Dr Mattias Larsson. Photo courtesy of Family Medical Practice

by Dr Mattias Larsson*

Vitamin D deficiency has emerged as a significant concern, linked to several diseases including osteoporosis, cancer, autoimmune disorders, cardiovascular diseases, type II diabetes, increased overall mortality and even stillbirth. In Việt Nam, the prevalence of Vitamin D deficiency (defined as serum 25(OH)D levels below 20 ng/mL), is alarmingly high, affecting 30 per cent of women and 16 per cent of men.  Women under 30 living in urban areas are most affected.  One of the contributing factors may be limited exposure to sunlight due to cultural practices. Despite the abundance of sunlight in Việt Nam, individuals often seek shade and wear protective clothing to avoid sun exposure.  The contraceptive pill, in contrast, appears to protect against the deficiency.

Vitamin D deficiency is alarmingly high in Việt Nam. Photo courtesy of Family Medical Practice

The main symptoms of Việt Nam D deficiency are often quite vague or general but can come in different combinations, including fatigue, sleeping problems, bone pain or ache, depression or sadness, hair loss, muscle weakness, loss of appetite, decreased immune capacity with frequent infections.

Around 90 per cent of vitamin D synthesis occurs in the skin through sunlight exposure. Only a minor portion of vitamin D is obtained through food including fatty fish, seafood, mushrooms, egg yolks, spinach, orange, and bananas. This suggests that tropical regions with ample sunlight might have a lower risk of deficiency. However, recent studies from Hong Kong, Malaysia, and Singapore challenge this assumption, revealing prevalence rates similarly found in Western populations with less sunlight, especially during winter.

There is also new research indicating that the foetus is affected by D-vitamin deficiency. Two Swedish studies reported a two to four times increased risk of hypoxia (lack of oxygen) in newborns at low plasma vitamin D levels, one also showed an increased risk of stillbirth.

A study in Finland and Sweden from 1994 to 2021 found that low vitamin D levels were common before 2003. In 2003, vitamin D fortification in certain food products was introduced and doubled in 2010. The incidence of stillbirths decreased significantly after these measures were implemented. Finland saw a decrease from 4.1 to 2.8 stillbirths per 1,000 pregnancies, the lowest rate in Europe. Sweden adopted a similar approach in 2018 with similar results. The study's large sample size (4.4 million births), dose-dependent effect, and timing support the idea that vitamin D deficiency is a stillbirth risk factor. Potential effects of vitamin D deficiency on the foetus include impaired nutrition transfer across the placenta, cardiac weakness and increased risk of infections. In Việt Nam, stillbirths occur in about 10 per 1,000 of pregnancies according to UNICEF.

In Việt Nam the sun is an abundant source of Vitamin D! However, many try to avoid the sun as it is socially desirable to be pale skinned. This may be related to the socioeconomic development level where dark skin is associated with rural agricultural outdoor work with high levels of sun exposure and pale to more socially desirable urban indoor office work. In high income countries, where a small proportion are agricultural workers and the majority white collar with mainly indoor work, tanned skin is socially desirable as it is connected to higher socioeconomic standards with more leisure time.

There are of course also risk factors of over exposure to sunshine for example skin cancer as malignant melanoma. The sun exposure to maintain healthy levels of vitamin D is however limited, about 15–30 minutes around midday three to four times a week is enough, people with darker skin may need more. This is also the recommended upper limit for sun exposure to prevent skin cancer. Protective measures as sunscreen can be used as it only marginally reduces the Vitamin D uptake but protects well against skin cancer.

In conclusion, addressing vitamin D deficiency requires a multi-faceted approach. Encouraging outdoor activities with sun protection can be beneficial, even more when combined with physical activity.  In case it is difficult to acquire the natural source of Vitamin D dietary supplement could be recommended to decrease risk for multiple diseases such as osteoporosis, cancer, diabetes as well as indicated by the research, to reduce risk for stillbirth among pregnant women. Family Medical Practice

*Dr Mattias Larsson is a paediatric doctor at Family Medical Practice and associate professor at Karolinska Institutet and has a long experience in research on infectious diseases. He has worked with the Oxford University Clinical Research Unit and the Ministry of Health of Vietnam. He is fluent in English, Swedish, Vietnamese, German and some Spanish.

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