Our immune system declines with age, making food-safety rules more important.
Photo Martin Sykes/NZH
Baby boomers are rewriting the rules of ageing by looking decades younger than their parents did at the same age and, in many cases, continuing to live their lives as vigorously and actively as their children. But though the baby boomers may have revolutionised the lifestyle of older adults, they can’t halt the inevitable decline in their immune system that leads to a greater risk of infections and food-borne illnesses from age 60.
Our immune defences range from our skin and gut lining, which prevent pathogens from entering the body, through to the natural killer cells and phagocytes that destroy pathogens that manage to enter our circulation. However, our immune system deteriorates with age; changes include a decline in the immune functioning of the gut lining and of the thymus, which produces T cells to fight invading pathogens. Add to that the antacids that many older people use – these reduce stomach acidity but also the ability of the body to resist food-borne infections – along with a propensity to overuse antibiotics, which allows excessive amounts of pathogens to grow in the gut.
Older people are also more likely to have a chronic disease, such as diabetes or cancer, that may make them more susceptible to an infection, according to a 2006 review published in the journal Clinical Infectious Diseases. The net result is that adults aged 60 years and over have a higher incidence of food-borne illnesses, along with a correspondingly greater risk of hospitalisation and death.
In New Zealand, more than half the listeriosis cases in 2010 were among adults aged 60 years or more. And though the rate of listeriosis is lower than those of other food-borne illnesses, the risk of death is real. In 2010 seven people died in New Zealand as a result of listeriosis: four perinatal and three others.
Older adults with either an E coli or salmonella infection were also more likely to be hospitalised than other age groups in New Zealand, even though their rate of infection wasn’t the highest. Similarly, although the highest New Zealand rate of campylobacteriosis was among people aged 20 to 29, those who were 60 or older had the highest rate of hospital admissions with this infection. Older people were also more likely to be hospitalised with Guillain-Barré syndrome, which can be triggered by Campylobacter jejuni.
Irrespective of how fit and healthy we are, this inevitable decline in immune function with age increases our susceptibility to infections and our ability to fight back if we are infected. So following food-safety guidelines is particularly important for all adults from age 60.
And although older adults are generally more careful than younger adults in following some food-safety practices, such as washing hands and food-preparation surfaces, many don’t follow all the recommended ones. Two recent US studies found many adults aged 60 years and over didn’t reheat meats until steaming hot, for example. And both studies found those less likely to follow food safety guidelines were men, and people with higher incomes or who were better educated.
Of more concern, older people are likely to believe their food handling behaviours aren’t causing them to become ill, according to a 2001 study published in the Journal of Nutrition Education. And of course, this may have been true when they were younger, but any shortcoming in food safety is more likely to cause a food-borne illness than it would have done in their younger years.
Clean, cook and chill is the mantra of the New Zealand Food Safety Authority. In addition, US researchers recommend older people place a special focus on ensuring that:
- hands are washed thoroughly before and after preparing foods;
- foods are cooked adequately;
- cross-contamination of raw/cooked foods is avoided;
- all foods are kept at safe temperatures; and
- foods from unsafe sources, such as ready-made delicatessen coleslaws, are avoided.
For more information on food safety guidelines visit www.foodsmart.govt.nz.