Why you need to take a vitamin D supplement in winter

There’s a lot to like about winter. I LOVE log fires, nourishing winter foods, getting wrapped up and going out for a brisk walk, then returning to a delicious hot drink. I won’t list all the things I don’t like about winter, but right up there must be catching a cold, and feeling a bit blue come January.

In this blog post, I’m going to explain why so much of that is down to your levels of vitamin D, which is sometimes called the ‘sunshine vitamin’ (and hence a lack of it in winter). I’ll explain why vitamin D is important and how you can tell if you might be a bit low, who should get tested, where to have it done and how to support your levels naturally through food (although food sources alone will NEVER give you enough vitamin D in winter).

Why you really, really need the D!

Vitamin D is a superstar vitamin. More correctly, it’s actually a hormone. Vitamin D receptors can be found all over the body, highlighting the multiple roles it has for health. It's needed for:

• Supporting calcium absorption in the gut and helping it get into bones

• Controlling cell growth and inhibiting abnormal cell growth (cancer)

• Supporting the immune system and preventing infections

• Supporting brain health and cognitive function

• Helping regulate insulin levels and control blood sugars

• Strengthening muscles

• Reducing inflammation

Vitamin D deficiency has been associated with an increased risk of many conditions including obesity, cancer, heart disease, diabetes, depression, dementia, osteoporosis and autoimmune diseases.

Why is vitamin D important for women in midlife?

Vitamin D is needed to support bone health and reduce the risk of osteoporosis. Oestrogen is an important regulator of bone metabolism, which means it promotes the growth of new bone and slows down the breakdown of tissues in bones. Declining levels of oestrogen at menopause is therefore associated with decreased bone density and increased risk of fracture and osteoporosis. Low vitamin D has been associated with hot flushes and night sweats, and with mood disorders such as anxiety and depression, all common symptoms of perimenopause.

What can contribute to low vitamin D levels?

• We make most of our vitamin D via the action of sun exposure on our skin. This can be a bit tricky in the winter months in the UK, where we see less sunlight, cover our skin with more clothing and spend less time outdoors.

• Sun cream. Your body makes vitamin D after contact with the sun’s UV rays but, as we’re a nation of sun cream fanatics (and this covers the skin, blocking the rays of sunlight from getting through), you might not be getting enough straight-up sun.

• Age. Among other things that go a bit wrong as you get older, your body is less good at turning the rays from the sun into vitamin D. Specifically, the kidneys are less good with age at turning it to the active form of calcitriol.

• Kidney or liver disease of any kind also means vitamin D is not converted to the active form.

• Tummy troubles. Problems with the digestive system can mean the digestive tract doesn't absorb the vitamin D as well.

• Obesity (technically that’s a BMI or body mass index of 30+) has the fat cells in your body hoover up the vitamin D. So then it’s stored – unusable – in your fat cells and is not whizzing around your body in your blood.

• Lack of sleep. Just as you need sunlight to make vitamin D, you need sleep to actually use it.

• Stress. The presence of the stress hormone cortisol reduces the uptake of vitamin D by special vitamin D receptors. It literally sits there, in the body, without being able to be used. What a waste!

• Your skin colour. The darker your skin, the less vitamin D you will make. This is due to the higher levels of melanin in your skin that protect against UV light. By blocking the sun’s rays, it also curbs the body’s ability to make the pre-cursor to the active vitamin D.

• Nightshift workers and anyone else who doesn’t spend much time in the sunlight, including children wearing sun cream all the time and babies. Quite simply, you need the sun on your skin.

10 signs you might be deficient in vitamin D:

1. Depression or anxiety (including mood changes or irritability)

2. Bone softening (low bone density), fractures

3. Feeling tired all the time / decreased performance

4. Muscle cramps and weakness

5. Joint pain (especially back and knees)

6. Difficulty regulating your blood sugar levels / post lunch energy crash

7. Low immunity

8. Slow wound healing

9. Low calcium levels in the blood

10. Unexplained weight gain

Symptoms like these are commonly overlooked because they don’t feel life threatening, and they’re often dismissed as normal, everyday aches and pains you have to deal with. But you don’t have to put up with these symptoms of ill health!

Who should get tested?

If any of the above resonates with you, you should definitely get tested. The test is the 25-hydroxy vitamin D test (also known as the 25-OH vitamin D test or Calcidiol 25-hydroxycholecalciferol test). It’s the most accurate way to measure how much vitamin D is in your body.

You might find your GP will do this for you but if your doctor won’t test, consider getting it checked out privately. It’s a finger prick test you can do it easily at home, then get your results emailed to you with guidance on how much to supplement safely. If you do take a test and you’re low, you’ll need to supplement and then re-test to see the impact it’s had.

My top tips for getting enough vitamin D:

1. Try to get outside for 30 minutes a day and expose your skin to the sun without suncream (which blocks vitamin D synthesis through the skin). In the summer months, go out at the start or end of the day to reduce the risk of sunburn.

2. Consume vitamin D-rich foods such as oily fish (salmon, mackerel, sardines, herrings), red meat, liver and egg yolks.

3. Check your vitamin D levels with your GP or a simple home fingerprick blood test.

4. Consider taking a vitamin D supplement, especially through the autumn and winter months if living in the northern hemisphere.

Remember that vitamins and minerals often work best alongside other vitamins and minerals and supplementing one nutrient might increase your need for another. As the body stores vitamin D, it is also possible to suffer from toxicity if you’re supplementing at very high doses. This is why it’s important to consult your GP or work with a nutritional therapist for a personalised dosage that’s right for you.