Why Does Hair Turn White as We Age?

White hair. Gray hair. It's a classic sign that we're getting older... but old age is not the only reason our hair loses its color. From vitamin B12 deficiencies to rare conditions like Waardenburg syndrome, gray hair is more complex than it seems. To fully understand this transformation, we need to review how our hair gets its color in the first place.

Are some gray hairs already popping up on your head? I think I was under ten when my first one appeared, but this last year has been a real explosion. A little older, a little crazier... it makes sense. Yet there is a scientific reason behind such a radical change. A mechanism that alters the "normal" functioning of hair, giving way to a white, gray, or "silver" variant. If you want to know why hair turns white as we age or under extreme stress, you first need to learn what gives it its original color.

The Science of Hair Color

The key is melanin, a series of natural pigments present in a surprising number of organisms. Melanin is produced from two amino acids, phenylalanine and tyrosine (hydroxylation of phenylalanine), thanks to a group of special cells called melanocytes, through the process known as melanogenesis. Melanocytes are throughout the human body, and their melanin is responsible for the color of our skin, eyes, and hair. In the case of hair, melanocytes are located in the bulbs of hair follicles.

The type of melanin defines the available colors: eumelanin, which favors black and dark browns, and pheomelanin, which leans toward reddish tones and various levels of yellow. The combination of melanocytes sets the color of our hair, and in some cases there is an important genetic influence. Once the melanin "formula" is created, its granules are transferred to nearby keratinocytes, responsible for producing keratin, the raw material of hair. The keratinocyte dies but retains the melanin, thereby "printing" the color. As the amount of melanin decreases, hair becomes grayer, while perfect white symbolizes a total absence of melanin.

Why Does Hair Turn White with Age?

The top reason is old age. As the years pass, the number of inactive melanocytes increases, and melanin production decreases until reaching its absolute minimum. Why? A study from Harvard dating back to early 2005 suggests that a failure in melanocyte stem cells is the cause. In 2009, another European study added that follicles produce very small amounts of hydrogen peroxide (the classic "hydrogen peroxide"). Now, it is supposed that this peroxide is neutralized by the enzyme called catalase, but our aging also reduces its production. The peroxide accumulates, blocking the creation of melanin.

Add to this genetic defects, abnormal hormonal production linked to stress spikes, poor distribution of melanin throughout the body, and even climatic factors (pollution, toxins, and local chemicals). The link between white hair and stress has been of particular interest to scientists. In 2011, biochemist Robert Lefkowitz (Nobel Prize in Chemistry 2012) and his team discovered a mechanism that could explain why stress turns hair white.

Stress releases neurotransmitters associated with the "fight-or-flight response." In normal situations this is good and lasts a short time, but if it extends too long... it begins to damage DNA. Lefkowitz's group showed that this damage accelerates aging and tumor growth, increases the risk of miscarriages and psychiatric conditions... and our hair ends up white. The combination and intensity of everything we've mentioned here define the speed of the transformation. In other words: if we're too crazy, the white hair will sprout.