Saviez-vous que les cheveux gris pourraient ne pas être permanents ? Les scientifiques ont découvert que le stress peut accélérer le grisonnement des cheveux, mais ce n’est pas toujours irréversible. Dans certains cas, quand les gens se détendent et stressent moins, leurs cheveux gris peuvent retrouver leur couleur originale ! Les chercheurs pensent que c’est parce que les follicules pileux ont des « souvenirs de couleur » et peuvent parfois recommencer à produire du pigment. Cela ne fonctionne pas pour tout le monde, et les chances dépendent de l’âge et du temps pendant lequel les cheveux ont été gris. Mais hé, c’est un rappel cool que notre corps peut parfois rebondir de manière étonnante ! Animation créée par Sympa.
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FunTranscript
00:00It could be that your hair could have traveled through time.
00:03Let me explain.
00:04They will not use a time machine and go back to the 1800s to talk to your great-grandparents.
00:10But everyone has done, or will do, the sad experience of discovering a strand of white hair
00:15by saying,
00:16I'm getting old.
00:17But listen.
00:18Scientists have good news for you.
00:21They may have found a way to reverse the process
00:24and give color to your beautiful curls,
00:26at least for a while.
00:28In a study dating from the 1970s,
00:30it was a question of a man who had three light hair at the tip and darker near the scalp.
00:35This seemed to mean that the usual process of graying hair,
00:39which begins at the root,
00:41had in its case done things the other way around.
00:44Today, a new study will bring us even more solid proof of this phenomenon.
00:49Specialists have examined the hair of several people of different ages and backgrounds.
00:54What they discovered may seem a bit surprising.
00:57It would seem that our white hair is linked to our level of stress.
01:01The way we feel psychologically could be reflected on our head.
01:05This new approach suggests that there could be a lapse of time
01:09during which our graying process could be reversed.
01:13A few years ago,
01:15an expert from the University of Columbia was wondering about the aging process.
01:20He thought that, just as some parts of our body age before others,
01:24our hair does not all turn gray at the same time.
01:27Perhaps the hair that turns white first
01:29are, in a way, the weak links of the chain.
01:32While talking to his colleague, he had a click.
01:35If he could find half-gray hair and determine its growth rate,
01:39he could know when it had started to lose its color.
01:43Luckily, his colleague found such hair on his head,
01:46and their project began.
01:48They soon found about 14 people,
01:50young and less young,
01:52with such meshes of bicolor hair.
01:55They even came up with a method
01:57to observe the tiny changes in color of their hair.
02:01The results were amazing.
02:03Some gray hair found their original color,
02:06and not only on the head, but also on the hair of the body.
02:10Today, we generally see that gray hair appears around the thirties.
02:16Well, these scientists think that this is the best time to expect a reversal.
02:21And even if your head is full of gray hair,
02:24some of them could still change.
02:27This study was considered promising by experts from different fields.
02:31They think it could show us
02:33how the changes related to the age in our body can be reversed.
02:37Of course, for now, it's just hair, but who knows?
02:41One day, perhaps, we will be able to reverse the signs of aging of our skin or muscles.
02:46This research is not limited to the color of hair.
02:49These scientists wanted to know
02:51if stress played a role in graying hair.
02:54Everyone has heard of people
02:56whose hair turns white overnight
02:59when they are confronted with traumatic events.
03:02The researchers therefore asked the participants
03:05to tell their most stressful moments over a period of one year.
03:08By associating these events with hair color changes,
03:11they found that the major moments of stress or relaxation
03:14corresponded well to changes in hair color.
03:18For example, the hair of a man
03:20had started to change color during his vacation,
03:24while a woman had gray hair,
03:26which corresponded to a very difficult period of her life.
03:30Of course, scientists from all walks of life praised these studies,
03:34but they did not fail to remind us that this project was just the beginning.
03:38Other studies must be carried out
03:40so that we can fully benefit from these results.
03:43What is the next step?
03:45Scientists now want to deepen the link
03:47between stress and gray hair.
03:49They hope to follow people over time
03:51to see how their hair and their level of stress evolve.
03:54Some think that in the future,
03:56our hair could be a window to our past experiences.
04:00Just like trees have horns that indicate their age,
04:03our hair could contain secrets about the events of our life.
04:07But stress or not,
04:08what is the process that causes graying hair?
04:11First of all, let's tackle a widespread myth.
04:14It turns out that hair does not really turn gray,
04:17it just loses its color.
04:19Once your hair has taken a certain color,
04:22whether it is brown, black, blonde or even red,
04:26it retains this shade all its life,
04:28unless you decide to give it a new color with a dye.
04:32As we age, our hair loses its memory a little and produces fewer colors.
04:37Thus, after a certain number of birthdays,
04:40when our old hair falls and new ones appear,
04:43there is more chance that it will be gray.
04:45If you wonder when you will see your first gray hair,
04:48check your family albums.
04:50Your genes, transmitted by your ancestors,
04:52generally decide the right time.
04:57Besides, why do we have more hair on the head than hair on the rest of the body?
05:02First, we must understand why most animals have fur.
05:06It turns out that, if they are a little old,
05:09it is to feel good in the heat when the temperatures drop.
05:12And also to protect themselves from the sun's rays.
05:15In this case, why did our ancestors lose most of their fur?
05:21Because they showed creativity.
05:24They found new ways to stay warm and protect themselves.
05:28By using fire, by building shelters and by dressing up.
05:32However, it is not because they could survive without fur
05:36that they lost all their hair like magic.
05:38They must have a good reason to become a beard.
05:41There are many theories on this subject.
05:44One of them suggests that it could have been too hot for us, at some point.
05:48Another indicates that some of our ancestors would have spent a lot of time in the water.
05:52The fact of having so much hair all over the body could have made them fat.
05:56Obviously, scientists have not yet found the exact reason.
06:02So, what about the hair on our heads?
06:05Why are they still there?
06:06The explanation is very simple.
06:08Humans have evolved to walk on their two feet.
06:11This means that our heads have become a bit like sunflowers,
06:14always facing the sun.
06:16However, we know that the sun can be very intense,
06:19especially in certain regions of our planet.
06:22Our hair therefore serves as an integrated cap.
06:25But that is not all.
06:26Our head, even if it is not very large compared to the rest of our body,
06:30is very busy.
06:31As it is always active, it creates heat.
06:34And our hair prevents this heat from escaping.
06:37Like an integrated natural cap.
06:39Whether it is gray or not,
06:41our hair strands could become more useful in the future.
06:44Do you wonder?
06:45Every time you go to the hairdresser,
06:47where are all these hair?
06:49For now, they are thrown away.
06:51Fortunately, the ingenious minds of Queensland had an incredible idea.
06:55Instead of considering hair as waste,
06:58they saw a potential energy source.
07:00They burned the hair delicately and extracted carbon from it,
07:04which they transformed into tiny grains,
07:06like the dust of the magic utensil.
07:08Because it really was magic.
07:10They sprinkled solar panels with this powder.
07:13And the panels started to work better and to be more stable.
07:19Your hair also contains a pigment called melanin.
07:23I spare you the complicated details,
07:25but this chemical substance is sensitive to light.
07:29Discovering this phenomenon,
07:31a Nepali teenager said to himself,
07:33why not use hair instead of expensive silicon in solar panels?
07:38Imagine that you did exactly that.
07:41You would give a large number of people
07:44the possibility of using energy in a less expensive way.
07:48This could well be the next important step
07:51to make solar energy more accessible and more affordable.
07:54Then, imagine this.
07:56You are grinding a delicious salad for lunch.
07:59Did you ever think that hair could help grow lettuce?
08:03Thanks to scientists from the University of Singapore,
08:06this could soon become a reality.
08:08They have developed a way to grow plants,
08:11especially in cities,
08:13using a method called hydroponics.
08:15No more need for soil.
08:18Instead, they use a special mixture based on hair.
08:22Let's go over the process.
08:24Researchers collected hair in places such as hair salons,
08:28and extracted a substance called keratin.
08:31They then mixed this keratin with cellulose fibers,
08:35which made it more resistant.
08:37Once dried, this mixture turns into a paste,
08:41perfect for growing plants.
08:44They chose to experiment
08:46with microgreens and delicious vegetables,
08:49such as chuchine and roquette.
08:51Well, that's enough.
08:53I'm going to make a little salad.