One would think that, as research on diet and health continues to pile up, we might start inching toward consensus about what is good to eat, and what isn't. But in many cases the opposite is happening. We can't even agree on the essential goodness or badness of basic macronutrients like fat or carbohydrates, with each side enjoying an all-you-can-eat buffet of studies to back up its case.
Everyone but the sugar and junk-food industries at least is in agreement about the toxic qualities of sugar, but there are some other commonly eaten foods that can hurt you as well, and much more immediately, with less controversy about them. Of course, too much of anything can kill you. Water intoxication, aka hyponatremia, for example, is a real, and really serious condition. But there are also some foods of which even a modest amount, consumed on a regular basis, can be bad. But unlike sugar, these foods are widely perceived as healthy.
Kidney beans and some species of lima beans are very high in phytohaemagglutinin, which is present at some level in most legume seeds.
Ten minutes in boiling water can deactivate this toxin, but it's not uncommon for people to soak beans and then add them to a salad, or cook them slowly in a crock pot at sub-boiling temperatures.
According to FDA, as few as five undercooked kidney beans can cause belly pain, vomiting, diarrhea, and other symptoms of severe gastrointestinal distress.
Legumes also contain a long list of anti-nutrients, so-called because they can impair the body's ability to properly digest them and extract their full nutrient value (some of which gets turned into the legendary flatulence).
These anti-nutrints include saponins, phytate, polyphenols (tannins, isoflavones), protease inhibitors, raffinose oligosaccharides, cyanogenetic glycosides, and favism glycosides. Some, like saponins, are not destroyed by cooking.
Dried Fruit (that isn't home-made or organic)
Sulfite preservatives are suspected to contribute to a number of chronic respiratory and neurological conditions, including ALS. Mass-produced dried fruits have some of the highest sulfite concentrations of all foods, from 500-2,000 parts per million (wine by contrast contains between 20-350 ppm).
Many commercial dried fruits also contain lots of added sugars. Organic dried fruits will be free of sulfites, but may still contain (organic) added sugars. A better alternative is to dehydrate fruit yourself when it's in-season and cheap.
Nature's most perfect food might not be as perfect as we once thought, at least for grown-ups, according to a large study conducted in Sweden last year that involved nearly 100,000 middle-aged people who'd previously filled out dietary questionnaires for other research projects. Surprisingly, higher levels of milk consumption appeared to make people more susceptible to broken bones, which is the opposite of what they expected.
Even worse, it also appeared to make them more likely to die earlier. But since these results came from data collected for other purposes, many scientists (not to mention dairy industry lobbyists) are cautioning that more studies are needed before its clear if, and at what age, we should wean ourselves from the mammary secretions of bovines, or perhaps dial down our consumption.
If you're alive to read this then you probably don't eat too much polar bear liver, which contains toxic levels of Vitamin A.
The more benign symptoms of Vitamin A toxicity include headaches and nausea, but depending on the dose they can also include skin peeling off in sheets, and death, as some arctic explorers found out the hard way after feasting on polar bear liver, a single ounce of which contains five times the amount of Vitamin A considered toxic to humans.
Vitamin A also occurs, in much lower levels, in the livers of turkey, cow and chicken. Retinol, which is converted to Vitamin A in the body, is found in many plant foods, like sweet potato, pumpkin, carrots and other orange things.
The problem comes from the fact that Vitamin A is also found in many supplements, and some foods, like breakfast cereals, are fortified with it. The resulting ubiquity of Vitamin A makes it possible to ingest too much of this good thing. A study of middle-aged men, for example, found that high retinol and Vitamin A levels made the participants seven times more likely to suffer broken bones.
The authors suggested that, "...current levels of vitamin A supplementation and food fortification in many Western countries may need to be reassessed."
Spinach and parsely?!?!?
If you have kidney issues, then yes. And you can add strawberries, star fruit, beets, rhubarb, and chard to this list as well. All of these foods are high in oxalates, which can build up in your kidneys and crystallize into stones, which are dangerous and painful to eliminate.
Pretty much anything from China
China's air pollution is so bad that respiratory issues represent one of the nation's biggest killers, responsible for 17 percent of deaths in China according to one recent study.
This pollution includes a lot of airborne heavy metals, which contaminate dirt and water, from which they enter plants, even plants that are grown organically.
(and other forms of salt)
Perhaps this belongs in the "enough of anything can kill you" category, but a lot less soy sauce will poison you than water. One 19 year-old American woke up convulsing in the emergency room with acute salt toxicity after drinking a quart of soy sauce on a dare.
In Asia, suicide by soy sauce is a real thing. But the biggest threat is to babies and small children, who could be put in danger by a much smaller dose. A gram of salt per kilogram of body weight can be lethal.
A tablespoon contains about 20 grams, and that bottle of soy sauce contains 170 grams of salt, which put the fellow who drank it at just under 2 grams per/kg. He lived to tell the tale, but I don't think he'll be doing that again.