For how we live.
Diets, supplements, and food claims tested against the evidence.
A meta-analysis of 10 randomised trials found ultra-processed diets raised weight and eating rate, yet the effect on how much people ate mostly disappeared when diets were not more energy-dense.
Ginger's strongest evidence is unglamorous: it eases nausea in pregnancy and during chemotherapy, and modestly relieves osteoarthritis pain. The trials are small and the quality is moderate at best.
Garlic supplements modestly lower blood pressure in hypertensive people, and may nudge cholesterol down a little. The cold-prevention evidence rests on a single trial, and no study shows garlic prevents heart attacks.
Beetroot juice really does lower blood pressure — the effect is one of the better-documented in food science, driven by dietary nitrate. But most trials are short and small, and no study shows it prevents heart attacks.
For people without coeliac disease, a large cohort found gluten intake was not linked to heart disease — and cutting it often means fewer whole grains, the foods tied to lower cardiovascular and mortality risk.
"Superfood" is a marketing word, not a scientific one. Blueberries carry real evidence for the heart and, tentatively, the ageing brain — but most of it is observational or short-term markers, not hard outcomes.
The large trials built to confirm vitamin E's promise came back null, and a meta-analysis tied 400 IU a day or more to a small rise in all-cause mortality.
In deficient populations, vitamin A supplements cut child deaths by 12% — among the best-evidenced global-health interventions. In the well-nourished, added vitamin A does no good and can do harm.
Oat drinks carry less saturated fat and no lactose, but far less protein than milk, and even unsweetened versions list free sugars. How they compare depends heavily on fortification.
Pooling 58 randomised trials, about 3.5g a day of oat beta-glucan lowered LDL cholesterol by 0.19 mmol/L. A separate meta-analysis of 28 trials found 0.25 mmol/L. Small per person, but consistent.
A 21,442-person trial of cocoa flavanol extract missed its main heart target. The blood-pressure effect is real but small — and nearly half of dark chocolate products exceeded a strict lead limit.
Cohort data link green tea drinking to lower cardiovascular death, but trials show only surrogate changes and concentrated extracts have caused liver injury at everyday catechin doses.
Trials can show cinnamon nudging fasting glucose down, but the effect is inconsistent, leaves long-term control (HbA1c) untouched, and cheap cassia cinnamon carries a coumarin safety flag.
A banana is mostly sugar and starch, but it comes with fibre and potassium, and large cohort studies link whole fruit — bananas included — to slightly lower type 2 diabetes risk, not higher.
Supplement makers sell K2 (menaquinone) for stronger bones and cleaner arteries. The observational signal is real; the randomised trials, so far, mostly are not.
Daily vitamin C does not stop you catching colds and does nothing once one starts. It trims a cold's length by about 8% in adults; for the heart, trials show no benefit.
Eating more potassium lowers blood pressure in people who already have hypertension, and a large trial of potassium-enriched salt cut strokes and deaths — but the benefit is not for everyone.
Pooled trials show a genuine but small fall in blood pressure, around 2 mmHg. The bigger pitches — sleep, cramps, energy, anxiety — run ahead of the evidence.
No long-term trial has tested an all-meat diet. The best direct data is a self-reported survey where people felt better but ran markedly high LDL cholesterol — the signal that should give pause.
Two meta-analyses of dozens of randomised trials agree that about 3 grams a day of oat beta-glucan lowers LDL cholesterol by a small, real amount. The effect is genuine, modest, and dose-dependent.
Two controlled studies compared vitamins in fresh and frozen fruit and vegetables. Frozen matched fresh in most cases and sometimes beat it, especially against fresh produce that had spent a few days in the fridge.
In people with healthy kidneys, trials find high-protein diets do not worsen kidney function. The picture changes for those who already have reduced function, where animal protein may speed decline.
A systematic review of human trials found the evidence weak and inconsistent. Where MSG seemed to trigger headaches, it was given in large doses dissolved in water without food, in studies that were not properly blinded.
A small 1990s trial hinted selenium supplements cut cancer, launching a supplement boom. The much larger SELECT trial found no benefit — and signals of harm, including more type 2 diabetes.
Randomised trials show a Palaeolithic diet trims weight and risk markers in the short term. A two-year trial found the early edge over an ordinary healthy diet had mostly faded — and that people struggled to stick to it.
A critical review went looking for clinical proof that commercial detox diets remove toxins or keep weight off. It found almost none, and no randomised trial of a commercial detox diet in humans at all.
Diets rich in colourful fruit and vegetables track with less cancer, so supplement makers bottled beta-carotene. Two large trials in smokers found the pills raised lung cancer and death — the opposite of the hope.
A 2024 trial randomised heart-risk patients to a dozen eggs a week or almost none. Over four months, blood cholesterol barely moved — echoing an earlier year-long trial in people with diabetes.
The line is marketing, not trial data. A meta-analysis of 13 randomised trials found adding breakfast raised daily calories and, if anything, nudged weight up, not down. A controlled feeding trial explains why.
Six months of dietitian sessions aimed at a high-fibre diet nudged diet quality but left estimated 10-year cardiovascular risk, HbA1c, cholesterol and blood pressure essentially unchanged versus standard care.
Meta-analyses found calcium pills raised heart-attack risk by around a quarter. A later review — funded by an osteoporosis foundation — found no such link. The disagreement is the story.
The sugar alcohol in many 'keto' and sugar-free foods is generally recognised as safe. But newer studies tie high blood levels to cardiovascular events and show it makes platelets more prone to clotting.
Honey and table sugar are both free sugars with almost identical calories. Trials hint at small metabolic differences in honey's favour, but the certainty is low and honey is still added sugar to be limited.
The US banned Red No. 3 in 2025 on a rat-specific cancer finding, not human data. The separate question — whether dyes affect children's behaviour — has better, and more unsettling, evidence.
Adults need about 2.4 micrograms a day, and most meat-eaters get it easily. Real deficiency clusters in older people, whose absorption fails, and in vegans, whose intake does.
Whole fruit and fruit juice behave oppositely for type 2 diabetes risk, and a trial that told newly diagnosed patients to eat less fruit found no benefit at all.
High-heat cooking makes compounds that damage DNA in the lab — heterocyclic amines, PAHs and acrylamide. The catch is that human diet studies have mostly failed to find a consistent cancer link.
Iron does leach from a cast-iron pan into food, and randomised trials in iron-deficient populations found it raised haemoglobin. The effect depends on what you cook, and means little for people who are iron-replete.
Organic produce carries far fewer pesticide residues and modestly more of some antioxidants. But there is no strong evidence that eating organic makes you healthier, and the cancer signal is observational.
Too little iodine, especially in pregnancy, is the world's leading preventable cause of impaired brain development. Salt iodisation fixed most of it — but mild deficiency has crept back in some rich countries.
In a tightly controlled feeding trial, swapping high-GI for low-GI carbohydrate inside a healthy diet did not improve insulin sensitivity, cholesterol or blood pressure. The wider evidence rates the GI case as weak.
Higher whole-grain intake is consistently linked to lower rates of heart disease, cancer and early death, with benefit rising up to about seven servings a day. Refined grains show no such signal.
The fear that soy fuels breast cancer is not supported by the human data; if anything, soy food intake tracks with lower recurrence and death after diagnosis. Its other health claims are weaker.
Cohorts link both to modestly higher rates of heart disease and early death, on low-certainty evidence. A 2019 guideline then told people to keep eating them — and split the field over how to weigh nutrition science.
Large randomised trials mostly find no cardiovascular benefit from ordinary fish-oil capsules. One high-dose prescription drug is the striking exception, and the case for brain protection is weak.
People who eat nuts have lower rates of heart disease and early death in large cohorts, and a Mediterranean diet with nuts cut cardiovascular events in one trial. Most of the evidence is observational.
The official figure is 0.8 grams per kilogram of bodyweight a day — but that number is a floor to prevent deficiency, not a target for optimal health, and that distinction drives most of the argument.
Whole fruit is linked to lower type 2 diabetes risk, sugary drinks to clearly higher risk, and fruit juice sits closer to the drinks than to the fruit it comes from.
For heart disease and death, dairy looks roughly neutral to modestly favourable in large cohorts, and the long-standing warning against whole-fat dairy is not well supported by outcome data.
Across nearly 1.1 million people, each extra daily cup tracks with lower diabetes risk in a clear dose-response. It is consistent and large — and still only observational.
Health authorities converge on a ceiling — under 10% of daily calories, and lower is better still. Large cohorts single out sugary drinks as the form most clearly tied to dying earlier.
A randomised trial found the Portfolio diet cut LDL cholesterol by about 13%, and a large cohort study links closer adherence to lower cardiovascular risk. Its authors' industry funding belongs in the record.
A twins trial found a vegan diet lowered LDL cholesterol, insulin and weight in eight weeks. The same pattern comes with real gaps — vitamin B12 must be supplemented, and iron stores tend to run lower.
Head-to-head randomised trials find low-carbohydrate and low-fat diets produce similar weight loss over a year or two. The differences that survive are in blood lipids and glycemic control, not the scale.
Two controlled-feeding trials found a diet rich in fruit, vegetables and low-fat dairy lowered blood pressure, most in people who already had hypertension, and more still when sodium was cut.
Spain's PREDIMED trial is the strongest randomised evidence that a dietary pattern lowers cardiovascular events. In 2018 its authors withdrew it over flawed randomisation and reissued corrected results.