Bear Spray

Where I'm living black bears are quite commonly seen around town. While I have yet to hear of a really bad bear encounter many bears are destroyed every year for getting too familiar with town. Most people here merely avoid them when they see them. Alternatively, aggressive responses to threatening bear encounters include firearms and pepper spray. While obtaining a firearm requires getting a firearms license and many restrictions, getting bear spray is as simple as purchasing some from Canadian Tire.

So what is bear pepper spray and does it work?

The active ingredient in bear pepper spray is the same compound that makes some peppers spicy. This spicy compound is caspaicin. Bear spray is also known as capsicum deterrent since capsicum is the genus of plants that includes caspaicin containing peppers.

Capsicum plants have evolved production of caspaicin in order to deter mammals from consuming the fruit of the plant. When consumed capsaicin produces a strong burning sensation in the mouth. This burning sensation is experienced by most other mammals, and is real, at least according to your brain. Capsacin binds a cellular receptor that is also activated by temperatures exceeding 43 degrees Celcius. The receptor, transient receptor potential cation channel subfamily V member 1 (TRPV1), is responsible for communicating pain and has a role in temperature regulation. Evolutionary pressure has caused capsicum plants to produce capsaicin to reduce their consumption by mammals. Exposing seeds to the mammalian gut prevents capsicum seeds from germinating. Bird TRPV1 receptors do not respond to capsaicin and therefore capsicum plants and seeds are readily consumed by birds. The avian digestive system doesn't not destroy the ability of the seeds to germinate and therefore birds contribute to capsicum seed dispersal.

So if this is the same compound found in hot peppers and salsa are we not just giving the bear a bit of a spicy snack? The difference between tasty and bear repellent is concentration. Spicyness or capsaicin concentration is usually quantified by an antiquated unit of measurement called the Scoville unit. The Scoville Unit tries to be objective but ultimately relies on 5 tasters determining the dilution factor that produces a solution with no caspasin taste. So for some spicy perspective, while an average jalapeño pepper has about 3500 to 8000 Scoville units, bear pepper spray has about 3.3 million Scoville units.

So spraying a bear with 3.3 MScoville Units causes the animal spicy pain, but does it actually work? In other words, in the real world are there statistics to show that being armed with a canister of pressurized capsaicin reduces harm to you and/or the bear? An article from 2008 reports that in 20 years worth of bear encounters reported in Alaska, bear spray was effective in reducing the severity of the encounter 92% of the time, while firearms were only 67% effective. This is the kind of evidence, almost convincing enough, to justify taking my gun rack off my mountain bike.

Chili, capsaicin and cancer

Speaking of the infamous journal "Medical Hypotheses", a paper published in 2002 tried to make a link between spicy food and stomach cancer:

"The 'hot' sensation produced by exposure to pepper is apparently due to two natural carcinogens: capsaicin in chili type peppers and safrole in black/white pepper. There are four cookeries in the United States that are noted for their high pepper content: Mexican-American, Cajun, white Creole, and black Creole. Each is largely confined to a single ethnic-cultural group which is concentrated in some counties. By use of county population and mortality data, significantly higher rates for stomach and liver cancer were found in counties inhabited by these four ethnic-cultural groups than in matched control counties."

Could it be true: chilies are carcinogenic? Might as well go to the source to find out, the country where chilies originated: Mexico. A Mexican study looking at associations between gastric cancers, chili consumption and H pylori infection found no independent association between the chilies and the Hp but a weak association with gastric cancer in heavy chili eaters (OR = 1.71; 95% CI = 0.76-3.88, p=0.026).

However there is mounting evidence that chilies may do more good than harm. Spices in general seem to make good candidates according to this recent review:

"the potential of turmeric (curcumin), red chilli (capsaicin), cloves (eugenol), ginger (zerumbone), fennel (anethole), kokum (gambogic acid), fenugreek (diosgenin), and black cumin (thymoquinone) in cancer prevention has been established."

You don't have to look very hard to find that in fact capsaicin has potential to inhibit the proliferation of cells in endometriosis , inhibit the growth of androgen-independent p53 mutated prostate cells, kill melanoma cells etc... The mechanism seem to included apoptosis, autophagy and ROS generation.

All this to say, you can eat your chilies without worrying too much about cancer, the harm done is mostly temporary and the jury is still out for the longer term...

Which organisms can feel pain?

I recently tasted raw habanero chili pepper for the first time. Just to give you an idea they rate at about 200 000-300 000 scoville units, compared to say jalapeños which have a measly 4000. This means that you have to dilute them over 200 000 times in sweet water before they stop burning. Needless to say it wasn't a very good idea and I had a near-death experience as my airways swelled so much that I could no longer breathe for nearly a minute. Do not underestimate the danger of hot peppers, they can be lethal. I was surprised to learn that birds can eat said peppers without so much as a sweat. Apparently it is mostly effective against mammals, and birds are immune to capsaicin, which makes for a clever way to get the damn squirrels out of your bird feeder. All of this is simply a segway to introduce another beer-fueled science debate we had at the pub. Is pain sensation limited to mammals? Warm blooded organisms? vertebrates?

You might recall that a while back a (very poorly conceived) paper about fish feeling pain created quite a stir. I suppose it all comes down to your definition of pain. For something we feel so ubiquitously pain's definition is rather elusive. Is it the "discomfort" you feel to a noxious stimulus, is it a reflex as a result of injury, is it the emotional suffering translated by our higher brain centers in response to the stimulus? As somebody who's worked with both fish and rodents I'd be inclined to think that all vertebrates feel pain. In fact by watching how slugs react to a poke, I think they might even be able to feel the essence of it. How else would they have survived this long if they couldn't learn from injuries to stay out of harm's way?

here is what the Wellcome Trust has to say about the subject:

"Nociceptive nerves, which preferentially detect injury-causing stimuli, have been identified in a variety of animals, including invertebrates. Indeed, the leech and sea slug are classic model systems for studying nociception. However, it is believed that invertebrates are capable only of stimulus-response reactions and lack the necessary brain system that vertebrates have to process pain.

In vertebrates, nociceptive information is collated and augmented in the brain and signals are relayed down the nervous system to alter the intensity of pain. All vertebrates possess the primitive areas of the brain to process nociceptive information, namely the medulla, thalamus and limbic system.

However, one area of great importance for pain perception in humans is the cortex and its relative size decreases as we descend the evolutionary tree. For instance, in relative terms, the cortex gets smaller going from humans, through primates, mammals, birds, reptiles, amphibia and finally to fish, which possess only a rudimentary cortex."

Spicy foods are good for you

I've always been a fan of spicy foods, and now there is even more reasons to like them. Apparently capsaicin, the pungent ingredient of peppers, seems to target mitochondria and cause cancer cell apoptosis. It has proven to be effective in a variety of cancers, with many publications showing efficacy on prostate cancer xenografts. Since we are on the subject of food and anti-cancer properties check out this great review: "we present evidence that numerous agents identified from fruits and vegetables can interfere with several cell-signaling pathways. The agents include curcumin (turmeric), resveratrol (red grapes, peanuts and berries), genistein (soybean), diallyl sulfide (allium), S-allyl cysteine (allium), allicin (garlic), lycopene (tomato), capsaicin (red chilli), diosgenin (fenugreek), 6-gingerol (ginger), ellagic acid (pomegranate), ursolic acid (apple, pears, prunes), silymarin (milk thistle), anethol (anise, camphor, and fennel), catechins (green tea), eugenol (cloves), indole-3-carbinol (cruciferous vegetables), limonene (citrus fruits), beta carotene (carrots), and dietary fiber. For instance, the cell-signaling pathways inhibited by curcumin alone include NF-kappaB, AP-1, STAT3, Akt, Bcl-2, Bcl-X(L), caspases, PARP, IKK, EGFR, HER2, JNK, MAPK, COX2, and 5-LOX."