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Word Cloud on a white background - Vitamin D

Vitamin D Deficiency: Fatigue, Flu and Other Symptoms

Winter is a good time to talk about vitamin D. In fact, it’s been precisely one year since we wrote a blog saying as much.

At no other time are blocked noses, hacking coughs, sneezing fits and sore throats quite so ubiquitous.

You may wonder how vitamin D ties into this roll call of seasonal symptoms, and if so, it’ll probably shock you to learn that vitamin D deficiency is at the very root of them.

The Importance of Vitamin D

In a year in which the British Medical Journal argued food should be fortified with the vitamin to spare three million from the cold and flu each year, it seems appropriate to look at the main symptoms of deficiency – and what topping up your levels could mean for your overall health.

Let’s get to it.

What Does Vitamin D Do?

A cursory glance at the EU Register on Nutrition & Health Claims indicates just how biologically favourable vitamin D is. Below is a list of claims approved by Commission Regulation:

• Vitamin D contributes to normal blood calcium levels; the maintenance of normal bones; the maintenance of normal teeth; the maintenance of normal muscle function; the normal function of the immune system; the normal absorption/utilisation of calcium and phosphorus

• Vitamin D has a role in the process of cell division

• Vitamin D (and calcium) help to reduce the loss of bone mineral in post-menopausal women.

• Vitamin D helps to reduce the risk of falling associated with postural instability and muscle weakness.

Evidently this is one vitamin you should not forego – particularly if you don’t get enough natural sunlight for the body to manufacture the requisite amounts.

It’s for this reason that we included Vitamin D in our recent blog, ‘4 Essential Nutrients for Better Overall Heath‘.

And it’s not just those in the natural health arena who rave about Vitamin D. Figures show that in Northern Ireland prescriptions for the Sunshine Vitamin have more than doubled in the last decade.

Public health advice recommends that all of us should take a Vitamin D supplement in autumn and winter.

And in addition to the aforementioned benefits, studies show Vit D can protect against severe asthma attacks, help to heal burns, reduce inflammation, improve cardiac function and assist in the prevention of rheumatoid arthritis.

Amid all that good press, it seems inconceivable that so many people would remain deficient. And yet it’s true: most of don’t get all the vitamin D we need, leaving immune systems compromised, blood calcium levels insufficient and inflammation unchecked.

The Vitamin D Council has gone so far as to claim we are experiencing a ‘vitamin D deficiency pandemic.’

Vitamin D Deficiency: Fatigue Isn’t the Only Symptom

There are a great many symptoms of Vitamin D deficiency, although not everyone connects the dots and realises they are deficient.

Ensuring an adequate intake means that, should you experience any of the symptoms given below, you can rule out lack of Vitamin D as the cause.

1. Fatigue

It’s not the only symptom, but it’s certainly one of the most prevalent. Low blood levels (anything less than 20 ng/ml is deemed deficient) can cause skeletal muscle fatigue and myopathy, as noted in a number of clinical trials.

Low Vitamin D levels have been linked with fatigue among cancer patients in particular, with normalisation shown to significantly lessen the severity of symptoms.

Since fatigue can affect pretty much every facet of life, it pays to boost your Vitamin D levels. If lethargy remains an issue, make an appointment with your GP or naturopathic doctor to identify the underlying cause.

2. Colds/flu

Contracting the cold or flu can be a sure sign your Vitamin D levels are too low. This at least partly explains why more people get the cold during winter than summer, since there’s enough sunlight midway through the year for our bodies to manufacture the vitamin.

If you want to fortify your immune system to avoid that nasty cold spreading like wildfire through the office, make sure to supplement. After all, no-one likes to be off work in December, beached on the couch watching Christmas films… do they?

3. Low Mood

Vitamin D has more than once been linked to depression, particularly in elder individuals.

This makes sense, since serotonin – the mood-stabilising brain hormone – increases when exposed to bright light and plummets when sun exposure is limited.

What’s more, Vitamin D receptors have been located on a handful of cells in regions of the brain linked with depression.

The Vitamin D Council have written a fairly exhaustive article reviewing the scientific literature on this topic.

In our view, it’s worth reaching for a Vitamin D supplement before an antidepressant.

4. Bone Pain

Never experienced bone pain? Count yourself lucky: it can be absolutely excruciating.

According to one controlled study, those with inadequate serum Vitamin D are almost twice as likely to suffer from such pain in the joints, ribs or legs.

Remember, without the Sunshine Vitamin our bodies are unable to efficiently absorb calcium, perhaps the most important nutrient for bone mineral status.

It’s not just bone pain, either; bone softening, which can in many cases lead to fractures, is a byproduct of severe deficiency.

5. Poor Sleep

A lesser-known symptom of Vitamin D deficiency is disrupted sleep – and not just insomnia but sleep apnea, intermittent awakenings and sudden jerking body movements.

While it’s true that there hasn’t been enough investigations into sleep and Vit D (the evidence is mainly observational), there’s enough data to suggest Vit D ahead of, say, sleeping pills when it comes to improving shuteye.

Particularly after an American study from earlier this year showed that supplements “improve sleep quality, reduce sleep latency, increase sleep duration and improve subjective sleep quality” in 20-50-year-olds with a sleep disorder.

Setting aside the symptomology for a second, there is evidence that Vitamin D has many benefits beyond those mentioned here.

Dr. Verner Wheelock penned an interesting article only last year, looking at the associations of Vitamin D with conditions such as cancer, Alzheimer’s disease and type-2 diabetes, and we ourselves have explored the link between low vitamin D and weight gain.

These associations certainly warrant further investigation.

Addressing Vitamin D Deficiency is Easy

There is some dispute about the ‘ideal’ daily Vitamin D dose. Public Health England recommends a mere 400 i.u., although the non-profit Vitamin D Council, a collective of health professionals and researchers, advise 5,000.

The VDC say this amount is required to obtain a serum level of 40 ng/ml for an average adult. The Endocrine Society, meanwhile, states that up to 10,000 i.u. daily is safe for most adults. It’s little wonder the public are confused.

It should be noted that Vitamin D toxicity is extremely uncommon. The fact that the body can make around 1,000 i.u. in just ten minutes of sunlight probably illustrates this better than anything.

Toxicity can, however, occur if you take tens of thousands of Vitamin D on a daily basis for several months, leading to high levels of calcium in the blood.

Should you wish to address symptoms of Vitamin D deficiency – fatigue, low mood, bone pain, dizziness and others – the best way is to take a daily supplement.

Providing you get out in the sun during spring and summer, this might only be necessary for six months of the year.

Assessing your Vitamin D levels with an at-home testing kit is an excellent way of knowing for sure.


To quickly boost your vitamin D levels, try our Planet Source Vitamin D3 Drops, or Planet Source Vitamin D3 + K2 Drops. Both contain Vitamin D3 5000iu and are bound in natural oils for easy absorption into the body. The oils are organic olive oil, organic MCT oil and organic chia seed oil.

Whatever supplement you choose, ensuring a healthy intake of vitamin D is absolutely vital if you wish to maintain high levels of wellbeing and year-round immunity.

Water for Health Ltd began trading in 2007 with the goal of positively affecting the lives of many. We still retain that mission because we believe that proper hydration and nutrition can make a massive difference to people’s health and quality of life. Click here to find out more.