The real reason behind 'eat a rainbow' advice — different plant colours, different protective compounds.
Polyphenols are a large family of plant compounds — including flavonoids, resveratrol and curcumin — that plants produce partly as their own defence mechanisms, and which have been studied extensively for antioxidant and anti-inflammatory properties in humans.
Berries, dark chocolate, coffee, tea, olive oil, red wine, and colourful vegetables are among the richest common sources — the "eat a rainbow" advice is largely a proxy for polyphenol diversity, since different plant pigments correspond to different polyphenol compounds.
Beyond direct antioxidant activity, some research suggests polyphenols interact with gut bacteria in ways that support a healthier microbiome — connecting this topic directly to our gut health deep dive.
Practical takeaway: variety matters more than any single polyphenol-rich food — different plant colours generally mean different compounds, so a rotating variety captures more of the benefit than eating the same "superfood" daily.