Sampler Platter 2

Feed your curiosity by tuning in to our next Sampler Platter episode. We share why cutting onions brings a tear to your eye, why some produce has a waxy coat, and about a possible weight loss device that involves swallowing a pill-sized vibrating motor. Join us!

Shownotes: yournutritionprofs.com

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Get ready for our second Sampler Platter! We’re serving up bite-sized answers to a variety of your burning nutrition questions, from why onions make us cry to exactly what is that waxy coating on our produce.

M: I’m Professor Megan 

S: and I’m Professor Susan, and we’re

Both: Your Nutrition Profs!

M: We are registered dietitians and college professors who have taught more than 10,000 students about health and nutrition. We have answered a LOT of questions about nutrition over the years – 

S: Some questions we get asked every year and some are rarely asked but very interesting.

M: We’re here to share our answers to these common (and uncommon) nutrition questions with you.

S: So bring your curiosity and let’s get started. 

Both: Welcome to our class!

M: Welcome everyone to our second “Sampler Platter” episode. This is where we answer several questions in a single episode and we’ve got some good questions for you today. 

S: Yes we do and we love getting your questions. So if you have one you’d like Your Nutrition Profs to answer, visit our website, email us as YourNutritionProfs@gmail.com, or contact us on social media, Instagram or Facebook. 

M: Our first question is one that my students ask every semester: “Why does cutting onions make me cry?”

S: Such a good question, I mean why does such an unassuming root vegetable cause us such pain? I always cry when I cut onions, no matter what, and a lot, like down my face, and it’s just terrible. And I don’t know why. 

M: Well speaking of pain, have you ever rubbed your eye after cutting an onion? I do NOT recommend it.

S: Oh my god that’s so terrible! Yeah, definitely wash your hands after cutting onions. Well really after cutting anything.

M: Well before and after.

S: Yes, yes, definitely.  

M: But we use onions so often in cooking. Did you know that more than 9 million acres of onions are harvested annually? 

S: Nine million sounds like a lot. 

M: It is! But the average American consumes 20 lb of onions per year. 

S: Well they’re used in all sorts of dishes and you just eat a little bit at a time so I’m not surprised that it’s 20 lb.  

M: Ok, I see your point. Well all of this onion trivia is courtesy of the National Onion Association… And yes, that is a very real organization. 

S: I love it! Love it.

M: Here’s some more onion info. Onions are a root vegetable in the genus Allium. Other foods in this category include garlic, scallion, leeks, and chives. But the onion is the most cultivated of this genus. 

S: Oh, I really love all of those. But back to our question – what is it about cutting onions that makes us cry? 

M: Well the answer to this question lies in an enzyme… an enzyme called lachrymatory-factor synthase. 

S: Lachrymatory. That’s a fun word. 

M: It is. 

S: Well, lachrymatory it’s a sciencey word and it means relating to or causing tears. So that makes sense, right? And because synthase ends in -ase, we know it’s an enzyme. 

M: Exactly. Well, when you cut into an onion, this lachrymatory-factor synthase gets released and mixes with other chemical compounds creating – get ready –  syn-Propanethial-S-oxide molecules. These float up into the air irritating the lachrymal glands in your eyes to release tears. 

S: That’s a mouthful. Ok, so why would this happen? Well, guess what guys, it’s a defense mechanism. The onion’s trying to fend off the critters that want to eat it. So if you bite into an onion and start to cry you may think twice about continuing your assault on the vegetable. 

M: Right! Makes sens. It’s kind of like the pungent smell of the organosulfur compounds in cruciferous vegetables that also act as a defense mechanism. We discussed this in our kohlrabi snackisode last week.

S: You know, I’m still thinking about how good that kohlrabi was. 

M: It was so good. 

S: And yes, syn-Propanethial-S-oxide is also a type of organosulfur compound.

M: Interesting. Some onions actually produce more of this compound than others. So you can expect a greater risk of tears with red, white, and yellow onions because they have a higher concentration of lachrymatory-factor synthase. 

S: And sweet onions, green onions, shallots, and scallions, they have less of it. But I still cry when I cut them. 

M: So basically onions don’t want to be eaten, and I don’t blame them, but they’re so good. 

S: I know. Isn’t it interesting to think about how plants defend themselves? 

M: I know!

S: We’ve learned so much about that on this product. So things we didn’t know. Well onions are good. They add flavor and texture to dishes and they can serve toppings for things like chili and hamburgers. And they can be grilled, roasted, pickled, caramelized, deep-fried into onion rings - yum – or you can eat them raw. 

M: Quite versatile! And as we just said, there are many different types of onion and some are better than others depending on what you want to use them for. Sweet onions are best for frying and roasting, red onions are best for eating raw, and yellow onions are thought to be the best sort of all around for cooking.

S: And you might be wondering about nutrition… Well, a half cup of chopped raw onion has less than 30 kcal and provides fiber, vitamin C, B6, folate, selenium, and some potassium. 

M: Onions are also a source of several phytochemicals including thiosulfinates, quercetin, and specific to red and yellow onions, anthocyanins. 

S: Quercetin may be one of the more well-known flavonoids. We actually talked about these in two of our previous episodes. Remember dark chocolate?

M: Yes.

S: And the wine episode!

M: Yes! 

S:  So remember phytochemicals, those are those non-nutrient compounds in plant foods that provide additional health benefits, so that’s what makes them so good for you.

M: Yeah, it's because of these compounds that regular onion consumption has been linked to lower risk of cancer, cardiovascular disease, and even gastric ulcers. 

S: So lots of good reasons to consume them. But how can we enjoy this root vegetable without the tears? 

M: Well remember, red, white, and yellow onions are more likely to cause this reaction, so choosing other types of onions like sweet onions may help.

S: I’ve also read that using a really sharp knife can help… I guess the idea is that you’ll damage fewer onion cells which will release less lachrymatory-factor synthase. But none of my knives must be sharp enough because I really, really cry a lot. 

M: Mine either. But I’ve read that adding lemon or lime juice or vinegar to the onion can inhibit that enzymatic reaction… but, I’ve never tried that. 

S: Yeah, I haven’t tried that either. There are some other tips, like running the onion under water before cutting or even soaking the onion (after you cut it up into quarters) for just a little bit before you do the dicing.  

M: The American Academy of Ophthalmology offers some additional tips, including chilling the onion prior to cutting by putting it in the freezer for 30 min or so pre-chop. 

S: I’ve definitely heard that freezing helps but I’m usually not organized enough to remember to put it in the freezer 30 min before I want to use it

M: Same. They also recommend keeping a breezy kitchen by opening a window or turning on the stove fan…

S: And the most popular suggestion, of course, is to protect your eyes by wearing glasses or even goggles. They actually sell goggles specifically for this purpose. 

M: Which seems kind of silly, any goggles would probably work, but I’ve actually noticed less of an issue with tears just when I wear my regular glasses.

S: I actually have some onion goggles! And they do definitely help. 

M: I want to try them. 

S: Well I’ll let you try them and see what you think, I mean the problem for me is that I need regular glasses to see, and the goggles don’t fit over my regular glasses.

M: Ok so they need to make prescription onion goggles!

S: Oh  my god, that’s such a good idea! You know what? I have a friend who is an ophthalmologist – I’m going to ask her….

M: Do it!

S: …if that would be good. Maybe a new business venture for us?

M: I love it. Copyright!

S: Copyright! Trademark!

M: Another source suggests putting lubricating eye drops in your eyes just before you begin chopping. 

S: Hmm, why would that help? That would make me cry even before I even started on the onion!

M: I know! Me too.. I don’t know… well other than onion induced tears are there any other potential risks with onions? 

S: Yes for some people. So for example, if you have IBS, onions may not be the best choice for you. They contain a type of soluble fiber, called fructans. For most people, are good for us, right? They feed the bacteria in our gut microbiome. 

M: Right. And we discussed fructans in our IBS episode. Fructans are a type of oligosaccharide which is the O in the low FODMAPs diet. 

S: Oh, right. I remember. 

M: Yeah, some people with IBS are sensitive to one or more of theses FODMAPs nutrients and experience bloating and abdominal pain when consuming foods with one of more of them, like fructans. But this really only affects a small number of people. 

S: Ok , so anybody else who might need to avoid onions?

M: Well not people, but if you have pets, it’s important to know that dogs, cats, and horses, as well as some other animals, should never consume onions! They contain a compound called N-propyl disulfide that damages their red blood cells causing something called Heinz body anemia. 

S: Heinz body anemia. Guess it’s not related to Heinz ketchup! 

M: No. 

S: So these Heinz bodies are clumps of damaged hemoglobin that attach to red blood cells.

M: And Heinz body anemia happens when red blood cells break down faster than the body can replace them. You’ll feel tired and weak just like you would with any other form of anemia. And this type can happen in people or in pets although in people, onions don’t cause it.

S: It kind of sounds terrifying! 

M: I know! It can lead to blood clots, and kidney or heart failure. And in dogs especially, the condition can come on rapidly and escalate quickly. 

S: So definitely don’t feed your pets onions. That’s really interesting and very good to know!! 

M: Ok, let’s bottom line cutting onion induced tears. 

S: Ok, bottom line. Onions produce a compound that when exposed to the air release sulfur compounds which react with the water in our eyes making us cry. To reduce your risk of tears while cutting onions, you can chill the onion first, wear glasses while cutting, and/or you can cut it in a well ventilated space. 

M: And hopefully a few tears won’t be too much of a turnoff to consuming onions at home. They are extremely versatile and provide several nutrients. 

S: But only for humans. Let’s keep those onions away from our pets.

M: So true!

S: Well let’s get right into the next question or next questions, I guess I should say…These are pretty common each semester too. I know I usually have a couple of students ask… “Why is there wax on fresh produce? How can I remove it? And is it ok to eat?” 

M: Another great one! So some of the most commonly waxed fruits and vegetables include apples, peppers, cucumbers, eggplant, pears, squash, sweet potatoes, and tomatoes although there are several others, including several foods with peels that we don’t eat like avocado and oranges.

S: And, interestingly, most of these actually produce their own external wax layer, called the cuticle, but when they’re harvested, cleaned, and processed, the natural wax is lost. 

M: So is that why we add wax to food? Just to reapply what was lost? Well, yes, to an extent. That natural wax can help reduce moisture loss, and the main reason producers add their own wax is for food preservation.

S: Well for shelf life, right?

M: Exactly!

S: That makes sense!

M: The typical storage time for many types of produce prior to being sold in stores is several months! For example, apples can be stored from 6 to 12 months before making their way to your local grocery store.

S: What? I mean, that’s a long time.

M: It is! So they’re harvested from August to November, sorted, and cleaned. Wax is then applied to seal in moisture. Then they’re put in what’s called Controlled Atmosphere cold storage for those 6-12 months potentially.

S: So that’s why you can find fresh apples year round in most grocery stores in the US and other parts of the world. 

M: Exactly.

S: Wow, I didn’t know that.

M: But extended shelf life isn’t the only reason that wax is applied to produce. It can protect from bruising or other physical damage which may play a role in decreasing food waste.

S: Yeah, because consumers do not like ugly fruit! 

M: True. It can also inhibit mold growth and enhance appearance by making them shiny.  
S: Oh! They are shiny. We already mentioned apples, but cucumbers are another type of produce that’s waxed and it actually it has a vegetable oil applied to it. The reason is the same, it’s to reduce water loss, and that makes total sense because water is a main component of cucumbers. It also decreases decay and, again, makes them shiny. 

M: And adding wax to our fruits and vegetables is nothing new. We’ve been doing this it since the 1920s when it was first identified to prevent moisture loss. So we’ve been adding wax to food for over a 100 years! 

S: That’s really surprising to me.

M: I know! 

S: So what is the wax made of anyway? Well let’s point out here that when we use the term “wax” this can mean oils (like the vegetable oil we mentioned earlier) or resins in addition to actual wax. Or these could be combined in ways that are meant to mimic the naturally produced wax of the fruit or vegetable.

M: These “waxes” can be made from several different natural and food-grade ingredients, all of which are approved by the FDA. They all have to be generally recognized as safe, or GRAS. 

S: So these may include food grade vegetable-, petroleum-, beeswax-, or shellac-based wax. 

M: Petroleum and shellac? It’s understandable that those terms sound really scary! We don’t usually consider those to be consumable products. 

S: We definitely don’t. But if you recall our episode about food dyes, we did discuss petroleum-based food colorings. 

M: True. 

S: And these are still found in some food products that are on the market. So yeah, petroleum products part of some waxes on some foods. 

M: One commonly used produce wax is carnauba wax… and I always think of car wax when I hear the term carnauba, although I couldn’t tell you why that’s my first thought. Well, carnauba wax is a natural product. It’s derived from the carnauba palm tree in Brazil. So it’s actually vegan and apparently the harvesting process doesn’t hurt the tree.  

S: Well then that sounds like a good option.

M: It is! It’s non-toxic, hypoallergenic, durable, and not only used to coat many different types of produce, it’s also a common ingredient in chocolate covered candy, including M&Ms.

S: It makes them shiny!

M: Exactly!

S: I love M&Ms! There’s another common substance that’s used and that’s shellac. And this is  considered vegetarian but not vegan. It’s made from excretions of the female lac bug on trees in Southeast Asia. The lac bug spends its entire life sucking sap from a tree and producing a sticky reddish resin that we call shellac.  

M: And shellac has been used in wood furniture finishing, woodwind instruments, hair spray, and some nail polishes, and then also as a wax coating on citrus fruits. You know, I’ve actually had my nails shellacked a few times, but apparently not all shellac nail polishes use the lac bug resin. 

S: That’s really interesting. The shellac is also used to provide glossy protective coating on candies like whoppers and jelly beans. And so in this ase, it’s referred to as “confectioners glaze.” Shellac is insoluble in water so it prevents moisture loss!

M: It’s estimated to take 100,000 insects to produce a pound of resin. But shellac can also be made synthetically so it doesn’t always come from the lac bugs.

S: Gotta love it!

M: Science! 

S: Some students will ask if organic produce also has wax applied to it and the answer is yes. However, organic products have a slightly more limited list of possible waxes that can be used if they want to keep their organic label. 

M: So wax on produce sounds a little scary, but it is important to note that the amount of wax used is very small. It’s reported as a drop or two of microscopic coating per piece of produce.

S: Ok, so even though these waxes are food grade and edible, it is still important to wash your fruits and vegetables before eating! 

M: Yes, and not just because of the wax, but to remove dirt and other possible contaminants. 

S: And remember, even foods, like cantaloupe or watermelon need to be washed prior to cutting because... think about. You’re going to take a knife on an unwashed watermelon and then you’re going to cut through the unwashed outside. That could take contaminants from the outside to the inside flesh which is what you're going to eat. 

M: Exactly. 

S: So definitely wash it. Wipe it off with a wet paper towel or something. That’s what I usually do. 

M: And you should wash fruit like citrus as well as your hands….

S: Always! 

M: …before you peel it because otherwise contaminants can get on your hands and then when you use your hands to eat the fruit you’ve now contaminated it. 

S: Oh, man, that’s really good advice. So another question we get about this… I’ve had students ask if soap or that specialty produce cleaner instead of just water when they’re washing produce. 

M: No, you can just use your hands or a scrub brush for firmer produce while rinsing under running water. Research has not shown that vinegar, produce wash, or soap cleans produce any better than good old, potable water. 

S: So save your money!

M: Yes!

S: For more info about washing foods check out our show notes. We have linked to a blog from a woman called The Produce Nerd about how to wash fruits and veggies and it’s a really good one..  

M: Sounds good, let’s bottom line it. 

S: Ok bottom line. Many fruits and vegetables have a wax or resin coating to help extend shelf life, protect the produce from mild damage, inhibit mold growth, and to make it look shiny and pretty. 

M: These waxes are food-grade and FDA approved. And regardless of whether there’s a waxy coating or not, you should always wash all produce before eating.

S: Always. 

 M: Well those are the questions we have for today’s sampler platter but we have a couple more things! 

S: Yes, it has come to our attention that there may be a new weight loss… let’s call it device, on the markets in the future. It’s called VIBES, V-I-B-E-S, which stand s for Vibrating Ingestible BioElectronic Stimulator and it was created by researchers at MIT. 

M: First, let’s give some background… an adult human stomach is about the size of a large fist when empty, but it can stretch to hold up to 1.5 liters of food. 

S: That’s about a half gallon, so think of a half gallon of milk.

M: That’s a lot!

S: This capacity, of course, can vary, depending on your age, your body size, and several other factors.

M: You can think of the stomach like a muscular balloon. When it stretches, this is called distention, and it plays a really important role in digestion. Distention triggers the release of digestive juices to break down food and signals the brain that you’re getting full and to stop eating. 

S: It doesn’t necessarily mean we definitely stop eating, right ?

M: Right! 

S: I mean, I know I’ve eaten to and past that uncomfortable feeling… especially at Thanksgiving or like yesterday…

M: Well, it does play a role in signaling fullness, and that is important. This VIBES device is about the size of a large multivitamin supplement. It contains a vibrating motor and small battery which is surrounded by a gelatinous membrane. 

S: And here’s how it works. The key is it vibrates... 

M: Shocking!

S: Yes, so when the vibration is applied to a muscle, like the walls of the stomach, it creates the sensation of distension of the stomach or of being full. 

M: So the device is swallowed 20 to 30 minutes before eating a meal, when the stomach is empty. 

S: And once it’s in the stomach, the outer part, the outer casing of the pill dissolves and it releases a vibrating spring, which vibrates for an average of 38.3 minutes – which is really freakishly specific. This vibration tricks your body into thinking it’s full, so you eat less. 

M: Once it stops vibrating it passes through the digestive tract, along with whatever you’ve eaten and you poop it out within 4-5 days. 

S: Those MIT folks, they are  so clever!

M: I know, right? But there’s a but… This has not yet been tested in humans.

S: That’s a pretty big but….

M: It really is, yeah. But when tested in pigs, they consumed an average of 40% less food than the control group over 100 meals or so. 

S: That sounds pretty good. I mean, eating 40% less at most meals should help a person lose weight. 

M: It does. And although these pigs did not actually lose weight, they had significantly less daily weight gain. But these were young pigs.. They’re growing. They weren’t really expected to lose much weight.

S: So a vibrating pill seems much less invasive than having bariatric surgery.

M: And much cheaper. VIBES is estimated to cost in the “cents to dollar range” per device. 

S: Well that’s definitely cheaper than surgery. I mean, if you consume 3 per day at $1 per device, that’s about $90 a month. 

M: Yeah, that’s 10-15 times cheaper than current GLP-1 medications like Ozmepic and  Wegovy which cost approximately $900-1400 a month. 

S: I know, they’re so expensive! 

M: And more good news – No significant side effects have been identified in the pig participants. Of course, we have a long way to go before these are approved for human use. And I think they’re planning trials with dogs next.

S: That’s so interesting. Wow! So, maybe VIBES won’t be on the market that soon, but it's definitely something to keep an eye on and we’ll keep you posted!

M: And this is not the first application of a vibrating pill for a health issue. In August 2022, the FDA approved a vibrating capsule or pill, called Vibrant to assist those with chronic constipation. 

S: Oh, that’s so good. I mean, 10 to 20% of Americans suffer from chronic constipation, so it could help a lot of people. 

M: Vibrant stimulates specialized nerve cells, called mechanosensory cells, in the colon to trigger peristalsis. 

S: We’ve discussed peristalsis several times on this podcast. It’s the sciencey word for the wave-like muscle contractions that occur to help move contents through our digestive tract.

M: Right. These capsules are taken by mouth before sleep 5 days a week. They must be activated by a pod that comes with them and once activated they're swallowed with a glass of water. And they take about 14 hours to reach the colon. Once there they work by vibrating on and off for a number of hours, followed by a break and then it begins again.

S: So crazy! Eventually they get expelled as part of a bowel movement and they get flushed down the toilet.

M: Yeah, studies found that 40% of participants had at least one additional bowel movement weekly, softer stools overall, and less bloating compared to the placebo group, similar to the benefits of prescription drugs, but with fewer side effects. 

S: Oh my gosh, what a world we live in! But they’re not drugs, right? 

M: Right, they’re considered a Class II medical device, like contact lenses, syringes, and pregnancy tests. They are prescription only, and they’re not covered by insurance – yet. 

S: But wow, I mean I have this song in my head that “good vibrations” song! 

M: Ah, the Beach Boys!

S: Would you try it? 

M: You know, if I had chronic constipation, I might! 

S: Yeah, I think I would too, versus drugs. I mean, it works. It does the same thing as prescription drugs with fewer side effects. 

M: Yeah. 

S: I would. Come on insurance! 

M: Well, listeners, we’ll keep you posted if we hear any updates on VIBES or Vibrant. 

S: So crazy! I love technology!  Ok, finally, we wanted to give you an update about the alpha-gal carbohydrate that causes people to develop an allergy to meat after experiencing a tick bite. You may recall that we did an episode all about this last fall.

M: Ok, so just as a quick review – alpha-gal is a carbohydrate that is found in most mammals – cows, pigs, sheep, deer, dogs, cats, etc., especially in their organs. But it is not found in higher order apes or humans. 

S: Right. So let’s say a tick bites a mammal, like a pig. The tick takes in some of the pig’s blood that contains this alpha-gal carbohydrate. The tick carries that pig blood with him, and then when he bites a human, he transmits some of the pig blood into the human that contains this alpha-gal carbohydrate. 

M: Because humans don’t produce alpha-gal, it’s “foreign” and this causes the immune system to fight it by creating immunoglobulin E (or IgE) antibodies. After about 1 to 3 months, the body produces more and more of these IgE antibodies to protect itself from this foreign invader. 

S: Then when the human consumes food containing alpha-gal, it's usually some sort of meat, then they develop an allergic reaction, and that’s called alpha-gal syndrome or AGS.

M: Any time the internal human body comes into contact with this alpha-gal carbohydrate, the human’s immune system fights against it. So this is one of the main reasons that we are not able to successfully transplant organs from mammals like pigs into humans – until now.

S: Right! Pigs are considered the most ideal organ donors for humans because their organ size, physiology, and immune system are the most similar to humans. 

M: A company in Virginia called Revivicor has been working for more than 20 years to develop a pig that does not contain alpha-gal in the hope that the pig organs could be transplanted into people without rejection.

S: And this year they’ve done just that through genetic modification and cloning. Ten genes are modified to make sure the pig organs don’t grow too big, won’t cause blood clots, and won’t be rejected by a human immune system. A big part of the genetic modification is the elimination of the alpha-gal carbohydrate in these pigs. 

M: Theoretically all of the pig’s organs could be transplanted into humans, so lungs, hearts, kidneys, livers, etc. 

S: Once these genetically modified pigs are created, they can be cloned to make more pigs whose organs could be harvested for humans.

M: And keep in mind that more than 100,000 people are on waiting lists for organ transplants in the U.S. and about 17 die every day without getting one. 

S: So this could be a really big deal! 

M: Yes! So far this spring they’ve transplanted two pig hearts and two kidneys into humans under the FDA’s compassionate use policies which allows terminally ill patients without other options to access investigational medical products that they normally wouldn’t have.

S: Three of the 4 patients have died, but one kidney recipient is still alive and the kidney seems to be working well. And remember, these patients were really, really sick prior to this transplant. Most of them – the doctors don’t think they died from rejection of the organ. 

M: Scientists are learning so much about these organs and what it takes to make xenotransplantation, which is the sciencey word for transplanting tissue from one animal to a different species, work. Creating pigs who don’t make the alpha-gal carbohydrate is a huge step in this process.

S: So stay tuned! I mean, again, when things change we’ll provide some updates. But it’s an exciting time! 

M: It is! All right, well that’s it for our second Sampler Platter episode. We hope you learned something, we definitely did. 

S: Oh my god, this episode was so interesting to research! We’ve got vibrating weight loss things, we’ve got wax on veggies, and now I know why I cry when I cut onions.

M: Well make sure to join us next time when we’ll do a deep dive into caffeine!

S: Oh, I’m looking forward to it!

Both: Class dismissed.

S: We hope you enjoyed this episode. You can find the show notes and a list of sources on our website, yournutritionprofs.com. 

M: Your homework is to follow us at your nutrition profs on Instagram and to listen to our next episode. You can listen on Amazon Prime, Apple Podcasts, Spotify, YouTube, or anywhere podcasts are found. We’d appreciate it if you’d “like” us, write a review, subscribe, and invite your family and friends to join us too. 

S: If you have a nutrition or health question you’d like answered, let us know! We may even do a show about it! Send an email to yournutritionprofs@gmail.com or click on the “Contact Us” page on our website.

M: Thanks to Brian Pittman for creating our artwork. You can find him on instagram @BrianPittman77

Both: See you next time!