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What is the food that can really improve your eyesight?

Many people suffer declining eyesight as they get older, but is there something

we can eat to improve it, asks Michael Mosley.

My eyesight has never been good. I've worn glasses most of my life and as I get

older that's a situation that I've only expected to get worse. When the Trust

Me, I'm A Doctor team suggested that I try taking supplements to improve my

eyesight, though, I was sceptical, particularly as I am not a fan of

supplements.

Nonetheless I headed off to meet Prof John Barbur of City University in London

to have my eyesight thoroughly tested. He was particularly interested in my

retina, the light sensitive part of the eye, and made me stare at a computer

screen in the dark for hours, having tests flashed up at me which thoroughly

and precisely measured the limitations of my perception of different colours,

my night vision and my detection of faint and small objects.

He also measured the level of protection that the most delicate area of my

retina - the macula - had against damage from high energy blue and UV light.

This protection is, in effect, a kind of natural sunscreen that we have

covering the light-detecting cells, and is made up of yellowish "macular

pigments".

The results of my tests were both fascinating and depressing. My detection of

yellow and blue colours was extremely poor - something that Prof Barbur said

was likely the result of my brush with diabetes many years ago. My night vision

and perception of details were also poor compared with younger people - but

consistent with my age.

The Trust Me team then handed me a 90-day supply of supplement pills that were

supposed to help. They contained concentrations of certain compounds found in

coloured plants. These were extracted from marigolds, but two of the key

chemicals - lutein and zeaxanthin - are also found in a range of things we eat

more commonly.

A team in the United States devised a recipe for a daily smoothie for us that

they hoped could supply a similar level of lutein and zeaxanthin. It was a

heady mix of fruits and veg such as kale and kiwi fruit, along with fats such

as milk and wheat germ oil which help the absorption of the key compounds.

Twelve weeks later, I returned to City University to see whether my daily

pill-popping had made any difference to my eyesight. The results surprised even

Prof Barbur. There were significant improvements in several different aspects -

my blue and yellow colour perception was back to normal and my night vision was

much better. The levels of my protective macular pigments were also boosted.

The results were less of a surprise to Prof John Nolan, who I went to meet in

Waterford, in south-east Ireland. His team has been studying macular pigments

for many years, and recently completed a year-long trial with over 100

participants in which they had seen similar results to mine.

They found that boosting the diet with the three macular pigments - lutein,

zeaxanthin and meso-zeaxanthin - led to significant improvements in the

protection of the delicate macula, as well as improved eyesight.

There is also some evidence that such supplementation may help slow or possibly

even prevent, age-related macular degeneration (AMD) - the leading cause of

vision loss in the UK. However, this is still controversial.

Should we all, then, be taking supplements to protect and even improve our

eyesight?

Well, the research certainly shows that supplements work. Even for someone like

me, who has a relatively healthy diet with plenty of fruit and vegetables, and

whose blood levels of the compounds that weren't particularly low, the

supplements helped. However, some researchers believe that diet can simply be

enough, if we eat the right things.

More research needs to be done on the best dietary sources for each of the

three macular pigments.

Lutein is a yellow compound made only by plants. They make it in order to

absorb blue light, as part of their mechanism to capture energy from sunlight

through photosynthesis. Animals then get it from eating plants - good sources

are green kale and spinach, or the yellow yolks of eggs.

It is used as a supplement to feed industrially-reared chickens to make their

yolks a more attractive yellow (and, being fat-soluble, ends up turning their

skin and fat yellow too).

Zeaxanthin is another yellow compound, almost identical to lutein, made by

plants to absorb light. It is the chemical that gives corn, bell peppers and

saffron their yellow colour.

Meso-zeaxanthin is a form of zeaxanthin not generally found in plants, but it

is made in the body from lutein. More research needs to be done on how

efficient this process is. It is found in some fish (particularly in the

skins), but in supplements containing marigold extract, it appears that the

industrial processing that the marigolds undergo can create meso-zeaxanthin

(and it has been found to be in some marigold-extract supplements, even when

not listed on the label).

Our volunteers taking the smoothie containing amounts of plant sources

calculated to give them a boost of lutein and zeaxanthin did indeed boost their

lutein levels, but not their zeaxanthin. Clearly more work needs to be done to

refine the recipe. So, this might be a rare occasion where, given the current

state of research, I might end up on the side of supplements - especially for

those who don't eat as many leafy greens as they should, and for older people

(who absorb nutrients less efficiently).

However, for all of those whose mothers and grandmothers told them that carrots

would improve their vision the message is this - although lutein, zeaxanthin

and meso-zeaxanthin are all chemicals known as "carotenoids", and carrots do

owe the yellow portion of their colour to them, these particular key compounds

are found mainly in the green parts of plants above ground.

So, if you want to improve your eyesight, I'm afraid it's munching on leafy

greens (taken with some fats to help absorb these fat-soluble chemicals) that

will do the best job.