Your ability to avoid colds and flu is related to vitamin D. Vitamin D levels in your blood fall to their lowest point during winter due to lack of sunlight. Vitamin D is essential for the body to produce its own antibiotics so a person with a low vitamin D blood level is more vulnerable to contracting colds, influenza, and other respiratory infections. Studies show that children with rickets, a vitamin D-deficient skeletal disorder, suffer from frequent respiratory infections, and children exposed to sunlight are less likely to get a cold. The increased number of deaths that occur in winter, largely from pneumonia and cardiovascular diseases, are most likely due to vitamin D deficiency.
So can't I just eat more vitamin D rich foods to avoid colds this winter?
It is very difficult to get adequate amounts of vitamin D from your diet unless you are eating large amounts of offal, oily fish and seafood. Some estimates have been made on food composition with daily intakes of vitamin D between 2-3 μg /day (80-120 IU) for adults (Baghurst & Record 2002). This is well short of the 4000IU that we'd recommend for adults to achieve optimal levels of vitamin D (see here for how we justify this dose)
Hang on - I thought I could still get my vitamin D dose by getting outside in the sun?
Sun exposure on the skin is the other option for boosting your vitamin D levels. Vitamin D is produced by your skin in response to exposure to ultraviolet B rays from the sun. But these rays cannot penetrate glass, sun tan lotion, clothing, or dark skin to effectively generate vitamin D in your skin. In most parts of New Zealand and Australia a "vitamin D winter" occurs for around 4-6 months in which weather conditions make it impossible to produce enough vitamin D from sunlight.
The largest study of its kind (with over 19,000 subjects) from the Archives of Internal Medicine (2009) gave a summary:
"The findings of our study support an important role for vitamin D in prevention of common respiratory infections, such as colds and the flu. Individuals with common lung diseases, such as asthma or emphysema, may be particularly susceptible to respiratory infections from vitamin D deficiency."
If you're looking to optimise your vitamin D levels to reduce your risk of colds and flus this winter make sure you keep up your cod liver oil.
A common question that I’m asked is “How do I know if I’m deficient in vitamin D?”
The only sure way to find this out is to get your vitamin D levels tested.
A medical laboratory blood test 25(OH)D (also called 25-hydroxyvitamin D) is accepted to be the best test of overall D status in the body. 25(OH)D levels are most strongly associated with overall health. There are several types of vitamin D tests, so make sure you specify that the 25(OH)D test is the one you’d like to use. The test is quick and involves a small sample of blood to be drawn from the arm with a syringe.
Getting your 25(OH)D levels tested is pretty straight forward. Interpreting your results is a bit trickier. Optimal vitamin D levels are controversial.
Note: To convert your test results in nmol/L into ng/ml divide by 2.5 - i.e. 100 nmol/L = 40 ng/ml
To further answer the question - it's quite likely that you are vitamin D deficient.
While the optimal vitamin D levels in the body are controversial it is very clear that there are epidemic levels of vitamin D deficiency.
Green and colleagues (2004) showed that 31% of New Zealand children aged 5–14 years whose bloods were sampled in 2002 had a serum 25(OH)D concentration indicative of vitamin D insufficiency.For adolescents at or above 15 years and adults a staggering 28% were defined as vitamin D deficient. Note that deficiency was defined as lower than a mere 37.5 nmol/L in these studies!
Several studies in Australia and New Zealand have shown high rates of deficiency in the older population with restricted access to sunlight, many of whom live in institutions. Estimates of deficiency range up to 50% in Australia (Flicker et al. 2003, Inderjeeth et al. 2000). Similar levels were reported in NZ by Ley et al in 1999. Keep in mind that the researchers used a low benchmark of <37.5 nmol/L to define deficiency so the problem is much worse than the research shows.
Bottom line is that vitamin D deficiency is rampant in our community. Vitamin D levels are especially concerning in the 70yr+ population
In future articles I’ll be going through vitamin D recommendations and dosages to combat deficiencies
Unfortunately this isn’t a straight forward question. There is a wide range of recommendations
The Nutrient Reference Values for New Zealand are:
|Age||AI (Adequate Intake)|
|0-50 yr||200 IU|
|51-70 yr||400 IU|
|71+ yr||600 IU|
The Institute of Medicine’s Food and Nutrition Board (FNB) have the following recommendations for Vitamin D intake.
Note that these are considerably higher than the recommendations above.
|Infants 0-12 months||0 IU/day|
|1-18 years||600 IU/day|
|Over 70 years old||800 IU/day|
|Pregnant women aged 14-50||600 IU/day|
The New Zealand and the FNB’s recommendations are to achieve a 25(OH)D level of 50 nmol/L – which as I mentioned in this article is just far too low.
Many experts have publically criticised these recommendations. My personal belief is that these recommendations will increase dramatically over the next couple of years to be more in line with current research that shows the beneftis of higher levels of vitamin D.
Dr Mercola – Who has one of the largest health websites has the following vitamin D intake recommendations. Dr Mercola goes into detail on his site to justify these levels. These are around 10x higher than the recommendations above!
|Below 5||16 IU per kg per day|
|Age 5 - 10||2500 IU|
|Pregnant Women||5000 IU|
The Weston A Price Foundation - an organisation that provides health and nutrition education, recommendations are:
|Children age 3 months to 12 years||500-1000IU/day|
|Children over 12 years and adults||1000-2000IU/day|
|Pregnant and nursing women||2000-4000 IU/day|
Putting all this information shows the large variety in recommendations. It's also important to note that the amount of vitamin D required for the individual will vary depending on their vitamin D status – which can only be determined by a 25(OH)D test – see this article. Illness and medical conditions can also increase the vitamin D requirement.
In my opinion the New Zealand, and FNBs recommendations are far too low. If I’m asked to quote numbers my recommended intakes would be:
Children <12 yrs 2000 - 3000 IU/day
Adults 3000-4000 IU/day
Pregnant and nursing women 5000 IU/day
If you're looking to achieve this with Green Pasture cod liver oil the vitamin D levels of our cod liver oil varies from batch to batch. The latest test data can be found here
If we assume that cod liver oil carries 750 IU/ml.
This took a little bribing but the lure of being on on the internet brought my two little starlets out into the spot light.
My two girls - Maia (8) and Ella (5) talk you through the basics of why cod liver oil is important for growing kids
Our most frequent FAQs are about cod liver oil and kids.
Just to clarify a few points:
Our experience of using cod liver oil has been fantastic - so good that we decided to share this in business
If you're looking at one food to boost your kid's health we believe that this is it.
Some of the tips that parents have sent in to us to get their kids into the habit of taking cod liver oil are:
Here's to your health and the health of your children
Almost all cod liver oil is sourced from Norway and Iceland. Industrial cod liver oil manufacturing involves alkali refining, bleaching, winterization and deodorization. These processes remove natural vitamin D from the oil. Almost all factories either produce vitamin deficient cod liver oil (vitamin D <900 IU per teaspoon) or add synthetic vitamins back into the oil (the most common procedure eg. Nordic Naturals). Until early 2009 we were able to source cod liver oil from a factory that added the natural vitamins back into the processed cod liver oil. Unfortunately, this factory has now followed the cheaper more commercial path of producing synthetically enhanced cod liver oil.
For those of you that have been using our product lines over the last few years, you will notice that our standard high-vitamin cod liver oil is now "off the menu". Since we couldn't source a natural cod liver oil - we couldn't stock one. The only natural cod liver oil that is high in vitamins A and D on the market is the fermented cod liver oil produced by Green Pasture that we stock. This oil is batch brewed in Nebraska from cod livers using traditional lacto-fermentation and non-toxic methods without using heat and carbon filters that damage vitamins and omega-3 oils. The result is a high vitamin cod liver oil containing 4000-9000 IU vitamin A and 3000-4000 IU vitamin D per teaspoon. Super high-vitamin and exquisitely processed to preserve the natural qualities of cod liver oil.
We refuse to carry inferior products - and if you're already one of our customers we know that you've refused to use inferior products.