Health advice is often passed down through generations, sometimes becoming so ingrained in our culture that we rarely question its accuracy. But how many of these “old wives’ tales” actually stand up to scientific scrutiny? I have highlighted 10 of these myths below – each one is something I recall hearing during my childhood.
- Cracking your knuckles causes arthritis
There is no scientific evidence linking knuckle cracking to arthritis. The characteristic “pop” is caused by gas bubbles bursting in the synovial fluid of the joint, not by damage to the cartilage or bone. Multiple studies have found no increased risk of arthritis among habitual knuckle-crackers compared to non-crackers.
- Going outside with wet hair or being exposed to cold weather will make you sick.
Colds are caused by viruses, not by cold or wet conditions. While cold weather can slightly impair the immune response in the nose, making it easier for viruses to take hold, you still need to be exposed to a virus to get sick. The increased incidence of colds in winter is more about spending time indoors with others than the temperature itself.
- If you swallow gum, it stays in your digestive system for seven years.
While gum is not digestible, it does not linger in your body for years. It passes through the digestive tract and is excreted in a few days, just like other indigestible substances. Swallowing gum occasionally is harmless, though swallowing large amounts can (rarely) cause blockages.
- Eating sugar makes children hyperactive.
Despite widespread belief, scientific studies have consistently failed to find a direct link between sugar consumption and hyperactivity in children. The “sugar rush” is likely due to the context in which sugary foods are consumed (like parties), or parental expectations, rather than the sugar itself.
- Feed a cold, starve a fever
There is no scientific basis for this advice. When you are sick – whether with a cold or a fever – your body needs adequate nutrition and, most importantly, hydration. Fasting during illness can actually weaken your immune response.
- If you swim right after eating, you’ll get cramps and could drown.
There is no evidence that eating before swimming significantly increases your risk of cramps or drowning. While you might feel a bit uncomfortable if you have eaten a large meal, it is generally safe to swim after eating.
- Most body heat escapes through your head, so you should always wear a hat in cold weather.
Heat is lost from any exposed part of the body, not just the head. The head accounts for about 7–10% of body surface area, so you lose a similar proportion of heat through it. The myth likely arose because the head is often left uncovered.
- Shaving causes hair to grow back thicker, darker, or faster.
Shaving does not affect the thickness, colour, or rate of hair growth. The blunt tip of regrowing hair may feel coarser or look darker, but this is just an illusion. Hair growth is determined by genetics and hormones, not by shaving.
- Sweating in a sauna or during exercise removes toxins from your body.
Sweat is mostly water and salt. The liver and kidneys are responsible for detoxifying your body, not your sweat glands. While trace amounts of some substances can be found in sweat, sweating is not a significant route for toxin elimination.
- Humans only use 10% of their brains.
Brain imaging studies show that virtually all parts of the brain have some function and are active at different times. The “10% myth” is a persistent misconception; in reality, we use all of our brain, just not all at once.
Many health myths persist because they sound plausible or have been repeated for generations. However, scientific research often tells a different story.
A few links:
Harvard Health Publishing (2020) ‘Does cracking knuckles cause arthritis?’, Harvard Health, 6 July. Available at: https://www.health.harvard.edu/pain/does-cracking-knuckles-cause-arthritis (Accessed: 23 September 2025).
Harvard Medical School (2022) ‘Why Upper Respiratory Infections Are More Common in Colder Temperatures’, Harvard Medical School News, 5 December. Available at: https://hms.harvard.edu/news/why-upper-respiratory-infections-are-more-common-colder-temperatures (Accessed: 23 September 2025).
Mayo Clinic (2025) ‘Swallowing gum: Is it harmful?’, Mayo Clinic. Available at: https://www.mayoclinic.org/diseases-conditions/indigestion/expert-answers/digestive-system/faq-20058446 (Accessed: 23 September 2025).
Huynh, N. (2010) ‘Does Sugar Really Make Children Hyper?’, Yale Scientific Magazine, 1 September. Available at: https://www.yalescientific.org/2010/09/mythbusters-does-sugar-really-make-children-hyper/ (Accessed: 23 September 2025).
Cleveland Clinic (2023) ‘Fact or fiction: feed a cold, starve a fever’, Cleveland Clinic Health Essentials, 2 February. Available at: https://health.clevelandclinic.org/feed-a-cold-starve-a-fever (Accessed: 23 September 2025).
Mayo Clinic News Network (2018) ‘Mayo Clinic Minute: Should you wait 30 minutes to swim after eating?’, Mayo Clinic News Network, 22 June. Available at: https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-minute-should-you-wait-30-minutes-to-swim-after-eating/ (Accessed: 23 September 2025).
Cleveland Clinic (2021) ‘Do you really lose most of your body’s heat through your head?’, Cleveland Clinic Health Essentials, 3 December. Available at: https://health.clevelandclinic.org/body-heat-loss (Accessed: 23 September 2025).
Mayo Clinic (2024) ‘Does shaved unwanted body hair make it grow back thicker and darker?’, Mayo Clinic. Available at: https://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/hair-removal/faq-20058427 (Accessed: 23 September 2025).
Pallardy, R. (n.d.) ‘Can You Really Sweat Out Toxins?’, Britannica. Available at: https://www.britannica.com/story/can-you-really-sweat-out-toxins (Accessed: 23 September 2025).
Solan, M. (2021) ‘You don’t say? Brain space’, Harvard Health, 1 October. Available at: https://www.health.harvard.edu/mind-and-mood/you-dont-say-brain-space (Accessed: 23 September 2025).
