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Vitamin D and female health - everything you need to know!

Three weeks after giving birth to my son, I developed painful eczema on my hands and woke up each morning with extreme muscle and joint soreness. It was so severe that I convinced myself I had developed arthritis at the age of 27.

Like many new mums, and despite a relatively easy pregnancy, the postpartum period hit me like a ton of bricks. Even as a newly qualified nutritionist specialising in women’s hormonal health, I had overlooked the importance of postnatal supplements and specific nutrients to support this phase.

When I revisited my training notes, I found that many of my symptoms could be linked to low vitamin D. An at-home test confirmed that my vitamin D levels were on the floor! Within just a few weeks of taking a high-quality, high-strength dose of vitamin D, my eczema cleared up, and my muscle soreness completely vanished. These symptoms have never reappeared since I started diligently monitoring my vitamin D levels. Fast forward seven years, and after extensive reading and training, optimising my clients' vitamin D levels has become a passion of mine.

In this article, I’ll give you the lowdown on all things vitamin D, including what it is, how much we need, where to get it tested, and why it’s crucial for balanced hormones.

What is Vitamin D?

It’s a well-documented fact that vitamin D, a.k.a the ‘sunshine vitamin,’ is essential for overall health. Despite its name, vitamin D is actually a hormone produced by your skin when exposed to sunshine. Besides helping to keep your bones strong and healthy (it’s key for calcium absorption), it’s also one of the most important vitamins for your immune system to work optimally, enabling your body to fight against infection and disease. However, you may not be aware that vitamin D also plays a vital role in supporting cardiovascular function, skin health, mental well-being, regulating your period, and optimising your fertility.

What are the symptoms of Vitamin D deficiency?

Getting enough vitamin D during the colder months can be really tricky here in the UK, and 1 in 6 adults and 20% of children are said to have low levels of vitamin D. This is not surprising, given our bodies produce the most vitamin D when exposed to direct sunlight.

While it is possible to get a small amount of vitamin D from foods such as oily fish, butter, and egg yolk, even NHS guidelines advise that adults should consider supplementing with 400IU of vitamin D through autumn and winter.

You might also be experiencing low levels if you are struggling with any of the following:

  1. Bone and muscle weakness

  2. Prone to catching colds or other infections

  3. Experiencing tiredness and fatigue

  4. Having trouble sleeping

  5. Experiencing low mood, anxiety, or depression

  6. Struggling to lose weight

  7. Experiencing skin or gut problems

Certain groups are at higher risk of vitamin D deficiency.


You may also not get enough vitamin D if:


✅ You are pregnant or are breastfeeding

✅ You don’t get enough sunlight (especially during winter!)

✅ You don’t take supplements (it’s hard to get enough vitamin D from the foods you eat alone)

✅ You have darker pigmented skin (which makes it harder for your body to make vitamin D from sunlight)

✅ You’re aged 65 or older

✅ You are overweight

✅ You have coeliac disease

✅ Spend too much time indoors



How can I test my vitamin D?

Personally, I would always advise getting your levels tested before supplementing so you know your baseline level, as you may well need more than the NHS recommendation of 400IU to reach optimal levels. You can also overdose from too much vitamin D, so you don’t want to overdo it without knowing your levels first!

If you think you may be experiencing a vitamin D deficiency, you can take a test to determine whether you need to boost your levels. Unfortunately, in my experience with clients, it can be very difficult to convince your GP to run a vitamin D test, unless you are part of a high-risk group. However, you can buy a simple at-home test rather inexpensively to see your exact level. I tend to recommend Medichecks (you can use my code HAYLEYDOWN10 for 10% off – not an affiliate link).

After testing, your result will reveal whether you fall into one of four categories. The NHS advises the following measurement guidelines:

  • <25nmol/l = deficient

  • 25 - 50nmol/l = insufficient

  • 50nmol/l+ = adequate

·       250nmol/l = high

However, the Vitamin D Council actually suggests that an optimal reading of vitamin D is between 100-150nmol/l to offer effective resistance against many diseases such as diabetes, IBS, multiple sclerosis and a growing number of cancers (as mentioned in the table below).  It is estimated that the presence of many of these diseases could be reduced by 20%-50% or more, if vitamin levels were optimised. This is the range I want my clients to be in, especially if they are struggling with issues.


Vitamin D + Female Health


There is also a growing body of research suggesting that vitamin D may help with certain aspects of female health. Here is quick snapshot of some of the research I came across while investigating the importance of vitamin D for women!

  • PCOS: Studies indicate that up to 85% of women with PCOS have low vitamin D levels.

  • Irregular Cycles: Insufficient vitamin D levels (50-75nmol/l) are associated with a twofold increase in the likelihood of longer menstrual cycles compared to women with levels above 100nmol/l. Adequate vitamin D levels are also linked to proper ovarian function and may help increase progesterone production, supporting regular periods.

  • Infertility and IVF Success: An astonishing 93% of women facing infertility issues have low vitamin D levels. Additionally, women with higher levels of vitamin D3 are four times more likely to conceive via IVF than those with lower levels. Optimal vitamin D levels are also associated with higher implantation rates during IVF.

  • Pregnancy: Sufficient vitamin D levels are linked to a significantly lower risk of pregnancy complications like preeclampsia and postpartum bleeding.

  • Period Cramps: Some research suggests that vitamin D may help reduce period cramps in women with levels below 125 nmol/L.

  • Fibroids: Vitamin D supplementation has been found to reduce the size of uterine fibroids in one animal study. While this was observed in animal studies, the findings suggest vitamin D could be a non-surgical approach to managing fibroids. Notably, African American women, who are 2-3 times more likely to experience fibroids than white women, often have lower vitamin D levels, which well be a contributing factor.

How to Optimise Your Vitamin D Levels

  • Sun Exposure: One of the best ways to improve vitamin D status is through sun exposure. Aim for 15-20 minutes of sun exposure daily, though this can vary based on the time of year and weather conditions. Note that sunscreen with SPF blocks almost 98% of UVB rays, making vitamin D synthesis nearly impossible. A UV index of about 4 or greater is necessary to produce vitamin D. Check your local UV index at

  • Vitamin D-Rich Foods: Some foods contain small amounts of vitamin D, including oily fish (salmon, mackerel, sardines), eggs, and dairy. However, for those with suboptimal levels, supplementing with vitamin D3 can be beneficial, especially if therapeutic levels are needed.

  • Supplementation: In my clinical practice, I often recommend a spray form of vitamin D3/K2, typically between 1,000 IU and 4,000 IU daily as a maintenance dose once optimal serum levels are achieved. I prefer liquid/spray supplements because they allow for dosage adjustments. Brands like BetterYou are reliable, and you can use my discount code HAYLEYDOWNNUTRITION for 10% off. This handy calculator can help estimate your recommended vitamin D intake to reach your target serum level. It’s advisable to recheck your vitamin D levels every three months after starting supplementation.

  • Vitamin D2 vs. D3: There are two types of vitamin D supplements: ergocalciferol (D2) and cholecalciferol (D3). Our bodies naturally produce D3, which is more efficiently utilized than D2. Unfortunately, most vitamin D-fortified foods and supplements contain D2, which is not as well absorbed. To maximize benefits, supplementing with D3 is generally considered superior.

DISCLAIMER: It is not recommended to supplement with high amounts of vitamin D without medical guidance, as it is possible to reach toxic levels. Only take high doses under the supervision of a qualified health practitioner or GP who knows your full health history and has tested your serum levels.

Vitamin D is a vital nutrient with huge benefits to female health, from hormonal balance to reproductive health. If you're experiencing symptoms like fatigue, mood swings, irregular periods, or skin issues, it may be worth considering your vitamin D levels. Testing and appropriate supplementation can make a significant difference in your overall wellbeing.

Key Points Summary:

·       Vitamin D is an essential hormone produced by the skin when exposed to sunlight; crucial for bone health, immune function, cardiovascular health, skin health, mental wellbeing, menstrual regulation, and fertility.

·       Testing and Supplementation: Testing vitamin D levels is recommended before supplementing. Optimal levels are between 100-150 nmol/l (even though the NHS only recommend you to be higher than 50 nmol/l).

·       Vitamin D and Female Health: Low levels are linked to PCOS, irregular menstrual cycles, infertility, PMS, pregnancy complications, period cramps, and fibroids.

·       Optimising Vitamin D:

o   Sun Exposure: Aim for 15-20 minutes daily without sunscreen.

o   Diet: Include vitamin D-rich foods like oily fish, eggs, and dairy.

o   Supplementation: Use vitamin D3/K2 supplements, preferably in liquid/spray form. Consult with a health professional before taking high doses.

Interested in learning more?

Are you curious about how optimising your vitamin D levels can improve your health? Book a free discovery call with me today to chat further and see how I can help you improve your hormonal health. Click here to schedule your appointment!

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