2018NEJM
Estruch et al. (PREDIMED)
7,447 adults at high heart risk
A Mediterranean diet with extra olive oil or nuts cut heart attacks, strokes and heart deaths by about 30% compared with a low-fat diet.
Find on PubMed ↗Research library · Food & life
Food and fibre: what's on your plate
Poor diet is linked to more deaths worldwide than smoking. No single superfood matters as much as the overall pattern: mostly plants, whole grains, beans, nuts, olive oil and fish, with little ultra-processed food.
Strong evidenceUpdated Oct 2026 · 4 new studies−30%heart attacks, strokes and heart deaths on a Mediterranean diet with olive oil or nutsPREDIMED 2018, NEJM, 7,447 people
−15–30%death risk for people eating the most fibre vs the leastReynolds 2019, Lancet, 185 studies + 58 trials
11Mdeaths worldwide in one year linked to poor diet, more than any other riskGBD 2017 Diet Collaborators, Lancet 2019
01
The basics
What a healthy pattern looks like
The diets with the strongest evidence, like the Mediterranean and DASH diets, share the same base: lots of vegetables, fruit, beans and lentils, whole grains, nuts and seeds, olive oil and fish, with modest dairy and little red or processed meat and sugar.
Fibre is a common thread. It feeds the trillions of bacteria in your gut, which turn it into short-chain fatty acids that calm inflammation, support the gut lining and help regulate blood sugar and appetite. Most people eat under 20 g a day; benefits peak around 25–30 g or more.
Ultra-processed foods (packaged snacks, sugary cereals, soft drinks, processed meats, ready meals) are engineered to be easy to overeat. They now make up more than half of the calories in many Western diets.
Build a healthy plate
Based on the Harvard Healthy Eating Plate: half vegetables and fruit, a quarter protein, a quarter whole grains, healthy oils and water to drink.
02
How it works
How fibre works for you
1
You eat plants
Vegetables, fruit, beans, whole grains, nuts and seeds deliver fibre.
2
Gut bacteria feed
Fibre passes to the large intestine, where microbes ferment it.
3
Helpful compounds
Bacteria make short-chain fatty acids like butyrate.
4
Whole-body benefits
Less inflammation, steadier blood sugar, lower cholesterol and better fullness.
03
Measure it
How to check your diet
- Count plants: aim for 30 different plant foods a week (vegetables, fruits, beans, grains, nuts, seeds, herbs and spices all count). People who hit this had more diverse gut bacteria in the American Gut Project.
- Estimate fibre: a cup of beans has about 12–15 g, a pear 6 g, a bowl of oats 4 g, a slice of wholemeal bread 2–3 g.
- Check labels: a long list of ingredients you wouldn't find in a kitchen is a sign of ultra-processing.
Try your number
LowBelow targetOn targetHigh
545
Benefits in Reynolds 2019 peaked at 25–29 g and kept rising above that. Increase slowly to avoid bloating.
04
What the research says
The key studies
2019Lancet
Reynolds et al.
185 studies + 58 trials
People eating the most fibre had 15–30% lower death and heart disease risk, and less stroke, type 2 diabetes and bowel cancer. Whole grains showed similar benefits.
Find on PubMed ↗2019Cell Metabolism
Hall et al.
20 adults, controlled trial
On an ultra-processed diet, people ate about 500 calories a day more and gained weight in 2 weeks, even though meals were matched for sugar, fat and fibre.
Find on PubMed ↗2019Lancet
GBD 2017 Diet Collaborators
195 countries
Poor diet was linked to 11 million deaths in 2017. Too much salt, too few whole grains and too little fruit were the top problems.
Find on PubMed ↗1999Circulation
de Lorgeril et al. (Lyon Diet Heart)
605 heart attack survivors
A Mediterranean-style diet cut repeat heart attacks and heart deaths by about 50–70% over 4 years.
Find on PubMed ↗2021Cell
Wastyk et al.
36 adults
Eating more fermented foods (yoghurt, kefir, kimchi) for 10 weeks increased gut microbe diversity and lowered 19 markers of inflammation.
Find on PubMed ↗05
New in 2025–26
What the newest research adds
The first trial to compare ultra-processed and minimally processed versions of the same healthy diet found the less processed version roughly doubled weight loss. A 30-year study links plant-rich eating patterns with ageing well, and US guidelines now tell people to cut highly processed food.
The new studies, in order
Every study added to this page since January 2025. Green rings are the strongest evidence: large trials or meta-analyses.
Same healthy diet, less processed, twice the weight loss
UPDATE trial, 2025. 55 adults ate two diets that both met UK healthy-eating advice, 8 weeks each, eating as much as they liked.
NewAug 2025Nat Med
Dicken et al. (UPDATE)
55 adults, two 8-week diets (crossover)
Both diets met UK healthy eating advice, yet people lost 2.06% of body weight on minimally processed food versus 1.05% on ultra-processed food, without being told to eat less.
Early evidenceRead the source ↗
NewMar 2025Nat Med
Tessier et al.
105,015 adults, 30 years
People who ate most in line with the Alternative Healthy Eating Index (lots of fruit, vegetables, whole grains, nuts, pulses and healthy fats) were 86% more likely to reach 70 free of major disease and in good mental and physical health.
Good evidenceRead the source ↗
NewNov 2025Lancet
Monteiro et al. (Lancet Series on ultra-processed foods)
review of 104 studies, 43 experts
A three-paper series concluded that diets high in ultra-processed food are linked to obesity, type 2 diabetes, heart disease, depression and some cancers. Ultra-processed food makes up over half of calories in the UK and US.
Good evidenceRead the source ↗
NewJan 2026US federal guideline
USDA and HHS (Dietary Guidelines for Americans 2025 to 2030)
national guideline
New US guidelines say 'eat real food': more whole foods and protein, fewer highly processed foods and added sugars. They now allow full-fat dairy but still keep saturated fat under 10% of calories. Some experts note the evidence on processing is still debated.
Good evidenceRead the source ↗
What this changes for you
Cook from whole ingredients more often and treat ultra-processed food (long ingredient lists, things you wouldn't find in a kitchen) as occasional. Even 'healthy' ready-made products helped less in the UPDATE trial than the home-made versions.
06
Take action
Simple swaps that add up
Add good things first. It's easier than banning foods.
- 1
Half your plate plants
Vegetables, salad, fruit or beans at every meal.
- 2
Beans or lentils most days
The cheapest, easiest fibre and protein boost.
- 3
Whole grains
Oats, brown rice, wholemeal bread, barley and quinoa instead of white versions.
- 4
Olive oil and nuts
Cook with extra-virgin olive oil; a handful of nuts a day.
- 5
Fish twice a week
Especially oily fish like salmon, sardines and mackerel.
- 6
Fermented foods
Yoghurt, kefir, sauerkraut or kimchi a few times a week.
- 7
Cut the ultra-processed
Fewer packaged snacks, processed meats and sugary drinks. Cook simple meals more often.
07
Myth or fact
Common myths, checked
✕ MythCarbs are bad.
✓ FactRefined carbs and sugar are the issue. Whole grains, beans and fruit are linked to longer life.
✕ MythSupplements can replace a good diet.
✓ FactTrials of single vitamins mostly failed. Whole foods work as a package.
✕ MythAll fat is unhealthy.
✓ FactOlive oil, nuts and oily fish are among the healthiest foods studied.
✕ MythOrganic or 'natural' means healthy.
✓ FactOrganic crisps are still crisps. The food type matters more than the label.
08
Questions
Frequently asked
Do I need to go vegetarian?
No. Mediterranean diets include fish, some dairy and small amounts of meat. Eating more plants is what matters.
How do I add fibre without bloating?
Add a few grams a week, drink enough water and give your gut bacteria time to adjust.
Is red meat harmful?
Processed meat (bacon, ham, salami) is most clearly linked to bowel cancer and heart disease. Unprocessed red meat a few times a week is less of a concern.
09
Test yourself
True, partly true or myth?
Read each claim and pick an answer: the card flips to show the verdict and why. Not sure? Use “Just reveal”.
Card № 01True or myth?
Most adults eat far less fibre than recommended.
True
Most adults eat far less fibre than recommended.
Guidelines suggest 25–30 g a day or more; many people eat around 15–20 g.
Card № 02True or myth?
Eating 25–29 g of fibre a day is linked to 15–30% lower risk of death and heart disease.
True
Eating 25–29 g of fibre a day is linked to 15–30% lower risk of death and heart disease.
Reynolds 2019 (Lancet) pooled 185 studies and 58 trials; more fibre was even better.
Card № 03True or myth?
Carbs are the main cause of weight gain.
Myth
Carbs are the main cause of weight gain.
Diets low in carbs or low in fat lead to similar weight loss when calories match (DIETFITS trial).
Card № 04True or myth?
All ultra-processed foods are equally bad.
Partly true
All ultra-processed foods are equally bad.
Sugary drinks and processed meats show the clearest harm. Some, like wholegrain bread or plain yoghurt, look neutral or even helpful.
Card № 05True or myth?
Mediterranean-style eating cut heart attacks and strokes in a large trial.
True
Mediterranean-style eating cut heart attacks and strokes in a large trial.
PREDIMED found about 30% fewer major cardiovascular events with extra olive oil or nuts.
Card № 06True or myth?
Frozen vegetables are less nutritious than fresh.
Myth
Frozen vegetables are less nutritious than fresh.
They're frozen soon after picking, so they often hold vitamins as well as or better than fresh ones stored for days.
Card № 07True or myth?
Beans and lentils are among the best sources of fibre.
True
Beans and lentils are among the best sources of fibre.
One cup of cooked lentils has around 15 g of fibre, plus protein.
Card № 08True or myth?
Eggs are bad for your cholesterol.
Partly true
Eggs are bad for your cholesterol.
For most people, eating an egg a day has little effect on heart risk. People with diabetes or high LDL may want to be more careful.
Card № 09True or myth?
Processed meat is classed as a cause of bowel cancer.
True
Processed meat is classed as a cause of bowel cancer.
The WHO's cancer agency (IARC) classified it as Group 1 in 2015; each 50 g a day raises risk by about 18%.
Card № 10True or myth?
Eating late at night automatically makes you gain weight.
Myth
Eating late at night automatically makes you gain weight.
Total intake over the day matters more, though late eating can hurt sleep and blood sugar for some people.
Nothing here yet. Try another filter.
10
Sources
References and related topics
- Estruch et al. (PREDIMED) (2018). NEJM. 7,447 adults at high heart risk. PubMed ↗
- Reynolds et al. (2019). Lancet. 185 studies + 58 trials. PubMed ↗
- Hall et al. (2019). Cell Metabolism. 20 adults, controlled trial. PubMed ↗
- GBD 2017 Diet Collaborators (2019). Lancet. 195 countries. PubMed ↗
- de Lorgeril et al. (Lyon Diet Heart) (1999). Circulation. 605 heart attack survivors. PubMed ↗
- Wastyk et al. (2021). Cell. 36 adults. PubMed ↗
- Dicken et al. (UPDATE) (2025). Nat Med. 55 adults, two 8-week diets (crossover). Source ↗
- Tessier et al. (2025). Nat Med. 105,015 adults, 30 years. Source ↗
- Monteiro et al. (Lancet Series on ultra-processed foods) (2025). Lancet. review of 104 studies, 43 experts. Source ↗
- USDA and HHS (Dietary Guidelines for Americans 2025 to 2030) (2026). US federal guideline. national guideline. Source ↗