[00:00] No, you're not making it up. Spinach and other  dark leafy greens can make your mouth feel kind of   weird, kind of gritty or chalky or pasty. Indeed,  this is one reason why I think mouthfeel is a real  
[00:18] thing and not some made-up foodie nonsense, as  many have accused. But we'll get back to that.   Spinach is unusually high in a class of organic  compounds known as oxalates, like oxalic acid,  
[00:30] which is named after the plant genus oxalis,  or in the U.S. it might be pronounced oxalis.   Wood sorrel, which is a thing that people eat  sometimes, and it was the first kind of plant   from which scientists isolated oxalates, which are  toxic in large quantities, but perform a number of  
[00:47] biological functions inside plants. They can  protect against fungi and other pathogens.   Oxalates will bond with heavy metals, thus helping  the plant to detoxify itself. This is also why   oxalic acid is good at dissolving rust, which is  why they put it in lots of cleaning products like  
[01:03] Bar Keepers Friend. Oxalates will also bond with  calcium, giving you a calcium salt of oxalic acid,   which forms tiny little crystals as salts  tend to do. Plants integrate these hard,  
[01:15] sharp little crystals into their tissues as a  kind of armor to protect against the mouths of   tiny herbivores. It is these same calcium  oxalate crystals that make your mouth feel   weird when you eat spinach. You chew, you release  oxalic acid in your mouth where it binds with  
[01:32] calcium in your saliva and your enamel and it  precipitates in little crystals on your teeth,   and that is what you are feeling. Some people describe it as fuzzy teeth,   teeth that are just covered in teeny tiny  little crystals that do not dissolve in water,  
[01:46] which is why this feeling persists until those  crystals just wear off physically or are dissolved   by other acids like maybe citric acid in your  salad dressing. And it's not just spinach. Here's   an analysis of the oxalate content of various  foods. Sorrel, obviously, and then there's the  
[02:03] spinach. There's just as much in Swiss chard and  other dark greens. Cassava is high in oxalates,   but nobody notices because they're broken down  by the cooking process. Nobody eats raw cassava,   and even if you did, you probably wouldn't be  able to break it down very much in your mouth  
[02:18] where this chemical process has to happen if  you're going to feel those little crystals.   Spinach, on the other hand, is delicate and  easy to physically break down in your mouth,   thus releasing all of those chemicals. And it's  the rare example of a dark green that we tend to  
[02:34] cook very lightly or often not at all. So the  oxalates are not chemically broken down in the   cooking. They end up in our mouths and in our  guts. Oxalates can combine with calcium in your  
[02:46] kidneys to create stones. And kidney stones are  bad news bears. A healthy person's body has a   number of ways of preventing this phenomenon. One  is to host oxalate-degrading bacteria in our guts,  
[02:59] which we do. We have gut bacteria that literally  eat the oxalates before we can absorb them through   our intestinal lining. Just one of many  examples of how gut health is important,   which is why I take Symbiotic Plus  from Ritual, sponsor of this video.  
[03:15] As I have gotten older, I have needed to take  my digestion a little more seriously and I   will not get any more specific than that in the  context of a food video. I eat lots of plants,   I take a fiber supplement with my protein  shakes, and I take Symbiotic Plus, Ritual's  
[03:31] three-in-one prebiotic, probiotic, and post-biotic  to support a healthy gut microbiome. Prebiotics   support the growth of beneficial bacteria and  post-biotics support gut barrier function.  
[03:43] The probiotic itself is the bacteria,  and this contains two of the world's most   clinically studied probiotic strains, all inside  a shelf-stable minty capsule that you can take   any time with or without food. And it's delayed  release to deliver live bacteria to your colon  
[03:59] where they can actually do their thing, helping  to break down your food to make it pass through   your system without incident, let's just say. Well, I'll be specific about gas. I do notice   less gas when taking my Symbiotic Plus, even  with the vegetable and legume-heavy diet that I  
[04:14] eat. Get 25% off your first Ritual order with my  link and code in the description, adamragusea25,   for 25% off. Thank you, Ritual. Anyway, oxalic  acid, the stuff in spinach and other plants that  
[04:27] binds with calcium in your mouth to make your  mouth feel kind of weird. People who like to   advance meat-based diets for various cultural  and ideological reasons that we've discussed,   people like that try to scare the rest of us  about eating vegetables because oxalic acid is  
[04:42] an example of an "anti-nutrient," something that  inhibits the absorption of vitamins and minerals   in the gut. This is true. This is real. It's  just a terrible reason to avoid eating spinach.  
[04:54] Popeye was right. Spinach is exploding with  micronutrients. It's historically notable   that cartoonists in the 1930s hyped up spinach  as a strength-enhancing food rather than, say,  
[05:07] beef or some other protein source. Why? Well,  the specific historical reasons vis-a-vis Popeye   are complicated and somewhat disputed, but  I can speak to the broader state of health   in the early 20th century. When otherwise  healthy people were weak 100 years ago,  
[05:23] it generally wasn't for lack of muscle tone per  se, or even for lack of calories. It was for lack   of iron and B vitamins and other micronutrients  that are necessary for metabolism. If you don't   have enough of those micronutrients, you are  unable to extract energy from your macronutrients  
[05:40] and you get weak and tired even if you're  eating enough calories from bread and stuff.   This is a phenomenon that's well-documented  in centuries of history and literature,   especially stories about soldiers on campaign  or sailors at sea. It's why they used to say  
[05:55] that vitamins promote vitality, which is part of  why they're called vitamins. Anyway, spinach is   a great source of vitamins A, C, and K, folic  acid, iron, and spinach has a lot of calcium,  
[06:08] but it is not a great source of calcium.  Because as much as 95% of that calcium is   going to be bound up with the oxalic acid in  tiny little crystals that cannot pass through   your gut lining. You just eliminate them. But  that's okay because you can eat other foods  
[06:25] to get more calcium. Spinach doesn't have to have  everything, and it's good that calcium binds with   oxalic acid because, otherwise, that oxalic acid  ends up in your kidneys where it makes stones.  
[06:38] A long time ago, they used to tell people with  these kinds of kidney stones to minimize calcium,   but now the mainstream medical advice is to do  the exact opposite. If you're going to eat high  
[06:50] oxalate foods, eat them with a lot of calcium  so as to form indigestible crystals that you   safely dispose of in your bathroom. Now, there  is one other high oxalate food that I notice will   sometimes make my mouth feel a little weird, and  that's chocolate, particularly very, very dark,  
[07:08] minimally processed chocolate. Coco solids contain  a whole lot of oxalates, and depending on how the   beans were processed, you can end up with a  decent concentration of oxalic acid in your   mouth that forms those tiny calcium crystals  on your teeth. It's not as dramatic as spinach,  
[07:23] but it happens. Is that part of the texture of  dark chocolate or spinach? No, I don't think so.   I think that texture is a physical property of  food. It's how the food structure feels as you  
[07:37] bite into it and you mash it around in your mouth.  In contrast, this fuzzy teeth feeling is the   result of a chemical process that happens in your  mouth when you eat certain foods. It is not the   feeling of the food structure itself. Therefore,  I think that we can aptly describe this and  
[07:54] other sensations as "mouthfeel", a category that  includes texture but is not limited to texture.   There's other chemical things that affect how your  mouth feels when you eat, like the astringency  
[08:06] that you get from acidic foods like dark  chocolate or the lemon, that puckering feeling.   It's a similar sensation with a different chemical  cause that we will discuss on a different day.