If you've spent any time on foodie Instagrams lately, you're probably familiar with the vibrant yellow of golden lattes. These lattes are usually made with some kind of nut milk and cinnamon, but they get their color from turmeric, a spice that's been used in Indian cuisine and ayurvedic medicine for millennia. Touted as the next miracle superfood, turmeric has some bold health claims behind it. Like, that it can prevent and even cure cancer.

And while there have been a surprising number of studies conducted on the spice, there isn't a lot of evidence to support its superfood status. The dozens of supposed health benefits of turmeric certainly seem too good to be true. People and even scientists claim it makes your skin glow, improves brain function, can prevent cancer, diabetes, and heart disease, and can even cure the incurables, from cancer to arthritis, Alzheimer's, and more.

But the studies underlying these claims haven't really looked at the effects of turmeric-heavy diets on health. When researchers study the "medicinal effects of turmeric", most of the time, they're actually using concentrated curcumin, an active ingredient in turmeric. Or a mix of it and similar molecules collectively called curcuminoids.

These are polyphenols - compounds with multiple carbon rings - so they're somewhat similar in structure to the "healthy" stuff in red wines. And they also happen to be highly reactive molecules, so in lab tests, they might seem like they can do a lot.

But there's a lot of contradictory science too. For example it's often said that curcumin has health benefits because it's an antioxidant, a compound that binds to electron-hungry molecules called oxidants which can damage cells. But some studies have found it acts as an anti-antioxidant, as it can worsen the damage of these compounds or even cause damage all by itself.

Such conflicting findings tend to happen with highly reactive compounds because they don't actually solve a specific biological problem. They interfere with the lab tests being run. Biochemists have even come up with a special name for such annoying molecules: They're classified as Pan Assay Interference Compounds, or PAINS.

And curcumin earned that cheeky description because despite over 10,000 studies on the stuff, and more than 120 trials testing it for different medical conditions, there isn't really conclusive evidence that adding turmeric to your diet does anything special. That's partially because the vast majority of those trials were conducted in rats. And you know, it can't be said enough, that rats aren't people.

While they can be useful to see if something has potential, many rat cures completely fail in us. And the trials that have been conducted in people have had mixed results at best and vary widely in methodology. Those that do suggest benefits often have critical design flaws.

Like that they aren't double blinded clinical trials. Those are the gold standard studies, where neither the experimenter nor the participant knows whether they're getting the drug or a placebo to minimize the error that comes from bias. And most don't use dietary turmeric, like in a latte.

Instead they stick purified curcumin or curcuminoids in a capsule. The dose in that pill varies from study to study, from as low as 36 milligrams to as high as 8,000 mg per day.

Curcuminoids make up anywhere from 1-4% of turmeric powder. So to get the same amount from lattes, well, let's assume you use a generous teaspoon of ground turmeric to make your drink.

That weighs a little over 2 grams and contains anywhere from 20 to 90 mg of curcuminoids. So to down 8,000 mg, you'd have to drink between 88 and 400 lattes a day. Every day.

That's a lot of cashew milk. And it's not clear how much of the curcumin you eat actually gets into your bloodstem so that it can travel around and do the things people claim it does. That's because curcumin basically goes right through you.

In animal studies, ingested curcumin quickly ends up excreted in feces - which is why you might noticed your poops become nice and yellow after you eat curry. And in people, researchers often fail to detect any curcumin in a person's blood, even after they've consumed as much as 12 grams of the stuff. So while there are few things you can do to increase how much curcumin your body absorbs, like eating pepper or fat at the same time, even then it's really unclear if basically any curcumin you eat stays around long enough to actually do anything.

All that said, curcumin isn't the only component of turmeric. So it's possible that other things in the spice, either combined with curcumin or alone, could be good for you if eaten regularly as part of a healthy diet. Probably not, like cure your cancer good for you, but maybe a little better than the same meals without the spice?

And the good news is that turmeric as a food, and even curcumin as a supplement are thought to be pretty harmless. So you can sprinkle a large pinch of turmeric on your latte and you probably won't experience any negative side effects. Other than maybe some yellow tinted feces.

And whether you're boosting your health or not, at least you'll get a pretty yellow Instagram out of it.

[Hank] Excellent. Yellow-Tinted feces. That's what I've always wanted.

[Hank] So long as we're talking about stuff you put into coffee, we might as well mention chocolate. Every now and then you'll hear some food blog claim that you should put dark chocolate powder in your coffee or eat a square of chocolate candy bar every day. But while there is some truth to this, you can probably guess what's up. Here's Michael with more:

[Michael] Chocolate: as if we needed anymore excuses to indulge in the sweet stuff.

There are constantly claims floating around that "Hey, chocolate might actually be good for you." There is some science to back that up, but you guessed it! The devil's in the details. Most of these claims involve flavonoids, a class of compounds found in lots of plant, including cacao, the plant whose seeds are used to make cocoa and chocolate.

Some studies have linked flavonoids to a decreased risk of heart disease. Some experimental studies, which are considered the best type of study for establishing cause and effect, have shown decreases in blood pressure when healthy adults were given specially developed high flavonoid cocoa drinks or chocolate. For example, one 2015 study found that 100 adults who drank a high cocoa chocolate drink twice a day for one month had a drop in blood pressure of around 4 millimeters of mercury, which is a measure of pressure.

And a drop of blood pressure of just 2 millimeters has been associated with the decreased risk of stroke or heart problems, at least on average within a population. There are also a few experiments that hint the flavonoids could improve blood flow to the brain, which in turn might mean better brain function. For example, a 2014 study in Nature Neuroscience found that older adults did better on a memory task, and had increased blood flow to particular memory centers in the brain, if they'd had a high-flavonoid cocoa drink for three months.

But, there are a bunch of other studies that only show changes in brain blood flow and not improvements in cognition. And there are a few key points in these experiments that mean that a candy bar now and then isn't going to give you any benefit. For one, in most of these trials it took weeks or months to see any health benefits.

And most of the cocoa drinks in the experiments were specially made to have high levels of flavonoids, between 400 and 1,000 milligrams, using cocoa that's processed differently than regular supermarket chocolate. Even 400 milligrams is more flavonoids than chocolate normally has, and you'd need to eat at least two large bars of regular dark chocolate every day to get that much. Even if you did, the way cocoa is processed to make it less bitter, as well as adding milk or sugar, has been shown to reduce the level of flavonoids or the body's ability to absorb them. Plus, the flavonoid enriched chocolate used in these types of experiments isn't particularly tasty. Some participants were even put off from eating it. Yeah these studies managed to make chocolate taste bad. So you won't be finding these flavonoid rich drinks and bars at the supermarket.

So overall, there is evidence that flavonoids in chocolate and other foods have a small beneficial effect on heart and maybe brain health. But how that works isn't fully understood yet and more importantly, these compounds occur in small enough quantities in your average bonbon or candy bar, that to get an effective dose, you'd have to eat quite a bit more chocolate than you should. I mean, all that sugar and fat that comes with that chocolate is going to outweigh any benefits. So enjoy chocolate as a treat, but don't expect to be living longer because of it.

[Transition: "Sci-show"]

Well if there was some truth to that one. Also chocolate is very good and I love it. Now we couldn't make a video about health food trend without asking about a big one: antioxidants.

The obsession with them probably got started because of some seemingly convincing evidence. But the longer studies go on, the less straight-forward things seem.

[Transition: "Are Antioxidants Actually Good for Anything?"]

It seems like every week there's a news article claiming you should consume more antioxidants be it through fancy smoothies or sciency sounding supplements. This antioxidant craze goes back a long time to the 80s and early 90s when some early research suggested antioxidants could maybe protect against certain diseases. Food and supplement companies jumped on that research and have been touting the benefits of antioxidants ever since.

But the follow-up research investigating those benefits has actually been pretty inconsistent and scientists aren't totally sure why yet. Health food commercials will give you the impression that an antioxidant is a thing, a healthy thing you should be eating and drinking. But chemically, the word antioxidant is actually more of an adjective than a noun. It describes a range of chemicals and enzymes that can neutralize free radicals: compounds with single, unpaired electrons. Free radicals can cause real havoc in our cells: altering DNA, damaging the proteins our cells need to function, and messing with the sophisticated membranes holding everything together. And these free radicals can come from practically anywhere: From the food we eat, to the air we breathe- even sunlight can produce free radicals in our bodies.

Now our cells try to contain them by employing a large network of antioxidant chemicals and enzymes to deactivate the different types of free radicals our bodies encounter. But when the amount of free radicals being produced outpaces the rate at which our bodies can quench them, our cells enter a state known as oxidative stress. Unfortunately slipping into a bubble bath and decompressing with an episode of Queer Eye is not a viable way for our cells to de-stress though that does work for my mind.

And if our cells stay oxidatively stressed for long periods of time, there can be serious health consequences. In the 80s and 90s, scientists started gathering evidence that cancer, heart and neurodegenerative diseases, the negative side effects from aging could all be linked to damage from oxidative stress-- at least, in part.

Research during that time also found that a Mediterranean diet, which is rich in antioxidants, was associated with a lower incidence of those diseases. Scientists put two and two together that supplementing people's diets with antioxidants might prevent or even reverse the problems associated with these diseases.

It's an elegant idea, but unfortunately, it's been difficult to find support for. Researches began by looking at how supplementing single antioxidant chemicals would affect cells grown in test tubes and saw some promising results. For example, studies showed that chemicals like vitamin E could successfully act as antioxidants to reduce damage from oxidative stress in cell membranes. But when they tried to extend the benefits that they saw in cell cultures to randomized, clinical trials with real humans taking those same antioxidants, they found inconsistent effects.

For instance, in a study called the Women's Health Study published in 2005, a group of almost 40,000 women took either a vitamin-E supplement or a placebo every other day for 10 years.  That is a big study population, which should enable you to see robust results.  The rates of cancer and heart disease were unchanged compared to control, but researchers did observe a 24% reduction in heart-related deaths in the group who took the vitamin, except another study published in 2005 which tracked nearly 4,000 people over seven years found that vitamin-E supplements increased the risk of heart failure, which would indicate an increased risk of heart-related mortality, the opposite of what the first study showed, and such contradictory claims about antioxidant supplements are so common in the field that it's virtually impossible to take the findings of any individual study at face value.

In fact, a meta-analyis of 78 randomly controlled trials with a combined sample size of almost 300,000 people of various health backgrounds found antioxidant supplements to have no net beneficial effect.  The one exception for supplements is that a combination of three antioxidants moderately reduce the risk of age-related eye disease, which, yay.  It's something, we guess.  Despite the lack of reliable evidence for antioxidant supplements, though, many studies have found that people who follow diets containing fruits and vegetables rich in antioxidants have lower incidence of diseases related to oxidative stress, so we can see benefits from antioxidant supplements in a petri dish.  We can see benefits from antioxidant-rich diets in people, but we can't seem to demonstrate any benefit from antioxidant supplements in people.

It could be a simple problem of dosage.  We may be over or under administering these antioxidants so they're not doing the job we want.  It could also be that our cells compensate for the elevated antioxidant levels from supplements by slowing down their own antioxidant production, so overall in our bodies, the levels don't change, or maybe it's just that individual antioxidants are not effective at protecting against a disease in large organisms.

 Instead, we may need a wide variety of antioxidants rather than just one at a time.  You know how we said that our bodies use a variety of antioxidants?  Naturally, that's true of fruits and veggies, too, and that variety might help our bodies deal with the wide variety of free radicals we naturally encounter.  Each antioxidant compound acts a little differently, so if someone has an excess of a particular free radical, giving a high dose of the wrong antioxidant could be like giving a band-aid to someone with the flu, just not the right treatment.

It might also be that studying nutrition is just plain hard and we have a whole video on why that is, which we'll put a link to at the end of the video.  Whatever the reason, antioxidant supplements don't have much evidence to recommend them.  That's even though we know the chemistry and even though we know having them in your diet is linked to beneficial effects.  Our bodies are complicated and science is weird about connecting dots sometimes, but that's why we do it, to really know what we know, and right now, we just don't know about those antioxidant pills.

[Transition: "Sci-show"]

That's the thing about health research, sometimes things aren't as clear as you want them to be, and other times the research is actually pretty straight-forward. Like, in this next example. If you've ever browsed the drink section at your local grocery store, you've probably come across something called alkaline water that claims to mess with your body's chemistry. If that sounds like a terrible idea, it is! But it's alright, he's Olivia with more about why you shouldn't worry.

[Transition: "Is Alkaline Water Really Better for You?"]

You may have heard of alkaline water, it's the newest health trend hitting grocery shelves. These products are essentially just water treated to have a more basic pH between 8 and 10 instead of water's usual neutral 7.

And supposedly, they take your internal chemistry from acidic to alkaline, leaving you more hydrated and healthy. Drinking alkaline water can even prevent bone loss and cure cancer!... if the health gurus are to be believed. But science doesn't back it up as any kind of miracle drink.

The claim is based on an old idea often called the acid-ash hypothesis: that a more acidic body leads to health problems like cancer and osteoporosis. And if an acidic body creates bad health, then making things a little more alkaline could prevent all kinds of diseases. So for decades, folks have been coming up with special diets and, now, beverages like alkaline water that are supposed to raise your bodily pH and thereby cure cancer.

But, there isn't one bodily pH. Human blood has a pH around 7.4, for example, while muscles are a bit more acidic at a pH of about 6.1. And it's not easy to change those numbers with what you eat or drink.

For example, a study published in 2001 is often touted as showing that special diets can tweak internal pHs but even it didn't actually find much of an effect. The researchers prepared two meal plans for 8 volunteers an acidifying one, where the foods had higher amounts of phosphates in them and participants drank a low-pH water and an alkaline one with loads of calcium and a high-pH water. But after 4 days on the alkaline diet, while the subject's pee was noticeably less acidic, the average blood pH only went up 0.014 units on average.

That's less than the participants' daily variation, and likely within the level of error for the instrument used to detect it. It's actually a good thing they didn't find any big changes to blood pH based on diet. The range of pH where your cells work well is really narrow so big swings in either direction can damage your organs and even be fatal.

That's why your body has several systems in place for keeping acid-base levels balanced. For example, it can respond to decreasing pHs by getting rid of one of the most common acid forming molecules, carbon dioxide by well, breathing a little more. But usually, it's your kidneys that jump into action.

They take whatever you have too much of in your blood and put it into your pee. And that's why urine pH does change based on what you eat or drink. In that 2001 study, for example, the alkaline diet raised the subjects' urine pH by an average of 1.02 units.

So if you wanted to alter your blood pH by drinking an alkaline beverage, you'd have to interfere with your kidneys which, just to be clear, is a really bad idea. And other parts of the body also regulate their local acidity, either by making acidic or basic compounds or by throwing whatever they don't want into the blood and letting the kidneys take care of everything. That means that your urine is pretty much the only bodily fluid you can alter by chugging alkaline water with one other exception.

You do have some external control over the pH in your stomach, at least temporarily because you can directly neutralize some of the acid there with what you put in it. And it's why alkaline water might be effective against one particular health issue: acid reflux. Acid reflux is thought to occur because acidic stomach juices activate a digestive enzyme called pepsin.

If there's too much pepsin or it sloshes up into your esophagus or other places it doesn't belong, it binds to tissues and causes symptoms like burping and heartburn. And an article published in 2012 did find that alkaline water can deactivate pepsin. But that was done in dishes in a lab, not in an actual human body.

And we already have lots of cheap, readily available meds for neutralizing stomach acids, that's the whole idea behind antacids. When you look closer at the other purported health benefits of drinking alkaline water, the evidence just isn't there.

Take cancer, for example. Some scientists noticed that tumorous tissues are often more acidic than healthy tissues which is likely where people got the idea that reducing acidity could cure or prevent cancer. And if that were the case, you'd think that bladder cancers would be especially susceptible to alkaline diets because urine pH can actually be influenced by what we eat.  But a study of over 27,000 men from Finland in 2005 found a lower urine pH didn't significantly increase the risk of developing bladder cancer.

Similarly, many have claimed that alkaline water can prevent or help treat osteoporosis, a disease where bones become less dense and more likely to break. That's because, if your kidneys slack on the job, another way your body can buffer too much acid is to pull calcium and bicarbonate from bone, and less calcium means less bone mass. However, a study from 2010 found no association between urine pH and a subjects' bone mass density or how many bones they broke.

And meta-analyses have failed to find any connection between excreted acids and bone health. So for all the conditions drinking alkaline water might prevent, so far we haven't seen a real case for any of them. And despite the acid-ash hypothesis existing for half a century, there hasn't been any direct research showing that an alkaline diet or alkaline water can improve a person's health.

Luckily, there don't seem to be any side effects, either, so if you want to drink alkaline water because you like the taste, more power to ya. You'll just have some slightly more expensive pee. 

[Transition: "Sci-Show"]

Finally, for our last example, let's switch things up a little bit because this last food myth is not about something that is supposedly good for you, it's about something that many people claim is bad, MSG. People love to rage against the monosodium glutamate, but turns out, it's fine. Here's Stefan with the details.

[Transition: "The Truth about MSG and Your Health"]

Foodies can’t stop talking about umami — the savory taste that’s taking over the culinary scene and which, along with sweet, sour, bitter, and salty, is one of the five basic tastes that our tongues perceive. But if you’re a fan of Chinese takeout, you’ve been team umami from the get-go.

That’s because MSG— that flavoring often associated with American Chinese food— is umami in its purest form. And while you might have been told it’s bad for you or causes the so-called “Chinese Restaurant Syndrome,” science disagrees. As much as we associate MSG with Chinese food, there isn’t anything inherently Chinese, or even Asian, about the compound.

MSG stands for monosodium glutamate—the sodium salt of glutamate— an amino acid that the human body can synthesize, but that we also get from our food. Like other amino acids, glutamate is an important building block for proteins, and it also helps nerve cells send signals to other cells in the body— it’s the most abundant excitatory neurotransmitter in vertebrates. Since it’s so important for our bodies, it’s not surprising we’ve evolved a taste for it.

We have umami-specific receptors on our tongues and in our stomachs, and these drive our love for foods that contain glutamate like tomatoes, mushrooms, and aged cheeses. And umami-rich foods have been staples in human diets for, well, /forever/. For example, historians call the concoction known as Garum— an umami-filled sauce made from fermented fish guts—the ketchup of ancient Rome.

And we’ve been concentrating available, naturally-occurring glutamate by sun-drying tomatoes and curing meats for centuries, long before we knew what amino acids were. Even babies seem to like MSG, which makes sense, because human milk is naturally rich in glutamate. But purified MSG wasn’t a thing until 1908, when a Japanese chemist realized that the base made from kombu seaweed in his soup imparted a delicious flavor that wasn’t one of the four previously-established tastes.

He soon isolated the crystalline salt of glutamate from the kelp, striking culinary gold. He called the crystals Ajinomoto, which means essence of taste. And it wasn’t long before MSG became commercialized.

In Asia, it was branded a staple for any modern cook, and quickly became ubiquitous in kitchens across Japan and China. By the early 1930s it had gone global, with companies like Heinz and Campbell’s adding MSG to their products. And even the US military hopped on the MSG train.

During World War II, the army used the best available food science to develop nutritionally dense rations with long shelf lives, called K-rations, but soldiers hated them because they were super bland. So, in the late 1940s, they started adding MSG to them, and suddenly, they weren’t so reviled. Our universal love for MSG isn’t just from its savory goodness.

Studies have shown that umami functions as a flavor enhancer, creating a harmony between various flavors and aromas and adding a sort of dimension to both— a phenomenon known as umami synergy. That sounds kind of nebulous, but consider a 2007 study published in the European Journal of Neuroscience. Researchers as Oxford University had twelve volunteers sip an umami drink made of water, MSG, and the nucleotide ii while sniffing a vegetable aroma.

On their own, both the umami drink and the vegetable aroma were considered unpleasant and bland. But when combined, they were rated higher, and they just seemed to go together better than a salty drink paired with the same smell. What was really telling, though, was that brain activity maps showed way more neurons associated with flavor and pleasure lit up from the combo than would have been estimated by adding up the isolated effects of each.

Given all this, you might be wondering why companies now proudly proclaim their food doesn’t contain MSG, or people say it makes them sick. Well, while our love of MSG comes from biology, a lot of people’s aversion to it seems to have roots in something else entirely—racism. It all started with a 1968 letter to the editor of the New England Journal of Medicine describing the author’s and his friends’ so-called Chinese Restaurant Syndrome following the consumption of Chinese food, including symptoms like heart palpitations, generalized weakness, and radiating numbness.

The idea took hold, spurring years of biased science based on the flawed assumption that Chinese Restaurant Syndrome was a real thing, and that MSG caused it. Subsequent animal studies seemingly confirmed the idea, but these often consisted of injecting super concentrated doses of MSG directly into creatures’ abdomens, which is not exactly a scientific approach to determining the effects of MSG sprinkled into saucepans. More recent research on MSG aversion has taken into account the xenophobia and racism that fueled it.

And over the last 3 decades, a number of double-blinded, placebo-controlled studies, including studies of subjects with reported sensitivity to MSG, have failed to find a reproducible response to ingesting foods with MSG. A much more likely explanation for feeling crummy after Chinese takeout is the nocebo effect, where you feel sick simply because of the belief that something will make you ill. Fortunately, scientists are one step ahead of the haters.

Investigation into potential health benefits of MSG is ongoing, with research suggesting it can help increase salivation and appetite in the elderly, increase satiety and therefore reduce caloric intake in those trying to lose weight, and help impart flavor while reducing overall dietary sodium. So yeah, MSG doesn’t deserve its toxic reputation, and you don’t need to avoid your favorite restaurant just because they use a little.

[Transition: "Sci-Show"]

So there you have it, from turmeric to MSG there's a lot of misleading claims out there, but usually if you just give those
headlines a critical look and find out where they got their information, things get at least a little bit clearer. And I'll tell you one thing, the best nutritional supplement is a grain of salt.

Thanks for watching this episode and thank you to all the patrons who have helped make this content possible. We've done a lot of episodes over the years and we've been able to do that and we are able to keep going and trying new things because of you. If you want to learn more about supporting this show you can head on over to patreon.com/scishow.