Why Women Should Track Their Vitamin D

Why Women Should Track Their Vitamin D. In the wake of reducing our risk for and recovering from COVID-19, and as we come into full summer, Vitamin D is on the tip of everyone’s tongue.  And research is giving us plenty on the pros (and the cons) of supplementing D.  But why should women be particularly concerned to track their D? vitamin d and women's health

COVID-19 is bringing the role and health benefits of Vitamin D to the fore, and it’s become a hot topic, many of today’s conventional clinicians receive little or no training in medical school for vitamin D and may not be in the habit of testing for vitamin D deficiency. Or, if they are testing their patients they may not be familiar with treatment. But practitioners from both sides of the conventional/alternative aisle are seeing more cases of D deficiency and awareness is on the rise.

What is Vitamin D?

Vitamin D is somewhat misunderstood as a ‘vitamin’ because it isn’t like most other vitamins. Our body makes its own vitamin D when we expose our skin to sunlight. But our body can’t make other vitamins – we need to get these from the foods we eat. For example, you need to get vitamin C from fruits and vegetables.

Importantly, our body turns vitamin D into a complex and potent hormone – sometimes called activated vitamin D, or ‘calcitriol’ and it’s this status that is key to understanding D’s importance to our health. Although it’s generally associated with calcium metabolism (for instance brain cell signalling, bone and tooth health) it’s a big player: nearly every tissue and cell in the body has a vitamin D receptor. This alone alerts us to D’s importance; the only other hormone to have receptors at every cell is thyroid hormone (responsible for directing energy to every cell in the body).

D starts off its life as cholecalciferol – made by the action of specific UVB wavelengths of sunlight on the cholesterol in our skin. In this early form, D isn’t active and so our wise body sends it off to our liver to be converted to calcidiol and then to our kidneys, where we convert to calcitriol – the active form of vitamin D3 (25(OH)D).  And then, we neatly store it in our fatty tissues. When your doctor talks about vitamin D levels, s/he means the amount of you have in your blood.

vitamin d metabolism

What’s the problem?

Although we’ve evolved to spend our time outdoors (actively!) over generations we’ve done the opposite of what Mother Nature intended for us and developed sedentary, indoor lifestyles.  Our fear of sun exposure, obsessive use of sunscreens and not least, our cholesterol phobia has scored big hits on our health in widespread vitamin D deficiency.

Not so smart, eh?

And if that wasn’t enough, we can see from the chart below that where we live in the world determines how much vitamin D is even available to us at any time of year…. so this alone is how most of us end up not getting anywhere near enough vitamin D.


Add this into the mix: As we age, our ability to actually make vitamin D at all is reduced by a whopping 75%. And, although we store vitamin D in fatty tissues, it can get trapped in body fat – so if we carry a lot of fat we can expect a 55% reduction in blood levels of vitamin D!  Who knew?!  (1)

All this is hurting us – and especially so at this time of year.  And it’s even worse for those of us with darker skin (a very effective filter) who live in northern time zones with limited sunlight; we know that darker skins need longer sun exposure to make optimum levels of Vitamin D.

Darker-skinned people have more melanin, a compound that protects against skin damage by reducing the amount of UVB light absorbed. Darker-skinned people need more time in sunlight to make the same amount of vitamin D as lighter-skinned people. Studies estimate that darker-skinned people may need anywhere from 30 minutes to three hours longer to get sufficient vitamin D, compared to lighter-skinned people. This is a major reason why darker-skinned people have a higher risk of deficiency. (Healthline 2018)

For all of us, low blood levels of vitamin D increase the risk of a heart attack, heart failure, stroke, diabetes or high blood pressure later in life. (2)

Why women should track their vitamin D… where to start?!

While for everyone, no matter what age or gender, vitamin D deficiency is one of the quickest ways to sabotage our health, for women, our physiology makes us particularly at risk for a wide range of low-D related conditions.

As you read on, bear in mind that associations, relationships, links and impacts do not prove causality – but they do indicate concern.

LOW vitamin D…

# Is associated with heart disease: the leading cause of death for women, as well as for men. D deficiency is a risk factor in heart attacks, congestive heart failure, peripheral arterial disease, strokes and the conditions associated with cardiovascular diseases, such as high blood pressure and diabetes. (3)

# Is related to breast, ovarian, cervical and endometrial cancers: vitamin D blocks the growth of cancer tumours (4) Statistics show that one in EIGHT women will receive a breast cancer diagnosis in her lifetime and that one in FIVE will be under the age of 50. Many studies have now shown an association between low vitamin D status and increased breast cancer risk.

A recent study (17) which pooled results from over 5000 women aged 55 and older, found that women with Vitamin D status of above 150 nmol/l had an 80% lower risk of breast cancer, over those with Vitamin D concentrations of below 50 nmol/l (see table below). Testing your vitamin D status and optimising levels to >150 nmol/l could be considered as part of a strategy for breast cancer prevention.

# Is associated with progression of uterine fibroids: a major reason for a hysterectomy.  Although they are non-cancerous tumours of the uterus, fibroids can cause pelvic pressure or pain, prolonged or heavy periods, frequent urination. Women who report spending more than one hour outside per day have a 40% decreased risk of fibroids. (5)  

# Reduces the benefits of progesterone: another sterol hormone, whose wide influence throughout the body is only just being better understood. (6) (11)

# Is related to oestrogen dominance: Low D reduces the benefits of progesterone, which opposes the action of oestrogen (6) (11)

NOTE: It’s particularly important for women to maintain an adequate level of vitamin D and progesterone: Progesterone acts in opposition to oestrogen; oestrogen dominance is associated with a wide range of health and age-accelerating conditions. (11)

# Impacts fertility levels: D suppresses ovulation, encouraging conception and subsequent birth at times of the year when babies can be exposed to optimum levels of vitamin D from sunlight and when optimum nutrition to be available for mothers to make breast milk (6)

# Is related to PCOS: low D inhibits ovulation and ovaries can get stuck at the stage of producing too many eggs trying to mature provoking the development of cysts (6)


# Is associated with the onset and severity of endometriosis: During menstruation, low D can result in endometrial tissue going back up the fallopian tube(s) into the abdomen, instead of downward to flow out from the cervix.  The fallopian tubes are open to the abdomen and endometrial tissue pushed out to the cervix by wave-like movements in the fallopian tubes. Vitamin D receptors in the tubes influence these propulsive movements (and also promote fertilisation, or prevent it if the D level is low).

Then, because endometrial cells don’t belong in the abdomen, white blood cells are sent to find and destroy them. However, low D affects the function of the white cells and endometrial tissue isn’t properly destroyed or eliminated – resulting in ‘fixed’ implants of endometrial tissue in the abdomen, causing abdominal pain during menstruation (6) (7)

# Is linked with adverse pregnancy outcomes: miscarriage, pre-eclampsia, gestational diabetes and other adverse outcomes (2)

# Underlies osteoporosis: vitamin D helps the GI tract absorbs calcium and keeps it from leaking in urine, suggesting osteoporosis is a D deficiency, not a calcium deficiency (6)

vitamin d and thyroid health

# Is associated with thyroid disorders, specifically with autoimmune thyroid disease (AITD) and autoimmune-mediated thyroid dysfunction (8)

# Is implicated in insulin resistance & diabetes: D regulates insulin secretion, sensitivity and balances blood sugar (8)

# Is implicated in a low-fat diet: vitamin D is a fat-soluble vitamin and needs fat in the diet to be absorbed (8)

# Is related to leaky gut syndrome: a leaky or inflamed gut reduces D absorption. In common with other medications (anti-inflammatories, antibiotics), oral contraceptives may alter our gut microbes and pave the way for dysbiosis, inflammation and a compromised gut lining (8) (9)

# Is associated with high cortisol levels: cortisol is released under stress – consider the stress levels of women juggling careers, finances, relationships and family commitments? (8)

# Is associated with depression, anxiety and mood changes: research has found that women with low D are 11 times more at risk (10)

# Is related to sleep disorders: low D causes insomnia, sleep apnoea, REM related apnoea and their associated disorders, all of which disrupt or prevent the process of healing during sleep (6)

# Depletes our daily dose of B vitamins: low D changes our intestinal bacteria, which produce the B vitamins which convert our food to fuel to keep our bodies running like well-oiled machines (6)

# Increases our risk of multiple sclerosis (MS) an immune-mediated disease of the central nervous system which disrupts the flow of nerve signals between the brain and spinal cord to the rest of the body. Symptoms may include fatigue, weakness, numbness or tingling, cognitive impairment, pain, vision loss, depression.

How much is enough D?

Testing your vitamin D

The blood test that measures vitamin D is called a 25(OH)D blood test.  In the UK we measure vitamin D in nmol/l (nanomoles per litre), while the US measures it in ng/ml (nanograms per millilitre).

vitamin d levels

Source: Holick MF. Calcium and Vitamin D. Diagnostics and Therapeutics. Clin Lab Med. 2000 Sep;20(3):569-90)

The UK > US conversion factor is 2.5:

  • To convert a UK test result measured in nmol/l to ng/ml
    • divide the nmol/l number by 2.5
    • so 50 nmol/l = 20 ng/ml (50÷2.5)
  • To convert a US test result measured in ng/ml to nmol/l
    • multiply the ng/ml number by 2.5
    • so 20 ng/ml = 50 nmol/l (20 x 2.5).

When you’ve had your vitamin D levels tested, it’s important to understand what the results mean and what actions you might need to take.

Your GP will be able to arrange a vitamin D test for you – but if you have a problem you can use a home-testing kit which is analysed, interpreted and supported in collaboration with Sandwell and Birmingham NHS Trust.  

But wait, maybe MAGNESIUM is the real problem?

Magnesium is responsible for over 300 biochemical reactions in the body, impacting blood pressure, metabolism, immune function and many other aspects of our health.

All the processes in our body are synergistic – we don’t use nutrients, vitamins and minerals in isolation, so for us to be to convert vitamin D into its active form, we need sufficient magnesium.

This means that an underlying magnesium deficiency can show up as a low vitamin D blood level and supplementing with D alone may not raise D blood levels.

Magnesium and vitamin D work in a two-way partnership:

  • Our body NEEDS sufficient magnesium to convert vitamin D into its active form.
  • Our body USES UP magnesium when converting vitamin D into its active form

So magnesium is not just depleted, but we won’t convert vitamin D unless we have enough magnesium in the first place.

Mistaken identity?

If, when supplementing D, tests still show low levels, this can be mistakenly interpreted as vitamin D absorption problem when it’s actually an underlying magnesium deficiency. (12).  This is not helped by the fact that symptoms experienced by those taking vitamin D alone, are ALSO the signs of underlying magnesium deficiency:

Insomnia, jitteriness, muscle cramps, anxiety, palpitations, constipation, headaches, body pain, bone pain.  

Magnesium deficiency is widespread

Depleted soil conditions mean that plants (and meat from animals that feed on these plants) are lower in magnesium.  Use of chemicals like fluoride and chlorine in the water supply make magnesium less available in water since these chemicals can bind to magnesium.  Caffeine and sugar also deplete the body’s magnesium levels… so does stress.

Ways to get your D

THE SUN: Nothing can replace the sun for optimising D levels, so prioritising spending time in safe sunbathing during the summer months to optimise stored D is really importantMemorise the Sunshine Calendar and make sure to get out there… safely!

Memorise this quick guide – but DO make sure that your sunscreen is free of junk chemicals – or you’ll be doing your body more harm than good!

And did you know that the sun isn’t only for D production – spending time outside in the winter sunshine brings us a host of extra benefits

UVB BEDS: Don’t run for the hills! The Vitamin D Council has this to say:

Your skin can also make vitamin D if you use an indoor tanning bed. As with natural sunlight, making the vitamin D you need from a tanning bed happens within minutes. You don’t need to tan your skin, or use a tanning bed for a long time to get the vitamin D you need.

If you choose to use a tanning bed, the Vitamin D Council recommends using the same common sense you use in getting sunlight. This includes:

  • Getting half the amount of exposure that it takes for your skin to begin to burn.
  • Using low-pressure beds that have good amounts of UVB light, rather than high-intensity UVA light.”

A SUPPLEMENTOn the face of it, supplements are probably the most ‘convenient’ way to maintain D levels – but as we’ll see below, we can have too much of a good thing.

We’re all individual and there is no ‘one-size-fits-all’ advice for the dosage of vitamin D supplements.  It is the D blood level, not the dose of the supplement that determines good health.  Regular testing is important; most of us can make D3 up to 20,000IU/day, however others (1 in 50) make and need only 2,000 IU/day. (6)

YOUR FOOD: Unfortunately, we are not able to get sufficient vitamin D from food sources. While good quality wild/organic foods such as salmon, herring, sardines, tuna, shrimp, egg yolks and mushrooms can help and are important to our diet in other respects, they contain nothing like the amounts we need to maintain our optimal vitamin D levels.

The Vitamin D Council says:

The two main ways to get vitamin D are by exposing your bare skin to sunlight and by taking vitamin D supplements. You can’t get the right amount of vitamin D your body needs from food.

Vitamin D supplements: a double-edged sword!


D is a ‘fat-soluble’ vitamin (stored in fatty tissue) so we can’t easily excrete it (as we can excrete excess vitamin C in urine, for example).  High levels of D can result in high levels of calcium in the blood (hypercalcaemia) and ultimately, excess circulating calcium is deposited in soft tissue and can lead to calcification of blood vessel walls (arteriosclerosis) and calcium stones in the kidneys.

Vitamin K2

Whereas vitamin D helps us absorb calcium (from our diet) to support bone development, vitamin K2 directs the calcium to our skeleton, while preventing it from being deposited where we don’t want it – in your organs, joint spaces and arteries (hence the term “hardening of the arteries”).

Without the help of vitamin K2, the calcium that vitamin D so effectively lets in might be working AGAINST us by building up coronary arteries rather than our bones.

Sensible supplementing:

There is an enormous range of vitamin D supplements on the market – with huge variation in their efficacy and quality and it’s always best to supplement under the guidance of a health care practitioner experienced in supplements.

Here are some basic guidelines when considering supplementing:

  • ALWAYS get a blood test done* before supplementing with vitamin D to check if you are deficient and to set a baseline against which to monitor and adjust supplement dosage
  • SUPPLEMENT with vitamin D3, not D2: this is the form of D that your body produces in response to sun exposure
  • ALWAYS tandem D3 with vitamin K2: K2 keeps calcium in the blood and out of soft tissue (16)
  • CONSIDER a B-vitamin complex: Low D changes intestinal bacteria that produce our daily dosage of the B vitamins, which help convert our food into energy to fuel  our body throughout the day
  • CONSIDER a magnesium supplement.  Consider it anyway… the majority of us (including men) need it!

There’s no doubt that maintaining optimal vitamin D levels is fundamental to everyone’s health, low D status can impact widely on women’s health.

As part of a comprehensive approach to your whole health, I encourage you to investigate your personal vitamin D level and consider what action to take to optimise this important nutrient.

Practising real self-care


We women are great at putting our partners, families, friends and careers first.  And ourselves last.

To show up for others, we need to learn to show up for ourselves first. Your body is much wiser than you are and ignoring its whispers (cries?) for attention and struggling on exhausted, stressed and in pain serves no-one.

YOU MATTER.  If this article has resonated with you, please take some time to stop and think about how you’ve been feeling, what your body might be trying to tell you and what changes you might need change.

If you feel drawn to it arrange a 30-minute health clarity consultation with me.

Izabella Natrins

I'm here to inspire and support women at midlife and beyond to re-ignite purpose and meaning to take back control of their health and create the radical, resilient heath they want and deserve. As a whole-health expert with over 30 years experience in the field, a qualified Health and Wellness Coach and Ballymaloe-trained nutritional chef, my real food nutrition and lifestyle medicine programmes support women fighting fatigue, struggling with overwhelm, weight gain, sleep, energy and niggling or multiple diagnosed health issues. As an advocate for real food nutrition, regenerative agriculture and whole-health, my book 'The Real Food Solution' is an evidence-based treasury wisdom for energy, vitality and better health for people and planet and a call to action to change the way we grown, source and cook our food. As the CEO at The UK Health Coaches Association, I'm proud to continue the task of leading the first professional association for Health and Wellness Coaches in the world and the gold standard for the UK and Ireland.

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4 Responses

  1. July 4, 2018

    […] In fact, the sun’s rays at the right time of day, at the right time of year, is our most important source of vitamin D and that’s especially so for women’s health!  Discover the many reasons why in my article “Why Women Should Track Their Vitamin D This Winter”. […]

  2. March 13, 2019

    […] In fact, the sun’s rays at the right time of day, at the right time of year, is our most important source of vitamin D and that’s especially so for women’s health!  Discover the many reasons why in my article “Why Women Should Track Their Vitamin D”. […]

  3. June 22, 2020

    […] a FULL DISCUSSION on all aspects of vitamin D (health impact, co-dependencies, supplementation, safe sunbathing), I […]

  4. May 12, 2021

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