1 00:00:01,960 --> 00:00:07,160 Speaker 1: Welcome to brain stuff production of iHeartRadio. Hey, brain stuff, 2 00:00:07,200 --> 00:00:11,520 Speaker 1: laurin vogel bomb here. When people can't digest milk, we 3 00:00:11,560 --> 00:00:15,960 Speaker 1: call that lactose intolerance. This might seem to signify that 4 00:00:16,000 --> 00:00:19,800 Speaker 1: it's an unusual condition that most people are just fine 5 00:00:19,880 --> 00:00:23,840 Speaker 1: consuming dairy products like milk, cheese, and ice cream, But 6 00:00:23,920 --> 00:00:27,480 Speaker 1: it turns out that we pour souls who get gassy, crampy, 7 00:00:27,560 --> 00:00:31,880 Speaker 1: and otherwise digestively miserable after eating dairy products are actually 8 00:00:31,920 --> 00:00:35,360 Speaker 1: in the majority worldwide. It's the people who can handle 9 00:00:35,400 --> 00:00:39,520 Speaker 1: milk where the weird ones. A. Lactose is the main 10 00:00:39,560 --> 00:00:42,559 Speaker 1: sugar in all mammal milk, and everyone is born with 11 00:00:42,560 --> 00:00:45,600 Speaker 1: the gene that codes for producing lactase, which is the 12 00:00:45,680 --> 00:00:49,479 Speaker 1: enzyme in our bodies that processes lactose, so when we're babies, 13 00:00:49,600 --> 00:00:52,960 Speaker 1: we all have the ability to digest milk. The human 14 00:00:53,000 --> 00:00:56,440 Speaker 1: body produces lactase in the small intestine, where it breaks 15 00:00:56,440 --> 00:01:00,200 Speaker 1: down lactose into glucose and glactose, which are bodies can 16 00:01:00,240 --> 00:01:04,640 Speaker 1: easily absorb into our bloodstream, But for reasons unknown, the 17 00:01:04,720 --> 00:01:07,440 Speaker 1: gene for lactase tends to shut off at about the 18 00:01:07,480 --> 00:01:09,240 Speaker 1: time that most of us would be weaned off of 19 00:01:09,280 --> 00:01:13,280 Speaker 1: breast milk and onto solid foods. Most people's bodies don't 20 00:01:13,319 --> 00:01:15,920 Speaker 1: create any lactase, or very little of it by the 21 00:01:15,920 --> 00:01:19,160 Speaker 1: time they're five years old or so. In the absence 22 00:01:19,160 --> 00:01:22,040 Speaker 1: of lactase, the excess sugar sitting around in your small 23 00:01:22,040 --> 00:01:25,080 Speaker 1: intestines causes your body to try to flush it out 24 00:01:25,400 --> 00:01:29,280 Speaker 1: by secreting fluids and moving things along faster than normal. 25 00:01:30,400 --> 00:01:33,400 Speaker 1: By the time the lactose reaches your colon, the mostly 26 00:01:33,440 --> 00:01:38,399 Speaker 1: helpful microorganisms there eat it and poop things like carbon dioxide, hydrogen, 27 00:01:38,520 --> 00:01:42,960 Speaker 1: and methane. In combination. This can lead to those unpleasant 28 00:01:42,959 --> 00:01:48,600 Speaker 1: symptoms of diarrhea, gas, and cramps. Some lucky people, however, 29 00:01:48,800 --> 00:01:51,800 Speaker 1: carry a genetic mutation that allows the lactase gene to 30 00:01:51,960 --> 00:01:55,400 Speaker 1: keep working. Sometimes it continues for just a few more years, 31 00:01:55,640 --> 00:01:59,480 Speaker 1: sometimes for a lifetime. Up to ninety percent of Americans 32 00:01:59,520 --> 00:02:02,440 Speaker 1: have a functional lactase gene, so in the US it's 33 00:02:02,440 --> 00:02:06,440 Speaker 1: a little unusual to be lactose intolerant. About worldwide, more 34 00:02:06,480 --> 00:02:09,760 Speaker 1: than sixty percent of people lose the ability to process lactose. 35 00:02:10,320 --> 00:02:13,840 Speaker 1: Because lactose intolerance is the more common condition around the globe, 36 00:02:14,120 --> 00:02:16,919 Speaker 1: scientists and researchers in the field actually use the term 37 00:02:17,080 --> 00:02:20,399 Speaker 1: lactase persistence for the rarer case of people who can 38 00:02:20,480 --> 00:02:23,960 Speaker 1: digest dairy. Because the function of the gene is genetic, 39 00:02:24,400 --> 00:02:27,919 Speaker 1: certain populations are more prone to lactase persistence than others. 40 00:02:28,800 --> 00:02:32,000 Speaker 1: Northern Europeans, especially Scandinavians, tend to hang on to a 41 00:02:32,040 --> 00:02:35,640 Speaker 1: functional lactase gene, along with some populations from West Africa, 42 00:02:35,840 --> 00:02:39,799 Speaker 1: East Africa, and the Middle East. People from Southern Europe, 43 00:02:39,840 --> 00:02:42,720 Speaker 1: the rest of Africa, much of the Americas, Central Asia, 44 00:02:42,800 --> 00:02:45,960 Speaker 1: and Northern Asia are less likely to have tolerance, and 45 00:02:46,240 --> 00:02:50,600 Speaker 1: it's super rare in Southeastern Asia. Based on these patterns 46 00:02:50,639 --> 00:02:53,640 Speaker 1: and non genetic research, it seems that the mutations that 47 00:02:53,720 --> 00:02:58,000 Speaker 1: code for keeping the lactase gene active appeared about seven thousand, 48 00:02:58,080 --> 00:03:01,560 Speaker 1: five hundred years ago among cattle farming populations in Central 49 00:03:01,560 --> 00:03:04,600 Speaker 1: Europe and Eastern Africa, and in camel herders in the 50 00:03:04,639 --> 00:03:08,520 Speaker 1: Middle East. The theory is that the mutation was random, 51 00:03:08,639 --> 00:03:12,880 Speaker 1: as all mutations are, but it became genetically advantageous in 52 00:03:13,000 --> 00:03:17,720 Speaker 1: these dairy eating populations and thus spread rapidly. To this day, 53 00:03:17,760 --> 00:03:20,560 Speaker 1: there are still high rates of lactase persistence in these areas. 54 00:03:21,520 --> 00:03:24,679 Speaker 1: Lactase persistence might not be a necessity for survival in 55 00:03:24,720 --> 00:03:27,600 Speaker 1: the modern world, but it can make life easier and 56 00:03:27,760 --> 00:03:33,440 Speaker 1: perhaps more delicious. So if you can enjoy conventional ice cream, Sundays, milkshakes, 57 00:03:33,440 --> 00:03:36,240 Speaker 1: and pizza with no problem, remember that you're one of 58 00:03:36,240 --> 00:03:39,120 Speaker 1: the lucky ones. If you're not, remember that there are 59 00:03:39,160 --> 00:03:47,400 Speaker 1: lots of dairy alternatives out there. Today's episode is based 60 00:03:47,400 --> 00:03:49,880 Speaker 1: on the article are humans built to drink milk as adults? 61 00:03:49,960 --> 00:03:52,880 Speaker 1: On How stuffworks dot Com? Written by Alison Cooper. Rain 62 00:03:52,920 --> 00:03:54,920 Speaker 1: Stuff is production of by Heart Radio in partnership with 63 00:03:54,960 --> 00:03:57,200 Speaker 1: how stuffworks dot Com, and is produced by Tyler Klang. 64 00:03:57,760 --> 00:04:00,200 Speaker 1: For more podcasts from My heart Radio, visit the heart 65 00:04:00,240 --> 00:04:02,920 Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your 66 00:04:02,920 --> 00:04:03,640 Speaker 1: favorite shows.