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Tim Spector

MD, OBE · Professor of genetic epidemiology, King's College London · founder of TwinsUK · scientific co-founder of ZOE

Go-to expert for: gut microbiome and plant diversity

Who and why

Tim Spector trained as a doctor and worked as a rheumatologist before moving into research at King's College London, where he founded the TwinsUK study of identical and non-identical twins. His work on the gut microbiome and personal food responses made him one of the best-known voices on gut health. He has written several books, including The Diet Myth and Food for Life.

Why it matters after 50: A varied, fibre-rich diet supports a diverse gut microbiome, which is linked to markers of metabolic and heart health. Many older adults eat a narrow range of foods, so adding variety is a simple change.

What Spector recommends

  • Aim for about 30 different plants a week. Vegetables, fruit, beans, whole grains, nuts, seeds, herbs and spices all count.Some evidence
  • Eat a small amount of fermented food every day, such as kefir, live yoghurt, sauerkraut or kimchi.Some evidence
  • Choose colourful plants, such as red or purple leaves and berries. They are rich in polyphenols that feed helpful gut bacteria.Some evidence
  • Focus on food quality rather than counting calories, and cut back on ultra-processed foods.Some evidence
  • Give your gut a break with a 12 to 14 hour overnight fast.Personal habit
  • People respond very differently to the same meal, so general rules may not suit everyone equally.Note

Signature: 30 plants a week

His best-known message is that variety of plants matters more than following any particular diet. The figure comes from American Gut Project data, which compared people eating more than 30 plant types a week with those eating fewer than 10.

In your plan

Choose him for eating: plant variety and fermented foods. He gives no protein number, so we add a target of 1.2–1.6 g per kg.

Build my mix

Research and honest caveats

PREDICT 1: personal responses to food

In about 1,000 UK adults, blood sugar and fat responses to identical meals varied widely between people.

Berry et al., Nature Medicine, 2020

Gut microbes and habitual diet

In over 1,000 people, healthy and plant-based foods were linked to gut microbes that were in turn linked to better heart and metabolic markers.

Asnicar et al., Nature Medicine, 2021

  • The 30-plants figure comes from a comparison of two extremes in a self-selected group, so it is a useful nudge rather than a proven threshold. Spector co-founded ZOE, which sells personalised nutrition programmes and products such as a 30-plant blend; some doctors have questioned whether its personalised advice improves health more than standard advice. A 2024 ZOE-run trial found its programme modestly improved triglycerides, weight and some other markers compared with standard advice, but not LDL cholesterol or blood pressure.

Career highlights

  1. 1992Founded the TwinsUK study at King's College London
  2. 2015Published The Diet Myth
  3. 2017Co-founded the nutrition science company ZOE
  4. 2020Awarded an OBE for the COVID Symptom Study app

Sources