Although it mostly comes down to the natural ageing process, stress, nutritional deficiencies and other factors can cause hair to turn white prematurely.
If you have spotted a couple of white hairs on your head you might want to read on and find out why hair turns white.
In this article, we shall look at:
- Why does hair turn white?
- Can white hair turn black?
- How you can prevent hair from turning white prematurely
But before we get there,
Did you know that people of Asian and African descent tend to show less grey or white hair than those of Caucasian origin?
Also, did you know there are people whose hair turns white before they turn 20 due to aging disorders or autoimmune diseases?
Why Does Hair Turn White?
Hair turns white when the hair follicles produce fewer melanocytes, which means the hair loses its natural pigment.
The hair follicles contain special cells that contain and produce the pigment melanin. This pigment is the one responsible for the black, red or blonde color of hair.
In the absence of the pigment, hair loses its color. This causes the hair to have a more transparent color such as grey or white.
There are several reasons that may cause this to happen such as:
Genes play a huge role in determining what age the hair starts to turn white.
If for instance your parents’ hair started turning white when they turned forty, your hair is also probably going to turn white at around that time.
2. Nutritional Deficiencies
Deficiencies in nutrients that are vital for hair growth such as vitamin B12, folic acid, and biotin affect production of melanin.
Particularly, one research has shown that deficiencies in all 3 nutrients (Vitamins B12, Folic acid and biotin) is common in people whose hair had started to turn gray/white. 
Inadequate levels of vitamin D and Iron have also been shown to cause hair to turn white.
In a study conducted in India, it was found that patients whose hair turned white at an early age had low levels of vitamin D and Iron in their bodies.
The researchers believed that there is a strong connection between low levels of the two nutrients in the patients and premature hair graying. 
3. Oxidative Stress
Oxidative stress plays a major role in hair turning white.
This refers an imbalance in antioxidants and free radicals in the body.
The body has defense mechanisms in place to ensure that free radicals are neutralized and do not cause harm to the body.
As one get older, these mechanisms slow down increasing the number of free radicals in your body.
When melanocytes, the cells responsible for the production of the pigment melanin, are exposed to these free radicals, there is usually a reduction in the amount of pigment produced. 
Studies show that there is a link between hair turning white and smoking. Toxins present in cigarettes may cause damage to the hair follicles affecting melanin production.
5. Harsh Products
The products that you use on your hair, can contribute to turning white early.
Some of these products may contain harmful ingredients such as hydrogen peroxide, that may affect the production of melanin.
Excessive and the wrong use of hair dyes, hair relaxers and bleaches also may cause your hair to turn white.
6. Thyroid Disorders
Either condition reduces the amount of melanin produced. This may cause your hair to turn white as there is little or no pigment being produced.
7. Autoimmune Diseases
Autoimmune diseases happen when the body can’t recognize the difference between foreign and body cells.
This causes the immune system to mistakenly attack harmless body cells. Sometimes these cells may be the pigment cells located in the hair follicle.
In diseases such as vitiligo and alopecia areata, your hair cells are attacked affecting melanin production.
It is thought that stress may lead to your hair changing color. Although this has not been extensively studied, one research published in nature has shown a possible link between stress and hair greying.
Can White Hair Turn Black Again?
Whether or not your hair turns black from white is dependent on why your hair ended up white in the first place.
If the cause is genetic or natural, as, with aging, it’s not possible to reverse the process.
However, there are claims that it’s possible for the hair to turn black again if the following causes are resolved:
- Nutritional deficiencies
- If your hair turned white due to stress-related factors, once you can control the stress, black hair MAY start growing again. More studies are needed to support this, so take it with a grain of salt.
How to Prevent Hair from Turning White Prematurely
1. Increase vitamin intake
Ensure that your diet comprises foods rich in vitamins to prevent deficiencies that would otherwise cause white hair as discussed above.
2. Eat foods rich in antioxidants
Antioxidants are substances that inhibit oxidation from taking place.
Eating foods rich in antioxidants helps prevent the formation of free radicals, that we talked about earlier, that may damage melanin cells.
Foods rich in antioxidants include: Broccoli, spinach, carrots, Goji berries, onion, eggplant among others.
3. Get thyroid levels checked
Visit your doctor to get a medical examination done to check the levels of thyroid in your body if you suspect that you have a thyroid disorder.
Your medical caregiver will then guide you on how best to deal with the condition.
4. Quit smoking
Smoking not only affects your hair but also other body organs such as your lungs.
As such quitting the practice will do your body a lot of good.
5. Herbal remedies
There are several natural remedies available that can help you slow down the rate at which your hair is turning white.
Some of these remedies include:
- Curry leaves
- Black tea
- Indian gooseberry
- Ride Gourd
6. Check your products
As you purchase your hair products, take a look at the ingredient list to ensure that you are not buying harmful products. Look out for ingredients such as hydrogen peroxide that you should avoid.
As we’ve seen there are several factors that may cause hair to turn white, some can be reversed and some can’t.
Nonetheless, whether your hair is black, grey or even white, as long as you take good care of it, it will still flourish and look beautiful.