It’s time for the Nutrition Facts Grab Bag, where we look at the science behind a whole array of topics. And, we start with how the adverse effects of industrial pollutants in seafood may counteract the benefits of nutrients in fish.
Although the levels of industrial pollutants, like dioxins and PCBs, continue to decline in the food supply, there is one dietary source that still remains a major threat: fish. Everything eventually flows into the sea. Yes, we can get some dioxins from eating horses, but most of our exposure comes from eating fish.
The U.S. Environmental Protection Agency puts the tolerable upper limit of dioxin intake per kilogram of body weight at 0.7 picograms—less than one trillionth of a gram—per day. W’re already skirting the max by just consuming dairy, and fish takes us right over the top, even at low levels of consumption.
So, the adverse effects of chemical contaminants in seafood may counteract the benefits of any nutrients in fish. So much so that many dietary guidelines recommend no more than one serving a week of fish and seafood to cut down on exposure to toxic pollutants. But which is worse? Wild-caught or farmed?
Take salmon, for example. Salmon had the highest toxic equivalents of PCBs, followed by canned tuna, as well as the highest neurotoxic equivalents of PCBs. If you compare the levels of PCBs in salmon farmed in Maine and Canada, versus salmon wild-caught in Alaska, versus organically farmed salmon from Norway, compared to the wild-caught salmon, the farmed salmon, organic or otherwise, had significantly higher PCB levels.
This appears to extend to other contaminants too. Based on the testing of literally tons of salmon samples from around the world, for every toxin the researchers tested, the samples of farmed salmon had higher levels than did the wild-caught salmon—higher levels of DDT and other banned pesticides. Over 10 times more PCBs in farmed salmon; over 10 times more dioxins. In order to not exceed EPA safety levels, we wouldn’t want to eat supermarket salmon more than once every two weeks in Denver or New Orleans, more than once a month in LA, Vancouver, DC, Seattle, Chicago, or New York, just once every two months in Edinburgh, Paris, London, Oslo, Boston, San Francisco, or Toronto, and just a few times a year in Frankfurt, Germany.
We can track pollutants from the ocean to the table, and it’s through the fish oil. The fish oil used in the feed for farmed fish transfers pollutants to the fish themselves, and then the fish carries the pollutants to human consumers. So yes, salmon have the healthy omega-3 fatty acids, but they also contain high levels of toxic chemicals, and not just the PBCs, dioxins, and pesticides. Farmed salmon test positive for antibiotic residues, higher levels of forever chemicals, flame retardants, and also test positive for endocrine disrupting compounds—hormone disruptors like BPA – something you don’t see in samples of sea vegetables like seaweed, presumably because of their low-fat content.
Farmed salmon may also have higher levels of mercury than wild-caught, though the opposite may be the case for farmed tuna. Arsenic also goes both ways, with more arsenic in wild sea bream compared to farmed, but less in wild sea bass. However, all the arsenic levels were bad, exceeding cancer benchmark values indicating a moderate risk of cancer due to fish consumption.
Some analyses have found dioxin and PCB levels similar across the board, but in general, you can think of aquaculture fish as “farmed and dangerous” compared to wild-caught in terms of higher levels of most pollutants. So, that’s why researchers emphasize the importance of labeling as a means to help consumers avoid unnecessary exposure to highly contaminated fish. Unfortunately, mislabeling is rampant.
So, the farmed versus wild-caught question may be largely academic, given the extent of seafood fraud and mislabeling. An investigation by the New York Attorney General found that consumers who bought what was advertised as “wild” salmon actually often received farm-raised salmon instead. Up to 43% of salmon tested across the United States, for example, were mislabeled, most commonly passing off farmed salmon as wild-caught.
In our next story, NutritionFacts.org’s Senior Research Scientist Dr. Kristine Dennis joins us with a fascinating look at how turmeric extract supplements can cause liver injury.
Liver injury associated with turmeric: Ten cases from the drug-induced liver injury network in the United States, and there are others too, including three cases reported in Australia and a series reported to the Italian Ministry of Health. Is turmeric really a new hepatotoxic substance? First of all, regardless of what the titles of the papers say, these cases appear to be from turmeric extract supplements, rather than turmeric the spice. It’s like green tea and green tea extract pills. Brewed green tea appears to be completely safe for the liver, but give people green tea extract supplements, and the livers of as many as 1 in 17 people become inflamed. So, we should consume our green tea in beverage form, not pill form, and similarly our turmeric in spice form at culinary doses, not capsules, unless they contain just a single ingredient: whole spice turmeric, not curcumin, not an extract, no other ingredients.
While turmeric extract supplements have a relatively safe side-effect profile, even at high doses, there is an increasing number of case reports linking them to liver injury, especially when combined with agents such as piperine, a compound found in black pepper. As we’ve covered before, compounds like piperine are added to turmeric to enhance the bioavailability of curcumin––potentially contributing to its toxicity, as one reason curcumin may be so safe is that it is poorly absorbed. As we have cautioned before, piperine blocks liver detox enzymes that can make some substances like curcumin more potent. And turmeric curcumin supplement formulations with high bioavailability, such as nanoformulations, or those with added piperine, have been less investigated. There is a mistaken assumption that if a little is good, then more must be better. We’d never make that assumption for drugs; so, why is it made for supplements?
In this case, more does not necessarily mean better. A review of nearly a hundred randomized controlled trials of turmeric or curcumin supplements for nonalcoholic fatty liver disease found that they successfully calmed liver inflammation. And guess which worked better? Low-dose supplements worked about 10 times better than high-dose ones.
There are caveats, though, even for whole food turmeric. As Dr. Greger has covered before, people who have a tendency to form kidney stones should be careful due to turmeric’s relatively high oxalate content. Dr. Greger recommends only a quarter teaspoon a day in his Daily Dozen.
There’s also been concern about lead contamination of the whole food spice. Lead chromate has been used to make turmeric appear more yellow in Bangladesh, where much of turmeric sold in the United States is imported from, leading to multiple recalls. The wonderful news is food safety policies can work! Since the original paper of lead chromate contamination in turmeric from Bangladesh, the portion of market turmeric samples with detectable lead went from about 50% to zero. Unfortunately, there is still more work to be done, though. In four South Asian countries where more than 80% of the world’s turmeric is produced, 14% of samples had detectable lead above 2 ug/g. For context, this is 20 times higher than the U.S. Food and Drug Administration’s maximum allowable level for lead in candy. And some stores sold turmeric containing much higher levels of lead that would result in projected blood lead levels in children up to 10 times higher than the U.S. Centers for Disease Control’s threshold for concern.
This is a reminder that just because something is natural doesn’t mean it can’t cause harm. Turmeric dietary supplements are big business, estimated to account for $69 million in sales in the United States alone––though its popularity does help put the recent spate of liver toxicity cases in context. More than 10 million people in the United States take turmeric or curcumin supplements; so, that would be like one case in a million. Some people may just be more susceptible genetically—in this case series, seven of the 10 patients had a genetic variant that’s relatively rare in the general population. Still, it’s safer for everyone to use the real thing and not some extract in some supplement. And, please don’t let anyone inject turmeric or curcumin into your veins.
Finally today, we look at how pawpaw fruits contain neurotoxins that may cause a neurodegenerative disease. Yikes!
The pawpaw is the largest fruit native to North America, weighing up to two pounds (1 kg). Pawpaws taste like a mixture of bananas, mangos, and pineapples. They’re like a tropical banana mango custard but found in temperate forests across the eastern United States, nourishing humankind for thousands of years and now complete with their own pawpaw festivals. Papayas are sometimes called pawpaws, but they’re completely different fruits. The real pawpaw is also known as the dog banana, false-banana, Indiana banana, prairie banana, poor man’s banana, Ozark banana, Banango (I like that one), Indiana banana (has a nice ring to it, too), and the Kentucky banana.
Pawpaws are my favorite fruit, or should I say were my favorite fruit. One of the reasons I moved to rural Virginia was because the property had a whole grove of pawpaw trees. I was going to be set for life—that is, until I ate a few too many on the first harvest, became quite ill, and actually looked them up. Pro tip: in the future, look to see if a food is toxic before you eat lots of it. Little did I know, the pawpaw belonged to an infamous family of fruits that contains three different types of neurotoxins. I had actually done a video years ago warning people not to eat soursop, also known as graviola, but didn’t realize pawpaws were related.
The family includes soursop, guanabana, sweetsop, sugar apple, cherimoya, and custard apple, which are all linked to a neurodegenerative disease called progressive supranuclear palsy, which is like a treatment-resistant Parkinson’s, with hallucinations, widespread brain atrophy, and dementia. And consumption of these fruits is associated with about 20 times the odds of having this kind of atypical Parkinson’s syndrome. Expose rats to even a fraction of the dose the people were exposed to, and they develop the same kind of brain lesions you see on autopsy in human victims. And, in several patients who stopped consuming these fruits, the progression of their condition ceased, and in one patient the symptoms even disappeared after a change of diet. There is an urgent need to raise public awareness about the neurotoxicity of this family of fruits, which are often ironically praised for their taste and medicinal values.
In fact, you can find dietary supplements containing these plants, promoted for their purported anticancer effects. And a soursop extract can inhibit cancer cell growth in a petri dish, but only at concentrations much higher than the amount that kills off brain cells. Even a low cumulative consumption may worsen disease severity and cognitive deficits in degenerative Parkinson’s type disease, as in 0.2 fruit-years; so, that’s just one-fifth of a fruit a day for a year, or a single fruit a month for six years or just one fruit a year throughout your entire life. The bottom line is that these fruits could contribute to the development of degenerative Parkinsonism in humans, and so as a precaution, more restrictive public health preventive recommendations should be made regarding their consumption.
So, okay, consumption of these tropical fruits potentially constitutes a serious public health problem, but what about pawpaws? So, why aren’t pawpaw eaters getting sick? Well, it’s only ripe for a few weeks a year, so unlike the tropical fruit that can be eaten year-round, people may not have a lot of exposure to them. Fresh pawpaws aren’t really even sold commercially either since they bruise so easily, but now the fruit’s available in any season, sold as frozen pulp or jam, and there are the supplements out there too. Not to mention, if you’re like me, trees in your backyard.
When the U.S. Food and Drug Administration was asked about them, they noted that pawpaw has a long history of food use, and it didn’t have any evidence that the fruit was unsafe to eat. You’ll hear things like this: “Currently, there have been no reports of neurogenerative diseases linked to the consumption of the pawpaw fruit,” until of course, there are. Progressive supranuclear palsy and pawpaw: Poor guy had trouble speaking and walking as his brain was atrophying in his skull. Tragically, he actually died before they figured it out, but his wife disclosed that they owned pawpaw trees, and he had been eating dozens a year. And, when researchers started looking, they indeed seemed to find a link between this neurodegenerative disease and pawpaw consumption in the United States. So alas, no more pawpaw for me.
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