How much sugar is too much?
There is no universal threshold, but for tooth decay, getting less than 10% of your daily calories from free sugars is the evidence-based guideline. Sugar-sweetened drinks deserve the most attention: they raise the risk of diabetes more clearly than sugar from solid food.
Tooth decay provides the sharpest boundary. Research across dozens of studies shows that people who get less than 10% of their daily calories from free sugars develop fewer cavities than those who exceed that level. The WHO also mentions a target of less than 5% of energy, but that advice is based on weaker ecological research. Free sugars are all sugars added to food, plus sugars in fruit juice and honey, but not the sugars naturally present in whole fruit or milk.
For children, the advice from the European paediatric organisation ESPGHAN is even stricter: less than 5% of daily calories from free sugars, and for children under two years of age probably even less. That organisation also states that the body has no need for free sugars at all. Sugar-sweetened drinks are specifically discouraged for children; water and unsweetened milk are the better choice.
In diabetes, the form matters more than the amount of sugar as such. In large-scale cohort research, each additional serving of a sugar-sweetened drink was associated with a 25% higher relative risk of type 2 diabetes, and each additional serving of fruit juice also showed a measurably increased risk. Sugar as part of solid food showed no increased risk in the same analysis. That difference suggests that liquid sugar works differently in the body than sugar from a slice of bread or a piece of fruit.
For mood, there is an association but no proven cause. In a large American population study, people with a higher sugar intake reported more depressive symptoms. But this type of research captures a single moment in time: people in a low mood may also reach for sugar more often. You cannot therefore conclude that cutting sugar will make you feel better. On the question of whether sugar crowds out vitamins and minerals from your diet, the available studies still contradict each other too much to draw a conclusion.
Claims based on multiple meta-analyses, systematic reviews and prospective cohort research. The figures of 10% and 5% energy intake can be found directly in the sources (PMID 24323509, 26773022, 28922262). The diabetes risk associated with sugar-sweetened drinks (RR 1.25 per serving) and fruit juice (RR 1.05) are reported in PMID 40122386. No claims used without a cited source.
How bad is ultra-processed food, and what does it do to you?
Eating a lot of ultra-processed food is consistently associated with higher risks of cardiovascular disease, diabetes, depression and premature death. The evidence is observational and not always of high quality, but the associations are broad enough to make limiting intake a sensible choice.
Is too much zinc harmful?
Too much zinc is certainly harmful: as an adult, stay below 25 mg per day (the EFSA limit) and be cautious with high-dose zinc supplements, because even moderate over-supplementation can disrupt copper balance.
How much water do I really need to drink per day?
There is no magic number: for a healthy adult who is not very active, thirst is a reliable guide, with a total fluid intake of roughly 2 to 3 litres per day from all sources as a reference point. Drink more as soon as you exercise, when it is warm, or as you get older.
Can you get too much vitamin D?
Too much vitamin D is genuinely harmful, but that risk only arises at blood levels far above the recommended values. Stick to the dosage on the packaging, and unsure about your level? Have it measured by your GP.
How many fruits and vegetables do I actually need per day?
Five portions of fruit and vegetables per day (two pieces of fruit, three serving-spoon scoops of vegetables) is the number with the strongest evidence base; eating more does not provide additional benefit, but most people do not even reach this minimum.
Am I consuming too much protein, and is that bad for my kidneys?
For people with healthy kidneys there is little reason to worry about a generous protein intake, but anyone who has kidney disease or was born with one kidney would be wise to limit their intake and consult a dietitian.