When I was at medical school I learnt that blue eyes are associated with an increased risk of succumbing to the blood disorder pernicious anaemia. For years, I have taken comfort from the belief that having brown eyes afforded me some degree of immunity from disease. This month, however, new research has linked brown eyes with a substantially increased risk of cataract (cloudiness in the lens of the eye).

While I and other dark-eyed folk might feel somewhat aggrieved at this fact, it turns out that even those with eyes of lighter hue are at significant risk of developing cataracts: almost everyone over the age of 65 has some degree of cataract formation, and the incidence of this condition is set to treble in the next 50 years.

Fortunately, research suggests that upping our intake of certain foods and nutrients can dramatically reduce cataract risk. A healthy lens is composed of a transparent, jelly-like material that is rich in protein. Over time, the protein in the lens may become damaged, causing it to become cloudy. This process is similar to the change that occurs when an egg white is cooked: while a raw egg white is transparent, it becomes opaque when the protein within it is damaged during cooking. The damage to the lens that can ultimately lead to cataract formation is wrought by destructive molecules known as free radicals. Free radicals are neutralised in the body by substances known as antioxidants. Some of these are manufactured within the body, but many come directly from the food we eat. Research has found that consuming foods rich in antioxidants known as carotenoids may protect against cataract development. While betacarotene is perhaps the best-known carotenoid, its less celebrated relatives lutein and zeaxanthin (pronounced zee-ah-zanthin) are believed to play a special role in terms of combating free-radical damage to the eye.

One food that is rich in both lutein and zeaxanthin is spinach, while others include leeks, peas, and cos lettuce.

While the right diet certainly has a role to play in preserving the health of the eyes, supplementation with antioxidants such as vitamins C and E can help too. One study published in the Archives of Ophthalmology last year showed that individuals taking a multivitamin and mineral containing either or both of these nutrients for 10 years or more enjoyed a 60 per cent reduction in risk of cataract.

The evidence suggests that eating our greens in addition to taking a multivitamin and mineral supplement and 250-500mg of vitamin C a day can be an effective long-term strategy for keeping our eyes clear of cataracts.

Nutrition news

Organic fruit and vegetables are often said to be more nutritious than conventionally grown produce.

One downside of organic farming, however, is that yields are generally lower. For this reason, detractors say that organic farming is inefficient. Recently, a European study of farming methods was published. Crop yields for organically farmed produce were indeed found to be 20 per cent lower than for conventional produce. However, organic methods incurred considerably lower fertiliser and pesticide costs. Taking these savings into account, it turns out that, for most crops, organic farming is actually more efficient than conventional farming practices.

This study thus actually served to add weight to the argument in favour of organic, environmentally friendly farming.

Dear John

I travel a lot on business and seem to be increasingly prone to jet lag as I get older. Have you got any advice for me?
Barry Whitaker, Cheltenham

One factor that makes problems with jet lag much more likely is sleep deprivation. Avoid taking very early outbound flights or those that reach your destination very late at night.

Jet-lag symptoms may also be worsened by dehydration. So go easy on the caffeine and alcohol - both of which tend to increase dehydration - and drink plenty of water before, during and after the flight instead.

One natural treatment that has been advocated for combating jet lag is melatonin - a hormone produced in a tiny gland in the brain called the pineal gland which induces sleep. Studies suggest that melatonin can significantly reduce the symptoms of jet lag and increase the speed of recovery after long-haul flying. While melatonin is available over-the-counter in the US, you'll need a prescription to get it in Britain.

The normal recommended dose of melatonin is 3mg, to be taken just before nightfall. For more information about melatonin, phone Pharma Nord on 0800 591 756.