Among foods that inspire a cult-like following, pork often leads the pack, as evidenced by the 65% of Americans eager to name bacon the country’s national food.
Unfortunately, that popularity comes at a cost. Along with being the most commonly consumed meat in the world, pork may also be one of the most dangerous, carrying some important and under-discussed risks that any consumer should be aware of.
1. Hepatitis E
Thanks to the revival of nose-to-tail eating, offal has redeemed itself among health enthusiasts, especially liver, which is prized for its vitamin A content and massive mineral lineup. But when it comes to pork, liver might be risky business.
In developed nations, pork liver is the top food-based transmitter of hepatitis E, a virus that infects 20 million people each year and can lead to acute illness (fever, fatigue, jaundice, vomiting, joint pain and stomach pain), enlarged liver and sometimes liver failure and death.
Most hepatitis E cases are stealthily symptom-free, but pregnant women can experience violent reactions to the virus, including fulminant hepatitis (rapid-onset liver failure) and a high risk of both maternal and fetal mortality. In fact, mothers who get infected during their third trimester face a death rate of up to 25%.
In rare cases, hepatitis E infection can lead to myocarditis (an inflammatory heart disease), acute pancreatitis (painful inflammation of the pancreas), neurological problems (including Guillain-Barré syndrome and neuralgic amyotrophy), blood disorders and musculoskeletal problems, such as elevated creatine phosphokinase, indicating muscle damage, and multi-joint pain (in the form of polyarthralgia).
People with compromised immune systems, including organ transplant recipients on immunosuppressive therapy and people with HIV, are more likely to suffer from these severe hepatitis E complications.
2. Multiple Sclerosis
One of the most surprising risks associated with pork — one that’s received remarkably little airtime — is multiple sclerosis (MS), a devastating autoimmune condition involving the central nervous system.
The robust link between pork and MS has been known at least since the 1980s, when researchers analyzed the relationship between per capita pork consumption and MS across dozens of countries.
While pork-averse nations like Israel and India were nearly spared from MS’s degenerative grips, more liberal consumers, such as West Germany and Denmark, faced sky-high rates.
In fact, when all countries were considered, pork intake and MS showed a whopping correlation of 0.87 (p<0.001), which is much higher and more significant than the relationship between MS and fat intake (0.63, p<0.01), MS and total meat intake (0.61, p<0.01) and MS and beef consumption (no significant relationship).
For perspective, a similar study of diabetes and per capita sugar intake found a correlation of just under 0.60 (p<0.001) when analyzing 165 countries.
As with all epidemiological findings, the correlation between pork consumption and MS can’t prove that one causes the other (or even that, within MS-stricken countries, the most enthusiastic pork consumers were the most diseased). But as it turns out, the evidence vault goes much deeper.
Earlier, a study of inhabitants of the Orkney and Shetland Islands of Scotland, a region teeming with unusual delicacies, including seabird eggs, raw milk and undercooked meat, found only one dietary association with MS — consumption of “potted head,” a dish made from boiled pig’s brain.
Among Shetland residents, a significantly higher proportion of MS patients had consumed potted head in their youth, compared to healthy, age and sex-matched controls.
This is particularly relevant because — per other research — MS that strikes in adulthood might stem from environmental exposures during adolescence.
The potential for pig brain to trigger nerve-related autoimmunity isn’t just an observational hunch, either. Between 2007 and 2009, a cluster of 24 pork plant workers mysteriously fell ill with progressive inflammatory neuropathy, which is characterized by MS-like symptoms such as fatigue, numbness, tingling and pain.
The source of the outbreak? So-called “pig brain mist” — tiny particles of brain tissue blasted into the air during carcass processing.
When workers inhaled these tissue particles, their immune systems, per standard protocol, formed antibodies against the foreign porcine antigens.
But those antigens happened to bear an uncanny resemblance to certain neural proteins in humans. And the result was a biological calamity: confused about who to fight, the workers’ immune systems launched a guns-blazing attack on their own nerve tissue (30, 31).
Although the resulting autoimmunity wasn’t identical to multiple sclerosis, that same process of molecular mimicry, where foreign antigens and self-antigens are similar enough to trigger an autoimmune response, has been implicated in the pathogenesis of MS.
3. Liver Cancer and Cirrhosis
Liver problems tend to trail closely on the heels of some predictable risk factors, namely hepatitis B and C infection, exposure to aflatoxin (a carcinogen produced by mold) and excessive alcohol intake. But buried in the scientific literature is another potential scourge of liver health — pork.
For decades, pork consumption has faithfully echoed liver cancer and cirrhosis rates around the world. In multi-country analyses, the correlation between pork and cirrhosis mortality clocked in at 0.40 (p<0.05) using 1965 data, 0.89 (p<0.01) using mid-1970s data, 0.68 (p=0.003) using 1996 data and 0.83 (p=0.000) using 2003 data.
In those same analyses, among the 10 Canadian provinces, pork bore a correlation of 0.60 (p<0.01) with death from liver cirrhosis, while alcohol, perhaps due to an overall low intake, showed no significant link.
And in statistical models incorporating known perils for the liver (alcohol consumption, hepatitis B infection and hepatitis C infection), pork remained independently associated with liver disease, suggesting the association isn’t just due to pork piggybacking, as the case may be, on a different causative agent. Beef, by contrast, remained liver-neutral or protective in these studies.
Liver cancer, too, tends to follow in the hoof steps of the pig. A 1985 analysis showed that pork intake correlated with hepatocellular carcinoma deaths as strongly as alcohol did (0.40, p<0.05 for both). (Considering liver cirrhosis is often a prelude to cancer, this connection shouldn’t be surprising.
4. Yersinia
For years, pork’s precautionary motto was “well-done or bust,” a consequence of fears about trichinosis, a type of roundworm infection that ravaged pork consumers throughout much of the 20th century. Thanks to changes in feeding practices, farm hygiene and quality control, pig-borne trichinosis has dropped off the radar, inviting pink pork back onto the menu.
But pork’s relaxed heat rules may have opened the doors for a different type of infection — yersiniosis, which is caused by Yersinia bacteria. In the US alone, Yersinia causes 35 deaths and almost 117,000 cases of food poisoning each year. Its chief entry route for humans? Undercooked pork.
Yersiniosis’s acute symptoms are rough enough — fever, pain, bloody diarrhea — but its long-term consequences are what should really ring alarm bells. Victims of Yersinia poisoning face a 47-times higher risk of reactive arthritis, a type of inflammatory joint disease triggered by infection.
Even children become post-Yersinia arthritis targets, sometimes requiring chemical synovectomy (the injection of osmic acid into a troubled joint) to relieve persistent pain.
And in the less-common instances where Yersinia doesn’t bring the typical feverish, diarrheic unpleasantries? Reactive arthritis can develop even when the original infection was asymptomatic, leaving some victims unaware that their arthritis is a consequence of food-borne illness.
Although reactive arthritis usually subsides on its own over time, Yersinia victims remain at higher risk of chronic joint problems, including ankylosing spondylitis, sacroiliitis, tenosynovitis and rheumatoid arthritis, for years on end.
Some evidence suggests that Yersinia can lead to neurological complications. Infected individuals with iron overload may be at higher risk of multiple liver abscesses, potentially leading to death. And among people who are genetically susceptible, anterior uveitis, inflammation of the eye’s iris, is also more likely following a bout of Yersinia.
Lastly, via molecular mimicry, Yersinia infection could also raise the risk of Graves’ disease, an autoimmune condition characterized by excessive thyroid hormone production.
So, should health-savvy omnivores scrap pork from the menu?
The jury’s still out. For two of pork’s problems — hepatitis E and Yersinia — aggressive cooking and safe handling are enough to minimize the risk. And due to a shortage of controlled, pork-centric research capable of establishing causation, pork’s other red flags spring from epidemiology — a field rife with confounders and unjustified confidence.
Worse, many diet-and-disease studies lump pork together with other types of red meat, diluting whatever associations might exist with pork alone.
These issues make it hard to isolate the health effects of pig-derived products and determine the safety of their consumption.
That being said, caution is probably warranted. The sheer magnitude, consistency and mechanistic plausibility of pork’s connection with several serious diseases make the chances of a true risk more likely.
Until further research is available, you might want to think twice about going hog-wild on pork.