Redheads are better at synthesizing vitamin D

Red hair is thought to be a natural part of human evolution in the northern regions, where there is less sunshine. According to a Czech study that is published in Experimental Dermatology, redheads produce more vitamin D than people with other hair colors. Also, redhaired women live longer than women with other hair colors, according to a Swedish study that is published in PLoS One.

Most cells in the body have receptors for vitamin D, a nutrient that is essential for our immune function, mood, bones, and health in general. The body’s vitamin D synthesis is rather complicated and depends on factors like sun exposure, skin color, and genes. The first step in the process is when we synthesize a vitamin D precursor called cholecalciferol in a process where UV rays from sunlight convert cholesterol in our skin. For this to take place, the sun must be sufficiently powerful. We are only able to make vitamin D during the summer period and at a wavelength in the range of 280-320 nm.
Cholecalciferol is then converted into 25(OH)D3 in the liver and stored for later use. This is the type of vitamin D that is measured in blood tests. When the body needs vitamin D to fuel its many functions, it converts 25(OH)D into to the active steroid form of the vitamin called 1,25dihydroxtyvitamin D3. This process takes place in the kidneys, the immune cells, and various other places.

Light-skinned people make more vitamin D than dark-skinned individuals do

In people with dark skin color, the vitamin D synthesis takes place at a rate that is 6-10 times slower than in light-skinned people. Dark-skinned individuals have their ethnic roots in Africa, where one can easily make sufficient vitamin D from the strong sun and where the dark skin protects against sunburns. Thousands of years ago, some dark-skinned people started migrating to the northern parts of the globe. Evolution changed their skin and made it lighter to help it adapt to the scarce sun. However, there are great genetic variations because redheads appear to have a better ability to synthesize and utilize vitamin D.

Redheads and their genetic advantage

Only 1-2 percent of people in the world have red hair. In Ireland, 10 percent are redheads, and in Edinburgh (Scotland), the number is 13 percent. A higher percentage of people in these parts of the world have the recessive red hair gene called MC1R. This gene causes people to produce more pheomelanin, a type of pigment that is also linked to freckles and pale skin that doesn’t tan easily.
In 2020, a Czech scientist named Jaroslav Flegr in collaboration with his research colleagues published an article in Experimental Dermatology about how red hair has originated in response to sun-deprived climates in the north. The scientists also analyzed blood samples from 73 redheads and 130 people who did not have red hair and measured levels of vitamin D and folic acid (vitamin B9). They found that redheads had higher concentrations of 25(OH)D3 and approximately the same levels of folic acid in their blood compared with the other participants. The scientists also used two different methods to measure how red the hair was. They found that having redder hair was determined by blood levels of vitamin D. Quite as expected, the researchers found that blood levels of vitamin D in non-redheads was linked to their skin tone and how much sun they got exposed to, while this correlation was not seen in redheads. The study suggests that the blood levels of vitamin D in redheads depend more on genetic and physiological factors and less on UV exposure.

Women’s red hair is associated with longer lifespan

Apparently, the MC1R gene and the more effective synthesis and utilization of vitamin D in redheads is also linked to their general health and lifespan. This was seen in a Swedish study from Karolinska Institutet in Stockholm. Here, scientists compared 12,000 women with red hair and freckles with 12,000 women who had other hair colors and skin types. The red-haired women had eight percent lower mortality and generally lived longer than other women. The scientists adjusted for confounding factors such as smoking, income level, education. Still, redheads have a higher mortality rate linked to skin cancer and should therefore be careful not to get sunburns. Everyone should strive to have optimal levels of vitamin D in their blood, regardless of hair color or skin type.

References:

Iver Mysterud. Rødhåret – en velsignelse i nordlige strøk? Helsemagasinet Vitenskap og Fornuft. Nr. 5, 2023

Flegr J, Sykorova K et al. Increased 25 (OH) D3 level in read haired people: Could read headedness be an Adaptation to temporate climate? Experimental Dermatology. 2020.

Pelle G Lindqvist et al. Women with fair phenotypes seem to confer a survival advantage in a low UV miljø. A nested matched case control study. PLOS ONE 2020

Nymann C. Rødhårede er genetisk overlegne. Illustreret Videnskab 8, 2021

Helene Sandström. Den optimala D-vitamindosen i vinter? Det beror på dina genar. Nordic Nutrition Council. Sep. 3 2020

Morten K B Bogh. Vitamin D production after UVB: aspects of UV related and personal factors. Scand J Clin Lab Invest Suppl. 2012