This piece originally appeared on Fix.com.
Looking to clean up your diet? Dark, leafy greens including spinach and Swiss chard, fiber-rich kidney beans and brown rice, heart-healthy nuts, lean proteins such as tuna, and plenty of water all make up a healthy diet. But believe it or not, it is possible to have too much of a good thing when it comes to some healthy staples. While overdoing it on most of the nine foods below is rare - most require a person to eat or drink a lot of servings in one sitting - others can cause issues when consumed regularly over time.
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9 Foods You Shouldn’t Eat in Large Quantities
Spinach, Beet Greens, and Swiss Chard
Dark, leafy greens are a nutritional powerhouse, packed with essential nutrients including vitamins A and C, iron, and folate. But some - namely spinach, beet greens, and Swiss chard - are also high in oxalic acid, the compound that gives hearty greens their signature earthy, slightly bitter taste. Consume too much and you may be in for unpleasant symptoms such as kidney stones, abdominal pain, low blood pressure, tremors or convulsions, vomiting, and weak pulse. But don’t think this means dark, leafy greens aren’t part of a healthy diet: In moderation, they’re perfectly fine. Some research shows it would take about 25 grams of oxalic acid to cause death in a 145-pound person, which would equate to about 7.3 pounds of spinach.
Chowing down on too many Brazil nuts can cause selenosis, or an overdose of the mineral selenium. Symptoms can include upset stomach, hair loss, fatigue, irritability, diarrhea, brittle hair or nails, discolored teeth, nervous system issues, a metallic taste in the mouth, and a garlic-like odor in the breath. Untreated, selenosis can even lead to difficulty breathing, tremors, kidney failure, heart attack, or heart failure.
Don’t go avoiding selenium completely, though. Selenium is an essential mineral needed to produce selenoproteins, which function as antioxidants. It also plays an important role in reproduction, thyroid function, and DNA production. So just how many Brazil nuts is too many? One Brazil nut contains 68 to 91 micrograms of selenium, and the upper limit of consumption for adults is 400 micrograms; try to keep your daily dose to four or five nuts. Keep your intake below this level and you shouldn’t have any problems.
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Tuna contains more mercury than many other fish, and excessive mercury can cause some alarming side effects, including vision, hearing and speech problems, lack of coordination, and muscle weakness. So just how does mercury contaminate fish? First, industrial sources such as power plants release mercury into the environment. The molecules then make their way into clouds, where they stay until they return to the ground (and bodies of water, where fish live) when it rains. Canned tuna can still be part of a healthy diet, but follow these rules: Stick to “light” varieties, which are made from smaller skipjack tuna that typically have lower levels of mercury than larger albacore tuna. Keep consumption to no more than three to five cans per week, and you should be safe.
Don’t worry: Tomatoes themselves are perfectly safe to eat. Stay away from the leaves and stems, though. Tomato leaves contain an alkaloid toxin called tomatine. While studies have not shown any apparent toxic effects on humans, too much of the compound can lead to digestive issues. And definitely keep all parts of the tomato plant away from pets; tomatine has a much stronger impact on dogs and can lead to a host of dangerous side effects, including digestive and nervous system issues.
Nutmeg contains a compound called myristicin, which can lead to myristicin poisoning in large doses. It would take commitment to consume enough nutmeg to make a human sick: Throwing a pinch into a quiche or baked good isn’t going to hurt, but consuming too much (think tablespoons) can lead to not-so-great side effects, including headaches, nausea, dizziness, and even hallucinations.
There’s a reason rhubarb makes its way to grocery store shelves without leaves. While rhubarb stalks are fine to eat, the leaves contain oxalic acid, a compound that’s used in bleach and antirust products. Eating rhubarb leaves can cause a burning sensation in the mouth and throat, and lead to vomiting, nausea, convulsions, and even death. Just how many leaves would you have to chow down to get sick? One study determined that a 130-pound woman would have to eat about 10 pounds of rhubarb leaves to show symptoms of oxalic acid poisoning.
If you ever come across a green potato, especially one that has started to sprout, toss it. Green potatoes contain solanine, a natural pesticide that is toxic to humans when consumed in large quantities. Too much of this compound can cause vomiting, diarrhea, and cardiac arrest. Luckily, it would be nearly impossible for an adult to consume enough green potatoes to get sick: A 100-pound adult would have to eat a full pound of completely green potatoes before showing symptoms.
Red Kidney Beans
Raw red kidney beans contain a toxin called phytohaemagglutinin. To remove it, the beans have to be boiled for at least 10 minutes before consuming. And don’t try to simmer them for a longer period of time in place of boiling: Cooking the beans at temperatures below boiling multiplies their toxicity. Fail to remove the toxin before eating and symptoms could include severe nausea and vomiting.
Believe it or not, there is such thing as consuming too much water. Overconsumption can lead to water intoxication, a condition that occurs when extreme water intake dilutes the sodium in the blood, which can then lead to impaired brain function and even death. Don’t let this be a deterrent to drinking enough water every day; hyponatremia is usually only a problem for ultramarathoners and people who force themselves to drink too much water.
So should you remove these foods from your diet altogether? Don’t give up the hearty greens and red kidney beans quite yet! Thankfully, it is nearly impossible to overdose on most of these foods, since each serving contains so little of the toxins. Continue to enjoy these healthy staples - but as with everything, in moderation.