The Food Safety Risk of Organic versus Conventional

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The stated principles of organic agriculture are "health, ecology, fairness, and care," but if you ask people why they buy organic, the strongest predictor is concern for their own health. People appear to spend more for organic foods for selfish reasons, rather than altruistic motives. Although organic foods may not have more nutrients per dollar (see my video Are Organic Foods More Nutritious?), consumption of organic foods may reduce exposure to pesticide residues and antibiotic-resistant bacteria.

Food safety-wise, researchers found no difference in the risk for contamination with food poisoning bacteria in general. Both organic and conventional animal products have been found to be commonly contaminated with Salmonella and Campylobacter, for example. Most chicken samples (organic and inorganic), were found to be contaminated with Campylobacter, and about a third with Salmonella, but the risk of exposure to multidrug-resistant bacteria was lower with the organic meat. They both may carry the same risk of making us sick, but food poisoning from organic meat may be easier for doctors to treat.

What about the pesticides? There is a large body of evidence on the relation between exposure to pesticides and elevated rate of chronic diseases such as different types of cancers, diabetes, neurodegenerative disorders like Parkinson's, Alzheimer's, and ALS, as well as birth defects and reproductive disorders--but these studies were largely on people who live or work around pesticides.

Take Salinas Valley California, for example, where they spray a half million pounds of the stuff. Daring to be pregnant in an agricultural community like that may impair childhood brain development, such that pregnant women with the highest levels running through their bodies (as measured in their urine) gave birth to children with an average deficit of about seven IQ points. Twenty-six out of 27 studies showed negative effects of pesticides on brain development in children. These included attention problems, developmental disorders, and short-term memory difficulties.

Even in urban areas, if you compare kids born with higher levels of a common insecticide in their umbilical cord blood, those who were exposed to higher levels are born with brain anomalies. And these were city kids, so presumably this was from residential pesticide use.

Using insecticides inside your house may also be a contributing risk factor for childhood leukemia. Pregnant farmworkers may be doubling the odds of their child getting leukemia and increase their risk of getting a brain tumor. This has lead to authorities advocating that awareness of the potentially negative health outcome for children be increased among populations occupationally exposed to pesticides, though I don't imagine most farmworkers have much of a choice.

Conventional produce may be bad for the pregnant women who pick them, but what about our own family when we eat them?

Just because we spray pesticides on our food in the fields doesn't necessarily mean it ends up in our bodies when we eat it, or at least we didn't know that until a study was published in 2006. Researchers measured the levels of two pesticides running through children's bodies by measuring specific pesticide breakdown products in their urine. In my video, Are Organic Foods Safer?, you can see the levels of pesticides flowing through the bodies of three to 11-year olds during a few days on a conventional diet. The kids then went on an organic diet for five days and then back to the conventional diet. As you can see, eating organic provides a dramatic and immediate protective effect against exposures to pesticides commonly used in agricultural production. The study was subsequently extended. It's clear by looking at the subsequent graph in the video when the kids were eating organic versus conventional. What about adults, though? We didn't know... until now.

Thirteen men and women consumed a diet of at least 80% organic or conventional food for seven days and then switched. No surprise, during the mostly organic week, pesticide exposure was significantly reduced by a nearly 90% drop.

If it can be concluded that consumption of organic foods provides protection against pesticides, does that also mean protection against disease? We don't know. The studies just haven't been done. Nevertheless, in the meantime, the consumption of organic food provides a logical precautionary approach.

For more on organic foods:

For more on the infectious disease implications of organic versus conventional, see Superbugs in Conventional vs. Organic Chicken. Organic produce may be safer too. See Norovirus Food Poisoning from Pesticides. Organic eggs may also have lower Salmonella risk, which is an egg-borne epidemic every year in the US. See my video Who Says Eggs Aren't Healthy or Safe?

More on Parkinson's and pesticides in Preventing Parkinson's Disease With Diet.

Those surprised by the California data might have missed my video California Children Are Contaminated.

In health,

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:

Image Credit: IFPRI -IMAGES / Flickr. This image has been modified.

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How to Protect Our Telomeres with Diet

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In my video, Does Meditation Affect Cellular Aging?, I discussed how stress reduction through meditation might be able to lengthen telomeres, the protective caps at the tips of our chromosomes that tend to deplete as we age.

What about exercise? We can't always change our situation in life, but we can always go out for a walk. London researchers studied 2,400 twins, and those who exercised more may have pumped up their telomeres along with their muscles. Apparently it doesn't take much either. The "heavy" exercise group was only averaging about a half-hour a day.

These were mostly folks in their 40's, but does it still work in your 50's? Yes. A study out of South Korea found that people in their 50's who work out three hours a week had longer telomeres.

In my video, Telomeres: Cap It All Off with Diet, you can see the telomere lengths of young healthy regular folk controls at around age 20, and then at age 50. As we'd expect, the older subjects' telomeres were significantly shorter. What about athletes? The young athletes started out in the same boat, with nice, long, young, healthy telomeres capping all their chromosomes. The older athletes, in contrast to the controls, appeared to still have the chromosomes of 20-year-olds. But these were marathon runners, triathletes running 50 miles a week for 35 years.

What was it about the Ornish intervention that so powerfully protected telomeres after just three months? We saw that stress management seems to help, but what about diet and exercise? Was it the plant-based diet, was it the walking 30 minutes a day, or was it just because of the weight loss? In 2013 a study was published that can help us anser just that question.

The researchers took about 400 women and randomized them into four groups: a portion-controlled diet group, an exercise group, a portion controlled diet and exercise group, and a control group for a full year. In the video, you can see a comparison of the length of each group's telomeres. After a year of doing nothing, there was essentially no change in the control group, which is what we'd expect. The exercise group was 45 minutes of moderate-to-vigorous exercise like jogging. After a year of that, they did no better. What about just weight loss? Nothing. The same thing for exercise and weight loss, no significant change either.

So as long as we're eating the same diet, it doesn't appear to matter how small our portions are, or how much weight we lose, or how hard we exercise. After a year, the subjects saw no benefit. On the other hand, the Ornish group on the plant-based diet, who lost the same amount of weight after just three months and exercised less than half as hard, saw significant telomere protection.

It wasn't the weight loss or the exercise: it was the food.

What aspects of a plant-based diet make it so protective? Studies have associated more vegetables and fruit, and less butter, with longer telomeres. From the latest review, foods high in fiber and vitamins are strongly related to longer telomeres. However, the key may be avoiding saturated fat. Swapping just 1% of saturated fat calories in our diet for anything else can add nearly a whole year of aging's worth of length onto our telomeres.

Saturated fats like palmitic acid, the primary saturated fat in salmon, and found in meat, eggs, and dairy in general, can be toxic to cells. This has been demonstrated in heart cells, bone marrow cells, pancreatic cells, and brain cells. The toxic effects on cell death rates happen right around what you'd see in the blood stream of people who eat a lot of animal products. It may not be the saturated fat itself, however, as saturated fat may just be a marker for the increased oxidative stress and inflammation associated with those foods.

With this link to saturated fat, it's no wonder that lifelong low cholesterol levels have been related to longer telomeres and a smaller proportion of short telomeres--in other words, markers of slower biological aging. In fact, there's a rare congenital birth defect called progeria syndrome, where children age 8-10 times faster than normal. It seems associated with a particular inability to handle animal fats.

The good news is that "despite past accumulated injury leading to shorter telomere lengths, current healthy behaviors might help to decrease a person's risk of some of the potential consequences like heart disease." Eating more fruit and vegetables and less meat, and having more support from friends and family, attenuate the association between shorter telomeres and the ravages of aging.

To summarize: inflammation, oxidation, damage and dysfunction are constantly hacking away at our telomeres. At the same time, our antioxidant defenses, healthy diet, exercise and stress reduction are constantly rebuilding them.

I've asked this diet versus exercise question in a few other contexts. See:

Though dietary change appears more impactful, I'm a big fan of walking. See Longer Life Within Walking Distance and for my personal favorite exercise, Standing Up for Your Health.

For more on the role saturated fat may play in disease, see, for example, my videos Heart Disease Starts in Childhood and Treating Multiple Sclerosis with the Swank MS Diet.

In health,
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, From Table to Able, and Food as Medicine.

Image Credit: AJC / Flickr

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Eating Garlic and Raisins May Help Prevent Preterm Birth

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The United States has one of the worst premature birth rates in the world, now ranking 131st worldwide. Even worse, over the last few decades, the rate of preterm birth in the U.S. has been going up.

We've known that preterm delivery is associated with significant problems during infancy, and almost three quarters of all infant deaths. Unfortunately even preemies who survive past infancy may carry a legacy of health issues, such as behavioral problems, moderate to severe neurodevelopmental disabilities and psychiatric disorders in half of those born extremely preterm by the time they reach school-age. There's even evidence now that adults born very prematurely are at increased risk for things like heart disease and diabetes. And babies don't even have to be born that premature to suffer long-term effects. Even so-called near-term births at 36 or 37 weeks are now thought to be related to subtle developmental problems. So what can pregnant women do to decrease this risk?

66,000 pregnant women were studied to examine whether an association exists between maternal dietary patterns and risk of preterm delivery. Researchers compared a so-called "prudent," which was more plant-based versus a Western or traditional Scandinavian diet (vegetables, fruits, oils, water as beverage, whole grain cereals, fiber rich bread) versus the "Western" (salty and sweet snacks, white bread, desserts, processed meat products), and found that the "prudent" pattern was associated with significantly reduced risk of preterm delivery.

Inflammation is thought to play a role in triggering delivery, so a diet characterized by high intakes of vegetables, fruit and berries can reduce both systemic and local inflammation, and the lower saturated fat levels would also be associated with reduced inflammation. Any foods in particular?

A significant percentage of preterm deliveries are thought to be related to infections and inflammatory conditions in the genital tract. Garlic is well-known for its antimicrobial properties, and also has probiotic dietary fibers that feed our good bacteria. Dried fruit is also packed with fiber and has antimicrobial activities against some of the bacteria suspected to play a role in preterm delivery.

Researchers (highlighted in my video, Garlic and Raisins to Prevent Premature Birth) studied the garlic, onion and dried fruit intake of nearly 19,000 pregnant women, and indeed, they observed a reduced risk of spontaneous preterm delivery related to groups of garlic and onion family vegetables and dried fruits. In particular, garlic stood out for the vegetables and raisins stood out for the dried fruit. Both were associated with a reduced risk of both preterm delivery and preterm pre-labor rupture of membranes, which means your water breaking prematurely (before 37 weeks). And it didn't seem to take much. The so-called "high" garlic intake associated with the lowest risk was just about one clove a week or more, and "high" raisin intake was defined as just one of those mini snack boxes of raisins a month.

Here's the video on aspartame (NutraSweet) and diet soda during pregnancy: Diet Soda and Preterm Birth.

Some other popular pregnancy videos include:

More on garlic in #1 Anti-Cancer Vegetable and Cancer, Interrupted: Garlic and Flavenoids.

Videos on dried fruit include:

In health,
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, From Table to Able, and Food as Medicine.

Image Credit: Isabel Eyre / Flickr

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Why are Chickens Fed Prozac?

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Between 1940 and 1971, the synthetic estrogen DES was prescribed to several million pregnant women with the promise that it would "help prevent miscarriages." Problems were first highlighted in 1953 when it became clear that DES was not only ineffective but potentially harmful. However, a powerful and emotive advertising campaign ensured that its use continued until 1971, when it was found to cause cancer of the vagina in the daughters of the mothers who took it. DES was also used to stunt the growth of girls who were predicted to grow "abnormally tall." As one pediatric textbook put it in 1968, "excessive tallness in girls can be a handicap ... it provides difficulty in the purchase of smart clothes; the victim is ineligible for certain sought-after professional positions such as air line hostess; and poses problems in selecting suitable dancing partners."

What most people don't know is that the greatest usage of DES was by the livestock industry, used to improve "feed conversion" in cattle and chickens. Within a year of approval, DES was fed to millions of farm animals. Although it was shown to be a human carcinogen in 1971, DES used in meat production was not completely banned until 1979. (Now, the meat industry just uses different synthetic estrogen implants.) Even decades after DES was banned, we're still seeing its effects--an elevation of birth defects even down to the third generation.

Arsenic is another human carcinogen that was fed to chickens. This time by the billions. The arsenic not only ends up in the meat (as I've talked about previously in Arsenic in Chicken and How Many Cancers Caused by Arsenic Laced Chicken?), but also in the feathers, which are fed back to the animals. Because a third of the bird is inedible, the industry takes billions of pounds of heads, bones, guts, and feathers and uses them as fertilizer and animal feed. This feather meal is fed back to chickens, pigs, cows, sheep, and fish. Straight feathers are not particularly nutritious; so guts, heads, and feet may be added for a little extra protein, and manure added for minerals. The problem is that feather meal used as animal feed could contribute to additional arsenic exposure in persons who consume meat. This gave researchers at John Hopkins University and Arizona State an idea. By testing feather meal, they might be able to find out what else chickens are fed. In their study, "Feather Meal: A Previously Unrecognized Route for Reentry into the Food Supply of Multiple Pharmaceuticals and Personal Care Products," (highlighted in my video, Illegal Drugs in Chicken Feathers) they found that all feather samples tested positive for antibiotic type drugs (between two and ten different kinds in each sample), including fluoroquinolones, which have been banned for years. Either the poultry industry is illegally still using the stuff, or it's being used in other animals fed to the chicken. Regardless, when feather meal is fed back to chickens, they are getting exposed to this drug that is against the law to feed to chickens, creating a cycle of re-exposure to banned drugs.

Then it just gets weirder. The feathers contained a half dozen other drugs: Prozac, an antihistamine, a fungicide, a sex hormone, and caffeine. Why doesn't the poultry industry just say no? Evidently, the antihistamines are to combat the respiratory problems from packing so many tens of thousands into the confinement sheds, and the caffeine helps keeps the chickens stay awake so they eat more and grow faster.

The drugs fed to chickens are one reason used to explain why poultry has been tied to increased cancer risk. See Chicken Dioxins, Viruses, or Antibiotics?.

The most concerning drugs currently in the U.S. poultry supply are the antibiotics, though. See, for example:

Ironically, not only may antibiotics in chicken contribute to antibiotic resistant infections, but to the infections in the first place. Check out my video Avoiding Chicken to Avoid Bladder Infections.

Then as if adding potentially harmful chemicals to the chickens themselves wasn't bad enough, more are added in the processing plant: Phosphate Additives in Chicken.

In health,
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, From Table to Able, and Food as Medicine.

Image Credit: U.S. Department of Agriculture / Flickr

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How Contaminated Are Our Children?

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In a study highlighted in my video, California Childen Are Contaminated, researchers analyzed the diets of California children ages two through seven to determine the cancer and non-cancer health effects from food contaminant exposures. It turns out food may be the primary route of exposure to toxic heavy metals, persistent pollutants, and pesticides. "Though food-borne toxic contaminants are a concern for all ages, they are of greatest concern for children, who are disproportionately impacted because they're still developing and have greater intake of food and fluids relative to their weight. Pediatric problems that have been linked to preventable environmental toxin exposures include cancer, asthma, lead poisoning, neurobehavioral disorders, learning and developmental disabilities, and birth defects."

The good news is that changing one's diet can change one's exposure. Quoting from the study, "A diet high in fish and animal products, for example, results in greater exposure to persistent pollutants like DDT and dioxins and heavy metals than does a plant-based diet because these compounds bioaccumulate up the food chain." Plants are at the bottom of the food chain. The sample of California kids, however, was not eating a plant-based diet. Cancer benchmark levels were exceeded by all 364 children for arsenic, the banned pesticide dieldrin, a metabolite of DDT called DDE, and dioxins.

Children exceeded safety levels by a greater margin than adults. This is especially of concern for children because all of these compounds are suspected endocrine disruptors and thus may impact normal development. Cancer risk ratios were exceeded by over a factor of 100 for both arsenic and dioxins.

Which foods were the worse? For preschoolers, the number one food source of arsenic was poultry, though for their parents, it was tuna. The number one source of lead was dairy, and for mercury it was seafood. And the number one source of the banned pesticides and dioxins was dairy. (See Preventing Parkinson's Disease With Diet.)

The researchers also recommended children should eat lower quantities of chips, cereal, crackers, and other crispy carbs to reduce acrylamide intake.

The California study didn't split up the groups by gender, but a similar study in Europe found that men had higher levels of some of these pollutants than women. For example, levels of the banned pesticide chlordane were higher in men, but women who never breastfed were right up there alongside men, with the lowest levels found in women who breastfed over 12 months. Therefore, it is likely that the lactation-related reduction in blood pollutant levels partly explains the lower body burdens among women compared with men. So cows can lower their levels by giving some to us, then we can pass it along to our children.

What non-cancer effects might some of these pollutants have? They can affect our immune system. Studies clearly demonstrate the "ability of dioxins and related compounds to have a long-lasting and deleterious impact on immune function." This manifests as increased incidences of respiratory infections, ear infections, cough, and sore throat. At first, most of the data was for during infancy, but now we have follow-up studies showing that the immunosuppressive effects of these toxins may persist into early childhood, so we should try to reduce our exposure as much as possible. Because these pollutants accumulate in animal fat, consuming a plant-based diet-decreasing meat, dairy, and fish consumption-may reduce exposure for children and adults alike.

These findings should come as no surprise to those who saw my video Pollutants in California Breast Tissue. For an overview see CDC Report on Environmental Chemical Exposure and President's Cancer Panel Report on Environmental Risk.

Pollutant exposure may affect the ability to have children in the first place (Male Fertility and Diet and Meat Hormones & Female Infertility). Such a delay, though, may allow one an opportunity to reduce one's toxic burden through dietary change (Hair Testing for Mercury Before Considering Pregnancy and How Long to Detox From Fish Before Pregnancy?).

During pregnancy, pollutants can be transferred directly (DDT in Umbilical Cord Blood), and after pregnancy through breastfeeding (The Wrong Way to Detox). Once our kids are contaminated, How Fast Can Children Detoxify from PCBs? The chemicals have implications for older children too: Protein, Puberty, and Pollutants.

Seafood is not the only source of toxic heavy metals. See:

Videos on primary food sources of other industrial pollutants include:

There are some things we can eat, though, to counteract some of the toxins:

-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: Kevin Krejci / 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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How Seafood Can Impact Brain Development

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In my video Fish Intake Associated With Brain Shrinkage, I discussed evidence suggesting that mercury exposure through fish intake during pregnancy may decrease the size of the newborn's brain. However, just because fish-eating mothers may give birth to children with smaller brains doesn't necessarily mean their children will grow up with neurological defects. In the video, Mercury vs. Omega-3s for Brain Development, you can see real-time functional MRI scans of teens whose moms ate a lot of seafood when pregnant. Because these kinds of scans can measure brain activity, as opposed to just brain size, we can more accurately determine if exposure to mercury and PCBs affected these kids. You can see an MRI of what a normal brain looks like when you flash a light in someone's eyes, but the MRI is significantly different for the mercury and PCB exposed brains, suggesting toxicant related damage to the visual centers in brain. (For more on the effect of mercury on teens, see Nerves of Mercury). Fish consumption may also increase the risk of our children being born with epilepsy.

So does maternal fish consumption have an effect on how smart our kids turn out? The DHA in fish--a long chain omega 3 fatty acid--is good for brain development, but mercury is bad for brain development. So a group of researchers looked at 33 different fish species to see what the net effect of these compounds would have on children's IQ. For most fish species, they found that "the adverse effect of mercury on the IQ scores of children exceeded the beneficial effects of DHA." In fact, so much brainpower may be lost from fish consumption that the United States may actually lose $5 billion in economic productivity every year.

For example, if pregnant women ate tuna every day, the DHA would add a few IQ points. But the mercury in that very same tuna would cause so much brain damage that the overall effect of eating tuna while pregnant would be negative, wiping out an average of eight IQ points. The only two fish that were more brain-damaging than tuna were pike and swordfish.

At the other end of the spectrum, the brain boosting effect of DHA may trump the brain damaging effects of mercury in salmon by a little less than one IQ point. Unfortunately, IQ only takes into consideration the cognitive damage caused by mercury, not the adverse effects on motor function and attention and behavior deficits. We think that attention span may be particularly vulnerable to developmental mercury exposure, probably due to damage to the frontal lobes of the brain.

And the IQ study didn't take into account the relatively high levels of PCBs in salmon and the accompanying concerns about cancer risk. Sustainability concerns are another wrinkle, as farm-raised salmon are considered a "fish to avoid." While king mackerel is considered a best choice for sustainability, the mercury levels are so high as to warrant avoiding consumption--exceeding both the FDA and EPA action levels for mercury contamination. But why risk any loss in intelligence at all when pregnant women can get all the DHA they want from microalgae supplements without any of the contaminants? We can then get the brain boost without the brain damage.

More on PCBs in:

-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.

Images thanks to Dion van Huyssteen / Flickr

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Why Pregnant Women Should Avoid Tuna

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All fish contain small amounts of methylmercury, the most toxic form of mercury, and "fish consumption represents the main source of methylmercury exposure." In my videos Nerves of Mercury and Fish Fog, I discuss how mercury exposure through fish consumption, even within the government's safety limits, can have adverse neurological and behavioral effects on child development. Severe exposure can cause overt structural brain abnormalities like microcephaly, a shrunken brain disorder. But we didn't know whether low exposure could also affect brain size until recently.

Autopsy studies suggest mercury preferentially affects the developing cerebellum, so researchers used ultrasound to measure cerebellum size in newborns of mothers who had high body levels of mercury.

Let's put those levels into practical terms. In the video, Fish Intake Associated with Brain Shrinkage, you can see the results of a study measuring mercury concentration in human hair. Just one can of tuna a week raises human hair mercury concentration to levels nearly three times as high as the "high" group in the ultrasound study. So the bodies of the women suffering high mercury contamination were considered heavily contaminated, but even just a little canned tuna once in a while could bump our levels even higher. So the high really wasn't that high. But what did they find?

The researchers demonstrated that babies born to mothers with higher hair mercury levels had cerebellums up to 14% shorter than those born to mothers with lower hair mercury levels. They conclude that prenatal exposure to what may be considered low-levels of methylmercury does indeed influence fetal brain development as evidenced "by decreased size of a newborn's brain."

But what about the long chain omega-3 DHA in fish--isn't that necessary for healthy brain development? That's the topic of my video Mercury vs. Omega-3s for Brain Development.

For more on canned tuna in particular, check out:

-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.

Images thanks to Thomas Hawk / Flickr

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