There is no shortage of nutritional advice to be found on cereal boxes, supplement packages, influencer posts in the wellness space, and sometimes even from well-intentioned family members. The problem is that much of the advice out there has yet to be backed up by science in an empirical sense. Indeed, some of the most commonly cited rules of nutrition science stem from marketing schemes and observational studies rather than rigorous scientific research.
This list rounds up the top myths in nutrition investigated by this site, including misleading food labeling and claims about gut bacteria and a few more myths that need just as much debunking as the rest.
Why Nutrition Myths Spread So Easily
A few things are typical of nutrition myths: they are straightforward; they are emotionally appealing; and they always originate from a legitimate yet narrow study or a successful marketing campaign. As described in detail on this website, the labeling terms "natural" and "low-fat" create what researchers term "a health halo," a single term that creates an impression of the trustworthiness of an entire product or a piece of advice 1. The very phenomenon of the health halo provides an explanation as to why nutrition myths survive debunking of the related evidence.
7 Nutrition Myths, Debunked
1. "Detox diets and juice cleanses flush toxins out of your body"
The claim: A juice cleanse or detox tea clears accumulated toxins your body can't handle on its own.
The fact: Wesley McWhorter, a registered dietitian who speaks for the Academy of Nutrition and Dietetics, said that detox diets, liver flushes, or colon flushes do not make one healthier in any way at all 2. Detoxification is done by the liver, kidneys, lungs, and skin on a constant basis, and juices do not help increase their capacity. Most of the weight lost through a juice fast is temporary. 2 3 For the full breakdown of every detox and cleanse claim, see our complete guide to whether detox diets actually work.
2. "Natural and low-fat labels mean a product is healthy"
The claim: Front-of-package claims like "natural" or "low-fat" are reliable health signals.
The fact: Based on the detailed analysis of misleading food labels that we have provided, "natural" lacks a legal definition, while "low-fat" foods often undergo changes by adding sugar to keep their taste the same, making them similar in terms of calories compared to their regular versions 1.
3. "Probiotics and fermented foods work the same way"
The claim: Any probiotic product, pill, or food restores your gut bacteria equally well.
The fact: The above-mentioned study was covered extensively in our other blog post dedicated to gut health fallacies. To be more precise, the Weizmann Institute’s research revealed that many people have healthy gut microflora that is resistant to colonization by commercial probiotics, while the Stanford experiment revealed that fermented foods increased diversity and reduced inflammation 4.
4. "Carbs make you fat; cutting them out is the fastest way to lose weight"
The claim: Carbohydrates are uniquely fattening compared to fat or protein.
The fact: The results of the DIETFITS study, a year-long randomized experiment conducted by Christopher Gardner at Stanford University, which involved 609 participants, revealed no statistical differences in terms of weight loss when comparing a healthy low-fat diet to a healthy low-carb diet 5. The findings by Christopher Gardner suggest that the quality of the food consumed is more important than reducing any particular macronutrient 5. For a full breakdown of the carbohydrate-insulin debate and what actually drives weight gain, see our complete guide to whether carbs make you gain weight.
5. "Breakfast is the most important meal of the day"
The claim: Skipping breakfast wrecks your metabolism and causes weight gain.
The fact: According to a randomized controlled study conducted by James Betts et al. from the University of Bath, there is no metabolic difference in energy balance for breakfast eaters and non-eaters 6. Another study in the form of a meta-analysis, involving 13 randomized trials and published in The BMJ, found that people eating breakfast consumed more calories per day compared to those who skip breakfast 7. For the full picture, including what the Bath Breakfast Project and the BMJ meta-analysis found, see our deep dive on the breakfast myth.
6. "Eating late at night automatically causes weight gain"
The claim: Food eaten after a certain hour gets stored as fat regardless of your total daily intake.
The fact: Various research reviews have indicated that after taking into account total calorie intake throughout the day, the impact of meal time becomes less prominent; people who eat late are prone to gaining weight due to higher consumption of food, especially evening snacks, rather than due to any unique metabolic consequence of the clock 8.
7. "You need supplements to eat healthily"
The claim: Whole food alone can't deliver what a targeted supplement can.
The fact: All of the different strands that run through the myth-debunking articles on this website seem to lead to the same place, whether it's the gut health expert Sarah Berry proving that a combination of plant-based foods beats a single-strain probiotic pill 4, or the findings of Gardner regarding the quality of one's diet 5.
How to Evaluate a Nutrition Claim Before You Believe It
Determine if the study is a randomized experiment or an observational study. Observational studies demonstrate correlation, not causation, as the breakfast myth illustrates 6, 7.
Exercise caution if the claim depends on a single "toxin" or "superfood." That is not how human physiology typically operates 2.
Consider who is claiming it and what they have to sell. Detox teas and probiotic capsules are products; peer-reviewed scientists are not compensated according to outcomes 2, 4.
Seek consistency among multiple independent studies, not just one sensational headline.
In cases of doubt, always go with the boring answer. "Eat a balanced diet and do not overdo any particular component" may not be flashy, but it's what keeps popping up 5.
Frequently Asked Questions
Do detox diets actually remove toxins from the body?
No, registered dietitians and physicians consistently note that the liver, kidneys, lungs, and skin already handle detoxification continuously, with no added benefit from cleanses 2.
Is breakfast really the most important meal of the day?
Randomized trials have found no significant difference in weight or metabolic outcomes between habitual breakfast eaters and skippers, challenging this long-held claim 6, 7.
Do carbs make you gain more weight than fat does?
A year-long Stanford trial found no significant difference in weight loss between low-fat and low-carb diets, suggesting overall diet quality matters more than avoiding one macronutrient 5.
Does eating late at night cause weight gain by itself?
Not independently of total calorie intake; research shows the effect largely disappears once total daily calories are accounted for 8.
Are "natural" and "low-fat" reliable indicators of a healthy product?
No. "Natural" has no enforceable legal definition, and "low-fat" products are often reformulated with added sugar 1.
Do I need a probiotic supplement for good gut health?
Not necessarily. Research suggests many people's guts resist colonization by standard probiotic supplements, while whole, fiber-diverse foods may support the microbiome just as well or better 4.
Key Points
Nutrition myths exist because they are simple and comforting, rather than because they have scientific backing. Detoxing does not provide detoxification capabilities that your body does not already have 2. Words such as “natural” and “low-fat” on food packaging can be misleading 1. Probiotics cannot solve all problems, and eating fermented foods might be more effective than taking a pill 4. Carbs are no more fattening than fats 5. Skipping breakfast has no impact on metabolism 6, 7. And timing does not matter as much as the content and quantity of food 8.
It turns out that in close to 10 years of nutrition research, there is one constant theme: the quality and pattern of your diet always beats any rule or product. For other popular nutrition claims that don't hold up to scrutiny, see our breakdowns of whether breakfast is really the most important meal of the day, whether detox diets actually work, and a full roundup of common nutrition myths for more.
References
[1] See this site's full breakdown: Misleading Food Labels, drawing on Chandon, P., & Wansink, B. (2007). The Biasing Health Halos of Fast-Food Restaurant Health Claims: Lower Calorie Estimates and Higher Side-Dish Consumption Intentions. Journal of Consumer Research, 34(3), 301–314. doi.org/10.1086/519499; and Petty, R. D. (Babson College) research on "natural" label regulation.
[2] McWhorter, W., registered dietitian and Academy of Nutrition and Dietetics spokesperson, quoted via PBS News: pbs.org/newshour/health/how-to-detox-your-body-for-free-without-juice-teas-or-flushes
[3] University of Rochester Medicine — nutrition experts on juice cleanses and detox diets: urmc.rochester.edu/news/publications/health-matters/do-juice-cleanses-detox-the-body
[4] See this site's full breakdown: Gut Health Myths, drawing on Zmora, N. et al., & Elinav, E. (2018). Personalized Gut Mucosal Colonization Resistance to Empiric Probiotics Is Associated with Unique Host and Microbiome Features. Cell, 174(6), 1388–1405. doi.org/10.1016/j.cell.2018.08.041; Wastyk, H. C., Sonnenburg, E. D., & Sonnenburg, J. L., et al. (2021). Gut-Microbiota-Targeted Diets Modulate Human Immune Status. Cell, 184(16), 4137–4153. doi.org/10.1016/j.cell.2021.06.019; and Berry, S. (King's College London / Zoe) trial research.
[5] Gardner, C. D., Trepanowski, J. F., Del Gobbo, L. C., et al. (2018). Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA, 319(7), 667–679. jamanetwork.com/journals/jama/fullarticle/2673150
[6] Betts, J. A., Richardson, J. D., Chowdhury, E. A., Holman, G. D., Tsintzas, K., & Thompson, D. (2014). The causal role of breakfast in energy balance and health: a randomized controlled trial in lean adults. American Journal of Clinical Nutrition. ncbi.nlm.nih.gov/pmc/articles/PMC4095658
[7] Sievert, K., Hussain, S. M., Page, M. J., et al. (2019). Effect of breakfast on weight and energy intake: systematic review and meta-analysis of randomised controlled trials. BMJ, 364, l42. doi.org/10.1136/bmj.l42
[8] Baron, K. G., Reid, K. J., Kern, A. S., & Zee, P. C. (2011). Role of Sleep Timing in Caloric Intake and BMI. Obesity, 19(7), 1374–1381. pmc.ncbi.nlm.nih.gov/articles/PMC4794259
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