How to correct vitamin D deficiency in winter safely

Title: How to correct vitamin D deficiency in winter safely Author: Wang Lu, Registered Dietitian Reviewer: Ruan Guangfeng, Deputy Director of the Information Exchange Center for Food and Health, and Member of the Health Communication Branch of the Chinese Preventive Medicine Association Planning: Yang Yaping Editor: Yang Yaping Proofreading: Xu Lai, Zhang Linlin Source: Popular Science China WeChat Official Account Introduction: Winter increases vitamin D deficiency risk, leading to health issues. Tips include food, sunlight, and supplements for adequate intake.

Recently, the claim that "eating sun-dried mushrooms can replenish vitamin D" has gained significant popularity online. It may sound like a rumor, but surprisingly, this time it's true! Mushrooms have cell walls that contain a large amount of ergosterol, which can be converted into vitamin D2 under ultraviolet (UV) light. Numerous studies have found that exposing mushrooms to sunlight, whether natural or artificial, can significantly increase their vitamin D2 content, with post-exposure levels being dozens to hundreds of times higher than before exposure, thereby indirectly promoting bone health. This phenomenon has been observed across various mushroom types.

As the cold winter months approach, we should indeed focus more on vitamin D supplementation. This is not only due to the characteristics of winter weather, which can easily lead to vitamin D deficiency—research shows that the average level of serum 25-hydroxyvitamin D in winter is about 65% to 80% of that in summer—but also because the consequences of vitamin D deficiency in winter can be more severe than in other seasons!

A lack of vitamin D may lead to osteoporosis and increased risk of fractures. A deficiency in vitamin D directly impacts the absorption and utilization of calcium, potentially leading to osteoporosis in adults and osteomalacia in adolescents. Research indicates that insufficient vitamin D increases the risk of fragile bones, with this risk being more pronounced in winter due to seasonal factors. Another study suggested that low vitamin D levels not only elevate the risk of fractures but also significantly prolong healing time after an injury.

In winter, with low temperatures, heavy snow, and strong winds, roads can become slippery. Under such conditions, populations at risk of osteoporosis due to vitamin D deficiency are particularly vulnerable, and a fall may easily result in fractures. If an elderly person suffers a hip fracture as a result, the situation becomes even more dangerous. Hip fractures are often termed "the last fracture of a lifetime." Post-hip fracture, elderly individuals may face extended bed rest, a loss of mobility, and an increased risk of serious complications, which can prove fatal in severe cases.

Vitamin D is commonly insufficiently consumed among our residents. Dietary guidelines recommend that adults in our country should consume 400 International Units (10 micrograms) of vitamin D daily, and individuals over 65 should consume 600 International Units (15 micrograms) daily. However, in reality, it is difficult for residents to meet this vitamin D intake standard.

The results of a national survey conducted in 2017-2018 revealed that the rate of vitamin D "deficiency" stands at approximately one-third, with an even higher rate of "insufficiency." The deficiency rate is markedly higher in northern regions compared to the south, with women and urban residents experiencing a more significant shortfall. Another study tracking vitamin D levels in children and adolescents indicated that the combined rate of "deficiency" and "insufficiency" exceeded 60%, with a somewhat improved situation for southern adolescents and children compared to their northern counterparts.

When supplementing vitamins during winter, three practical tips should be remembered. First, consume more vitamin D-rich foods, such as fatty sea fish (like salmon, sardines, and tuna), animal liver, and egg yolks. However, the intake of these foods among residents is generally not high, and the vitamin D content in food is also limited, making it crucial to rely on synthesis from ultraviolet ray exposure as a primary vitamin D source.

Second, sunbathing should be prioritized. During winter, effective sun exposure can be achieved between 11:00 AM and 2:00 PM when the sun's intensity is greatest. Exposing one's limbs to sunlight is preferable to exposing the face due to the larger skin area on the limbs, which allows for more vitamin D synthesis. Additionally, individuals should avoid being indoors, sitting behind glass, wearing clothing that covers the skin, or applying sunscreen, as these actions can hinder UVB exposure and significantly lessen vitamin D synthesis. A longer duration of sun exposure, around 30-40 minutes, is advisable in winter compared to summer.

Third, consider increasing vitamin D supplementation. It is recommended to actively take vitamin D supplements during winter, favoring vitamin D3. Attention should be paid to appropriate dosages, and it is best to consult a healthcare professional before starting supplementation. Additionally, a serum vitamin D level test after 3 to 6 months of supplementation can help assess effectiveness. Foods fortified with vitamin D, such as fortified milk and bread, can also contribute to intake.

In summary, vitamin D is a crucial nutrient that is frequently lacking in the diet. During winter, prioritizing its intake is essential, particularly for elderly individuals and children in the household.

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