Behind the Headlines

Wednesday June 17 2009

Always check the use-by date

Listeria poisonings are on the rise because the elderly are taking chances with use-by dates, newspapers reported. The Times said that the 'waste not, want not' ethos of the post-war period could be responsible for the increase in the number of cases of food poisoning. The Daily Mail said that rising food prices and fixed incomes mean that pensioners are keeping food for longer than they should.

The news reports are based on information from The Food Standards Agency (FSA), which says that people aged 60 and over are more likely than younger people to take risks with use-by dates. The FSA said that eating food past its use-by date increases the risk of food poisoning from listeria. There has been a recent surge in the number of cases of listeria, many of which have been in the over-60s, a high-risk group for the potentially deadly bug.

Dr Andrew Wadge, chief scientist at the FSA, said, "There are some really simple steps people can take to prevent getting ill in the first place. Be aware that use-by dates indicate how long food will remain safe, and then make sure you stick to them. Always follow the storage instructions on the label. And keep your fridge cold enough: between 0°C and 5°C is ideal."


What is listeria?

Listeria (full name Listeria monocytogenes) is a type of bacteria that can cause food poisoning when eaten. It can live and grow in a wide range of foods, in particular chilled ready-to-eat foods such as packaged sandwiches, butter, cooked sliced meats, smoked salmon, certain soft cheeses and pâté. Listeria is killed by pasteurisation and cooking, but these foods are a particular risk for harbouring the bug as processed or pre-cooked foods can become contaminated during the packaging process.


Who is most vulnerable to listeria?

Pregnant women, young children, the elderly and adults with weak immune systems (for example, people with HIV or AIDS, transplant patients, those who have cancer or those who regularly take steroids or other medications that weaken the immune system) are most vulnerable to listeria infection. These groups may become ill after eating food contaminated with only a small number of bacteria, which a healthy person would be able to eat without being harmed. People who are at risk are particularly advised to avoid eating any soft cheeses or pâté (including vegetarian pâté).


What are the symptoms?

Listeria infection has a variety of symptoms. Healthy adults may experience mild flu-like symptoms, such as fever, muscle aches and mild gastrointestinal symptoms, including nausea or diarrhoea. Headache, confusion and altered consciousness may develop if the infection progresses and becomes severe.

Vulnerable groups are more likely to experience severe illness or complications. In particular, pregnant women can experience miscarriage, premature delivery or stillbirth or can pass the infection on to their baby. Serious illness and complications can be prevented by prompt medical treatment and antibiotics. Dr Andrew Wadge, chief scientist at the FSA, has said that 95% of cases need hospital treatment.


Why is this warning being made now?

During Food Safety Week (June 15–21), the FSA wants to raise awareness about the dangers of listeria poisoning and the steps that can be taken to avoid it.

The FSA reported that the number of cases of listeria food poisoning has doubled since 2000 and rose by 20% in 2007. This increase in cases was mostly among people over 60. The main findings of a survey of 3,219 people in autumn 2008 were:

  • Only 42% of older people questioned could correctly identify the use-by date as an important indicator of whether a food is safe, compared to 51% of 25 to 44-year-olds and 53% of 45 to 64-year-olds.
  • Older respondents were more likely to eat food past its use-by date: 40% of older people said they would eat dairy products up to three days past their use-by date.
  • Only 39% of people over 65 checked their fridge temperature at least every six months. (Setting the fridge temperature between 0°C and 5°C is important to control listeria growth).


How do I avoid listeria infection?

There are several simple ways to avoid a listeria infection. The FSA advises the following:

  • Don’t eat foods that are past their use-by date, even if they smell fine. Use-by dates indicate how long a food will remain safe (if food is frozen or cooked before the use-by date, it can be kept for longer).
  • Follow the storage instructions on food packaging, such as 'freeze on day of purchase', 'cook from frozen' or 'defrost thoroughly before use and use within 24 hours'.
  • Make sure your fridge is at the right temperature, ideally between 0°C and 5°C.

Cases of food poisoning double in frequency during the summer months, when food exposed to the heat can go off more quickly. It is important to be careful when handling and preparing food:

  • Wash your hands and keep work surfaces clean.
  • Reheat pre-prepared foods thoroughly, so that they're steaming hot before you eat them.
  • Only eat pasteurised dairy produce.
  • Be careful when storing foods from tins or packages. For example, don’t keep opened tins in the fridge.

As a side issue, the best-before date, which also appears on a wide range of foods, is an indication of the quality of food, rather than its safety. Food eaten after a best-before date may not taste as good as it did before, but it will not do you any harm (with the exception of eggs, which should not be eaten after best-before date).

As a follow-on to this research, the FSA has carried out further surveys to determine the listeria content of some packaged foods, including smoked fish and sliced meats. It is also investigating the reasons behind the increased vulnerability to listeria infection in the over-60s. The FSA gives out information about listeria infection through GPs and community groups using posters and leaflets and printed messages on prescription bags.

Analysis by Bazian

Edited by NHS Choices

Links to the headlines

Rise in listeria food poisoning as elderly take ‘use by’ date gamble. The Times, June 17 2009

Listeria surge as cash-strapped pensioners ignore use-by date. Daily Mail, June 17 2009

Old people at risk from Listeria poisoning if they ignore food dates. Daily Telegraph, June 17 2009 

Links to the science

Older people taking more risks with food safety. FSA press release, June 15 2009

Campaign to tackle food poisoning in over 60s. FSA press release, June 15 2009


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