What’s the difference between food poisoning and gastro? A gut expert explains
- Written by Vincent Ho, Associate Professor and Clinical Academic Gastroenterologist, Western Sydney University
If you’ve got a dodgy tummy, diarrhoea and have been vomiting, it’s easy to blame a “tummy bug” or “off food”.
But which is it? Gastro or food poisoning?
What’s the difference anyway?
What’s gastroenteritis?
Gastroenteritis, or gastro for short, is a gut infection caused by a virus, bacterium or other microbe.
The gut is teeming with cells including healthy microbes and the cells lining the gut. But when viruses, bacteria and other microbes start to invade your gut, they colonise, build up in large numbers and eventually cause the cells lining the gut to inflame. The “-itis” at the end of gastroenteritis means inflammation.
Gastroenteritis is extremely common. In Australia there are an estimated 17.2 million cases a year.
So where do these gastro-causing microbes come from? Eating contaminated food is often the source.
However you can acquire these microbes in other ways. For example, if you touch a surface where someone sick from viral gastroenteritis had vomited on, that virus could transfer to your hands. And if your hands touched your mouth, you in turn could contract viral gastroenteritis.
What’s food poisoning?
Food poisoning refers to getting sick from eating food contaminated with chemicals, microbes or toxins.
For example if you ate food contaminated with insecticides or methyl alcohol (methanol) that would count as food poisoning. If you ate puffer fish or poisonous mushrooms that would count too. But food poisoning doesn’t include the effects of eating a food you’re allergic to.
The vast majority of food poisonings are as a result of food contaminated by microbes and their toxins. When you eat or drink them it’s like a missile strike. The toxins in particular can rapidly cause inflammation and damage the lining of the gut.
To add to the confusion, food poisoning is often referred to as foodborne gastroenteritis.
Food poisoning (or foodborne gastroenteritis) is also common in Australia. It accounts for about one-third of all cases of gastroenteritis or an estimated 5.4 million cases every year.
How can we tell the two apart?
Both gastroenteritis and food poisoning have symptoms such as diarrhoea, vomiting, nausea, abdominal cramps, fever and headaches. But these symptoms can come on in different ways.
Viral gastroenteritis, such as with norovirus, usually causes symptoms 24–48 hours after exposure, which can last for one to two days.
But food poisoning after eating microbial toxins can come on very quickly. For example, toxins from the bacterium Staphylococcus aureus can cause symptoms within 30 minutes of eating contaminated food, such as undercooked meat. Fortunately, symptoms usually get better within 24 hours.
Symptoms don’t always come on so quickly in all cases of bacterial food poisoning. For example, it can take as long as 70 days between exposure to Listeria and symptoms occurring, although, on average it’s about three weeks. This long incubation period can make it difficult to work out if a particular food is responsible for someone getting sick.
As a general guide food poisoning occurs quite quickly (within hours of eating contaminated food) while gastroenteritis can take a day or more after eating to get sick. But there is no hard and fast rule.
How do I prevent them?
The same precautions when handling food apply to preventing both gastroenteritis and food poisoning. These steps not only lower your risk of being affected in the first place, they lower your risk of you infecting others.
Wash your hands thoroughly with soap and water before preparing food. Use separate cutting boards and utensils for raw and cooked foods to help avoid cross-contamination. Cook food thoroughly and store it at safe temperatures.
Gastroenteritis can involve transmission of microbes through means other than food, for instance, via poo on your hands if you don’t wash your hands after using the toilet or after changing a child’s nappy. So wash your hands afterwards.
To prevent others from becoming sick, make sure you quickly disinfect contaminated surfaces thoroughly after someone vomits or has diarrhoea. First, put on gloves and wash surfaces with hot water and a detergent. Then disinfect using household bleach containing 0.1% hypochlorite.
How can I get better?
Treating both gastroenteritis and food poisoning focuses on preventing dehydration and relieving symptoms.
To avoid dehydration, drink plenty of fluids. For moderate or severe cases, you can buy commercial oral rehydration solution from a pharmacy.
You can also make your own oral rehydration solution by adding 6 teaspoons of sugar, ½ teaspoon of salt and ½ teaspoon of sodium bicarbonate to a litre of water. You can splash in some cordial for taste.
If symptoms are severe or persist you should see your GP or go to the emergency department.
Read more: Got gastro? Here's why eating bananas helps but drinking flat lemonade might not
Authors: Vincent Ho, Associate Professor and Clinical Academic Gastroenterologist, Western Sydney University
