What rhythm does throbbing pain follow? (McGill OSS)

1 minute read

There are many kinds of pain—Piercing, burning, aching, shocking—but the type I want to focus on today is throbbing. Throbbing pain is often associated with toothaches, headaches, migraines, and pain in the extremities but can occur nearly anywhere in the body. Its pulsing nature can be incredibly annoying to those affected, but it also raises an interesting question: when pain throbs, what rhythm is it following?

Contrary to what you might think, throbbing pain is not beating to your heartbeat or pulse. A 2012 study looked at the throbbing rate of 29 dental patients’ pain, as recorded by patients pushing a button every time they felt a painful throb, compared to their arterial pulse measured in their earlobes. The mean arterial pulse rate was 73 beats per minute (bpm), compared to a throbbing pain rate of just 44 bpm. Researchers further analyzed the simultaneous recordings and found that the two rhythms weren’t synchronous in any way.

If throbbing pain isn’t paced against our heartbeat or pulse, then what determines its rhythm? Simply put, we don’t know! The study’s authors theorize that the pacemaker of throbbing pain is contained somewhere within the central nervous system, but we currently do not have any more specific theories. For now, we just have to accept that throbbing pain marches to the beat of its own drum.

This article was written for. the McGill Office for Science and Society. View the original here: https://www.mcgill.ca/oss/article/did-you-know/what-rhythm-does-throbbing-pain-follow


Why do we wake up feeling cold? (McGill OSS)

1 minute read

A few different bodily processes in humans follow a stable, roughly 24-hour cycle. For example, the cortisol and melatonin levels in our blood. Physical parameters like your blood pressure and heart rate too.

Also under a circadian cycle is our core body temperature. We reach our minimum temperature about halfway through our sleep cycle. By the time we wake up, our bodies have warmed up slightly, but often not yet to our typical body temp.

So, we wake up feeling cold because we are cold. From a normal body temperature of 36.4-37.2 °C (97.5-98.9 °F), normal circadian fluctuations can take us up or down about 1 ˚C. It might not feel like a lot, but remember that most doctors consider fevers to start at 38 ˚C.

Interestingly, there seems to be some variation in when we reach our minimum temperature during the night. A 2001 study measured the temperatures of 172 young men and women and sorted them according to their self-declared status of “morning person,” “evening person,” or “neither.” They found that morning people hit their minimum temps after an average of 3.5 hours, compared to 5.02 hours for neither types and 6.01 hours for evening types. Since individuals tend to feel more alert and perform better on cognitive tasks at higher body temperatures, these differences in the circadian rhythm of body temperature may be one reason some of us struggle to wake up and feel alert immediately.

Image source: https://www.mdpi.com/2079-7737/10/1/65

This article was written for the McGill Office for Science and Society. View the original here: https://www.mcgill.ca/oss/article/medical-you-asked/why-do-we-wake-feeling-cold

Why is poop brown? (McGill OSS)

1 minute read

A certain amount of the muddy colour can be attributed to the different colours of food we eat. Like mixing all the paint colours together, the result is a dull brown. But, much bigger factors for humans’ brown poop are bilirubin and bile. Bilirubin is a yellow substance found in the liver, the product of the breakdown of old red blood cells. Bile is dark brown or green and is produced by the liver to help digest fats. Both of these substances are secreted into the small intestine during digestion, and slowly make their way into poop, bringing with them a dark brown hue.

Bird poop, on the other hand, is not brown but white. That is because—unlike mammals—birds don’t pee!

To read the entire article, click here: https://www.mcgill.ca/oss/article/health-and-nutrition-did-you-know/why-poop-brown

The Food Babe has No Idea how Physiology Works

Originally posted here: https://mcgill.ca/oss/article/quackery/food-babe-has-no-idea-how-physiology-works

Our good friend the Food Babe has published an interesting piece of pseudoscience writing entitled ‘Are Natural Flavors Really That Bad? (MUST WATCH)’. If you’re looking for the quick answer to this superfluous, click-bait title, let me tell you that it’s no: natural flavours are perfectly safe and healthy. But if you’re looking for an explanation of how taste actually works (and why her claims about natural flavours are utter nonsense), then please read on!

Vani Hari bases her distaste for natural flavours off the idea that “flavor in nature doesn’t come without nutrition.” Regrettably I’m here to tell her that this is unequivocally false. Hari thinks that “foods naturally taste amazing to us because they contain the nutrients we need. Flavors are the cue that tells us where to and the nutrients we need”. Not quite, Babe. Taste =/= nutrition. There are poisonous things that taste great, and very healthy foods that taste awful.

Following this same logic, she also believes that food companies add natural flavour to foods to “trick consumers into thinking they are getting nutrition that isn’t there.” Now, for once, this idea isn’t exactly wrong, but it is misleading. Food producers definitely do add natural flavours to all kinds of foods, but they do so in general to make things taste better, not to make them seem healthier. Think about it, do you really think your soda is healthier if its blueberry flavoured instead of cream soda? Doritos list natural flavours on their label, presumably those are natural flavours of tomato and cheese, but did you really think that Doritos are good for you like homemade tomato soup with cheddar on top?

Following your tongue to guide your diet probably isn’t a good idea, but I think we all knew that. If I only ate what I was craving, I’d live off of French fries, and I don’t think that’s because my body needs a lot of sodium and no protein. Besides, what tastes good is fairly subjective, but what’s healthy isn’t.

So what is flavour, if not nutrition? It’s all chemistry. We taste things because of interactions between the chemicals (gasp!) in food and the chemoreceptors in our mouths. You know how they say there are only 5 tastes: sweet, sour, salty, bitter and umami (savoury)? That’s a result of the taste receptorspresent in humans.

Salty and sour tastes are the simplest in many respects. Saltiness is detected by sodium ion channels in our tongues. When sodium ions (usually from sodium chloride or table salt) interact with these taste receptors, they are allowed to enter the cell. Being positively charged, they change the voltage inside the cell, which starts the process of sending an electrical signal to your brain that tells it, ‘hey, this tastes salty’. Sour tastes use a similar process, but with hydrogen ions entering sour taste cells.

The other 3 tastes are a bit more complex in how they’re detected. Instead of ions entering receptors directly and starting the signal to the brain, various molecules (depending on the taste) interact with different G-protein-coupled receptors. This interaction begins a whole pathway of signaling that eventually reaches the brain to convey taste.  Many different molecules may activate these: for sweet tastes, it’s commonly sugars and molecules similar to sugars; for bitter, it’s more than 670 compounds; and for umami, it’s salts ofglutamic acid, the most commonly encountered of which is monosodium glutamate (MSG).

So food produces a taste because of the molecules inside of it, but why does it taste good? Because of physiology!

Our body does use the tastes of foods to get us to eat varying amounts of them, but not because of their nutrient contents like Hari thinks. In general, we find salt to be a pleasant taste because it is necessary to maintain homeostasis. Without salt, our kidneys would cease to function, so in an attempt to get us to ingest it, our brain makes it taste ‘good’.

Sugar, similarly, is absolutely integral to life. Carbohydrates are just chains of sugars and they are rich in calories, so they are desirable for a body that needs energy, hence the enjoyment that sweet tastes elicit. Umami tastes ‘good’ to encourage us to eat necessary fats and proteins.

Both salty and sour tastes are only ‘good’ in certain quantities. This is thought to be a result of evolution, since things that taste too acidic or salty tend to be spoiled, unsafely acidic or not ripe.

Bitter tastes bad to all humans naturally: just try to feed dark chocolate to a baby if you need proof of that, and it’s only through repeated consumption and some trick psychology that we come to enjoy bitter things. This is anevolutionary development due to many poisonous compounds tasting bitter, and why most medicines still taste bitter to us (our bodies think they’re poisons).

Now, there are many exceptions to these broad generalizations of what tastes ‘good’, proven in the fact that some (silly) people dislike dark chocolate, or the fact that I hate papaya, despite it tasting sweet. And in the modern world, as Food Babe warns us, there are artificial and natural flavours added to foods, so, surprise, surprise, there’s more to a healthy diet than just flavour.

Some good example include nightshade, which is incredibly toxic to humans, yet tastes quite sweet (making it even more dangerous to children who may ingest it), and apricot kernels which are quite toxic (as few as 10 of them could kill a child) due to their amygdalin content (this compound is metabolized into cyanide inside humans). But if you want to follow Vani’s logic, some people think they taste quite good, so they must be good for you, right?

Vani might be technically right about natural flavours being added to foods, but she’s wrong about why, and she’s wrong about a few other things too:

She says that “the flavors that humans love in tomatoes are synthesized in tomatoes from essential nutrients like beta carotene, amino acids, and omega 3’s”. Well, beta carotene is not an essential nutrient in humans, and indeedonly 9 of the 20 amino acids are. Studies on tomatoes have determined that there are about 27 compounds that contribute to their taste, 3 of which (geranial, 2-methylbutanal, and 3-methyl-1-butanol) actually influence how sweet a tomato tastes, regardless of sugar content (or ‘trick your brain!’ as she would say). So if the Food Babe believes compounds that alter how foods taste without altering their nutritional content are problematic, she should probably give up bruschetta.

Not to mention she claims that “soda without flavors is just carbonated water and sugar. No one would drink that without the flavor”’ somehow forgetting that the carbonated water industry is huge, and that billions of people do just that.

To recap, flavours are just the result of chemistry, things that are good for us do taste good, sort of, but not because of their nutrient content, and no one thinks that gummy bears are healthy just because they taste kind of like fruit.

So instead of asking yourself, “Did someone engineer this to be delicious or did nature engineer this to be delicious”, as Hari advises, I think I’d rather contemplate why it is I’d be taking diet advice from a blogger without a science degree.

Under the Microscope: Blood

Originally published here: https://mcgill.ca/oss/article/health/under-microscope-blood

Human blood contains many different components, from white blood cells to platelets, but the most abundant component by far are red blood cells.
More properly known as erythrocytes, red blood cells make up 70% of an adult human’s cells by count. They serve an integral purpose: transporting oxygen from the lungs to all other parts of the body and returning carbon dioxide to the lungs to be exhaled. To accomplish this, they have a few unique features.
In mammals, while developing red blood cells contain a nucleus and other organelles, before they mature fully, they extrude, or push out, these organelles. Having no nucleus, red blood cells are unable to create proteins or divide, but can they can store hemoglobin, the iron-containing molecule that binds oxygen and carbon dioxide. Each red blood cell can hold approximately 270 million hemoglobin molecules, each of which can bind 4 oxygen molecules. In total, your red blood cells hold about 2.5 grams of iron.
Red blood cells are shaped kind of like donuts that didn’t quite get their hole formed. They’re biconcave discs, a shape that allows them to squeeze through small capillaries. This also provides a high surface area to volume ratio, allowing gases to diffuse effectively in and out of them.
An adult human body produces around 2.4 million red blood cells every second, mostly within the bone marrow. A red blood cell will stay in circulation for 100-120 days, making a full circuit of the body ever 60 seconds. They transport inhaled oxygen to cells and return carbon dioxide to the lungs to be exhaled.
After this period is up, the membrane of the red blood cell undergoes a change that allows it to be recognized by a type of white blood cell called a macrophage, which breaks it down. Many of the components, including iron, are recycled and used to make more red blood cells. The main non-recyclable component is broken down into bilirubin, which is excreted in urine and bile. Although, if too much bilirubin is produced, it’s yellow colour can cause discoloration of the skin, as seen in jaundice.
Carbon monoxide has a 250 times greater binding affinity for hemoglobin than oxygen, meaning that if any carbon monoxide is present, it will bind to hemoglobin instead of oxygen. This is why carbon monoxide is such a danger, it reduces our bodies ability to get oxygen to our cells. This is also why many smokers are short of breath, as the carbon monoxide they inhale while smoking is out-competing oxygen for hemoglobin’s binding sites. In heavy smokers, up to 20% of oxygen binding sites may be blocked with carbon monoxide.
Because it is colourless and odourless, often times carbon monoxide’s effects aren’t noticed until they become really severe. To avoid a scary situation, every home should be equipped with a carbon monoxide detector.