Oats & barley
Strong evidence- Key compound
- Beta-glucan fibre
- Benefit
- Lowers LDL cholesterol and steadies blood sugar.
- How to eat
- Porridge, overnight oats, barley in soups.
Functional foods
Functional foods offer benefits beyond basic nutrition. Here are the best-studied ones, what they do and how strong the evidence really is.
Functional foods in numbers
3 g
oat beta-glucan a day helps lower LDL cholesterol (EFSA claim)
~30%
fewer heart attacks and strokes with a Mediterranean diet plus olive oil or nuts (PREDIMED)
28 g
of nuts a day — a small handful — linked to lower heart disease risk
2,000+
years that turmeric has been used in cooking and traditional medicine
The best-studied functional foods
Extra-virgin olive oil
Strong evidence- Key compound
- Monounsaturated fat, polyphenols
- Benefit
- Heart protection as part of a Mediterranean diet.
- How to eat
- 2–4 tablespoons a day in place of butter and other fats.
Legumes
Strong evidence- Key compound
- Fibre, plant protein, resistant starch
- Benefit
- Better blood sugar, cholesterol and gut health.
- How to eat
- Lentils, chickpeas, beans, hummus, ful.
Nuts
Strong evidence- Key compound
- Healthy fats, vitamin E, fibre
- Benefit
- Lower heart disease risk.
- How to eat
- A handful a day, unsalted.
Oily fish
Strong evidence- Key compound
- Omega-3 EPA and DHA
- Benefit
- Heart and brain health.
- How to eat
- Salmon, sardines or mackerel twice a week.
Berries
Moderate evidence- Key compound
- Anthocyanins
- Benefit
- Linked to heart and brain health.
- How to eat
- Fresh or frozen, with yoghurt or oats.
Fermented dairy
Moderate evidence- Key compound
- Live cultures, calcium, protein
- Benefit
- Gut health; yoghurt linked to lower type 2 diabetes risk.
- How to eat
- Plain yoghurt, laban, kefir.
Green tea
Moderate evidence- Key compound
- Catechins (EGCG)
- Benefit
- Linked to heart health; small effect on metabolism.
- How to eat
- 2–3 cups a day; avoid high-dose extracts, which can harm the liver.
Turmeric
Limited evidence- Key compound
- Curcumin
- Benefit
- Anti-inflammatory in the lab; human evidence is mixed.
- How to eat
- In cooking with black pepper; be cautious with high-dose pills.
Dark chocolate & cocoa
Limited evidence- Key compound
- Flavanols
- Benefit
- May help blood pressure slightly.
- How to eat
- A square or two of 70%+ — it is still high in calories.
Simple ways to add them
- Start the day with oats, berries and walnuts
- Use extra-virgin olive oil as your main fat
- Eat legumes at least four times a week
- Swap biscuits for a handful of nuts
- Drink green tea instead of a sugary drink
- Cook with turmeric, cumin, garlic and herbs
No single superfood
Benefits come from the overall diet. A few functional foods cannot make up for a diet high in sugar and processed food.
World health facts
All facts11M
Deaths linked to poor diet each year
Unhealthy diets were linked to about 11 million adult deaths worldwide in 2017 — more than any other risk factor, including tobacco.
Source: GBD, The Lancet 2019
1 in 5
Deaths tied to diet
Roughly one in every five deaths globally is associated with dietary risks.
Source: GBD, The Lancet 2019
17.9M
Heart disease deaths per year
Cardiovascular diseases are the world's leading cause of death; an unhealthy diet is a key risk factor.
Source: WHO 2021
830M
People living with diabetes
Adults with diabetes rose from about 200 million in 1990 to around 830 million in 2022.
Source: WHO / NCD-RisC, The Lancet 2024
Related articles
More in Eat Well
Sources
- • EFSA health claims register
- • PREDIMED trial (Estruch et al., NEJM 2018)
- • FDA oat beta-glucan claim
- • Harvard Nutrition Source
General information based on public health sources, not medical advice. Talk to a doctor or registered dietitian before major changes, especially if you are pregnant, have a health condition or take medication.