science

Lutein and bilberries: What does the science say?

Lutein and bilberries are both often associated with nutrition for the eyes. But they are very different ingredients, and the research behind them tells two different stories.

Lutein is a carotenoid found naturally in foods such as green leafy vegetables, corn and egg yolk. The bilberry, Vaccinium myrtillus, is a dark blue berry with a long tradition in northern Europe, naturally rich in anthocyanins.

Both have attracted interest in research on nutrition and vision. Understanding what happens to these substances in the body — and what has actually been shown in human studies — makes it easier to separate scientific evidence from well-known ingredient stories.

Marigolds in a brass vase beside a bowl of fresh bilberries on a wooden kitchen table

What is lutein?

What makes lutein particularly interesting is not just where it comes from, but where it is found in the body.

Lutein concentrates selectively in the retina, especially in a small central area called the macula. Together with zeaxanthin and meso-zeaxanthin, it forms part of the macular pigment.¹

The macular pigment also has an important optical property. It absorbs short-wavelength visible light, including blue light, before the light reaches the light-sensitive structures of the retina.²

Human studies have examined whether increased intake through diet or supplements can affect macular pigment optical density, MPOD. A systematic review and meta-analysis found that supplementation with lutein and zeaxanthin can increase macular pigment, with generally larger effects at higher intakes.¹

This creates a clear biological link between nutrition and the eye. Lutein and zeaxanthin come from the diet, they accumulate in the macula, they form part of a pigment that filters blue light, and intake can affect the density of that pigment.¹˒²

That link provides an important scientific basis for understanding why lutein continues to be studied in eye nutrition.

What about bilberries?

The bilberry, Vaccinium myrtillus, has an entirely different story.

The dark blue berry holds a long-standing place in northern European food culture. It contains a range of naturally occurring substances, in particular anthocyanins, the pigments that give many plants their red, blue and purple colours.

Anthocyanins are not unique to bilberries. They are also found in blackcurrants, blackberries, cherries, purple grapes and red cabbage, among other foods.

Even so, bilberries have gained a particularly strong association with vision, above all night vision.

One of the best-known stories dates back to the Second World War, when British Royal Air Force pilots were said to eat bilberry jam to improve their night vision.

It is a memorable story. But a memorable story is not the same as scientific evidence.

A systematic review examined placebo-controlled studies of bilberries and night vision. The more rigorous later studies did not support the idea that bilberries improve normal night vision in healthy people.³

This does not mean the bilberry is an uninteresting ingredient. It shows why traditional reputation and scientific evidence need to be assessed separately.

Two ingredients, two different stories

Lutein and bilberries offer a clear contrast.

Lutein has a clear biological connection to the eye. It concentrates selectively in the macula, forms part of the macular pigment that filters blue light, and human studies have shown that dietary intake can affect the macular pigment.¹˒²

Bilberries have a long tradition of use and are naturally rich in anthocyanins, but some of their best-known associations with vision, including improved night vision, are not supported by rigorous clinical evidence.³

Understanding this difference is an important part of evidence-based nutrition. Ingredients earn their place not because they carry a familiar story, but because there is a scientific reason to include them.

Follow the evidence, not the trends.

References

1. Wilson LM, Tharmarajah S, Jia Y, Semba RD, Schaumberg DA, Robinson KA. The effect of lutein/zeaxanthin intake on human macular pigment optical density: a systematic review and meta-analysis. Advances in Nutrition. 2021;12(6):2244–2254. DOI: 10.1093/advances/nmab071.
2. Kijlstra A, Tian Y, Kelly ER, Berendschot TTJM. Lutein: more than just a filter for blue light. Progress in Retinal and Eye Research. 2012;31(4):303–315. DOI: 10.1016/j.preteyeres.2012.03.002.
3. Canter PH, Ernst E. Anthocyanosides of Vaccinium myrtillus (bilberry) for night vision: a systematic review of placebo-controlled trials. Survey of Ophthalmology. 2004;49(1):38–50. DOI: 10.1016/j.survophthal.2003.10.006.