Many widely repeated claims about carbs, eggs, coconut oil and vitamin C are not supported by current evidence from bodies such as the World Health Organization and Harvard Health. This explainer compares common nutrition myths with the facts, using WHO's official dietary targets and findings summarised by Harvard Health and the European Food Information Council (EUFIC).
Nutrition advice circulates constantly on social media, in diet books and in casual conversation, and not all of it matches the evidence reviewed by public-health agencies. The World Health Organization (WHO) publishes numerical targets for fat, sugar, salt, fibre and fruit and vegetable intake, while reviews from Harvard Health and EUFIC (the European Food Information Council) have examined specific claims about carbohydrates, eggs, oils, fasting and vitamin C.
Common myths compared with the evidence
Myths vs. facts summarised from WHO, Harvard Health and EUFIC
Claim
What the sources say
Carbs make you gain weight
EUFIC states weight gain results from consuming more calories than are burned, regardless of whether those calories come from carbohydrates, fat or protein.
Eggs should be avoided for cholesterol
EUFIC reports that eating one egg a day does not significantly raise cholesterol in healthy people, because the body compensates by producing less cholesterol itself.
Coconut oil is a healthy fat
EUFIC notes coconut oil is about 92% saturated fat, compared with roughly 10% in olive oil, and advises using it only occasionally while choosing unsaturated oils for daily use.
Fresh produce is always better than frozen
EUFIC states fresh, frozen, canned and dried fruits and vegetables all count toward recommended intake, and freezing can lock in nutrients at peak ripeness.
Gluten should be avoided by everyone
EUFIC says there is no reason to eliminate gluten unless a person has been diagnosed with coeliac disease or gluten sensitivity.
Intermittent fasting is the best method for weight loss
EUFIC states intermittent fasting is not superior to standard calorie-restricted diets for weight management, since effectiveness depends on overall calorie balance rather than meal timing.
Meat is required for enough protein
EUFIC notes that varied plant sources such as beans, lentils and tofu, eaten across the day, can meet dietary protein needs.
'Low-fat' on a label means healthier
EUFIC explains that low-fat labels do not guarantee overall nutritional quality, since manufacturers often add sugar or salt to compensate for removed fat.
Vitamin C prevents the common cold
Harvard Health states regular vitamin C intake does not appear to reduce the chance of catching a cold, though some research suggests it may modestly shorten or ease symptoms.
What official dietary targets actually recommend
According to the WHO healthy diet fact sheet, adults should keep total fat intake at 30% or less of daily energy, with saturated fat under 10% and trans fat under 1%, favouring unsaturated fats from sources such as fish, avocado and nuts. WHO recommends free sugar intake stay below 10% of daily energy — roughly 50 grams on a 2,000-calorie diet — and says limiting it further to 5% or less may bring additional benefits. The agency also advises against relying on non-sugar sweeteners as a substitute strategy for cutting sugar.
On salt, WHO recommends adults consume less than 5 grams of salt per day (equivalent to 2 grams of sodium), noting that most dietary sodium comes from processed foods such as ready meals and bread rather than from salt added at the table. WHO also recommends at least 400 grams of fruit and vegetables daily for people over age 10, and at least 25 grams of naturally occurring dietary fibre per day, sourced from whole grains, fruit, vegetables and pulses.
Vitamin C: benefits that are supported — and ones that are not
Harvard Health lists adult vitamin C requirements as 90 milligrams a day for men and 75 milligrams for women aged 19 and over, with smokers needing about 35 milligrams more per day than non-smokers. Harvard Health also states that exceeding 2,000 milligrams a day risks side effects such as diarrhoea and nausea.
The source adds that vitamin C's established roles include supporting collagen production, bone health, iron absorption and immune function as an antioxidant. On heart disease, Harvard Health notes that observational studies have linked higher fruit and vegetable consumption to cardiovascular benefits, but that clinical trials testing vitamin C supplements specifically
have not shown consistent benefits
— Harvard Health
Ultra-processed foods and seed oils
EUFIC's review distinguishes between degrees of food processing rather than treating all processed foods as equally unhealthy: it cites whole-grain breads, fortified cereals and plant-based alternatives as examples that can remain nutritious, and recommends comparing labels for lower saturated fat, added sugar and salt, and higher fibre.
On seed oils, which have drawn criticism in some online discussions, EUFIC cites research indicating that linoleic acid — a common component of seed oils — does not increase inflammatory markers, and that these oils can help reduce LDL cholesterol and improve glycaemic control.
No single food "burns fat" or meaningfully speeds up metabolism on its own, according to the sources reviewed.
Weight change is driven by overall calorie balance, not by the specific macronutrient (carbohydrate, fat or protein) that calories come from.
Gluten-free and gluten-containing diets are both appropriate depending on individual medical status, not a universal rule.
WHO's numerical targets for fat, sugar, salt, fibre and produce intake apply to general adult populations and may differ for specific medical conditions.
Questions
Do eggs raise cholesterol and should they be limited?
According to EUFIC, eating one egg a day does not significantly raise cholesterol levels in healthy people, because the body compensates by producing less cholesterol itself.
Does vitamin C prevent colds?
Harvard Health states that regular vitamin C intake does not appear to reduce the chance of catching a cold, although some research suggests it may modestly reduce the severity or duration of symptoms.
How much sugar does WHO recommend per day?
WHO recommends keeping free sugar below 10% of daily energy intake — about 50 grams on a 2,000-calorie diet — and says reducing it further to 5% or less may provide additional health benefits.
Is intermittent fasting better than regular calorie counting for weight loss?
EUFIC states intermittent fasting is not superior to standard calorie-restricted diets for weight management; overall calorie balance, not meal timing, is the determining factor.
Can plant-based diets provide enough protein?
Yes — EUFIC states that varied plant protein sources such as beans, lentils and tofu, eaten across the day, can meet dietary protein needs without meat.
This piece was prepared with artificial intelligence and passed an automated source check before publication. If you see an error, ask for a correction. Request a correction or reply · How we make this
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