WEBVTT 00:00:00.000 --> 00:00:03.340 Right now, the summer sun is at its absolute peak. 00:00:03.340 --> 00:00:05.340 But despite all that heat and light, 00:00:05.340 --> 00:00:09.300 one billion people on Earth are starving for vitamin D. 00:00:09.300 --> 00:00:12.060 Just look at some of the sunniest places on Earth, 00:00:12.060 --> 00:00:15.180 like parts of Africa and Southeast Asia. 00:00:15.180 --> 00:00:18.940 You would expect their vitamin D deficiency rates to be zero. 00:00:18.940 --> 00:00:23.180 Instead, studies show that up to 70% to 80% 00:00:23.180 --> 00:00:26.540 of people in these regions are severely lacking it. 00:00:26.540 --> 00:00:27.700 How is this possible? 00:00:27.700 --> 00:00:30.260 Because the summer sun you think you are getting 00:00:30.260 --> 00:00:31.900 is actually a trick. 00:00:31.900 --> 00:00:34.540 Sunlight has two main types of rays-- 00:00:34.540 --> 00:00:37.980 UVA and UVB. 00:00:37.980 --> 00:00:41.660 Only the stronger UVB rays have the exact energy 00:00:41.660 --> 00:00:44.980 needed to enter your skin and create vitamin D. 00:00:44.980 --> 00:00:47.820 But standard window glass acts like a brick wall 00:00:47.820 --> 00:00:52.380 against UVB rays, completely blocking 100% 00:00:52.380 --> 00:00:54.300 of the vitamin D-making light. 00:00:54.300 --> 00:00:57.300 The UVA rays still pass through the glass, 00:00:57.300 --> 00:00:59.740 giving you a tan and a feeling of warmth. 00:00:59.740 --> 00:01:03.540 But your actual vitamin D production stays at zero. 00:01:03.540 --> 00:01:05.580 So you decide to beat the system. 00:01:05.580 --> 00:01:07.980 You wait until work ends at 6 PM, 00:01:07.980 --> 00:01:10.940 and you step outside into the bright evening sun 00:01:10.940 --> 00:01:12.300 to get your daily dose. 00:01:12.300 --> 00:01:15.220 At noon, when the sun is directly overhead, 00:01:15.220 --> 00:01:18.100 the path through the sky is at its shortest, 00:01:18.100 --> 00:01:20.820 allowing UVB to reach your skin. 00:01:20.820 --> 00:01:24.460 The best time to make vitamin D is strictly limited 00:01:24.460 --> 00:01:26.620 to peak midday hours. 00:01:26.620 --> 00:01:29.420 Usually between 10 AM and 2 PM. 00:01:29.420 --> 00:01:31.460 This gives us the shadow rule. 00:01:31.460 --> 00:01:34.180 If your shadow is taller than you are, 00:01:34.180 --> 00:01:36.380 the atmosphere has already filtered out 00:01:36.380 --> 00:01:39.340 the rays you need to make vitamin D. 00:01:39.340 --> 00:01:43.460 Modern humans spend up to 93% of their lives indoors. 00:01:43.460 --> 00:01:47.100 During hot summer days, we hide in air-conditioned buildings 00:01:47.100 --> 00:01:51.260 to escape the heat right during those peak midday hours, 00:01:51.260 --> 00:01:54.460 missing out on the only four hours of the day 00:01:54.460 --> 00:01:57.940 when our bodies can actually make vitamin D. 00:01:57.940 --> 00:02:01.820 This total lack of midday sun triggers a quiet 00:02:01.820 --> 00:02:04.780 but highly destructive crisis in your body. 00:02:04.780 --> 00:02:07.900 Because vitamin D is not just a regular vitamin, 00:02:07.900 --> 00:02:09.980 it is a powerful hormone 00:02:09.980 --> 00:02:13.540 that acts as the absolute gatekeeper for calcium. 00:02:13.540 --> 00:02:15.260 Every minute of every day, 00:02:15.260 --> 00:02:18.780 your blood needs calcium to send the electrical signals 00:02:18.780 --> 00:02:20.380 that keep your heart beating. 00:02:20.380 --> 00:02:24.060 Without vitamin D, your stomach is basically blind 00:02:24.060 --> 00:02:29.220 to calcium, absorbing only 10% to 15% of what you eat. 00:02:29.220 --> 00:02:32.980 With enough vitamin D, that number jumps up to 40%. 00:02:32.980 --> 00:02:36.540 When you spend your summer indoors, those gates close. 00:02:36.540 --> 00:02:39.900 Your blood calcium levels begin to dangerously drop. 00:02:39.900 --> 00:02:43.820 They flood your blood with a hormone called PTH, 00:02:43.820 --> 00:02:45.940 which makes a brutal choice. 00:02:45.940 --> 00:02:47.500 It saves your heart today 00:02:47.500 --> 00:02:50.140 by sacrificing your bones tomorrow. 00:02:50.140 --> 00:02:53.340 This hormone starts a literal bone heist. 00:02:53.340 --> 00:02:57.020 It commands bone-eating cells to attach to your skeleton. 00:02:57.020 --> 00:03:01.220 They release strong acids to rapidly dissolve your bones, 00:03:01.220 --> 00:03:04.700 dumping that stolen calcium back into your blood. 00:03:04.700 --> 00:03:08.580 Your skeleton is eaten away just to keep you alive. 00:03:08.580 --> 00:03:13.060 This continuous theft leads to weak, painful bones. 00:03:13.060 --> 00:03:15.540 We often hear about osteoporosis, 00:03:15.540 --> 00:03:18.100 where bones become brittle and break easily. 00:03:18.100 --> 00:03:20.580 But severe vitamin D starvation 00:03:20.580 --> 00:03:23.060 causes something entirely different. 00:03:23.060 --> 00:03:24.780 Osteomalacia. 00:03:24.780 --> 00:03:28.100 Osteomalacia is a problem with how your bones harden. 00:03:28.100 --> 00:03:30.700 Your body tries to build new bone tissue, 00:03:30.700 --> 00:03:33.220 but because you aren't absorbing calcium, 00:03:33.220 --> 00:03:36.220 this new tissue simply cannot harden. 00:03:36.220 --> 00:03:38.940 To pull an adult out of a severe deficiency, 00:03:38.940 --> 00:03:42.900 science shows you need about 4,000 to 5,000 units 00:03:42.900 --> 00:03:45.260 of vitamin D3 every day. 00:03:45.260 --> 00:03:49.140 But natural vitamin D is incredibly rare in human food. 00:03:49.140 --> 00:03:52.300 To hit that 5,000 unit target just by eating, 00:03:52.300 --> 00:03:55.740 you would need to drink 40 to 50 glasses of milk 00:03:55.740 --> 00:04:01.100 every single day, or eat over 110 egg yolks. 00:04:01.100 --> 00:04:03.900 Human beings are mathematically incapable 00:04:03.900 --> 00:04:07.660 of eating their way out of a severe vitamin D deficit. 00:04:07.660 --> 00:04:10.020 So what is the actual solution? 00:04:10.020 --> 00:04:12.580 If you want to make vitamin D naturally, 00:04:12.580 --> 00:04:16.740 you have to be outside at the exact right time. 00:04:16.740 --> 00:04:19.460 You need direct sun on your skin, 00:04:19.460 --> 00:04:22.660 strictly between 10 a.m. and 2 p.m. 00:04:22.660 --> 00:04:24.060 Remember the shadow rule? 00:04:24.060 --> 00:04:26.420 If your shadow is shorter than you are, 00:04:26.420 --> 00:04:29.100 the sun's rays can actually help you. 00:04:29.100 --> 00:04:32.620 If you can't stand under the blazing midday sun every day, 00:04:32.620 --> 00:04:35.500 you just need to bypass the system entirely. 00:04:35.500 --> 00:04:38.140 An oral supplement does exactly that. 00:04:38.140 --> 00:04:40.580 Something simple like a vitamin D tablet 00:04:40.580 --> 00:04:43.220 gives you the exact high potency dose 00:04:43.220 --> 00:04:47.380 of vitamin D3 you need, up to 5,000 units. 00:04:47.380 --> 00:04:50.340 This flips your stomach's gates back open 00:04:50.340 --> 00:04:53.860 and absorbs the calcium your bones desperately need. 00:04:53.860 --> 00:04:56.940 It's not magic, it's just basic biology. 00:04:56.940 --> 00:05:00.300 Take a supplement or go stand in the midday sun. 00:05:00.300 --> 00:05:03.460 But at least now you know why the evening summer breeze 00:05:03.460 --> 00:05:05.860 isn't saving your skeleton.