Why Deep Fried Foods May Cause Cancer

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In the latest study on dietary patterns and breast cancer risk among women, healthier eating was associated with eliminating three-quarters of the odds of breast cancer, whereas less healthy eating was associated with up to nearly eight times the odds. Included in the unhealthy eating pattern was the consumption of deep-fried foods, which have previously been linked to breast cancer, pancreatic cancer, lung cancer, oral and throat cancers, esophageal cancer, and cancer of the voicebox. No deep fried foods? What's a Southern belle to do? Instead of deep fried foods, how about the traditional Southern diet, characterized by high intakes of cooked greens, beans, legumes, cabbage, sweet potatoes and cornbread, which may reduce the risk of invasive breast cancer significantly.

What about the consumption of deep-fried foods and risk of prostate cancer? Researchers at the Fred Hutchinson Cancer Research Center and the University of Washington found that eating French fries, fried chicken, fried fish, and doughnuts was associated with about a third greater odds of prostate cancer. After stratifying for tumor aggressiveness, they found slightly stronger associations with more aggressive disease, suggesting that regular intake of deep-fried foods may contribute to the progression of prostate cancer as well.

What in deep fried foods is so bad for us? Just heating oil that hot can generate potentially carcinogenic compounds, and then known carcinogens such as heterocyclic amines and polycyclic aromatic hydrocarbons form when the muscles of chickens and fish are cooked at that temperature. Deep-fried plants, on the other hand, can form acrylamide.

I did a video about acrylamide back in 2008, suggesting it's a probable human carcinogen (See Acrylamide in French Fries). Since then, studies have suggested pregnant women may want to cut back on French fries to protect the growth of their baby's body and brain. Based on a study (highlighted in my video, Cancer Risk from French Fries) feeding people a little bag of potato chips every day for a month, it now seems acrylamide may also cause inflammation as well, which could explain its purported role in cancer progression.

Acrylamide intake has been associated with endometrial cancer, ovarian cancer, lung cancer, kidney cancer, and esophageal cancer. How much cancer risk are we talking about? Taiwanese researchers examined lifetime cancer risk and French fry consumption. The researchers picked on French fries because they comprise by far the greatest percentage contribution of acrylamide to the diets of children. They estimated that, at most, one or two boys and girls out of every ten thousand would develop cancer eating French fries that they would otherwise not have developed if they hadn't eaten French fries. So it's not as bad as eating something like fried fish, or fried chicken, but how much is that saying?

The level of cancer risk in both boys and girls associated with French fries depends on how long and hot they're fried. In Europe, the food industry swore that they'd self-regulate and control fry times to decrease acrylamide levels, but we've yet to see any subsequent change in acrylamide levels in French fries.

Researchers continue to urge that the cooking temperature should be as low as possible and the cooking time should be as short as possible, "while still maintaining a tasty quality" of course. We wouldn't want to reduce cancer risk too much--they might not taste as good!

Blanching the potatoes first reduces acrylamide formation, but potato chip companies complain that, not only would it muck with the flavor, but it would reduce the nutritional properties by leaching away some of the vitamin C. But if we're relying on potato chips to get our vitamin C, acrylamide is probably the least of our worries.

More on heterocyclic amines:

There are some things we can do to counteract the effects of these carcinogens, though:

I touch on polycyclic aromatic hydrocarbons in Meat Fumes: Dietary Secondhand Smoke and Is Liquid Smoke Flavoring Carcinogenic?
Certain fats may play a role in breast cancer survival as well: Breast Cancer Survival, Butterfat, and Chicken and Breast Cancer Survival and Trans Fat.

-Michael Greger, M.D.

PS: If you haven't yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.

Image Credit: Kim Love / Flickr

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Alkylphenol Endocrine Disruptors and Allergies

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In my video Preventing Childhood Allergies, I noted a study in Japan that found higher maternal intake of meat during pregnancy was significantly associated with about three times the odds of both suspected and physician-diagnosed eczema. The researchers suggest that certain components of meat may affect the fetal immune system. But what about the moms, themselves? A plant-based diet may also help alleviate allergies in adults. See Say No to Drugs by Saying Yes to More Plants and Preventing Allergies in Adulthood.

Seasonal allergies have exploded in Japan in the past few decades, starting with the first reported case in 1964 and now affecting millions every year. We've seen a rising prevalence of allergic diseases around the industrialized world in past decades, but perhaps nothing quite this dramatic.

Some have suggested that profound changes in the Japanese diet may have played a role. Over the latter half of the century total meat, fish, and milk intake rose hundreds of percent in Japan, so researchers decided to look into dietary meat and fat intake and the prevalence of these seasonal pollen allergies. No association with overall fat, but "higher meat intake was significantly associated with an increased prevalence."

Saturated fat wasn't associated with increased prevalence either, so what other constituents in meat may be to blame? The researchers considered the cooked meat carcinogens, the heterocyclic amines, the polycyclic aromatic hydrocarbons, and the nitrosamines.

A new review, highlighted in my video, Alkylphenol Endocrine Disruptors and Allergies, however, raised an intriguing possibility. There's a class of industrial pollutants called alkylphenols, recognized as common toxic endocrine disrupting chemicals that tend to accumulate in the human body and may be associated with allergic diseases. A variety of studies have shown how they may exacerbate allergen-induced inflammation, "suggesting that alkylphenol exposure may influence the onset, progression, and severity of allergic diseases." These toxic xenoestrogens can be found in human breast milk, in our body fat, in our urine, in our bloodstream, and even in the umbilical cord blood going to our babies. How did it get there? Through contaminated food.

It all goes back to a famous study about the reduction of penis size and testosterone levels in alligators living in a contaminated environment. I don't know what you do for a day job, but these researchers observed that a population of juvenile alligators living on one lake in Florida exhibited a "significantly smaller penis size" and lower blood concentrations of testosterone compared to animals on some different lake. The most important difference between the two lakes was that Lake Stubby was fed by relatively polluted waters. They attributed the "short penis phenomenon" to estrogen-mimicking (xenoestrogenic) environmental metabolites of DDT that still pollute our Earth. This seminal work introduced the concept of endocrine disruptors. Environmental xenoestrogens might result in feminization of exposed male animals. And that's just the shriveled tip of the iceberg.

Since then, endocrine-disrupting chemicals have been implicated in the dramatic rise over the last 50 years of diseases like breast cancer, prostate cancer, testicular cancer, diabetes, obesity, and fertility (such as dropping normal sperm counts), genital birth defects such as penile malformations, preterm birth, neurobehavioral disorders in children linked to thyroid disruption, and earlier breast development in young girls. Because genes do not change fast enough to explain these increases, environmental causes must be involved. Since our greatest exposure to the environment is through our gut, it's no surprise that our greatest exposure to these endocrine-disrupting chemicals is through diet.

To find out which foods may contain these alkylphenol endocrine disruptors, check out my video Dietary Sources of Alkylphenol Endocrine Disruptors.

More on endocrine disruptors in:

A different class of chemicals has been found to be associated with smaller penis size in humans. See Chicken Consumption and the Feminization of Male Genitalia.

-Michael Greger, M.D.

PS: If you haven't yet, you can subscribe to my free videoshere and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.

Image Credit: Mark Freeth / Flickr

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Is Liquid Smoke Safe?

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We know smoke inhalation isn't good for us, but what about smoke ingestion? Decades ago, smoke flavorings were tested to see if they caused DNA mutations in bacteria--the tests came up negative. Even as more and more smoke flavoring was added, the DNA mutation rate remained about the same.

But the fact that something is not mutagenic in bacteria may have little predictive value for its effect on human cells. A group at MIT tested a hickory smoke flavoring they bought at the store against two types of human white blood cells. Unlike the bacteria, the mutation rate shot up as more and more liquid smoke was added. But, "there is no evidence that mutagenic activity in a particular human cell line is more closely related to human health risk than is mutagenic activity in bacteria." In other words: just because liquid smoke causes DNA mutations to human cells in a petri dish, doesn't mean that it does the same thing within the human body.

A good approach may be to just analyze liquid smoke for known carcinogens, chemicals that we know cause cancer.

Damaging DNA is just one of many ways chemicals can be toxic to cells. A decade later researchers tested to see what effect liquid smoke had on overall cell viability. If you drip water on cells, nothing happens, they keep powering away at around 100% survival, but drip on more and more wood fire smoke, and you start killing some of the cells off. Cigarette smoke is more toxic, but three out of four of the brands of liquid smoke they bought at the supermarket killed off even more cells, leading them to conclude that the cytotoxic potential of some commercial smoke flavorings is greater than that of liquid cigarette smoke, a finding they no doubt celebrated given that the researchers were paid employees of the R. J. Reynolds Tobacco Co.

Unfortunately they didn't name names of the offending brands. That's one of the reasons I was so excited about a new study, where they tested--and named--15 different brands of liquid smoke. This maximum "response" they were measuring was p53 activation.

P53 is a protein we make that binds to our DNA, you can see this illustrated in my video, Is Liquid Smoke Flavoring Carcinogenic?. It activates our DNA repair enzymes. So a big p53 response may be indicative of a lot of DNA damage,and a few of the liquid smoke flavorings activated p53 almost as much as a chemotherapy drug like etoposide, whose whole purpose is to break DNA strands.

Other flavorings didn't seem as bad, though there was a hickory smoke powder that ranked pretty high, as did the fish sauce, though smoked paprika didn't register at all.

The p53-activating property in liquid smoke was eliminated by standard baking conditions (350°F for 1h), so if you're baking something with liquid smoke for long enough, it should eliminate this effect, though just boiling--even for an hour, or slow cooking doesn't appear to work.

They conclude "If the DNA-damaging activities of liquid smoke were thought to be deleterious, it might be possible to replace liquid smoke with other safer, smoky substances." Why do they say if thought to be deleterious? That's because they're not really measuring DNA damage, they're measuring p53 activation, and that's not necessarily a bad thing.

P53 is considered "Guardian of our Genome," guardian of our DNA. It's considered a tumor suppressor gene, so if something boosts its activity is that good or bad? It's like the broccoli story. Cruciferous vegetables dramatically boost our liver's detoxifying enzymes. Is this because our body sees broccoli as toxic and is trying to get rid of it quicker? Either way, the end result is good, lower cancer risk.

It's a biological phenomenon known as hormesis - that which doesn't kill us may make us stronger. Like exercise is a stress on the body, but in the right amount can make us healthier in the long run. So, for example, teas and coffees caused p53 activation as well, but their consumption is associated with lower cancer risk. So it's hard to know what to make of this p53 data. Due to the limitations of the available tests it's hard to calculate the genotoxic potential of liquid smoke, or any other food for that matter. A better approach may be to just analyze liquid smoke for known carcinogens, chemicals that we know cause cancer.

This was first attempted back in 1971. One of the seven liquid smoke flavors researchers tested contained one polycyclic aromatic hydrocarbon known to be cancer-causing, but there's a bunch of similar carcinogens researchers didn't test for. A later study, however, tested across the board, looking specifically at five different carcinogens in retail liquid smoke seasonings.

The recommended daily upper safety limit for these carcinogens is 47. Hickory smoke flavoring has only 0.8 per teaspoon, so we'd have to drink three bottles a day to bump up against the limit. And mesquite liquid smoke has only 1.1.

It turns out that most of the carcinogens in smoke are fat soluble, so when we make a water-based solution, like liquid smoke, we capture the smoke flavor compounds without capturing most of the smoke cancer compounds. The only time we need to really worry is when eating smoked foods--foods directly exposed to actual smoke. For example, smoked ham has 21.3 per serving, and smoked turkey breast has 26.7 per serving. One sandwich and we may be halfway to the limit, and one serving of barbequed chicken takes us over the top. Eating less than a single drumstick and we nearly double our daily allotment of these carcinogens. Nothing, however, is as bad as fish. Smoked herring? 140 per serving. And smoked salmon? One bagel with lox could take us ten times over the limit.

I've touched on those cooked meat carcinogens before. In Estrogenic Cooked Meat Carcinogens I explored the role of these cooked meat chemicals in tumor growth. PhIP: The Three Strikes Breast Carcinogen explored their role in cancer invasion. Reducing Cancer Risk In Meateaters offered some mediation strategies. Heterocyclic Amines in Eggs, Cheese, and Creatine? showed how even vegetarians may be at risk and Cancer, Interrupted: Green Tea and Cancer, Interrupted: Garlic & Flavonoids explored some counter measures.

Some smoke compounds may be a concern even if we don't eat them. See Meat Fumes: Dietary Secondhand Smoke. Even the smell of frying bacon may be carcinogenic: Carcinogens in the Smell of Frying Bacon.

Some plant foods exposed to high temperatures may also present a concern. See Is Yerba Mate Tea Bad for You? and Acrylamide in French Fries. What about Carcinogens in Roasted Coffee?

The broccoli liver enzyme boost story is covered in The Best Detox.

-Michael Greger, M.D.

PS: If you haven't yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of Death, More Than an Apple a Day, and From Table to Able.

Image Credit: eric forsberg / Flickr

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