I'm a doctor and here's how to maintain healthy Vitamin D levels this winter and why it's so important
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Over 80% of the body’s vitamin D comes from the skin following exposure to sunlight, so with the darker days coming, we need to take action now. Levels in the body drop by half every six weeks, meaning that by December, unless other precautions are made, most of us living in northern climates will have unhealthy levels of this vital nutrient, which can lead to significant problems for the body and mind.
Most of us are familiar with the importance of vitamin D and bone health. Rickets, highlighted by the book "Heidi", is a disabling deformity of the bones caused by inadequate vitamin D levels in children, which is still surprisingly common in many communities. In the UK, cases were prevalent in the 80s, when children from countries with sunny climates such as India arrived.
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Hide AdAs a poignant first-hand experience, at that time, our Indian landlord introducing his son to us - a house of first year medical students. He was in a wheelchair disabled by a spine curvature caused by rickets. Unfortunately, even with treatment, which started too late, he never walked again.
Deficiencies are not just confined to Asian communities. In 2014, a 14-year-old girl from the Isle of Wight tripped on the pavement and broke both legs. From birth, her parents had smothered her with sun block and were fanatical about covering her skin in the sun. In adults, vitamin D deficiency contributes to osteoporosis particularly common in nursing-home residents and the homebound elderly population.


What is less known about vitamin D, is the wide range of other medical conditions which are caused or made worse by not having enough - here are some key examples:
Reduced immunity: This causes more frequent Infections including urinary tract infections and colds. Both the Zoe app and UK Biobank study reported that people taking vitamin D even had less severe Covid. Fortunately, the World's largest nutritional intervention for people suffering from COVID, called the phyto-v study, gave a capsule containing vitamin D and five blends of Lactobacillus probiotics and found a significant improvement in severity of both early infection and long covid symptoms.
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Hide AdIncreased inflammation: Vitamin D reduces the production of anti-inflammatory cytokines which can cause excess inflammation, called the cytokine storm, that causes the severe respiratory distress associated with viral and bacterial infections. Research has found that low vitamin D increases joint inflammation and hence arthritis.
Autoimmune diseases: Links with multiple sclerosis (MS) and rheumatoid arthritis, asthma and even food allergies have been reported.
Heart disease: Chronic deficiency can reduce the efficiency of the heart muscle and increase the blood pressure, both resulting in a higher risk of heart attacks.
Low mood, depression and dementia: This can be all year particularly highlighted by a condition called Seasonal Affective Disorder (SAD). Over time, this leads to premature cognitive impairment causing poor memory, dementia and other neurodegenerative diseases.
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Hide AdDiabetes and metabolic Syndrome: Vitamin D is thought to play a role in insulin sensitivity contributing to an increased risk of type 2 diabetes, obesity, high blood pressure and cholesterol levels, a serious combination called called metabolic syndrome.
Muscle Weakness: Low vitamin D levels can contribute to poor recovery after exercise and muscle weakness, due to its role in calcium and phosphorus balance. In severe cases, this can lead to chronic fatigue syndrome and fibromyalgia.
Cancer: Deficiency has been linked to a higher risk of many cancers including bowel, prostate, breast and ironically melanoma. Vitamin D may help regulate cell growth and prevent the development of malignant cells. Deficiency is also associated with faster progression and higher relapse rates after initial treatments. Recently completed research showed that the capsule mentioned above containing probiotics and Vitamin D slowed prostate cancer progression.
Complications in Pregnancy: This includes pre-eclampsia, a condition characterised by high blood pressure and potential organ damage, as well as gestational diabetes.
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Hide AdHow to maintain Vitamin D levels this winter
Vitamin D is present in small amounts in nuts, egg yolks, oily fish, fresh vegetables and some grains, as well as meat from grass-fed animals and free-range chicken and game. Mushrooms, like animal skin, are able to generate it and some product expose mushrooms to UV light before sale, to boost vitamin D levels. Fortified vitamin D is sometimes added to breakfast cereals, breads and soy products. More recent research has found an interaction between gut bacteria and vitamin D absorption, so people for whom this is a problem should also consider strategies to improve gut health.
Even in the spring and autumn, try to sit in the garden with your shirt lifted up, exposing as much skin as possible. Only 10–15 minutes of exposure to outdoor sun can start the production of vitamin D. Investing in a winter holiday in the sun, budget allowing, is a sensible approach to top up levels but precautions need to be taken to avoid burning. After being exposed to sun, try to eat lots of phytochemical-rich foods, avoiding smoking and applying the correct olive oil-based after-sun creams to reduce oxidative stress in the skin cells and aid repair of sun-damaged DNA.
Vitamin D supplements are a very sensible dietary aid during the darker months but many of them have little impact on blood levels, if the taker has poor gut health. The best supplements therefore combine probiotic bacteria with vitamin D which has been shown to improve absorption. Similarly, vitamin D also acts as a prebiotic which encourages "friendly" gut bacteria to thrive, so they are an ideal combination.
In conclusion, due to the lack of sunlight, we are all likely to develop Vitamin D deficiency over the winter in the UK and other Northern Hemisphere countries. Deficiency of this essential vitamin is associated with a considerable number of medical conditions and chronic degenerative diseases so we need to take a proactive approach to maintain healthy levels.
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