As winter approaches and daylight fades earlier, many of us experience a noticeable dip in energy levels. This seasonal fatigue can be largely attributed to insufficient vitamin D—often referred to as the “sunshine vitamin.”
In the UK, the lack of sufficient sunlight during winter prevents individuals from producing adequate amounts of this essential nutrient. This is why many are advised to consider vitamin D supplements.
Let’s explore the significance of vitamin D, its sources, and the recommended intake for optimal health.
Why is vitamin D important?
Vitamin D is a fat-soluble vitamin, which means it is absorbed along with dietary fats and stored in the liver and fatty tissues of the body.
It plays a crucial role in calcium absorption from the digestive tract and in regulating calcium and phosphate levels—mineral balance is essential for maintaining healthy bones, teeth, and muscles.
Moreover, vitamin D is vital for bone development and the ongoing renewal of bone tissue. Insufficient vitamin D can lead to conditions like osteomalacia in adults (characterized by soft bones) and rickets in children (which often manifests as bowed legs).
When combined with calcium, vitamin D supplementation is beneficial for maintaining bone mineral density and has been shown to reduce fracture risk in individuals suffering from osteoporosis.
Additionally, various tissues in the body have receptors sensitive to vitamin D, suggesting that it also influences neuromuscular function and helps maintain muscle strength.
Low levels of vitamin D have been linked to an increased risk of several health issues, including cardiovascular diseases like hypertension and heart failure. However, it remains uncertain whether low levels of vitamin D directly cause these conditions or if they merely reflect overall poor health in those with chronic ailments.
While the research is somewhat inconclusive, some studies indicate that vitamin D may enhance immune function. There is evidence to suggest that regularly taking vitamin D can reduce the severity of respiratory infections, such as influenza or COVID-19.
Moreover, inadequate vitamin D levels have been correlated with multiple sclerosis. Some studies also propose a potential role for vitamin D in mood regulation, particularly for individuals suffering from depression or vitamin D deficiency—though more research is necessary to confirm these findings.
Where do we get vitamin D from?
Unlike many other vitamins that we obtain from our diet, vitamin D is primarily synthesized in our skin when exposed to sunlight.
In the UK, approximately 80-90% of our vitamin D requirement comes from sun exposure. During the months of late March to September, sunlight is typically adequate for most individuals to produce their necessary vitamin D naturally.
However, from October to early March, the sun’s strength in the UK is insufficient for the skin to synthesize vitamin D, even on clear days. This is why health experts recommend that everyone consider taking a daily supplement during the winter months to maintain optimal levels, especially since many spend more time indoors.
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Certain foods do provide vitamin D, including oily fish like salmon and sardines, red meat, egg yolks, and fortified cereals. However, only a small portion (approximately 10-20%) of our vitamin D comes from dietary sources.
How much vitamin D should I take?
Adults and children over four years should aim for a daily intake of 10 micrograms (400IU) of vitamin D during the autumn and winter months.
For babies under one, an intake of 8.5-10 micrograms of vitamin D is recommended throughout the year, particularly if they are breastfed or partially breastfed. Infants are born with limited vitamin D levels, primarily transferred from their mothers. While they can produce vitamin D from sunlight, this potential is often minimized due to protective measures against sun exposure, making supplementation advisable.
Since infant formula is fortified with vitamin D, babies consuming less than 500ml of formula per day should receive a supplement.
While a dose of 10 micrograms is sufficient for most, products containing up to 25 micrograms (1,000IU) are considered safe for general use.
Vitamin D exists in two primary forms: D₂ (ergocalciferol) and D₃ (cholecalciferol). While they are both absorbed well in the small intestine, some studies suggest that vitamin D₃ is more effective for raising and maintaining vitamin D levels in the body.
Some individuals may need to take vitamin D supplements all year round. This includes those with darker skin tones, such as those of African, African-Caribbean, or South Asian descent, as their higher levels of melanin can inhibit efficient vitamin D synthesis from sunlight. People who cover their skin for cultural or medical reasons and those who spend long periods indoors or are housebound will also require a supplement due to limited sunlight exposure.
Adults over the age of 65 should also consider taking vitamin D year-round, as the body’s ability to produce and process vitamin D tends to decline with age.
Can you take too much?
It’s crucial to adhere to the recommended dosage of vitamin D, as exceeding this amount may be unnecessary and potentially harmful. Higher doses should be taken only under medical supervision in cases of confirmed deficiency.
Very high intakes (over 100 micrograms daily) sustained over a long period can lead to elevated calcium levels in the body—leading to weakened bones and potential issues with the kidneys and heart. Because vitamin D remains in the body for an extended period (around two months), any symptoms of overdose can linger for several weeks.
While it’s impossible to overdose on vitamin D from sunlight alone, it’s still essential to protect your skin to minimize the risk of sun damage and skin cancer.
During the winter months in the UK, maintaining sufficient vitamin D levels is a straightforward yet effective way to support overall health. With limited sunlight, a daily supplement serves as a reliable means to ensure strong bones and muscles throughout the dark days of the year.
