Full transcript of “75% മലയാളികൾക്കും പാൽ ദഹിക്കാത്തതെന്തുകൊണ്ട്? Lactose Intolerance Explained.”. Click a timestamp to open the video at that moment. Need another video? Use the YouTube transcript generator.
0:02 a food that is considered a symbol of health and nutrition, but of all the milk-producing animals on earth, only babies have the ability to digest milk. As they grow up, all animals lose their ability to digest milk. Now, if we take the case of humans, 65 percent of adults in the world do not have the ability to digest milk. That is, within a few years of birth, 65 percent of those people lose their ability to digest lactose, the main nutrient in milk. In short, the way of almost all milk-producing animals in nature is to not digest milk after they become adults. There is one exception to this, only 35 percent of humans. If we look at human history, some humans have acquired this ability through a very recent genetic mutation,
0:50 so this ability has not yet reached all humans. If we look at the global population, 85 percent of people in many countries are lactose intolerant. If we take the case of India, most people in South India and East India are lactose intolerant, but In North and West India, we can see more Huddles that can digest milk. What is lactose intolerance? How can we tell if we have lactose intolerance? Should people with lactose intolerance not eat milk and milk products? Why are only some humans able to maintain the ability to digest milk even after they grow up? What is the genetics behind it? Let's watch a [music] video through this video.
1:35 Hi friends, welcome to a new video from Science for Mass. The greatest feature of mammals is giving birth to and raising babies. That is, it is one of the very few things that are produced specifically for consumption. Milk is often described as a complete food because it contains many different nutrients such as carbohydrates, proteins, fats, vitamins, and minerals. Therefore, it is enough to give milk to babies as food right after birth. The most important nutrient contained in milk is lactose, from which babies get the energy they need. Since the molecules of lactose are relatively large, our body
2:22 cannot digest it as it is. This is where the role of the enzyme lactase, which is produced by the body, comes in. The enzyme lactase breaks down the lactose contained in milk into two smaller components: glucose and galactose . This process takes place in the small intestine . The body can absorb the resulting glucose and galactose and use it to produce energy. The problem is that organisms only have the ability to produce the enzyme lactase at a young age. Most organisms lose that ability as they grow older. Along with that, the ability to digest lactose in milk will also be lost. When this happens, undigested lactose passes from the small intestine to the large intestine. Getting lactose for the bacteria there is like winning the lottery. They will ferment it and
3:08 use it for their own purposes. The problem is that the byproducts of fermentation can cause us all sorts of problems commonly known as indigestion, such as stomach ache, gas, loose motion, bloating, etc. This loss of the ability to digest lactose, and as a result, indigestion like discomfort when consuming milk, is called lactose intolerance. This is not a problem for other animals except humans because they do not drink milk after they grow up. Now, if we take the case of humans, until about 12,000 years ago, all humans had the ability to digest lactose only when they were young. As they grew up, all humans would have lost that ability. When we say 12,000 years ago,
3:55 humans had a hunter-gatherer lifestyle, meaning they lived by hunting and eating fruits from trees. They did not start raising cattle or milking them. At that time, no one drank milk except when they were young, so lactose intolerance was not a problem in the world. In many places, humans transitioned from a hunter-gatherer lifestyle within about 10,000 to 12,000 years. Two main lifestyles emerged at that time: agriculture and cattle breeding. These styles were shaped by the topography of each place. Agriculture developed mostly in areas with rivers and fertile, hilly soil. Cattle
4:41 raising has increasingly developed on hillsides and grasslands. Thus, for the first time, a group of people who have adopted a livestock-raising lifestyle have emerged who do not lose their ability to digest lactose even as they grow older. This characteristic, the ability to digest lactose even as we grow older, is called lactose persistence. Now, we need to know how this lactose persistence came about in only a very small group of people. As we said, the enzyme lactase is responsible for digesting lactose. It is present in our body during childhood. Therefore, it is certain that the gene to produce lactase is present in our DNA. However, for some
5:28 reason, the function of that gene turns off as we grow older. Many studies have been conducted to find out why this happens. The gene required to produce lactase is called the LCT gene. It is located on our second chromosome. However, the function of this gene is controlled by an area called MCMC, which is located a little further away on the same chromosome. The LCT gene is activated during childhood and then deactivated when we grow older. Some DNA codes in this MCMC area are found. However, in people who are lactose persistent, it has been found that mutations have occurred in some DNA codes in this MCMC area.
6:14 Our genes are made up of four letters: AT CG. We have seen in previous videos that DNA is coded. The letter C is usually found in the DNA code 1391 letters from the starting point of the LCT gene. In the same position, the letter T is replaced by the letter C. This type of mutation is called a lactase start mutation. If we have a lactase start mutation in our inherited DNA, our lactase gene will remain active even after we grow up. In such people, the ability to digest lactose is greater, but it can be seen that such people
7:02 are lactose persistent. It was said that only 35% of the world population is lactose persistent . More people than that have this mutation called the startle mutation. This mutation was first discovered around 7,000 to 10,000 years ago in a group of people who lived by herding cattle in the area of Central Europe, which is now Hungary and Ukraine. Later, through various migrations and interbreeding, this gene was transferred to many areas. Today, 90 percent of lactose-persistent people in Northern and Western Europe have this mutation. However, there are
7:47 other mutations that cause lactose persistence. For example, lactose-persistent people in the Middle East and East Africa have the mutation 9vafastarji, which means that this mutation is not a mutation that was inherited from Central Europe, but a mutation that developed separately in another group of people. Some relatively rare mutations such as vafasovavasostarzivatnaso7starji also cause lactose intolerance. This is due to persistence. All of this must have developed independently in tribes that settled in different areas with their cattle. In any case,
8:40 all of these mutations are in the MCMC area of the second chromosome mentioned earlier. The name of this mutation changes depending on the letter of the DNA code there. One thing to note here is that any mutation will first occur in one person in a group or tribe. After a few generations, this mutation will be passed on to a few more people. Imagine a famine or a time when it is difficult to get food. In such cases, people who are lactose persistent will get an advantage. They can depend on milk as a source of food, but people who are lactose intolerant will not get that advantage. When that happens, at the end of the famine,
9:26 if only 100 people in that tribe survive, perhaps 70 of them will be lactose persistent. Only 30 people who were lactose intolerant would have survived. Over thousands of years, the number of people who were lactose persistent in that area would have increased. This is how nature itself selects for a particular genetic trait. Another thing to note here is that this mutation is something that can happen to anyone at any time and randomly. The mutation that helps with lactose persistence may have happened to some people when humans were hunter-gatherers, but we didn't raise livestock back then. Therefore, an individual with that mutation or
10:12 his descendants would not have had a special advantage at that time. Therefore, that trait would have disappeared from the population soon after. Now, if the same mutation had occurred in people who settled on the banks of rivers by cultivating crops, it would not necessarily have been an advantage there either because the main way of life there was agriculture, not cattle raising. When this happened in the tribes that made it their livelihood, it became an advantage and spread to more people and became an important genetic trait. Initially, it was a trait that was developed only in some tribes that lived in some selected areas, but
10:58 today the mutation that causes lactose persistence has spread to many parts of the world. That is how 35 percent of the total world population got that trait, but its ratio varies in different places. In places like Denmark in Northern Europe, 90 percent of the people are lactose persistent. Naturally, Denmark is a place that is very famous for its dairy products. This means that such genetic traits of the people of that country play a big role in determining the cultural and economic nature of a country. Now if we look at India, the percentage of people who are lactose persistent is relatively high in the Northwestern states of India, where 30
11:43 to 50% of the people drink milk. Has the ability to digest. But if we look at South India and East India, about 75 to 85 percent of the people here are lactose intolerant, meaning that most people here lose the ability to digest lactose as they grow older. This difference can be seen very clearly in the food habits and customs of these two places. Now if we go to South and East Asian countries like Japan, China, Korea, more than 85% of the people there are lactose intolerant. Only 10 to 15% of people retain the ability to digest milk. Even products like ice cream made with milk are very
12:30 less popular in such places. An estimate is that more than 75 percent of people in Kerala are lactose intolerant. So, naturally, we must have wondered how to find out if we are lactose intolerant or persistent. Some of us must have already realized it on our own from the difficulties we experience when consuming milk. However, there is an easy way to find out. All you need is a meter that checks the glucose level. First, check what our normal glucose level is. You should check this after a long time after eating. It would be better if you look at it in the morning . Then drink two glasses of unsweetened milk. Then check your glucose level after an hour. Check again after half an hour .
13:16 No other foods should be eaten in between . If we have the ability to digest lactose, we can see our glucose levels increase significantly after drinking milk. If not, there will be no significant change in glucose levels. The next question is whether there is any problem in a lactose intolerant person consuming milk. As I said earlier, if lactose is not digested in our small intestine, when it reaches the large intestine, the bacteria there will ferment this lactose, so it will not be beneficial for us. However, the byproducts of this fermentation will cause us a lot of problems such as gas, abdominal pain, loose motion, bloating, etc. This is why lactose intolerant people say that it is better to avoid milk. However, if we consume milk in small quantities with other
14:04 foods, the problems caused by it will be greatly reduced. Then one thing we should know is that although the main nutrient in milk is lactose, in addition to that, milk contains various proteins, fats, vitamins, and minerals that our body needs. Even if the lactose in milk is not digested, our body has the ability to digest and absorb other nutrients. Therefore, lactose intolerance If we avoid the harmful effects, there are benefits to consuming milk. When normal milk is fermented and turned into yogurt, the lactose in it is almost completely eliminated. Therefore, even if a person is lactose intolerant, there will be no major problems from consuming yogurt. In this way,
14:49 dairy products with low lactose content can also be consumed by people who are lactose intolerant. I hope that through this video, you will get a small understanding of lactose intolerance and the genetics that cause it. If you like this video, do not hesitate to like it. If you can, leave a comment and share it with your friends who may like such videos. Remember, knowing a little is not enough. Now the question of what is the benefit is irrelevant. Knowledge is complete in knowledge itself. Thank you.
