
Vitamin D, known as the "sunshine vitamin," is a fat-soluble nutrient that plays a critical role in maintaining overall health. Yet, many people don’t get enough of this vital nutrient. In the UK, shorter daylight hours and weaker sunlight during autumn and winter mean that the government advises everyone to consider a daily vitamin D supplement during these months.
In this article, we’ll cover what vitamin D is, its essential functions, how to ensure you’re getting enough, and the health risks of deficiency.
What Is Vitamin D?
Vitamin D is produced when your skin is exposed to sunlight, and it's found in certain foods and supplements. Uniquely, vitamin D acts more like a hormone, influencing processes throughout the body, from bone health to immune support.
There are two main forms of vitamin D:
Vitamin D2 (Ergocalciferol):Â Found in plant-based foods like mushrooms.
Vitamin D3 (Cholecalciferol):Â Found in animal-based foods and produced by your skin when exposed to sunlight. Vitamin D3 is more effective at raising blood levels of vitamin D than D2.
Don't forget K2!
Vitamin K2 works with vitamin D3 by ensuring calcium is properly absorbed and utilised. K2 is also fat-soluble, found in certain animal-based and fermented foods, and is available as a food supplement.
Why Is Vitamin D Important?
Bone Health
Vitamin D helps the body absorb calcium, a mineral essential for bone formation and strength. Without enough vitamin D, bones can become thin, brittle, or misshapen, leading to osteoporosis in adults and rickets in children.
Immune System Support
Vitamin D plays a crucial role in supporting immune health, helping to fight infections and reducing the risk of chronic diseases. Low levels of vitamin D are associated with higher risks of respiratory infections and autoimmune conditions.
Mood and Mental Health
Research suggests that vitamin D may influence mood regulation. Low levels have been linked to an increased risk of depression and seasonal affective disorder (SAD), which often occurs in winter when sunlight is scarce.
Muscle Function
Vitamin D is key for muscle health, helping to maintain muscle strength and function. Adequate levels can reduce the risk of falls and fractures, especially in older adults.
How to Get Enough Vitamin D
Sunlight Exposure
The most natural way to get vitamin D is through exposure to sunlight. Spending about 10-30 minutes in the sun a few times a week can help most people produce enough vitamin D. However, factors like skin tone, age, location, and sunscreen use can affect how much vitamin D your body makes.
Diet

Few foods naturally contain vitamin D, but some are fortified with it. Here are some sources:
Fatty Fish:Â Salmon, mackerel, and sardines are excellent sources of vitamin D3.
Egg Yolks:Â Contain small amounts of vitamin D.
Fortified Foods:Â Many dairy products and cereals are fortified with vitamin D.
Mushrooms:Â Some mushrooms exposed to sunlight or UV light contain vitamin D2.
Supplements
If you’re at risk of deficiency or can’t get enough vitamin D from sunlight and food, supplements are a convenient option. Vitamin D3 supplements are usually recommended as they are more effective at raising vitamin D levels. You can shop for supplements here.
Who Is at Risk of Vitamin D Deficiency?
People with Limited Sun Exposure
Those who spend most of their time indoors (how many of us make the effort to leave the office and get out in the sunlight for 30 minutes a day in the spring and summer?). Wearing clothing that covers most of your skin reduces your absorption.
Older Adults
As people age, their skin becomes less efficient at producing vitamin D from sunlight.
People with Darker Skin
Higher levels of melanin reduce the skin’s ability to produce vitamin D from sunlight.
People with Certain Health Conditions
Conditions like Crohn’s disease, celiac disease, and kidney or liver disorders can affect vitamin D absorption.
The Risks of Vitamin D Deficiency
Vitamin D deficiency can lead to several health problems, including:
Bone Disorders
Rickets in children and osteomalacia in adults, both of which involve softening and weakening of the bones.
Increased Risk of Chronic Diseases
Deficiency has been linked to higher risks of heart disease, diabetes, and multiple sclerosis.
Weakened Immune Function
Low levels of vitamin D can impair the immune system, making you more susceptible to infections.
Fatigue
Vitamin D is involved in the production primary energy carrier in your cells, known as ATP. Without adequate vitamin D, your body may struggle to produce enough ATP, leading to persistent fatigue.
Low Mood
Vitamin D influences the production of serotonin, a neurotransmitter often referred to as the "feel-good" chemical, which plays a key role in mood stabilisation.
Conclusion
Vitamin D is essential for maintaining bone health, supporting the immune system, and promoting overall well-being. While sunlight is the best natural source of vitamin D, it’s important to balance sun exposure with skin protection. Incorporating vitamin D-rich foods into your diet, and considering supplements if needed, can help ensure you get enough of this vital nutrient. If you’re concerned about your vitamin D levels, you can ask your GP for a blood test or you can order a private one here.
This table will help you evaluate your results and let you know if you need some more in your diet or may need supplements:
Vitamin D level | Amount in Blood (ng/ml) | Amount in Blood (nmol/l) |
Severe Deficiency | <7 | <17.5 |
Deficient | <20 | <50 |
Insufficient | 20-29 | 50-75 |
Sufficient | 30 + | 75+ |
Ringe, J.D. and Kipshoven, C., (2012) 'Vitamin D-insufficiency'. DematoEndocrinology, 4(1): 72-80.
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