An attack of food poisoning can be pretty grim, and more than half a million of us have to deal with it every year.
That’s the official figure — the true number is probably even higher, as many won’t bother their GP about it.
But while most people will recover after days, or even a few weeks, some can suffer for months, or be left with other health problems — sometimes lifelong, including irritable bowel syndrome, lactose intolerance, arthritis, high blood pressure and even kidney failure.
Now, research has shown that certain strains of Salmonella bacteria, a major culprit in food poisoning, may permanently damage the DNA in our cells.
Ten years on from an infection after a meal to celebrate her 28th birthday, Nancy Fahmy (pictured) is still living with life-changing repercussions
A study by Cornell University in the U.S., looking at human cells in a lab which were infected with four types of Salmonella, found all had permanent DNA damage.
The authors likened the effect to that of sunburned skin which is then left vulnerable to skin cancer.
The longer-term impact of food poisoning was first identified many years ago, says Peter Whorwell, a professor of gastroenterology at the University of Manchester.
‘But it’s been pretty much ignored, and is grossly underestimated,’ he adds.
The problem, he says, is no one makes the connection, and typical symptoms can then worsen into chronic diseases.
‘When doctors see a patient’s symptoms they don’t tend to take a proper history of where symptoms started or try to pin down the original trigger — which, in my experience, may well be gastroenteritis [gut problems as a result of food poisoning].
‘A tummy upset doesn’t even need to be particularly bad to have lasting effects.’
Professor Qasim Aziz, a professor of neurogastroenterology at Queen Mary, University of London, adds: ‘When these complications occur the original infection has cleared and there’s no evidence of that infection left so not everyone makes the link.’
Someone who knows the long-term effect of food poisoning is Nancy Fahmy, from Harrow, Middlesex.
Ten years on from an infection after a meal to celebrate her 28th birthday, she is still living with life-changing repercussions.
‘I went home after my night out with friends, and woke at 2am. I had stomach cramps, was dripping with sweat and I was sick,’ she recalls, describing typical food poisoning symptoms.
For months after her bout of food poisoning, Nancy was still repeatedly sick and having constant abdominal pain. Her GP diagnosed irritable bowel syndrome
‘My boyfriend at the time took me to A&E, where they said I had food poisoning and sent me home with anti-sickness tablets and told me to drink plenty of fluids. But from that day, I’ve never felt well.’
Months passed and Nancy was still repeatedly sick and having constant abdominal pain. Her GP diagnosed irritable bowel syndrome, saying it might pass.
But over the next few months her condition worsened. ‘Some evenings I would be sick multiple times and couldn’t keep anything down.
‘The weight kept dropping off,’ says Nancy, a DJ who is also a qualified chef.
‘At one point I was losing 1-1.5kg (2½ -3 lb) a week, and while that slowed down, over a year I dropped 16kg.’ By March 2011 she weighed 34kg, less than 5½st (she’s 5ft 7in).
It took four years of hospital referrals and appointments with all kinds of specialists — including gastroenterologists, neurologists and psychotherapists — before the cause was finally identified: the food poisoning had essentially stopped Nancy’s stomach and intestines working, and they were not pushing food along.
And as a result of her rapid weight loss, Nancy has developed arthritis, osteoporosis and heart problems
The damage caused by food poisoning depends on what bug causes the infection.
For example, studies have linked infection with E.coli (often due to poor hygiene) to kidney failure, says Professor Whorwell.
‘Part of the problem is that with severe gastroenteritis that causes vomiting and diarrhoea, a lot of fluid is lost and people become dehydrated — if you are dehydrated for long enough then the kidneys will fail,’ he says.
Meanwhile, Salmonella poisoning (typically caused by infected meat, poultry and eggs) has been blamed for a form of arthritis; and Campylobacter bacteria (passed on in infected raw poultry and fresh produce) has been linked to bowel function problems such as irritable bowel syndrome.
In other cases, damage to the lining of the gut causes the longer-term complications.
For example, a severe case of gastroenteritis can strip off cells in the gut lining that make enzymes that break down lactose (the sugar in milk), so the patient can no longer digest it, causing bloating, diarrhoea and stomach cramps.
‘Thankfully, the lining of the gut, known as the brush border, heals itself, and so this lactose intolerance usually only lasts a few weeks,’ says Professor Whorwell.
But for patients like Nancy, there’s not always a clear-cut explanation.
One theory is that a prolonged infection causes excessive damage to the gut, and the constant low-grade inflammation in the body is what causes the lasting complications.
‘A certain degree of inflammation is part of the normal immune response to food poisoning,’ explains Charles Murray, a consultant gastroenterologist at the Royal Free London NHS Foundation Trust.
‘Most cases will settle down, but in a small minority, inflammation can lead to problems with food moving through the gut, an alteration of bowel habits and severe pain.’
The damage caused by food poisoning depends on what bug causes the infection. Studies have for example linked infection with E.coli (often due to poor hygiene) to kidney failure
Another suggestion is that prolonged low-grade inflammation makes the gut ‘leaky’, so too many food particles get through the gut wall.
This triggers an immune response which drives further inflammation and an attack on healthy cells in the intestine.
Over time, there’s just too much damage to healthy tissue than the immune system can repair.
What is known is that inflammation can damage the muscles and/or nerves that supply the gut wall, and if it does, it can stop that part of the gut functioning permanently — it doesn’t then contract properly, so food isn’t moved along correctly.
‘Patients are given medicines — such as painkillers — and nutritional support [such as a feeding tube], but in these rare cases, gut function cannot be restored,’ says Dr Murray.
Some patients may be more vulnerable, he adds. Diseases that affect gut muscles, such as scleroderma (where the immune system attacks healthy connective tissue around the body), or a family history of gut problems, can make these patients more prone to ‘excessive, long-term reactions’ to seemingly harmless food poisoning, for example.
Inflammation can damage the muscles and/or nerves that supply the gut wall, and if it does, it can stop that part of the gut functioning permanently
Nancy’s food poisoning triggered an illness lying dormant in her body, known as chronic idiopathic intestinal pseudo-obstruction, where the gut stops moving food.
But there were no signs to suggest her life would change after her birthday meal on October 5, 2007.
‘I used to run and play hockey, and went to the gym three or four times a week right up until the day before my food poisoning,’ she says.
‘Now I can’t run or swim as I get out of breath quickly. If I have an event to go to, I make sure I have a week off in advance to build up my energy.’
Nancy was finally told what was wrong with her in May 2011 when she was referred to St Mark’s Hospital in London, which has a specialist bowel clinic.
As well as chronic idiopathic intestinal pseudo-obstruction, she has gastroparesis, where the stomach cannot empty itself properly.
And as a result of her rapid weight loss, Nancy’s other organs weakened and never recovered.
She has developed arthritis in her spine and hands; osteoporosis in her neck, spine and hip; postural tachycardia syndrome, where her heart beats abnormally fast if she stands up quickly, and is unable to empty her bladder properly.
‘I’m on a whole load of injections and patches, but I am always aching and in pain and still throw up about 20 times a day,’ says Nancy.
She has to have nutrients pumped directly into veins in her chest each evening as she can’t digest any food or drink.
‘I would have thought that, at 37, I’d be married with kids and have a successful career,’ she says.
‘Sadly it’s nothing like I’d imagined things to be — and certainly not from a bout of food poisoning.’