Many people experience their hair color changing from blonde as a child to a darker shade as they grow older. There are a few key reasons why this happens:
Hair follicles produce less melanin over time
Melanin is the pigment that gives hair its color. Dark hair has more melanin while lighter hair has less melanin. As you age, the pigment-producing cells in your hair follicles called melanocytes become less active and produce less melanin. This causes your hair to become darker.
Babies often have very little melanin in their hair when they are born. Over time, melanin production increases and hair becomes darker. But in childhood, melanin levels are still lower compared to adulthood. This is why it is common for children to be born with light blonde hair that transitions to a medium blonde or light brown as a toddler.
Changes in melanocyte stimulating hormone
Melanocyte stimulating hormone (MSH) is a hormone that triggers melanin production. Young children tend to have lower levels of MSH compared to adults. As MSH levels increase with age, more melanin is produced and hair becomes darker.
MSH is produced by the pituitary gland. During childhood, the pituitary gland is still developing and may not secrete hormones like MSH at full adult strength. Once puberty hits, pituitary function matures and MSH production increases, leading to darker pigmentation of hair.
Sun exposure impacts melanin production
Sun exposure naturally boosts melanin production as the skin tans to protect itself from UV damage. While young children may spend plenty of time outdoors, they receive less cumulative sun exposure over their lifetime compared to adults.
Prolonged sun exposure over many years prompts the body to ramp up melanin synthesis. More melanin results in darker hair pigmentation. People who tan easily tend to experience more dramatic lightening of their childhood hair color.
Changes in other hair pigments
Melanin is not the only pigment that contributes to hair color. The two other major pigments are:
– Eumelanin: Brown and black pigment
– Pheomelanin: Red and yellow pigment
Blonde hair has primarily pheomelanin with very little eumelanin. As you age, your hair follicles increase their ratio of eumelanin to pheomelanin. The boost in brown/black eumelanin pigmentation makes hair appear darker.
Genetics impact lifelong hair pigmentation
Your genetic makeup determines your hair’s pigmentation pathway over your lifetime. People inherit hair color genes from both parents.
Some genetic causes of hair darkening over time:
– Multiple genes control melanin production. Variations in these genes account for differences in melanin levels between childhood and adulthood.
– The MC1R gene helps regulate melanin synthesis. Certain variants lead to increased eumelanin production as you age.
– Genes may code for melanocyte cell receptors that influence pigment changes over time.
– Your genes impact the sensitivity of your hair follicles to hormones like MSH.
Nutritional deficiencies can lighten children’s hair
Nutrient deficiencies during childhood can inhibit melanin synthesis and cause very light blonde hair. As nutrition improves, hair color may darken.
Examples of micronutrient deficiencies that can lead to low melanin include:
– Copper: Helps tyrosinase activity which produces melanin.
– Vitamin D: Stimulates melanin production.
– Iodine
– Vitamin B12
– Iron
Once the deficiency is corrected either through diet or supplements, melanin production increases. This is why malnutrition early in life might cause blonde hair that turns brunette later on.
Hair color phenotypes by age
This table summarizes the most common natural hair color changes from childhood to adulthood:
| Hair Color as Child | Hair Color as Adult |
|---|---|
| Platinum blonde | Dark blonde or light brown |
| Golden blonde | Light brown or brown |
| Strawberry blonde | Reddish brown |
While hair usually darkens with age, some people experience the opposite. Occasionally, childhood brunette hair can turn into blonde or red hair by adulthood. The timing and degree of color changes depends on your unique genetics.
Other causes of hair color change
Sometimes hair color transformation is not simply due to age-related changes in melanin production and genetics. Other causes include:
– Damage from UV rays lightening hair over time.
– Smoking which depletes melanin levels.
– Chronic illness impacting pigment synthesis.
– Low protein intake which reduces tyrosine used to make melanin.
– Medications like chloroquine, azelaic acid, chemotherapy drugs.
– Vitiligo disease damaging melanocytes.
– Alopecia areata which causes new hair regrowth to lack melanin.
– Conditions that reduce MSH and melanin such as pituitary tumors.
Hair color is not set in stone
It is clear that many factors can lead to blond hair in childhood that progresses to a darker hue by adulthood. For some individuals, the natural hair color change is dramatic while others experience a more subtle shift. Environmental influences intersect with your genetic programming to alter pigment synthesis over your lifetime. So even if you are born towhead blonde, do not be surprised if your follicle functions change and you become a brunette later in life. Hair color is not set in stone.
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