Nutrition myths: what the evidence actually says

Myth: Dietary cholesterol is capped at 300 mg a day, so one or two eggs blows your budget.

Reality: The 2015–2020 Dietary Guidelines dropped the 300 mg cap from the 2010 edition. The authors added that this "does not suggest that dietary cholesterol is no longer important to consider."

The 2020–2025 edition repeated the National Academies' advice to keep dietary cholesterol "as low as possible without compromising the nutritional adequacy of the diet." The 2025–2030 Dietary Guidelines, released in January 2026, list eggs among the animal protein foods to eat. They still say saturated fat "should not exceed 10% of total daily calories." So the guidance moved away from counting cholesterol milligrams and toward looking at the whole diet, especially saturated fat.

Myth: Carbohydrates as a group cause weight gain, so cutting them is the healthy choice.

Reality: Harvard's Nutrition Source puts it directly: "The amount of carbohydrate in the diet – high or low – is less important than the type of carbohydrate in the diet."

Whole grains, beans, fruit and vegetables behave differently from white bread and sugary drinks. The 2025–2030 Guidelines tell people to "prioritize fiber-rich whole grains" while cutting "highly processed, refined carbohydrates." Their target is refined carbohydrates, not carbohydrates in general.

Myth: A slice of cake turns a calm child into a whirlwind.

Reality: A 1995 meta-analysis in JAMA combined 23 blinded, placebo-controlled studies and concluded that "sugar does not affect the behavior or cognitive performance of children."

The authors suggested that parents' strong belief "may be due to expectancy and common association." Parties come with sugar, but they also come with excitement, crowds and late bedtimes. The paper did add that "a small effect of sugar or effects on subsets of children cannot be ruled out." Mistaking that kind of coincidence for a cause is a classic post hoc fallacy.

Myth: MSG causes headaches and reactions and should be avoided.

Reality: The FDA considers adding MSG to foods "generally recognized as safe" (GRAS). When people who reported sensitivity were tested with MSG or a placebo, researchers could not trigger reactions consistently.

The FDA notes that glutamate occurs naturally in foods such as tomatoes and cheeses. The glutamate your body gets from digesting protein is chemically the same as the glutamate in MSG. Some sensitive people may have mild, short-lived symptoms after eating 3 grams or more of MSG without food, which is far more than a typical serving contains.

Myth: A cleanse flushes accumulated toxins and resets your body.

Reality: The NIH's National Center for Complementary and Integrative Health says the few studies of detox programs in people "have been of low quality." It also says "there have been no studies on long-term effects."

NCCIH warns that unpasteurized juices can make people sick and that colon cleansing can have serious side effects. It also reports that the FDA and FTC have acted against detox products containing hidden or harmful ingredients. Your liver and kidneys already do the detox work around the clock.

Myth: Healthy adults need exactly 8 × 8 oz of plain water, on top of everything else they drink.

Reality: Physiologist Heinz Valtin reviewed the evidence in 2002 and reported that "no scientific studies were found in support of 8 x 8." He also found that caffeinated drinks can count toward the daily total.

The National Academies set Adequate Intakes for total water from all drinks and food: about 3.7 liters a day for men and 2.7 liters for women. They estimate that food supplies roughly 20% of that water. The same report says thirst plus drinking with meals is enough for most people. Hot weather, hard exercise and some medical conditions change the picture.

Myth: A hard sear closes the surface of the meat so moisture can't escape.

Reality: America's Test Kitchen seared one batch of rib-eyes before roasting and another after. Both batches lost "around 22 percent of their weight."

Searing is still worth doing because browning (the Maillard reaction) builds flavor and texture. Juiciness depends mostly on the final internal temperature. You can hear the sizzle in the pan, and that sizzle is water leaving the meat.

Myth: Microwaves kill the vitamins in food.

Reality: Harvard Health calls microwave cooking "one of the least likely forms of cooking to damage nutrients," because cooking times are short.

Every cooking method destroys some heat-sensitive nutrients, vitamin C most of all. Long cooking times and lots of water cause the biggest losses, because nutrients break down with heat and leach out into the cooking water. Microwaving vegetables with a splash of water is gentler than boiling them in a big pot.

Myth: Food picked up off the floor within five seconds hasn't had time to pick up germs.

Reality: Rutgers researchers ran 128 scenarios: four foods, four surfaces and contact times from under one second to 300 seconds. They found that "some transfer takes place 'instantaneously,' at times of <1 s" (Miranda & Schaffner, 2016).

Longer contact did mean more bacteria, but the type of food and the surface mattered as much or more. Wet watermelon picked up the most bacteria and gummy candy the least. Carpet transferred less than tile or steel.

Myth: After any amount of cooking, a wine sauce or a flambé is alcohol-free.

Reality: USDA's Table of Nutrient Retention Factors measured how much alcohol stays in food:

Myth: A brown shell means a more natural or more nutritious egg.

Reality: The USDA's Egg-Grading Manual says "shell color does not affect the quality of the egg and is not a factor in the U.S. standards and grades." Shell color comes from the hen's breed. White Leghorns, for example, lay white eggs.

Myth: Cutting gluten is a healthy choice even without celiac disease.

Reality: In a 2017 BMJ study of more than 110,000 adults, summarized by Harvard Health, researchers found no significant link between gluten intake and coronary artery disease. They did "not support the promotion of a gluten-restricted diet" to lower heart risk.

For people with celiac disease, avoiding gluten is essential. For everyone else, cutting gluten can mean eating fewer whole grains. The study was observational, which means it shows associations, not cause and effect.

Myth: Organic produce and meat contain significantly more nutrients.

Reality: A Stanford systematic review of 240 studies, published in Annals of Internal Medicine in 2012, found that the literature "lacks strong evidence that organic foods are significantly more nutritious than conventional foods."

The same review did find that organic produce had a lower risk of detectable pesticide residues (a risk difference of 30%), and that conventional chicken and pork were more likely to carry bacteria resistant to three or more antibiotics. In most conventional produce, though, residues stayed within safety limits (Stanford Medicine). Some people choose organic for other reasons, such as pesticides or farming practices. Extra nutrients, on the evidence so far, isn't one of them.