There’s a certain wisdom attributed to grandmothers and their kitchen tips that goes something like this: put a bay leaf in the rice to draw out the arsenic; wash chicken before cooking it to get rid of germs and make it safer to eat; don’t use a microwave oven because it destroys vitamins; eat celery since you burn more calories chewing it than you consume by eating it. Such tidbits of kitchen wisdom get passed along because no one bothers to fact-check them.
We combed through published research and the USDA’s nutrient database to fact-check 20 claims about common foods. Some surprised us. Here’s what we found out, with each one rated false, mostly false or partly true. Spoiler alert: the bay leaf isn’t one of the surprises.
How Each Claim Was Checked
Opinions vary from scientist to scientist; where this happens, we point this out. References to the scientific evidence (PubMed-indexed research studies, USDA nutrient databases, government fact sheets) are provided inline. False: no scientific support for the statement, or the weight of evidence points in the opposite direction. Mostly false: some kernel of truth, but exaggerated beyond what the scientific evidence can support. Partly true: true in some situations and not in others.
The 20 Claims
Drop a bay leaf in the pot? There’s no research backing that one up. Searching the medical literature turns up no studies of cooking rice with bay leaves to reduce arsenic. Arsenic is both in the rice and on the rice, and leaches out in water, so the best ways to reduce arsenic levels involve discarding water. In an FDA lab study, cooking rice with more water than it could absorb and draining the extra reduced inorganic arsenic 40 percent in long-grain white rice, 50 percent in brown and 60 percent in parboiled. Using 12 times as much water as rice got rid of 57 percent. So far the most successful method tried at home: Briefly boil rice in an abundance of water, drain, then cook to absorption in fresh water. This reduced inorganic arsenic 73 percent from white rice and 54 percent from brown. Plain rinsing doesn’t reduce arsenic much, and it removes some of the iron, folate and B vitamins added to enriched rice.
Don’t rinse, soak, brine or wash chicken with vinegar or lemon juice before cooking. None of these methods will kill germs; only cooking chicken to an internal temperature of 165°F will do that. In fact, a 2019 USDA study that watched home cooks prepare a meal found that among people who washed or rinsed their chicken, 60 percent had bacteria in the sink afterward, and 14 percent still did after cleaning the sink. Twenty-six percent of the washers also moved bacteria onto the salad greens they prepared next. If you don’t like something on your chicken, blot it with a damp paper towel, then wash your hands for 20 seconds afterward.
Indeed, cooking can have a positive effect on nutrient bioavailability (making nutrients more readily absorbed by our bodies). However, cooking vegetables in water has traditionally been frowned upon by nutritionists. This is because some nutrients, especially vitamins, are water-soluble and can leach out of the food during preparation. So what’s a nutrition-conscious vegetable lover to do? Cook them, but avoid soaking them in water for too long. Research by a team of Spanish food scientists suggests microwaving, baking and griddling vegetables retain more of their antioxidant content than pressure-cooking and boiling. The team cooked 20 vegetables six different ways and tested the antioxidant power of each to determine which cooking method was most effective at preserving the goodness. The authors’ own summary: water is not the cook’s best friend when it comes to vegetables.
Frozen vegetables and fruits are picked at peak ripeness and are usually flash frozen within a few hours of harvest. According to a University of California comparison of eight fruits and vegetables, levels of riboflavin and vitamin E were equal or higher in frozen compared to fresh. Vitamin C levels were equal in five out of eight produce items, and higher in the remaining three. The only nutrient found in significantly lower amounts in the frozen versions was beta-carotene in spinach, peas and carrots. So, if you’re buying carrots, you’re better off with fresh, but for spinach and peas (as well as berries) go with whichever is the best deal.
Cooking tomatoes at 190°F for 15 minutes nearly tripled the amount of lycopene (an antioxidant) available for absorption (from 2.01 milligrams per gram to 5.45 milligrams per gram). After 30 minutes of cooking, the tomatoes’ total antioxidant activity increased by more than half, but they lost 29 percent of their vitamin C. Different nutrients respond differently to cooking, so it’s best to eat a variety of both cooked and raw vegetables. Some nutrients become more available for absorption when foods are cooked (as with lycopene in tomatoes), because cooking breaks down cell walls and releases nutrients. Other nutrients are sensitive to heat and are destroyed when cooking (as with vitamin C in tomatoes).
According to the USDA’s table of alcohol retention, based on a 1992 study that marinated, flamed, baked and simmered foods with alcohol to determine how much remained, simmering does eventually cook off a good amount of alcohol, but it takes time. Fifteen minutes of simmering leaves about 40 percent of the alcohol in the dish; an hour of simmering, 25 percent; two hours, 10 percent; and two and a half hours, 5 percent. Baking can cook off alcohol, too, but again, it depends on how the alcohol is incorporated and for how long the dish is baked. Baking for 25 minutes without stirring in the alcohol leaves about 45 percent of the alcohol in the dish. Flambéing leaves 75 percent of the alcohol in the dish. A sauce brought to a boil with the alcohol stirred in and then taken off the heat keeps about 85 percent, and an uncooked marinade left overnight keeps 70 percent.
That’s mostly false, and still hotly contested. In this study of 215,618 women and men followed for up to 32 years by Harvard researchers, those who ate an egg or more each day didn’t have an increased risk of heart disease or stroke compared to people who ate less than an egg a month. The same was true in a pooled analysis of data on 1.72 million people. This 2019 JAMA analysis of 29,615 US adults found that for every additional half egg per day there was a 6 percent increase in cardiovascular disease, but that went away when they accounted for cholesterol from other foods. For most healthy people it’s not the egg that’s the problem; it’s what you’re having on your plate alongside it.
But the sodium’s still sodium no matter what color the crystals are. Plus, table salt is fortified with iodine (important for thyroid function and overall health) and most sea salts and all pink salts don’t have it. According to a team of Australian researchers who compared 31 types of pink salt to iodized table salt, you’d have to eat six teaspoons (more than 30 grams) of the pink variety each day to reap any kind of health benefit from those extra minerals, and that’s a whole lot of sodium (way more than we’re supposed to be having on a daily basis). One type of pink salt they tested even had more lead than is allowed in Australia.
Glutamate occurs naturally in many foods, including breast milk, tomatoes, and parmesan cheese. There’s no way for your body to tell the difference between those naturally occurring glutamates and the glutamates in MSG. People who claim they are MSG sensitive typically blame headaches. However, a systematic review of every human trial found no more headaches in the six studies where MSG was given with food compared to placebo. Four of the seven studies that gave it without food did find more headaches, but they used solutions strong enough to taste, so they were not truly blind. In a multicenter double-blind challenge of 130 people who described themselves as MSG-sensitive, 38.5 percent reacted to a large dose taken on an empty stomach, 13.1 percent reacted to the placebo, and when the same people were re-challenged, their reactions weren’t repeatable.
One meta-analysis of 23 blinded studies found no effect of sugar on any of 14 measures of children’s behavior or cognition. In one study of 35 mothers and their sons, the mothers were led to believe their sons had been given a large dose of sugar, but all the boys had been given aspartame. The mothers rated their sons as significantly more hyperactive and interacted with them significantly more.
A medium 40 gram stalk of celery has roughly 6 calories in it, and your body uses 5 to 15 percent of the calories you eat to digest them, so a piece of celery would give you a net of maybe four or five calories. It’s basically all water and fiber, which is pretty much as close to zero-calorie as you can get with a whole food (and no, that’s still not the same as negative calories or “burning fat”).
No one can say where the number came from. When a Dartmouth College physiologist who studies kidney function tried to determine the scientific basis for the oft-repeated recommendation to drink eight 8-ounce glasses of water a day, he couldn’t find any studies to back it up. And according to surveys of thousands of apparently healthy adults, most people appear to do just fine drinking less than that (especially when you factor in the fluids in food, as well as coffee and tea). A 2022 study that tracked water turnover among 5,604 people living in 23 different countries found that a person’s actual daily needs varied greatly depending on age, climate, activity level and body size. Bottom line: Unless you’re exercising vigorously or it’s especially hot out, thirst is probably an adequate guide for most healthy people (though illness and certain medical conditions can alter the equation).
No detox diet sold commercially has been studied in a randomized controlled trial, according to a 2015 review in the Journal of Human Nutrition and Dietetics. What studies there are tend to be small and flawed. Your liver and kidneys are already on top of it, and there’s no evidence that juice cleanses help them out. They do seem to work, but only in that they’re a few days of very-low-calorie eating. Any weight you lose will bounce back the moment you sit down to a real meal.
There’s a wartime story behind this one. British propaganda suggested that their pilots owed their ability to make kills at night to carrots rather than radar. There is some truth behind this myth: one of the first symptoms of vitamin A deficiency is poor night vision, and carrots are a good source of vitamin A (a medium sized carrot provides about 500 micrograms, roughly 70 percent of a woman’s daily requirement of 700 micrograms). But eating carrots will only improve night vision in people who are vitamin A deficient, returning it to normal levels. In people who are not vitamin A deficient, carrots will not improve night vision.
Spinach gets a reputation for being a great source of iron. Sure, it does have some iron, but not as much as you’d think, and not much of it is absorbed. Raw spinach only contains 2.7 milligrams of iron per 100 grams, so a cup of raw leaves provides about 0.8 milligrams, not much against the 18 milligrams per day recommended for women younger than 50, or 8 milligrams for post-menopausal women. The type of iron in spinach is also plant-based, or “non-heme,” which isn’t as easily absorbed by the body. On top of that, the calcium and polyphenols present in spinach further inhibit iron absorption. In one Swiss study, women absorbed about a quarter less iron from a spinach-based meal compared to a similar kale-based meal. There are better ways to combat iron deficiency (red meat, lentils and beans can all help), but spinach is a vegetable with a cartoon agent.
Late-night calories aren’t necessarily fattening calories, but your body may process them differently. In a tightly controlled crossover trial at Brigham and Women’s Hospital, people ate the same meals early or late in the day; eating later made them hungrier, decreased the number of calories they burned while awake, and switched on genes in fat tissue that promoted storing calories as fat. In another study of 420 people in Spain who followed a 20-week diet, those who ate their main meal after 3 p.m. lost less weight than those who ate it earlier, despite similar calorie intake and sleep habits.
Breakfast might help keep energy levels more consistent and prevent poor food choices later on. But don’t count on it to shed the pounds. Breakfast eaters in 13 randomized trials of eating versus skipping breakfast pooled together consumed an average of about 260 more calories a day than non-breakfast eaters and weighed almost half a kilogram more.
A 2022 analysis of 371,463 people in the UK Biobank dispelled the heart-healthy halo around a daily drink. All the putative benefit had come from observational studies that hadn’t controlled for the fact that people who drank moderately also tended to exercise more, smoke less and eat better. Once the researchers accounted for those lifestyle factors and used genetics to tease out the impact of alcohol itself, any apparent benefit disappeared. In fact, alcohol increased the risk of cardiovascular disease at all levels of intake, only marginally so for a drink a day and markedly so for more. And as for red wine’s special claim on heart health, well, grapes contain polyphenols too, without the alcohol.
Bees gather pollen from flowers, but hay fever is caused by exposure to pollen from trees and grasses. Those types of pollen are carried on the wind, and there’s probably very little of it in honey. Proponents of local honey for allergies say that pollen from plants in your area could help desensitize your immune system. In the one study designed to test that theory, 36 people with seasonal allergies were given a tablespoon of either local, raw honey, national brand pasteurized honey, or honey-flavored corn syrup every day. Neither honey group fared any better than the syrup group. In a Malaysian study, subjects did get better with honey treatment, but they got 1 gram of honey for every kilogram of body weight, and for the average person, that is 70 grams a day, plus an antihistamine.
But Rutgers food scientists tested how many bacteria are transferred when watermelon, bread, buttered bread and gummy candy are set on tile, wood, steel or carpet for less than a second, five seconds, 30 seconds and five minutes. They found bacteria can transfer to food in less than a second. (Moist foods like watermelon transferred the most bacteria, up to 97 percent of the bacteria on the surface, while dry foods, like gummy candy, transferred the least.) And the longer the food sat on the surface, the more bacteria it picked up. So the five-second rule isn’t exactly right, but not for the reason you think. It’s not that five seconds is safe. It’s that what you drop and where you drop it are way more important than how long it sits.
What the Scoreboard Says
Of these 20, fourteen are myths, three are exaggerated and three are partly true. In each of the myths, some truth was exaggerated: since arsenic is leached out of rice when cooked in water, it must be leached out when cooked with leaves; since vitamin A helps night vision, eating more carrots must enhance vision. The solution to all this is simple. Find out what the study is about and stop there.
Cory Jones has spent 20 years in media and publishing and now leads the data and editorial operation behind The Greenest.
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