Spanish medical researchers have determined that the lack of sunshine during the wintertime, and the resulting decrease in vitamin D levels, is the cause for increased influenza and other infections, especially as we age.
The researchers also confirmed findings of other research that have found that vitamin D levels tend to drop as we age.
The researchers, from the University of Cantabria’s Medical School and led by Dr. Victor Manuel Martinez-Taboada, tested three groups of healthy adults: young adults (ages 20-30), middle-aged adults (aged 31-59) and elderly persons (aged 60-86).
The study found that higher levels of blood serum vitamin D (25OHD) were associated with lower viral infection rates, especially during the wintertime. The elderly adults showed the greatest association between vitamin D levels and wintertime viral infection rates.
Vitamin D is known as the sunshine vitamin because it is produced when UVB light hits the skin. It is then processed through the liver to produce the serum 25OHD. Because UVB radiation decreases in the winter, vitamin D levels go down, just as viral infection rates increase.
“There are numerous studies showing the benefits of maintaining adequate vitamin D levels. As more and more research into vitamin D is conducted, we are learning that it is extremely important for human health. Our study is no different, and vitamin D supplements should be considered one of many tools that might help when conventional therapies are not enough,” said Dr. Martinez-Taboada.
The research found that increased viral immunity appears to be related to vitamin D’s ability to increase the expression of a key immune marker called the toll-like receptor-7 (TLR7). This expression increases the ability of macrophages and lymphocytes to counteract viral infections.
Circulating 25OHD levels were determined through ELISA, and they found serum 25OHD levels were decreased with age.
Other toll-receptors were also found to correlate with vitamin D. These included TLR2, TLR4 and TLR5, which also increase immunity against various bacterial infections.
Alvarez-Rodriguez L, Lopez-Hoyos M, Garcia-Unzueta M, Amado JA, Cacho PM, Martinez-Taboada VM. Age and low levels of circulating vitamin D are associated with impaired innate immune function. J Leukoc Biol. 2012 May;91(5):829-38.
Adams C. Healthy Sun: Healing with Sunshine and the Myths About Skin Cancer. Logical Books, 2012.