Tuna sandwiches 'could help prevent sight loss in old age'

The old, old story: Speculative interpretation of an epidemiological correlation. One alternative possibility: Wealthier people eat more seafood and wealthier people are also healthier

Tuna sandwiches could help protect your eyesight in old age, say researchers. Regular consumption of fish – including canned tuna – and other foods containing omega-3 fatty acids can cut the risk of the most common cause of age-related blindness by 42 per cent, a Harvard study has found.

Around 200,000 Britons suffer from age-related macular degeneration, or AMD, each year. It is the most common cause of sight loss in those over 50 and robs sufferers of their central vision.

A team at Brigham and Women’s Hospital and Harvard Medical School in Boston compiled data on 38,000 women who had not been diagnosed with AMD. Information on their eating habits, including their intake of omega-3 and omega-6 fatty acids, was collected and their eye health tracked over ten years. During this time, 235 cases of AMD were reported.

The researchers found that women who consumed the most fish oils had a 38 per cent lower risk of developing AMD compared with those who ate the least.

And consuming one or more servings of fish a week was linked to a 42 per cent lower risk of sight loss compared with eating one serving a month.

Study leader Dr William Christen said: 'The lower risk appeared to be due primarily to consumption of canned tuna fish and dark-meat fish.' Although tinned tuna does not contain as much fish oil as fresh tuna, the finding is significant because it is so widely eaten in sandwiches.

The study will be published in the June issue of the Archives of Ophthalmology medical journal.

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Can a vibrating pill shake off constipation?

A vibrating capsule has been developed as a treatment for constipation. Once it’s swallowed, the high-tech device is programmed to shake, jolt and roll as it passes through the bowel.

The wave of movement triggered by the battery-powered capsule stimulates the muscles that drive the natural movements in the bowel, easing constipation.

The device will be tested in human trials next month. Researchers say that unlike other treatments for the condition, such as some laxatives, the single-use capsule has no side effects.

The usual causes of constipation are poor diet, lack of exercise or certain medications. Twice as many women suffer from it as men; it is also more common with age, with older people five times more likely to be affected.

The problem is that when the bowel becomes constipated, this slows down its muscular contractions, which makes the condition worse.

Earlier studies have suggested that external massage on the abdomen can help, by stimulating muscles in the bowel wall, kick-starting peristalsis — the natural waves of synchronised muscle movements that push food through the digestive tract.

Quite how this works is not clear, although one theory is that the muscles go into spasm during constipation and that massage helps them relax.

However, this technique is difficult and time-consuming, and can be ineffective in patients with a thick or muscular abdominal wall.

As well as kick-starting natural movement of the bowel, it’s thought the new device — which was developed by an Israeli-based company, Vibrant — will also help break up compacted stools.

In a new trial, starting next month, and registered with the U.S. National Institutes of Health, 30 patients will be given a 15.5mm long capsule to swallow. The capsule weighs 10 g, roughly the same weight as a pound coin (9.5g).

Inside the tubular casing is a tiny electrical motor and micro-battery. The motor has an off centre weight attached to it, which makes it spin, wobble and jolt when it is switched on, setting up a vibrating motion.

The capsule will be automatically programmed to start vibrating six hours after it’s been swallowed — the estimated time it will take for it to reach the bowel. It then vibrates for two hours before it’s excreted.

Researchers from Ichilov hospital in Tel Aviv, Israel, who are conducting the trial, will observe the patients for a week. If the gadget is proved safe, researchers will test it in a second trial of 30 patients, who will be observed for two weeks. The idea is that more capsules could be used over time if the problem persists.

Dr Ian McNeil, consultant gastroenterologist at Ealing Hospital NHS Trust and honorary senior clinical lecturer, Imperial College School of Medicine, said: ‘This is an interesting and novel approach to constipation.

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