In the approach to National Food Safety Week (June 11-17), experts give advice on how to eat safely on a budget, how stringently to stick to food 'best before' dates, and how to spot the difference between food poisoning and a tummy bug.
By Lisa Salmon.
As temperatures rise over the summer, so do the cases of food poisoning.
Around one million people get food poisoning in the UK every year, with around 120,000 extra cases occurring from June to August because warmer temperatures help germs grow faster.
During the forthcoming Food Safety Week (June 11-17), people are being encouraged to take more care with their food so they don't succumb to the terrible diarrhoea and vomiting caused by food poisoning.
The Food Standards Agency (FSA), which organises Food Safety Week, points out that a large chunk of current food poisoning cases are down to more people using leftovers to try to stretch household budgets. But they're not looking after those leftovers before eating them, and an upset tummy is often the unpleasant result.
Bob Martin, a food safety expert at the FSA, warns: "People are economising on budgets including food, but it's important not to economise on food safety as well.
"People are looking for shortcuts and using more leftovers, but unless we're careful, there's a chance we can risk food poisoning by not storing or handling leftovers properly.
"During Food Safety Week we're encouraging people to view their fridge as their friend and make the most of leftovers while staying safe."
Toxin or bug There are two main types of food poisoning, explains Dr Melita Gordon, a consultant gastroenterologist at the Royal Liverpool University Hospital.
The illness can either be caused by a toxin produced by bacteria, or it can be the bacteria itself that causes symptoms.
Eating toxins may produce diarrhoea just 15 minutes afterwards. Bacteria can also produce toxins once inside the body.
Alternatively, the bacteria itself may cause illness by damaging the gut - this typically occurs with bugs such as campylobacter, salmonella or E-coli.
Severe symptoms The hallmark of food poisoning is diarrhoea, says Dr Gordon, and possibly vomiting, stomach pain and fever or chills. Such symptoms overlap with those of a gastroenteritis virus.
Neither a virus nor mild food poisoning needs antibiotics, and the most important thing is to drink plenty of fluid, preferably non-sugary, says Dr Gordon.
A mild case of food poisoning will be self-limiting and will last a day or two, she says. Warning signs that food poisoning is severe include severe abdominal pain, major fluid loss resulting in dehydration, bloody diarrhoea, and fevers or chills. In serious cases, bacteria like salmonella may infect the blood.
"If the symptoms last for many days, that's a danger sign that you've got a more serious infection and you might need medical attention," warns Dr Gordon.
Those more at risk of getting a severe bout include the elderly, the very young, people on particular medications or who are immuno-suppressed, pregnant women, and those with conditions like colitis.
People who take acid suppression medicines for indigestion are also more susceptible to food poisoning.
Duration How soon you get symptoms of food poisoning depends on which bacteria or toxin has caused the illness, and who's infected.
Martin explains that if you get symptoms soon after eating a particular food, it either means there's been a huge amount of bacteria in it, or the bacteria has produced a fast-acting toxin.
"People always assume that food poisoning has been caused by the last thing they ate, but that's not always the case," he points out.
Incubation periods of around five days for bacteria like salmonella, E-coli or campylobacter are possible, but it's normally two or three days.
"This is why it's often very difficult to pin down what's caused food poisoning," explains Dr Gordon.
What's the date?
The Use By date is the safe limit when a food can be eaten, and the Best Before date means the food is at its best before the given date, if it's been stored properly. After that, its quality will decrease, but it doesn't relate specifically to the safety of the food.
However, Dr Gordon points out that it may be wise to adhere to the Best Before date for eggs, as a small number may contain salmonella.
"Because of the fairly small risk of salmonella nowadays, it wouldn't be a good idea to go too far beyond the Best Before date for eggs, particularly if you're in an at-risk group," she says.
Display Until dates help the shop know when it's time for the food to be removed from the shelves. They don't tell the buyer anything about when the final consumption date should be.
Stick to it Use By/Best Before dates are established through testing by the food producer, and Martin warns: "It's a safety limit that you really shouldn't go beyond.
"It's easy to think you can push your luck, but sometimes you really can't."
He stresses that Use By dates are a guide for consumers, and points out that it's possible to get food poisoning from eating food just a day after its Use By date.
"It sounds very prescriptive to say that after midnight on a certain day something suddenly becomes dangerous, but it's there as a guide to consumers."
Cook it through Food from animal sources such as raw meat and poultry are the biggest food poisoning offenders, but cooking kills most bacteria in them.
With sausages or burgers, for example, contamination can go all the way through and thorough cooking is essential.
Chicken's irregular shape and the nooks and crannies where bacteria can hide is part of the reason there are 700,000 cases of campylobacter poisoning - the type often found in chicken - a year in the UK, says Dr Gordon. She recommends that chicken should be cooked right through in the oven before putting it on a barbecue, for example.
Foods like shellfish may contain toxins which are heat stable, and Dr Gordon warns: "Even if you cook the shellfish and manage to kill the bug, the toxin will still be stable and if you eat the shellfish you'll be throwing up in next to no minutes after you've eaten.
"That's quite difficult to protect yourself against - it won't necessarily smell, for instance."
Sniffing it out Martin points out that there's a difference between food poisoning bacteria and food spoilage bacteria.
"Very often a food like milk will go off, and it's obvious from the smell that it's not right.
"But other milk products, like clotted cream and yoghurt, may look and smell OK but there could be dangerous bugs that have grown in there. There's no smell, colour or taste.
"The fact that it doesn't taste or smell or look any different from normal doesn't mean that a food hasn't got anything nasty in it. They don't always give themselves away by those things.
"It's an easy thing to do to try to smell whether something's bad or not, but it's risky."
Cook & clean Even after thorough cooking, foods can be cross-contaminated by other foods, so chopping boards should be kept very clean.
Martin stresses that the FSA's basic food hygiene messages are the Four Cs - cooking, cleaning, cooling and avoiding cross-contamination.
"Make sure you wash everything thoroughly beforehand," he warns.
"Peel it if you can, and remember to wash hands regularly so you're not swapping contamination from one food to another.
"Washing hands is a really effective measure against food poisoning - more so than people realise."
Look after leftovers The Food Standards Agency's advice on how to keep leftovers safe is: :: If storing leftovers in the fridge, cool them as quickly as possible, ideally within 90 minutes.
:: Keep leftovers covered, refrigerate quickly and eat within two days.
:: Make sure the fridge is the correct temperature - below 5 degrees C.
:: If freezing leftovers, cool first to minimise temperature fluctuation in the freezer.
:: Leftovers can be safely stored in the freezer almost indefinitely, but the quality will deteriorate gradually, so it's best to eat within three months.
:: Defrost frozen leftovers properly before use, either in the microwave or in the fridge overnight.
:: Eat leftovers within 24 hours of defrosting and don't refreeze. The only exception is if you're defrosting raw food such as meat or poultry, which can be refrozen after cooking.
:: Cook leftovers until steaming hot throughout.
Poisoning villains Dr Gordon highlights some of the most common food poisoning bacteria as: :: Campylobacter, the most common cause of food poisoning in the UK. It's found mainly in poultry, and particularly in chicken livers, which are often used in pates.
:: Listeria bacteria from chilled foods like soft cheeses, cooked sliced meats etc can be particularly dangerous to the elderly and people who have reduced immunity.
:: E-coli - the majority of E-coli strains are harmless, but certain types, like E-coli O157, are dangerous, particularly to children. The bacteria can be found on meat, fruit and vegetables.
:: Staphylococcus and bacillus cereus contaminate foods like dairy products, creating toxins which lead to severe but short-lived food poisoning.
:: Norovirus (winter vomiting bug) can be transferred via food.
:: Salmonella - although this has reduced a lot in recent years, there's still occasional infection of eggs and chicken, and some pork shows evidence of salmonella too.