Are you concerned that you might be deficient in vitamin D? According to the British Nutrition Foundation 1 in 5 people in the UK are deficient in this vitamin. Vitamin deficiencies in general are more common than most people realise and can significantly increase the risk of disease.
If you have been experiencing symptoms that you are worried about, or are simply interested in how much vitamin D you need, continue reading to find out what to do.
Fortunately vitamin D deficiency is relatively easy to fix.
What is Vitamin D?
Vitamin D is often referred to as the “sunshine” vitamin because your skin has the ability to synthesise it from UVB sun rays. Stored in the epidermal layer of your skin is a compound called 7-dehydrocholesterol which absorbs UVB (ultra violet radiation) from the sun.
UVB rays catalyse the photochemical conversion of 7-dehydrocholesterol to previtamin D3. Previtamin D3 is then sequentially metabolised in the liver and kidneys to produce 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D.
But did you know that vitamin D isn’t a single vitamin? In fact, it is a whole family of fat soluble vitamins known as secosteroids. The secosteroid family is a subclass of steriods, the difference being that their molecular structure has an open carbon ring, whereas in steroids this is closed.
Furthermore vitamin D isn’t a regular vitamin, and although it is referred to as a vitamin, it is actually a hormone.
So you might be wondering; what’s the difference between a vitamin and a hormone?
Simply put, a hormone is produced endogenously from various different glands within the body and has a specific influence on organ and tissue growth. In contrast, vitamins are not endogenously synthesised and are derived from the plants and animals that we eat.
Therefore classification of vitamin D appears to be somewhat a matter of opinion as some bodies refer to it as a vitamin, while others call it a hormone; technically it is a hormone.
The vitamin D family includes:
- D1 (ergocalciferol with lumisterol, 1:1)
- D2 (ergocalciferol [made from ergosterol])
- D3 (cholecalciferol [made from 7-dehydrocholesterol in the skin])
- D4 (22-dihydroergocalciferol)
- D5 (sitocalciferol (made from 7-dehydrositosterol))
As you can see there are several different forms of vitamin D, however the two most relevant to human function and nutrition are vitamin D2 and particularly vitamin D3.
What is Vitamin D good for?
Vitamin D has many important functions that support optimal health other than bone mineralisation. Multifaceted research exploring its effects upon various organs, metabolic responses and diseases, has uncovered a complex array of interactions.
These include various non-skeletal functions such as endocrine, brain and cognitive health, inflammation, increased testosterone, and interactions with diseases such as cardio vascular, atherosclerosis and cancer. In fact, its effects have been found to be so far reaching it has now been evidenced that vitamin D is known to influence over 200 genes highlighting links to diseases in cases of deficiency (1).
The importance of Vitamin D on bones
Vitamin D plays a vital role in maintaining bone health. It is largely responsible for improving the absorption of essential minerals such as magnesium, zinc, iron and in particular calcium and phosphorus (2). It is especially important for maintaining normal and healthy bone development in preadolescent children.
Bone mineral content (BMC) and bone mineral density (BMD) are standardised measures of bone health and indicate that around 70% of a healthy bone mass is from minerals, primarily calcium.
Osteoporosis, a degenerative bone disease, is directly linked to vitamin D deficiency. As a preventative measure, doctors regularly prescribe a combination of vitamin D and calcium to help safeguard against the onset of osteoporosis.
Fall short on vitamin D and the reality is that your bones may suffer.
Vitamin D is good for your immune system
Low levels of vitamin D are associated with increased risk of disease and increased autoimmunity (3).Have you ever noticed that colds & flu are synonymous with winter? Your vitamin D level usually declines during winter because you just dont get the sunlight.
In fact it is now understood how vitamin D influences immune function by its actions on T cells and neutrophils.
Furthermore, according to Dr. Joe Prendergast
“vitamin D is likely more powerful than any vaccine you could take, as German researchers have found it increases your immune system by a factor of 3 to 5”.
Perhaps the conglomerate of big pharma would argue the case against vitamin D and the benefits it has on immunity. Especially considering there is a ton of valid data to suggest high doses of vitamin D may even help with prevention of some cancers. Nevertheless bonafide research shows that vitamin D can boost immunity.
Vitamin D influences testosterone levels
In men 97% of testosterone is produced by the testes, with only 3% being produced by the adrenal glands. Vitamin D receptors are present in the testes which suggests that vitamin D has an interaction with endogenous testosterone production.
Researchers in endocrinology continue to study the relationship between vitamin D and testosterone and although the exact mechanism of vitamin D’s influence on testosterone is not yet fully understood, results of some studies do show a direct correlation between vitamin D and testosterone.
For example one study (4) tested 165 subjects who were split into 2 groups; group 1 received 3’332 IU of vitamin D per day for a year, group 2 received a placebo. Initial vitamin D levels of all subjects were in a deficiency range (< 50 nmol/l).
Results of the study showed that group 1 subjects experienced an average increase of 25% total testosterone and a 20% increase in bioactive testosterone. In contrast no significant increase in testosterone was recorded in the placebo group.
Vitamin D reduces SHBG (increases free circulating testosterone)
As a result of its metabolic pathways and effects on sex hormone binding globulin, vitamin D has been shown to positively influence unbound testosterone.
Additionally, zinc absorption is enhanced in the presence of Vitamin D, and combining the two further enhances levels of natural testosterone.
Testosterone that binds to SHBG (Sex Hormone Binding Globulin) becomes unavailable to lock onto to androgenic receptors and induce its anabolic effects. Essentially all testosterone bound to SHBG is dormant, having no effect.
Supplementing with vitamin D has been shown to reduce levels of SHBG. Reduced SHBG increases freely available and unbound testosterone pools, ergo the effects of testosterone become more pronounced.
Data from another study also confirmed that Vitamin D is significantly associated with total testosterone and sex hormone-binding globulin (5).
Therefore vitamin D may have additional benefits for men.
Vitamin D deficiency
Although there are many different symptoms of deficiency, there is currently only one way to accurately determine a deficiency. This is done via a blood test, which is commonly known as a vitamin D test. A deficiency is generally recognised if levels of Calcifediol 25(OH)D are measured below 30 ng/ml (6).
A deficiency of vitamin D can lead to serious health risks. For example, low levels have been directly linked to diabetes, hypertension, autoimmune diseases and even some cancers.
Here are some common risk factors associated with vitamin D deficiency. If any of these apply to you, you could be more at risk :
- Overweightness & obesity (7).
- A high amount of skin pigmentation (melanin).
- Of an older age.
- Always use sunscreens.
- You do not eat fish or dairy.
- You live far from the equator.
- Have an office based job/Stay indoors a lot.
Vitamin D insufficiency or deficiency: what’s the difference?
Insufficiency and deficiency differ only by degree and again appear to be a matter of opinion. A blood level of Calcifediol 25(OH)D between 20-30 ng/mL is recognised by the Vitamin D council as a deficiency.
Yet according to the endocrine society it’s an insufficiency. Opinions aside, a blood level of Calcifediol 25(OH)D ranging between 20-30 ng/mL is too low and poses an increased risk of disease.
What are the symptoms of low vitamin D?
Here is a list of the common symptoms associated with vitamin D deficiency:
- Bone softening due to low bone density.
- Low blood levels of calcium.
- Depression or anxiety.
- Fatigue and poor energy levels.
- Joint pain.
- Muscle weakness and/or cramps.
- Low immunity.
- Weight gain.
How to increase vitamin D levels?
There are three main factors that determine vitamin D levels:
- Sunlight (UVB)
- Vitamin D supplements
Sunlight and vitamin D3 synthesis
First and foremost, receiving an adequate amount of sunlight is the key to maintaining a healthy level of vitamin D. The amount of exposure to sunlight significantly affects vitamin D3 levels.
For example, indoor oriented lifestyles can increase the risk of deficiency due to lack of natural UVB rays, resulting in a reduction of the dermal synthesis of vitamin D3.
UVB synthesis of Vitamin D3 is also significantly influenced by other factors such as air pollution, season, age, time of day, geographic location (latitude & altitude), skin pigmentation, sunscreens, wearing UVB filtering clothes and how much skin you have exposed to sunlight.
Summer Sun is the best for vitamin D
The sun radiates both UVA (long wave ultra violet radiation) and UVB (short wave ultra violet radiation). It is the UVB that stimulates the dermal synthesis of vitamin D. During summer season, the months April through to September is when UVB is at its highest here in the UK.
Particularly between the hours of 10.00 am and 3.00 pm, UVB reaches its peak levels. For most people a 20 – 30 minute exposure of natural UVB should be enough to maintain a healthy level of vitamin D.
This can however significantly vary from individual to individual and is therefore difficult to give a catch all figure of how long you should spend in the sun.
Conversely too much exposure to sunlight is dangerous, and can of course cause skin burn.
Don’t be fooled, if you sit indoors next to a sunlit window, you will not get the vitamin D synthesis. Most modern windows, just like sunglasses, have UVB filters. Therefore, in most cases direct exposure to the sun is needed.
Winter sun is too low in UVB for vitamin D synthesis
During the months of October through to March, here in the UK the sunlight does not provide enough UVB radiation for adequate dermal synthesis of vitamin D. Consequently, maintaining a healthy level of vitamin D in winter, is solely reliant on provision from food.
The bottom line is lack of sunlight can lead to a deficiency.
Pro tip no 1: As simple as can be, don’t be scared to go out in the sun. During summer make sure you get at least 15 minutes a day of sun exposure in peak UVB hours.
What foods are highest in vitamin D?
There are few foods that contain vitamin D let alone contain it in abundance. Here is a list of some of the best food sources:
- Wild oily fish (non farmed) such as Tuna, Mackerel and Salmon
- Egg yolks from pastured hens
- Wild Mushrooms (8)
- Butter from 100% grass fed cows
Pro tip no 2: Eating a 200 gram portion of wild sockeye salmon will provide you with approximately 1976 IU’s of vitamin D. Aim to consume this portion 2 times a week during winter.
Choose your food wisely: nutrients are passed down the food chain
If you want to incorporate high quality food sources of vitamin D into your diet, it is important to note that not all foods are equal.
As an example, wild salmon are free to feed on their natural diet of squid and other smaller fish. Wild Sockeye salmon almost exclusively feed on plankton and other vitamin D rich marine plants.This is why wild salmon are a fantastic source of vitamin D.
Farmed fish on the other hand, deviate tremendously from their natural diet to that of low quality, low nutrient, man-made food pellets. Needless to say, this significantly lowers the nutrient quality and vitamin D content of farmed fish.
Thus farmed fish and produce from grain fed cows do not usually have the same vitamin D content as their non-farmed free-range and wild counterparts. Even if their foods are artificially fortified, it’s not as good.
Food is generally lacking in vitamin D (and everything else)
Commercially prepared foods are now a commodity and have become chemical laden in the interest of preservation and increased corporate profits.
Whether you’re a meat eater, vegetarian, pescatarian, or vegan, you cannot escape the food industry’s chemical fingerprint on pretty much anything you buy to eat.
Cattle are cooped up and administered hormones, antibiotics and other drugs. Fish are farmed and fed on man-made chemical feed, plants are genetically modified, sprayed with pesticides and grown in mineral depleted soils.
The net effect is that people are becoming overweight and malnourished. Food is not what it ought to be and is moving further and further away from being “thy medicine”. Statistics prove this – the incidence of diabetes and cancer and disease in general is ever increasing.
It would be naive to believe that you can receive all of the nutrients you require from food alone.
Plant-based sources of vitamin D
It was once thought that plants did not contain vitamin D, however research has shown otherwise and has now led to the discovery of vitamin D in plants (9). Scientists have also shown that animals grazing on specific types of plants are known to develop calcium intoxication similar to that caused by consuming too much vitamin D.
It is believed that this phenomenon is caused by vitamin D3 or a metabolite of vitamin D3 contained in the plants that stimulate calcium absorption.
If you are vegetarian or vegan and looking for some good plant-based sources of vitamin D, then look no further than our fungus friends; mushrooms. Mushrooms are genuinely a great food to eat and contain some amazing nutrients.
For example, a 100 gram portion of wild funnel chanterelle mushrooms has been shown to contain around 21.1 mcg of vitamin D2. The bad news is that if you are counting on getting your vitamin D from shop bought mushrooms – think again!
Retail mushrooms are usually farmed in atmospherically controlled dark growing rooms, with little or no UVB. Therefore the vitamin D content in commercially grown mushrooms is probably negligible. Other than mushrooms, lichens are also a great plant-based source of vitamin D and many vegan based supplements contain vitamin D from lichen.
Vitamin D supplements
In current times of “technological advancements” you’d think that food would be nutritious and that the need for food fortification or the use of vitamin and mineral supplements would be obsolete. In actuality, nothing could be further from the truth.
Combine the above with 6 months of low UVB with an office based job and you can bet you’ll be a likely candidate for vitamin D deficiency. A sure-fire way to maintain a healthy level of this sunshine vitamin, without the sunshine, is to consume a high quality vitamin D supplement.
Besides, when it comes to increasing your vitamin D level, your options are limited.
What dosage of vitamin d should I take?
It is impossible to follow an exact one dose fits all approach with vitamin D, simply because there are so many factors that affect your vitamin D level.
Nevertheless, I would suggest, and what I believe to be reasonable for the majority of people who want to maintain their vitamin D level at 50 ng/mL or above, is to supplement with 1000 IU (25 mcg) of vitamin D per day.
You can buy vitamin D3 (cholecalciferol) in regular capsule form at dosages between 400 IU – 5000 IU. If you want to be completely sure that your vitamin D level is within a healthy range, you will need to take a vitamin D test. The result will enable you to adjust your dosage accordingly and re-test to be sure it’s worked.
Pro tip no 3: Supplement with a minimum of 1000 IU’s daily.Vitamin D is fat soluble, consume it with a dessert spoon of organic flaxseed oil to optmise its absorption.
International units (IU’s)
An international unit is not measured according to weight or mass; rather it is set according to the biological activity and potency of a substance. It enables compounds of differing potencies to be dosed equally.
A vitamin D supplement for example can come as either D2 (ergocalciferol) or D3 (cholecalciferol). Vitamins D2 and D3 differ in their biological activity and therefore need a reliable and standardised way of measuring them.
A microgram is purely a measurement of weight (mass) and is quite simply a millionth of a gram. Micrograms can be expressed as either Mcg or μg.
Converting international units to micrograms
An international unit can vary in terms of mass from substance to substance because an international unit is dependent on the potency of the particular substance.
The exact measure of one international unit is specific to each substance and is established by “international” agreement.
Thus the conversion of international units to micrograms across the board for all substances with an agreed IU is not a simple fit all “conversion”. Rather, each conversion must be calculated individually and accordingly.
To make it easy for you, I have put together a vitamin D convertor. Simply input either IU or Mcg ( μg ) and the convertor will automatically calculate the according dosage for you.
Vitamin D IU/mcg (μg) Dosage Convertor
Vitamin D is imperative for maintaining optimal health and also for preventing disease. It is also a potent ergonomic sporting aid due to its positive influence on testosterone. High quality dietary sources are rare and therefore it is important to regularly consume foods such as wild salmon that are naturally high in vitamin D.
Exposure to sunlight stimulates the biosynthesis of D3 and is a contributing factor in maintaining a healthy level. In the UK we have around 6 months of the year where the UVB from the sun is inadequate for vitamin D3 synthesis.
All things considered, I’d recommend supplementing daily with a minimum dose of 1000 IU of vitamin D3 (Cholecalciferol) as a preventive measure against insufficiency and deficiency.
Article by Paul Jenkins CEO and founder of DNA Lean®
- Vitamin D and Bone Health; Potential Mechanisms
- Vitamin D found to influence over 200 genes, highlighting links to disease
- Vitamin D and the Immune System
- Effect of vitamin D supplementation on testosterone levels in men
- Vitamin D is significantly associated with total testosterone and sex hormone-binding globulin in Malaysian men
- I tested my vitamin D level. What do my results mean?
- Vitamin D in obesity
- A Review of Mushrooms as a Potential Source of Dietary Vitamin D
- Vitamin D in plants: a review of occurrence, analysis, and biosynthesis
- Emerging Evidence of Thresholds for Beneficial Effects from Vitamin D Supplementation
- The importance of body weight for the dose response relationship of oral vitamin D supplementation and serum 25-hydroxyvitamin D in healthy volunteers.