21 entries
Health & Nutrition
Food pyramids retired, fats rehabilitated, and dietary rules your health class stated as law that have since been rewritten.
Changes here run from 1990 to 2026.
- Disproved12
- Updated3
- Replaced3
- Refined2
- Reclassified1
- DisprovedNot in textbooks yet
TaughtThe blockbuster weight-loss and diabetes drugs (semaglutide, tirzepatide) are peptides, fragile protein-like chains your stomach digests. That is why they come as weekly injections. You cannot simply put them in a swallowable, mass-produced tablet.
NowOn 1 April 2026 the FDA approved Foundayo (orforglipron), the first small-molecule GLP-1 receptor agonist: a once-daily pill you can take any time of day, with no food or water restrictions, and that can be manufactured at pharmaceutical scale like an ordinary tablet.
- ReclassifiedNot in textbooks yet
TaughtObesity is one thing: a BMI of 30 or above. You either cross that line or you don't, and crossing it means you have the disease of obesity.
NowIn January 2025 a Lancet Diabetes & Endocrinology Commission of 58 experts split the concept in two ('clinical obesity,' an actual disease with organ dysfunction caused by excess body fat, and 'preclinical obesity,' excess fat with raised future risk but no current illness) and moved diagnosis beyond BMI alone.
- UpdatedNot in textbooks yet
TaughtFD&C Red No. 3 (erythrosine) is a federally approved color additive, used for decades in candy, drinks, and medicines. It is on the shelf, so it must be considered safe to eat.
NowOn 15 January 2025 the FDA revoked the authorization for Red No. 3 in food and ingested drugs, ordering it removed from the food supply. The dye had already been banned from cosmetics in 1990; the food ban closes a 35-year gap.
- Disproved
TaughtA daily multivitamin is basic health insurance; it fills the gaps in an imperfect diet and, over a lifetime, helps you stay healthy and live longer.
NowA June 2024 analysis in JAMA Network Open, pooling nearly 400,000 healthy US adults followed for more than 20 years, found that daily multivitamin use was not associated with any lower risk of death.
- Disproved
A daily glass of red wine is good for your heart
Changed in2023TaughtModerate drinking is healthier than not drinking at all. A glass of red wine a day protects your heart: the famous J-shaped curve, backed by the 'French paradox.'
NowIn January 2023 the WHO stated plainly that no level of alcohol consumption is safe for health, and better-controlled studies have shown the apparent benefit of moderate drinking largely dissolves once confounding is removed. Alcohol is a Group 1 carcinogen.
- Refined
BMI tells you whether you are healthy
Changed in2023TaughtCalculate your Body Mass Index, look it up on the chart, and find out if you are underweight, normal, overweight, or obese.
NowIn 2023 the American Medical Association adopted policy stating that BMI is an imperfect measure that should not be used alone, because it ignores body composition and differs in meaning across ethnic groups and sexes.
- Disproved
TaughtVitamin D builds strong bones, so a daily supplement is a sensible way for adults to keep their bones dense and guard against fractures as they age.
NowThe large VITAL trial, reported in the New England Journal of Medicine in July 2022, found that vitamin D3 supplements did not lower the risk of fractures in generally healthy adults who were not deficient: no reduction in total, non-vertebral, or hip fractures.
- Disproved
TaughtWeight is a matter of diet and willpower. The few prescription diet drugs that exist are marginally effective and often dangerous; the history of obesity medicine is a graveyard of withdrawn pills. Nothing on prescription reliably produces large, sustained weight loss.
NowOn 4 June 2021, the FDA approved Wegovy (semaglutide 2.4 mg), a once-weekly injection that produced an average weight loss of roughly 15–17% over 68 weeks in trials: results previously seen only with bariatric surgery, and far beyond any earlier weight-loss drug.
- Updated
A little added sugar in a baby's food is harmless
Changed in2020TaughtThere was no official national advice for feeding children under two, so the working assumption was that a little sweetness (a spoon of sweetened yogurt, a flavored puree, a sip of juice) was fine for babies and toddlers.
NowThe 2020–2025 Dietary Guidelines for Americans, released in December 2020, were the first edition ever to cover children from birth to 24 months, and they set a firm line: no added sugars at all for children under age 2.
- Updated
Eating cholesterol raises your blood cholesterol
Changed in2015TaughtLimit dietary cholesterol to 300 mg a day. Watch the eggs: no more than a few a week, and shrimp and liver are dangerous.
NowThe 2015 Dietary Guidelines Advisory Committee concluded that cholesterol is not a nutrient of concern for overconsumption, and the 300 mg cap was dropped. For most people, dietary cholesterol has a modest effect on blood cholesterol.
- Replaced
TaughtDo not give peanuts to children under three, especially if allergies run in the family. Avoidance prevents allergy.
NowThe opposite. The LEAP trial in 2015 found that early, regular peanut introduction in high-risk infants reduced peanut allergy by about 80%. Guidelines now recommend introducing peanut protein at around 4 to 6 months.
- Disproved
Margarine is the heart-healthy choice
Changed in2015TaughtButter is saturated animal fat and bad for your heart. Switch to margarine, which is made from vegetable oil.
NowThe hydrogenation that made margarine solid produced artificial trans fats, which are worse for cardiovascular health than the saturated fat they replaced. The FDA removed partially hydrogenated oils from the safe list in 2015 and the WHO has called for global elimination.
- Refined
Breakfast is the most important meal of the day
Changed in2014TaughtNever skip breakfast. It kick-starts your metabolism and skipping it makes you gain weight.
NowThe evidence is much weaker than the slogan. Randomized trials, including a 2014 study in the American Journal of Clinical Nutrition, found no significant weight effect from eating or skipping breakfast, and much of the supporting research was observational or industry-funded.
- Disproved
Cracking your knuckles causes arthritis
Changed in2011TaughtStop cracking your knuckles or you will get arthritis when you are older.
NowNo association has been found. A doctor cracked the knuckles on one hand only for over 60 years as a personal experiment and found no difference; a 2011 study of 215 people found no link either.
- Replaced
The Food Pyramid is how you should eat
Changed in2011TaughtEat 6 to 11 servings of bread, cereal, rice, and pasta a day. That is the base of the pyramid. Fats and oils go at the tiny tip: use sparingly.
NowThe USDA retired the pyramid in 2011 and replaced it with MyPlate, a divided dinner plate with half of it fruit and vegetables. The bread-heavy base and the blanket anti-fat message are gone.
- Disproved
TaughtSpinach has enormous amounts of iron, which is why Popeye eats it. Or, if you had a clever teacher: the iron claim came from a scientist misplacing a decimal point in 1870.
NowBoth versions are wrong. Spinach has a moderate amount of iron, poorly absorbed because of its oxalates. And the famous decimal point story is itself a myth, traced and debunked by Mike Sutton in 2010.
- Replaced
Always stretch before exercise to prevent injury
Changed in2007TaughtLine up and do static stretches before you run. Hold each one for 30 seconds. It prevents injury and improves performance.
NowStatic stretching before activity does not meaningfully prevent injury and temporarily reduces muscle power and strength. The current recommendation is a dynamic warm-up first, and static stretching afterward if at all.
- Disproved
Wait 30 minutes after eating before you swim
Changed in2005TaughtSwimming on a full stomach causes cramps that will make you drown. Wait at least half an hour. Preferably an hour.
NowThere is no evidence for it. Digestion diverts some blood to the gut, but nowhere near enough to cause dangerous cramping, and drowning statistics show no association with eating.
- Disproved
You must drink eight glasses of water a day
Changed in2002TaughtDrink eight 8-ounce glasses of water daily, and coffee and tea do not count because caffeine dehydrates you.
NowThere is no scientific basis for the 8x8 rule. Heinz Valtin searched for the evidence in 2002 and found none. Food contributes substantial water, and caffeinated drinks are net hydrating.
- Disproved
Sugar makes children hyperactive
Changed in1995TaughtSugar causes hyperactivity. Cut it out before a test, and blame the birthday cake for the chaos afterward.
NowA 1995 meta-analysis in JAMA covering 23 controlled studies found sugar does not affect children's behavior or cognition. The effect is in the parents' expectations, which has been demonstrated experimentally.
- Disproved
Carrots give you excellent night vision
Changed in1990TaughtEat your carrots and you will be able to see in the dark.
NowCarrots supply vitamin A, which is needed for normal vision, but if you are not deficient, extra carrots do nothing for your night vision. The exaggeration was seeded by British wartime propaganda.