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Science & Society : @McGillOSS

@McGillOSS - Sat, 07/25/2015 - 15:39
Dr. Joe of @McGillU live podcasting w @moshekasher & other comics chatting about as a part of http://ow.ly/i/c0Uao 

Science & Society : @McGillOSS

@McGillOSS - Sat, 07/25/2015 - 15:11
meets . @joeschwarcz, comedian @moshekasher & a bunch of other funnies weigh in on . 3:15pm EST @ the Hyatt

You Asked: Is it true that dogs are being poisoned by propylene glycol in some dogfoods?

You Asked? - Sat, 07/25/2015 - 10:32

Numerous Internet posts attempt to scare dog owners with questions like “Is It a Dog Food Aide or Automotive Antifreeze?” The reference is to propylene glycol, a chemical added to some dog foods to help retain moisture. Of course being an antifreeze component and serving as a food additive are not mutually exclusive. After all nobody worries about eating salt because it is also used in enemas. The potential risk of a substance is determined by studying it, not by making specious associations.

So what do the studies say? Unfortunately when it comes to dogs, not a whole lot. In humans, propylene glycol when ingested is pretty innocuous. Toxicity occurs when blood concentration reach 4 grams per liter, which is unachievable by consuming foods or beverages that contain the chemical. And yes, it is used in human food, mostly to retain moisture, although it also serves as a solvent for flavours. The pharmaceutical industry uses propylene glycol as a solvent in formulations of drugs that are insoluble in water. In beer it can stabilize head foam, in soft drinks and flavoured coffees it carries flavour, it stabilizes whipped cream and prevents the formation of crystals in ice cream.

Canada attaches no numerical value to the maximum amount of propylene glycol that can be used as long as it conforms to “good manufacturing practices.” In the U.S., it can be used up to 50 grams per kilogram of food or beverage. Europe allows maximum of 3 grams per kilogram. The reason for the discrepancy is not clear since there is no evidence that amounts greater than the European limit cause any problem. But this difference between amounts allowed in Europe and the U.S. did cause quite a kerfuffle when Fireball Whisky was recalled in Norway, Sweden and Finland. It seems the American version of the product found its way across the ocean with levels of propylene glycol above those acceptable in Europe.

This precipitated a public outcry in Europe where people recalled with horror the 1985 episode when some Austrian wines were adulterated with diethylene glycol, another chemical that can be used in antifreeze, to make the wines sweeter and more full-bodied in the style of late harvest wines. Nobody was hurt except the Austrian wine industry which suffered an almost complete collapse.

The publicity about the Fireball recall in Europe bounced back to the U.S. where this whisky is a popular choice among the college set due to its low cost and relatively high alcohol content. Rumors that a Fireball recall was underway sent ripples of upset across social sites.There was no recall, but as expected the chemophobes rallied around the “they’re putting antifreeze into our food” battle cry. The fact is that someone would perish from alcohol poisoning long before enough alcohol were consumed to cause a problem with propylene glycol.

Exactly why propylene glycol is found in Fireball whisky isn’t clear. The company goes no further than to say that “the secret to Fireball is buried in the depths of our souls and it’s so damn special that we just can’t share it. Although we’d love to talk Fireball, we have a strict policy that we let our whisky speak for itself.” In all likelihood propylene glycol is used as a solvent for some flavour that is added to the whisky.

While there is no issue with propylene glycol in human food, dogs may be a different case. They often eat the same food for all their meals and the continued ingestion of propylene glycol even in small doses may conceivably be a problem. That is just what a class action lawsuit launched by a California pet owner contends. He claims that two of his dogs got sick and one died after he began to feed his pets with “Beneful” produced by Nestle Purina Dog Care. The lawsuit describes over 3000 complaints on line about dogs developing liver problems, kidney failure, seizures and diarrhea due either to propylene glycol or ochratoxin, a fungal metabolite found in the food.

The manufacturer dismisses the notion that Beneful is the cause of the ailments. Dogs get sick, and owners then look for a cause, with food being a prime suspect, they say. And Beneful is not associated with symptoms any more than any other dog food, whether it contains propylene glycol or not. However, whether that is indeed the case is hard to know. Nobody it seems has actually done a study. Given that propylene glycol is known to be toxic to cats, causing “Heinz body anemia,” and since questions have been raised about its effects on dogs, it may be prudent to choose varieties of dog food that do not contain the chemical.

Read more

You Asked: Is it true that dogs are being poisoned by propylene glycol in some dogfoods?

Our OSS Blog - Sat, 07/25/2015 - 10:32

Numerous Internet posts attempt to scare dog owners with questions like “Is It a Dog Food Aide or Automotive Antifreeze?” The reference is to propylene glycol, a chemical added to some dog foods to help retain moisture. Of course being an antifreeze component and serving as a food additive are not mutually exclusive. After all nobody worries about eating salt because it is also used in enemas. The potential risk of a substance is determined by studying it, not by making specious associations.

So what do the studies say? Unfortunately when it comes to dogs, not a whole lot. In humans, propylene glycol when ingested is pretty innocuous. Toxicity occurs when blood concentration reach 4 grams per liter, which is unachievable by consuming foods or beverages that contain the chemical. And yes, it is used in human food, mostly to retain moisture, although it also serves as a solvent for flavours. The pharmaceutical industry uses propylene glycol as a solvent in formulations of drugs that are insoluble in water. In beer it can stabilize head foam, in soft drinks and flavoured coffees it carries flavour, it stabilizes whipped cream and prevents the formation of crystals in ice cream.

Canada attaches no numerical value to the maximum amount of propylene glycol that can be used as long as it conforms to “good manufacturing practices.” In the U.S., it can be used up to 50 grams per kilogram of food or beverage. Europe allows maximum of 3 grams per kilogram. The reason for the discrepancy is not clear since there is no evidence that amounts greater than the European limit cause any problem. But this difference between amounts allowed in Europe and the U.S. did cause quite a kerfuffle when Fireball Whisky was recalled in Norway, Sweden and Finland. It seems the American version of the product found its way across the ocean with levels of propylene glycol above those acceptable in Europe.

This precipitated a public outcry in Europe where people recalled with horror the 1985 episode when some Austrian wines were adulterated with diethylene glycol, another chemical that can be used in antifreeze, to make the wines sweeter and more full-bodied in the style of late harvest wines. Nobody was hurt except the Austrian wine industry which suffered an almost complete collapse.

The publicity about the Fireball recall in Europe bounced back to the U.S. where this whisky is a popular choice among the college set due to its low cost and relatively high alcohol content. Rumors that a Fireball recall was underway sent ripples of upset across social sites.There was no recall, but as expected the chemophobes rallied around the “they’re putting antifreeze into our food” battle cry. The fact is that someone would perish from alcohol poisoning long before enough alcohol were consumed to cause a problem with propylene glycol.

Exactly why propylene glycol is found in Fireball whisky isn’t clear. The company goes no further than to say that “the secret to Fireball is buried in the depths of our souls and it’s so damn special that we just can’t share it. Although we’d love to talk Fireball, we have a strict policy that we let our whisky speak for itself.” In all likelihood propylene glycol is used as a solvent for some flavour that is added to the whisky.

While there is no issue with propylene glycol in human food, dogs may be a different case. They often eat the same food for all their meals and the continued ingestion of propylene glycol even in small doses may conceivably be a problem. That is just what a class action lawsuit launched by a California pet owner contends. He claims that two of his dogs got sick and one died after he began to feed his pets with “Beneful” produced by Nestle Purina Dog Care. The lawsuit describes over 3000 complaints on line about dogs developing liver problems, kidney failure, seizures and diarrhea due either to propylene glycol or ochratoxin, a fungal metabolite found in the food.

The manufacturer dismisses the notion that Beneful is the cause of the ailments. Dogs get sick, and owners then look for a cause, with food being a prime suspect, they say. And Beneful is not associated with symptoms any more than any other dog food, whether it contains propylene glycol or not. However, whether that is indeed the case is hard to know. Nobody it seems has actually done a study. Given that propylene glycol is known to be toxic to cats, causing “Heinz body anemia,” and since questions have been raised about its effects on dogs, it may be prudent to choose varieties of dog food that do not contain the chemical.

Read more

Science & Society : @McGillOSS

@McGillOSS - Sat, 07/18/2015 - 18:37
, , Uri Geller...James Randi talks his career & retirement. http://ow.ly/i/bTv7u 

Science & Society : @McGillOSS

@McGillOSS - Sat, 07/18/2015 - 18:32
It’s not everyday you get to chat with James Randi.

McGilluMedia : @McGilluMedia

@McGillOSS - Fri, 07/17/2015 - 16:03
@ecolumiere @McGillU @McGillOSS Ms un organisme comme protégez-vous est p-ê plus équipé pour répondre sur un produit précis.

Jason Gencher : @JasonGencher

@McGillOSS - Wed, 07/15/2015 - 17:16
@McGillOSS 170+ @uoftmedicine students sign letter advocating teaching of evidence-based medicine, not pseudoscience. http://wp.me/p6tiCi-7 

The turf may be artificial but the issues are real

Our OSS Blog - Mon, 07/13/2015 - 07:08

The women’s World Cup provided us with some hot soccer but it also brought the simmering controversy about the safety of playing on artificial turf to a boil. That’s an apt term because these surfaces heat up in the sun much more than natural grass and players complain of greater risk of heat exhaustion. They also complain of carpet burns and blisters on the feet. But the bigger concern is potential toxicity.

The first synthetic playing surface was developed by Monsanto in the 1960s. Named “ChemGrass,” at a time when it was still acceptable to use a chemical connection in a positive way, it was made by melting together nylon pellets and a pigment, and then extruding the hot mix through spinnerets to produce ribbons which could be woven into a fabric. It was durable enough, but falling on it was no fun even though the nylon carpet was supported by a soft foam layer of polyurethane. When it was installed in Houston’s Astrodome as “AstroTurf,” ballplayers had to add “carpet burn” and “turf toe” to their vocabulary.

“Field Turf,” a Canadian company took the complaints to heart and came up with an improved version. Out went the stiff nylon fibers, in came soft, elastic polyethylene fibers lubricated with silicone oil. These were tufted into a rubberized plastic mat, just like a giant shag rug. The “tour de force,” though, was the “infill” composed of sand and granules of “crumb rubber” which kept the fibers upright and provided shock absorbency. Old rubber tires and athletic shoe soles were frozen and ground up to make the pellets that would eventually become the subject of heated debate.

The issue is that tires are made of a mix of natural and synthetic rubbers and contain an incredibly complex array of chemicals ranging from natural contaminants such as lead to zinc oxide used in the vulcanization process and polycyclic aromatic hydrocarbons in the oil blended with the rubber to provide proper texture. There are vulcanization accelerators like benzothiazole, amines added as antioxidants and butadiene and styrene residues from the synthetic rubber component. Many of these are known, probable or possible carcinogens. Carbon black, used as a reinforcing filler, can harbour “nanoparticles” which some researchers claim are carcinogenic and can penetrate cells, even finding their way to the brain. Lead-based pigments, now phased out, but once used to colour the grass, are another worry. There is also concern that dust from the rubber pellets can trigger allergies and asthma.

Of course the major question is extent of exposure. That can come from the inhalation of volatiles or dust released as the crumb rubber crumbles further under stress. There is also the possibility of swallowing any particles that are kicked up by action on the field, a special concern to goalkeepers who often dive to make a save and end up stirring up the rubber pellets. Can this be of any consequence? A preliminary collection of data by a soccer coach in the US suggests an unusual number of cancer cases among athletes who have spent a lot of time playing on artificial surfaces, and in the case of soccer, a greater incidence among goalkeepers than other players. So far this evidence is anecdotal, but science often starts with someone noting such a relationship and saying, “hmmm, isn’t that interesting?”

Given that the sporting landscape is dotted with artificial turf, and that thousands and thousands of children, who are more prone to the effects of toxins, play on such surfaces, further investigation is in order. Solid epidemiological data are needed to determine if there is indeed a link between artificial turf and cancer incidence, and we need experimental data about the extent and effects of exposure. The latter can be addressed by sampling the air above artificial fields for chemicals wafting out and by immersing samples of turf in fluids that simulate sweat, lung mucus and digestive juices. So far, the few experiments that have been carried out along these lines found that the chemicals detected were below what is considered to be hazardous, but there is great variation between turfs produced by different companies, so that small surveys cannot yield conclusive results. Furthermore, such studies do not address the possible cumulative effect that may be proportional to the time spent playing on artificial turf.

At this point it is impossible to quantify the toxicological risk, if any, of playing on artificial turf that may look like grass, and even feel like grass, but doesn’t behave like grass.

Read more

Hot Diggety Dog

Our OSS Blog - Tue, 07/07/2015 - 08:35

I have a confession to make. I like hot dogs. I couldn't eat 62, like Matt Stonie the winner of the Nathan's hot dog eating contest on Julky 4, but I could pack away one. Maybe two. In these days of nutritional correctness, that makes me feel as if I’m admitting to some criminal activity. At the risk of riling people devoted to subsisting on alfalfa sprouts, algae, tofu and diverse supplements, let me assure you that it is possible to occasionally indulge in hot dogs and still have a healthy diet. It is also possible to never eat a wienie and have a diet that is a nutritional nightmare. Individual foods should not be vilified or deified; it is the overall diet that determines whether we are eating in a healthy or an unhealthy fashion. In any case, like it or not, sausages in various forms have been with us a long time and are destined to remain part of our nutritional culture for the simple reason that they taste good.

People have been stuffing ground meat along with various spices and other ingredients into casings for thousands of years. Homer sang of sausages in the Odyssey, written around 850 BC. The Romans traditionally made sausages from ground pork and pine nuts for the celebration of Lupercalia, a feast of eating, drinking and wenching. These sausages became so intricately connected to debauchery that Constantine, the first Christian Emperor, actually banned them. Sausage bootlegging became a profitable enterprise.

By the Middle Ages, hundreds of varieties of sausages had been developed. Many of these, like Bologna, were named after the city where they were first made. But the variety that plays the greatest role in our lives originated in the German city of Frankfurt. The frankfurter was made with cured meat and was cooked by smoke.

Legend has it that the frankfurter was introduced into North America in 1904 by Anton Ludwig Feuchtwanger, a Bavarian peddler who set up a booth at the St. Louis World's Fair. Since the sausages he sold were greasy and hot, he loaned his customers white gloves with which to hold them. So many people absconded with the gloves that he needed another solution. His brother-in-law, a baker, came up with one. Why not put the frankfurter in a bun?

Everyone wanted to try the new-fanged hot "Dachshund sausages," as the franks were now called because of their resemblance to these lengthy canines. Soon the name was abbreviated to "hot dog," and a North American staple was born. Today there are hundreds of manufacturers vying to satisfy the North American craving for some 60 million franks a day!

We obviously eat a lot of hot dogs, but not without trepidation. We’re never really quite sure what they contain. Otto von Bismarck, the celebrated German statesman once remarked that the two things you don't want to see made are sausages and the law. Judging by some of the parliamentary behavior I've seen, he was right about the law. But sausages are not that scary. We can actually learn a lot of science from investigating how they are made.

No matter what you may have heard there are no ears, snouts or genitals in your hot dogs. So what is there? Hot dogs can be made from the edible parts of beef, veal, lamb, pork or poultry. This can include tongue, heart, esophagus and blood. If you find that hard to stomach, I probably shouldn't tell you that they also sometimes use the stomach. Kosher hot dogs do not contain any of these delicacies; they are made from good quality lean meat mixed with “plate trimmings,” which is essentially a pseudonym for fat.

Whatever the kind of hot dog, the basic process of manufacture is the same. The ingredients are finely chopped and then blended into a smooth paste which is eventually stuffed into a casing and cooked. The taste comes from a mixture of spices including garlic, pepper, paprika, smoke flavoring and MSG. Vitamin C or its chemical cousin, sodium erythorbate are also included in the mix. Why vitamin C? Because it mitigates the action of the curing salts which are added next. The curing salt is a mixture of about 98% regular salt and 2% sodium nitrite.

Nitrites are perhaps the most controversial components of hot dogs. They add flavor, color and prevent the growth of the deadly clostridium botulinum bacteria. But they can also react with other components in meat, called amines, to form nitrosamines. These substances are carcinogenic in test animals, and probably in humans. But their actual risk is very small. The odd study has linked hot dog consumption to some rare childhood cancers, but critics have pointed out that if this is indeed the case, it is so only in vitamin deficient children. Another reason to make sure kids are taking their multivitamins.

In any case, food processors have greatly reduced their use of nitrites since the discovery that vitamin C, potentiates the action of these chemicals. This means that less nitrite can be used if vitamin C is added to the mix. Studies have also shown that the added vitamin C reduces the chance of nitrosamine formation in the body. It is also possible to make nitrite free hot dogs, but these must be kept frozen.

If the nitrite issue isn’t that significant, why should we be concerned about feasting on hot dogs? The major problem is the fat content. By law, the protein content must be at least 11% but the fat content is not regulated. The average hot dog is 23% fat by weight. That’s a lot; a T-bone steak is 12% fat by weight. An average hot dog contains about 10 to 15 grams of fat, most of it saturated, although poultry and veal franks contain somewhat less. This is quite a bit considering that our daily fat intake should not routinely exceed 60-70 grams. Unfortunately, it is the fat in the hot dog that makes it taste so darn good.

Is it possible to have a low fat hot dog? Well, Hormel in the US has come up with "97% Fat Free Franks" which only have 1.3 grams of fat in each hot dog. The replacement of some of the fat by hydrolyzed vegetable protein is certainly a giant step in the right direction, especially when one considers that a panel of tasters found the Hormel product as tasty as regular hot dogs. Incidentally, the label "100% beef" on the packaging is meaningless on nutritional grounds. It just means that all components, including the fat, are derived from cows, steers or bulls. Actually bull meat is very flavorful, but because it is so fibrous, tends to be tough. However when macerated in a blender, it makes for an ideal hot dog. And that's no bull.

Then of course there are tofu hot dogs. These are getting better, but they still seem to develop those revolting “warts” when grilled. For now, I’ll still take the occasional regular hot dog, especially if you put a good ball game in front of it. But just to be on the safe side, I’ll take it with sauerkraut. Lots of vitamin C in there to take care of any nitrite problems.

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Timothy Caulfield : @CaulfieldTim

@McGillOSS - Mon, 07/06/2015 - 10:14
The Body of Evidence: E-Cigarettes - such a divisive topic! http://bodyofevidence.ca/#.VZqMzu4KrZw.twitter … @crackedscience @McGillOSS

Science & Society : @McGillOSS

@McGillOSS - Mon, 07/06/2015 - 09:23
Please. Explain to me. What’s the deal with ? New Body of Evidemce podcast: http://bit.ly/1NzktS4 

You Asked: Does taking a supplement of maca root have any merit?

You Asked? - Sat, 07/04/2015 - 20:20

A good story can sell a product especially when it comes to dietary supplements. Talk about some legendary use by natives, throw in terms like increased stamina, improved mood, natural and aphrodisiac, and you are off and running to the marketplace. Maca root powder, here we come! Maca is grown mostly in Peru and its cooked root, with a composition much like wheat or rice, has a long history as a dietary staple. But it is stories about the enhanced virility of Inca warriors who supposedly downed maca root before going into battle that captured the imaginnation of supplement manufacturers. Although there is no evidence that the Inca fighters actually did this, legends are often based on kernels of truth.

Couple this with anecdotes of Peruvians eating maca root for energy and improved sexual function, and you have a basis for carrying out studies that may potentially lay the groundwork for marketing. After all, plants are fascinating chemical factories and it is conceivable that maca may have some biologically active compounds. None have been detected so far, but that is not surprising. It takes a monumental effort to isolate, separate and identify the hundreds of compounds found in plants, and that is only the beginning. Then comes the even greater challenge of testing candidate compounds for biological activity. That’s why when it comes to herbal products, the simplest process is to test crude mixtures.

There have been studies of various maca root preparations, and although not compelling, they are suggestive of some potential benefit. In one small study, men taking 1500 or 3000 mg per day of powdered root claimed increased sexual desire compared with a placebo. There was no measurable change in sex hormones and curiously the effect was not dose dependent. Another study in young men showed a slight but significant improvement in erectile dysfunction, and one in postmenopausal women resulted in decreased anxiety and depression and some improvement in sexual function compared with placebo. Again, there were no changes noted in any hormone levels.

As usual with such dietary supplements, the consumer is at the mercy of the manufacturer in terms of product quality. There is no systematic checking by regulators that the product actually contains what it is supposed to contain or whether it harbours lead, cadmium or arsenic, all of which are possible soil contaminants and capable of ending up in the marketed product. Given that maca is widely consumed as a food, it is unlikely that any of the root powders pose a significant health risk, although headaches, stomach problems, sweating and sleep disruption have been reported in rare cases. It seems that for people looking for a little boost in stamina and sexual function, a daily dose in the range of 1500-3000 mgs of “Peruvian ginseng,” as maca is sometimes called, is an option. It may actually do something, especially if you think it will.

  Read more

You Asked: Does taking a supplement of maca root have any merit?

Our OSS Blog - Sat, 07/04/2015 - 20:20

A good story can sell a product especially when it comes to dietary supplements. Talk about some legendary use by natives, throw in terms like increased stamina, improved mood, natural and aphrodisiac, and you are off and running to the marketplace. Maca root powder, here we come! Maca is grown mostly in Peru and its cooked root, with a composition much like wheat or rice, has a long history as a dietary staple. But it is stories about the enhanced virility of Inca warriors who supposedly downed maca root before going into battle that captured the imaginnation of supplement manufacturers. Although there is no evidence that the Inca fighters actually did this, legends are often based on kernels of truth.

Couple this with anecdotes of Peruvians eating maca root for energy and improved sexual function, and you have a basis for carrying out studies that may potentially lay the groundwork for marketing. After all, plants are fascinating chemical factories and it is conceivable that maca may have some biologically active compounds. None have been detected so far, but that is not surprising. It takes a monumental effort to isolate, separate and identify the hundreds of compounds found in plants, and that is only the beginning. Then comes the even greater challenge of testing candidate compounds for biological activity. That’s why when it comes to herbal products, the simplest process is to test crude mixtures.

There have been studies of various maca root preparations, and although not compelling, they are suggestive of some potential benefit. In one small study, men taking 1500 or 3000 mg per day of powdered root claimed increased sexual desire compared with a placebo. There was no measurable change in sex hormones and curiously the effect was not dose dependent. Another study in young men showed a slight but significant improvement in erectile dysfunction, and one in postmenopausal women resulted in decreased anxiety and depression and some improvement in sexual function compared with placebo. Again, there were no changes noted in any hormone levels.

As usual with such dietary supplements, the consumer is at the mercy of the manufacturer in terms of product quality. There is no systematic checking by regulators that the product actually contains what it is supposed to contain or whether it harbours lead, cadmium or arsenic, all of which are possible soil contaminants and capable of ending up in the marketed product. Given that maca is widely consumed as a food, it is unlikely that any of the root powders pose a significant health risk, although headaches, stomach problems, sweating and sleep disruption have been reported in rare cases. It seems that for people looking for a little boost in stamina and sexual function, a daily dose in the range of 1500-3000 mgs of “Peruvian ginseng,” as maca is sometimes called, is an option. It may actually do something, especially if you think it will.

  Read more

Unexpected consequences are part and parcel of science

Our OSS Blog - Sat, 07/04/2015 - 20:17
 Science is as a quest for knowledge. Sometimes it ends with a clear-cut result, often not. The Earth goes around the sun. Water is composed of hydrogen and oxygen. The speed of light is 299,792,458 meters per second. These are facts and will never change. But knowledge is often fluid, conforming to new information as it comes to light. We no longer think maggots spontaneously arise from decaying flesh or that heart attack patients have to be kept on six weeks bed rest. These beliefs, though, were reasonable based on the knowledge available at the time.

Scientists are sometimes accused of being slipshod, too profit-motivated, or even incompetent for having made a decision that eventually turned sour. The prescribing of thalidomide, the introduction of DDT and the routine use of hormone replacement therapy at menopause are commonly cited as scientific errors, yet these were all backed by appropriate peer-reviewed studies. It often takes years for problems to emerge, and not having foreseen them does not mean that researchers erred or were motivated by interests other than the honest pursuit of science. Of course, when unexpected consequences do occur, it is important to recognize them. Making a change is not an admission of failure, indeed it is one of the hallmarks of science.

When back in the middle of the last century research revealed that cholesterol levels in the blood were associated with a risk for heart disease, it made sense to suggest that eggs, because of their significant cholesterol content, should be consumed in a limited fashion. That, though, was just an educated guess. Science dictates that such a guess be followed up and be properly evaluated. But it can take years of studies to determine if a hypothesis is correct, and such studies, particularly in the are of nutrition, are not easy to carry out. Food frequency questionnaires are notoriously unreliable, and there are all sorts of confounding factors such as genetics, age, weight and other dietary components that have to be taken into account.

Furthermore, no decision can be made based on any single study; a preponderance of evidence is required to arrive at a conclusion. With eggs, sufficient data has now been collected to indicate that their consumption does not have a significant effect on blood cholesterol levels. Indeed, the expert panel in the US that every five years makes dietary guideline recommendations has concluded that “cholesterol is not a nutrient of concern because cholesterol from foods doesn’t cause higher blood cholesterol levels.”

As far as scientific questions go, the effect of eggs on blood cholesterol was a relatively easy one to answer. But this is not always the case. Consider the question of chemicals that are suspected of causing cancer. Obviously people cannot be given suspected carcinogens and in any case, such trials would take decades to reveal an effect. Therefore, “knowledge” emerges from human epidemiological evidence along with studies in animals and cell cultures.

Various organizations classify carcinogens into different categories, with the most widely referenced one being the International Agency for Research on Cancer (IARC). Its Group 1 substances are definitely known to cause cancer based on human evidence and include tobacco, the combustion product benzopyrene, asbestos, benzene, formaldehyde, dioxin and ultraviolet light. Aflatoxins from molds, infection by helicobacter pylori bacteria, herbal remedies containing Aristolochia species, x-rays, occupation as a painter and alcoholic beverages are also on this list.

Group 2A is a compilation of “probable” carcinogens as determined by strong evidence from animal studies but limited human evidence. Lead compounds, acrylamide in baked goods, emissions from frying foods, hairdressing as an occupation, shift work, the herbicide glyphosate and insecticides such as diazinon and malathion are in this category. “Possible” carcinogens for which there is insufficient animal evidence and limited evidence in humans fall into Group 2B and include coffee, pickled vegetables, radiofrequency fields, titanium dioxide and DDT.

Combining all three groups, there are more than 450 substances or processes that are classified as known, probable or possible carcinogens. What do we do with this information? We can limit alcohol consumption, take care with sun exposure, treat helicobacter infection, avoid charred foods and of course shun smoking. As far as the other agents are concerned, sometimes we have to be satisfied with knowing that not everything can be known. Outside of occupational exposure, there just isn’t enough known to make sweeping recommendations. But if you are offered a job as a chimney sweep, don’t take it.

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Science & Society : @McGillOSS

@McGillOSS - Thu, 07/02/2015 - 11:22
Canada Day deals on @kobo! Get your copy of "Monkeys, Myths, and Molecules" for a great price: http://bit.ly/1IRAeRY 

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