose limbs even on sunny winter days and/or consuming sufficient dietary vitamin D during the winter period.
What do our dear governments do instead? Scare us away from sun exposure, tell us to cover up and/or use sunBLOCK every time the sun shines and advise us to keep avoiding fat in food.
Just to complete the trilogy of bad advice – vitamin D is made when sunlight synthesises cholesterol in skin membranes. Avoiding vitamin D rich foods AND blocking sunlight from the skin AND cholesterol lowering medications and dietary supplements (e.g. plant sterols) ALL conspire together to lower vitamin D.
Dr. Robert Scragg, Associate Professor in Epidemiology at the University of Auckland, New Zealand, proposed back in December 1981 that vitamin D deficiency plays a key role in cardiovascular disease. If he was right, our diet/sun/cholesterol advice is not only wrong – it’s doing the exact opposite of what it hoped to do – raising, not lowering, heart disease.