Francesca Lyon, lead nutritionist at FUTURE WOMAN, explores whether low vitamin D is a potential cause of your winter weight gain, low mood and missing libido.
Are you struggling with the winter blues? Feeling low energy, low libido, weight gain, hungrier all the time and feeling like your mood is lower than it normally is? It might not be the winter blues after all… it might be your vitamin D levels.
56-60% of adults in the UK have low vitamin D levels, which is concerning as vitamin D is connected to our thyroid health, hormone production, metabolic health, blood sugar balance and mood, therefore in the winter months it is common for people to feel the impact of low levels and not realise there is an easy fix!
So what is vitamin D?
Vitamin D is a fat-soluble vitamin that functions more like a hormone in the body. We obtain it through three main sources: sunlight exposure (when ultraviolet rays interact with our skin), certain foods like fatty fish and egg yolks, and of course dietary supplements.
This essential nutrient plays a critical role in hormone health by supporting reproductive hormone production and thyroid function. Specifically, vitamin D helps regulate insulin sensitivity, supports healthy hormone production, supports ovarian egg and follicle health and assists in balancing oestrogen and progesterone levels, making it a key player in maintaining overall endocrine system balance and metabolic health.
5 hormonal impacts of low vitamin D
Let’s dive into 5 hormonal impacts that result from low levels of vitamin D and how they may be mimicking your symptoms of the winter blues:
1. Low testosterone – Mood changes and low libido
Most women do not think about the benefits of testosterone for their health, we typically only focus on it if it’s very high (hello symptoms like head hair loss and acne) or very low (low libido and energy). But it is vital for our daily energy, mood, bone density, muscle mass and hormone production.
Research shows that vitamin D receptors are present in the ovaries and testosterone-producing tissues, indicating its direct influence on hormone synthesis. Women with optimal levels tend to have more balanced testosterone production, which can help with energy levels, mood regulation, and maintaining lean muscle mass.
Suboptimal vitamin D levels have been associated with decreased testosterone, potentially contributing to symptoms like fatigue, reduced muscle tone, and decreased libido and mood.
Read more about testosterone here.
2. Low progesterone – Poor sleep, anxiety and fertility issues
Low Vitamin D and Egg health:
Vitamin D plays a significant role in female reproductive health and egg quality. Research indicates that sufficient levels can improve progesterone levels, egg maturation, fertilisation rates, and overall reproductive outcomes. Women with optimal levels often demonstrate better ovarian response and improved reproductive function. For example; one paper showed that “Vitamin D supplementation contributed to higher pregnancy and ovulation rates, and lower androgen, LH, FSH and early miscarriage rates in women with PCOS”.
Low Vitamin D and Anxiety:
Adequate vitamin D levels also may enhance progesterone levels. Healthy progesterone levels are linked to better sleep and decreased anxiety. In fact, progesterone can stimulate GABA (our calming and feel good neurotransmitter) allowing us to feel calmer and more relaxed.
Read more about low progesterone.
3. Poor thyroid function – Low mood and hair loss
Vitamin D has a profound connection with thyroid health, particularly in managing autoimmune thyroid conditions as it is so vital in the body’s immune response. It helps modulate the immune system responses and reduce inflammation, which can be critical in preventing and managing thyroid disorders like Hashimoto’s.
Studies have shown that individuals with vitamin D deficiency are more likely to develop thyroid imbalances, and adequate levels may help improve thyroid hormone production and reduce the severity of autoimmune thyroid conditions.
Low thyroid function is linked to head hair loss, weight gain, low mood, feeling cold, poor sleep and fertility issues.
Read more about the symptoms of a dysregulated thyroid.
4. Dysregulated insulin and metabolism – Weight gain
Vitamin D plays a crucial role in insulin sensitivity and metabolic hormone regulation. It helps enhance the body’s response to insulin, potentially reducing the risk of insulin resistance which is linked to symptoms such as weight gain, mood changes, sleep changes, and impacted appetite hormones. This is particularly important for clients in perimenopause and menopause, where risks for insulin resistance increase, and also clients with PCOS where insulin resistance is the leading PCOS type.
Research suggests that adequate vitamin D levels can enhance insulin receptor sensitivity, balance blood sugar levels, promote more efficient glucose uptake by cells, and support overall metabolic health by helping to regulate hormones involved in energy metabolism, resulting in a stable and maintainable weight.
Read more about hormones and weight gain.
5. Dysregulated cortisol – Mood changes, weight gain and low energy
Vitamin D has a significant impact on stress hormone regulation, particularly cortisol production.
Optimal levels can help modulate the body’s stress response by supporting the hypothalamic-pituitary-adrenal (HPA) axis, which is responsible for managing stress reactions. Research shows that lower levels have been associated with increased cortisol production and heightened stress sensitivity. By helping to regulate this hormonal pathway, vitamin D can contribute to better stress management, improved mood stability, and reduced inflammation associated with chronic stress.
Read more about chronic stress and burnout.
I suspect I have low vitamin D levels, should I supplement?
So now you are thinking WOW vitamin D can do it all, should I be taking it, especially because it’s winter? Well it depends. We love to support clients with supplementation but the dose depends on the individual. It is really important to first get your levels tested with your GP before considering supplementation and then the dosage depends on your results, health goals and symptoms.
In general we always recommend vitamin D with K2 so that as your calcium absorption increases, it easily moves from the blood into your bones.
