Human Migrations in the Past Gave Rise To Vitamin D Deficiencies in the Present

According to a new study, the pattern of human migration from the last 500 years - moving from places of high sunlight to lower sunlight - impacts contemporary health outcomes in destination countries.

Researchers of a new study published in the journal Oxford Economic Papers suggest that the people's capability for synthesizing vitamin D received from sunlight declines with their skin pigmentation. Furthermore, the lack of vitamin D deficiency causes higher mortality risks from diseases such as cardiovascular disease, type 1 and 2 diabetes, hypertension, and certain types of cancer. Recent studies have also examined the impact of vitamin D deficiency in relation to COVID-19 severity.

Migration and Increased Vitamin D Deficiency Risks

In the new study, researchers focused on groups from high sunlight regions that migrated to low sunlight regions from 1500 AD to the present time. These observed migration patterns resulted in a significant rise in vitamin D deficiency. The study inquired on the aggregate health consequences of such actions over extended periods of time, from a historical context.

Researchers devised a method for calculating the risk of vitamin D deficiency across a given population. They then used this metric to track the difference in sunlight intensity in the population's two locations: their ancestral residence and their current residence. Recording the difference in sunlight levels in these locations, researchers could estimate the potential risks of developing disorders due to vitamin D deficiency. Also, researchers examined whether it also affected life expectancy.

Disregarding other factors, researchers concluded that greater risks of vitamin D deficiency negatively affect life expectancy.

The study also mentions the generally accepted idea that too much exposure to sunlight can also cause harm. Awareness of these harmful effects leads people to prevent them by using sunscreen and limiting their time outdoors. Also, compared to their ancestors thousands of years ago, people nowadays spend significantly less time outside, which leads to less exposure to sunlight. In return, premature death related to excessive sun exposure has also decreased since then.

Skin Pigmentation: An Indicator of Ancestral Locations

Researchers clarified that shorter times under the sunlight increases the risk of developing vitamin D deficiency. This is particularly true for people with higher skin pigmentations - generally descendants of people from high sunlight regions.

Therefore, an imbalance between skin pigmentation and sunlight levels, created by human migration over the ages, can help explain global health differences observed in the present. Places with lower sunlight and have received immigration from people in higher sunlight also have lower life expectancies compared to either place that has experienced no migration incidents.

"This research is important because it is the first research to document a link between an increased risk of vitamin D deficiency and differences in life expectancy across countries and regions," explains Dr. Thomas Barnebeck Andersen, one of the authors of the study, in a press release from Oxford University Press. He added that the study highlights the additional benefits of vitamin D supplements, especially during the low sunlight seasons of autumn and winter.