Can blueberries cause food poisoning? Yes, blueberries can make you sick if they carry harmful bacteria, viruses, or parasites. Blueberries have been identified as the source of illness caused by a range of microbes that infect the intestines including listeria, salmonella, and escherichia coli. Frozen berries were the most common identified cause of outbreaks of hepatitis A in the United States, Europe, and Australia and New Zealand during 2009 to 2019.
The good news is that blueberries remain one of the healthiest foods you can eat. Blueberries are one of the healthiest fruits for you. Studies show that they help protect against aging, cancer and damage to your DNA. With proper washing and storage, blueberries pose very low risk to most people.
What Germs Can Contaminate Blueberries?
Blueberries can carry several types of harmful germs.
- Hepatitis A virus causes liver infection with symptoms appearing 2 to 7 weeks after eating contaminated food
- Norovirus causes stomach flu symptoms like vomiting and diarrhea within 12 to 48 hours
- Listeria can cause serious infections in pregnant women, elderly people, and those with weak immune systems
- Salmonella causes stomach cramps, fever, and diarrhea within 6 hours to 2 days
- E. coli can cause bloody diarrhea and kidney problems
- Cyclospora is a parasite that causes watery diarrhea lasting days to weeks
An outbreak of E. coli O26 associated with consumption of raw blueberries was reported, where six people were sickened and one was hospitalized. In 2009 and 2010, blueberries contaminated with Salmonella resulted in 14 and six illnesses respectively.
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How Do Blueberries Get Contaminated?
Blueberries pick up germs at different stages from farm to table.
The main likely sources of fresh food contamination are being grown in contaminated water, getting contaminated by infected animals at some stage in the production cycle, being picked by people who are infected with hepatitis A, mixing with other ingredients contaminated with hepatitis A virus during processing, and being washed in contaminated water.
Workers who pick berries without proper hand washing can transfer germs. Dirty equipment during processing spreads contamination between batches. The primary reasons for berry contamination include being grown in contaminated water, berry pickers exercising poor hygiene, or cross contamination with infected berries during processing.
There is evidence that fruits such as berries can sometimes internalise bacteria and viruses during growing. This means that the disease causing agent may actually be inside the fruit and is almost impossible to kill except by cooking.
Are Frozen Blueberries More Dangerous Than Fresh?
Frozen blueberries can actually pose a higher risk for certain viruses because freezing does not kill germs.
Due to the structural integrity of the virus particles, freezing and repeated freeze thaw cycles do not reduce hepatitis A or norovirus to levels sufficient to ensure safety. Hepatitis A virus can survive for months on contaminated surfaces at room temperature and freezing has little effect on the virus.
Frozen berries also travel through longer supply chains. Fresh strawberries picked by an infected worker can be processed into frozen products within hours. Those products then enter complex supply chains, get repackaged under multiple brand names, and sit in freezers for months before reaching consumers.
While no enteric virus outbreaks associated with domestic berries have been reported in 35 years, there have been reported outbreaks linked to imported fresh and frozen berries.
What Are the Symptoms of Berry Food Poisoning?
Symptoms vary depending on what germ made you sick.
Bacterial food poisoning like salmonella or E. coli typically shows up within hours to 2 days. Symptoms tend to go away quickly too. They typically last 12 to 48 hours. You will experience stomach cramps, diarrhea, vomiting, nausea, and sometimes fever.
Hepatitis A takes much longer to appear. Illness usually occurs about two to six weeks after ingesting contaminated food or drink, and commonly lasts less than two months. Common symptoms are tiredness, fever, nausea and loss of appetite. The skin and the whites of the eyes may become yellow and the urine may become darker than usual.
Listeria symptoms include high fever, severe headache, stiffness, nausea, abdominal pain, and diarrhea. Listeria infection can cause miscarriages and stillbirths among pregnant women.
Who Is Most at Risk From Contaminated Blueberries?
Some people face higher danger from berry food poisoning.
- Pregnant women face serious risk from listeria including miscarriage
- Adults over 65 get sicker from most foodborne germs
- Young children under 5 have weaker immune defenses
- People with weak immune systems from illness or medication
- Anyone with chronic liver disease faces worse hepatitis A outcomes
Infections may lead to more severe health problems, including liver failure, in persons who are older or immunocompromised, have chronic liver disease, or have other underlying health conditions.
Illness is usually more severe in older people than in young children.
How Should You Wash Blueberries Properly?
Washing blueberries the right way removes dirt, bacteria, and pesticides.
Blueberries should be washed because they can carry dirt, debris, bugs, parasites, and other contaminants. These contaminants can also carry pathogens which may cause foodborne illness.
Here is how to wash them correctly.
- Before washing blueberries, inspect and remove ones that are moldy or broken, as well as debris like leaves or stems
- Place the blueberries in a colander. If you need to wash a lot of berries, do it in batches to avoid overcrowding
- Rinse the blueberries under cold running water, gently swishing them around with your hands to ensure all the berries are exposed to water
- Dry completely on clean paper towels before eating or storing
For a deeper clean, try a vinegar wash. Soak them in a vinegar solution of one part vinegar to three parts water. Let them sit for five minutes. This kills bacteria and mold spores. Rinse thoroughly and drain and rinse well under cold water to remove any vinegar taste.
Avoid washing blueberries with soap. The soap can be absorbed by the berries, potentially introducing contaminants.
Should You Wash Frozen Blueberries?
Yes, wash frozen blueberries before eating them raw.
Frozen blueberries should generally be washed before eating, especially if consumed raw. Commercial freezing typically includes 3 step washing with rinse, sanitize, and rinse. Home freezing often skips sanitization creating higher contamination risk.
Thaw slightly under cold running water for 30 seconds. Gently rinse in a colander and avoid soaking to prevent mushiness.
For high risk groups like pregnant women, elderly people, or those with weak immune systems, consider heating frozen berries before eating. Heating hepatitis A virus to more than 85 degrees Celsius for 60 seconds will inactivate the virus and renders potentially contaminated berries perfectly safe.
When Should You See a Doctor?
Most food poisoning goes away on its own within a few days. Most people recover in a few days without any treatment.
See a doctor if you have any of these warning signs.
- Fever above 38.6 degrees Celsius
- Bloody diarrhea or bloody vomit
- Diarrhea lasting more than 3 days
- Frequent vomiting and unable to keep fluids down
- Signs of dehydration like not urinating much, dry mouth, or dizziness
- Yellow skin or eyes which may signal hepatitis A
- Confusion, stiff neck, or severe headache
If you have eaten contaminated berries and started to develop symptoms, you should see a doctor as soon as possible.
How Can You Reduce Your Risk?
Follow these steps to enjoy blueberries safely.
- Buy from trusted sources and check packaging dates
- Store fresh blueberries in the fridge in a container with holes for air flow
- Do not wash until ready to eat because moisture causes mold
- Keep at proper temperature since berries spoil faster at room temperature
- Check for mold or soft spots and throw away damaged berries
- Heat frozen berries if high risk by cooking them into smoothies, pies, or compotes
- Wash hands before and after handling all produce
You might be wise to get into the habit of boiling your frozen berries, especially if you are unsure of where they came from. It will only take a minute, which will do little to affect the taste and texture of your average berry pie or smoothie.
Are Blueberries Still Safe to Eat?
Absolutely. The risk of getting sick from blueberries remains very low for most people.
It has been extremely rare for berries produced in New Zealand to be unsafe to eat fresh. You are unlikely to need to boil the strawberries, raspberries, blackberries or blueberries that turn up in your local fruit shop and supermarket this summer.
Blueberries deliver powerful health benefits. A one cup serving of blueberries contains 25 percent of the recommended daily value for vitamin C and 4 grams of dietary fiber, but only 80 calories. Research suggests regularly eating blueberries may improve memory and delay age related cognitive decline.
There is no downside to eating blueberries every day because they are so healthy. Just wash them first and follow basic food safety rules.
FAQ
Can you get food poisoning from unwashed blueberries?
Yes. Blueberries can carry dirt, debris, bugs, parasites, and other contaminants which may cause foodborne illness. Always wash blueberries under cold running water before eating.
How long after eating bad blueberries will you feel sick?
It depends on the germ. Bacterial food poisoning shows up within hours to 2 days. Hepatitis A takes 2 to 7 weeks to cause symptoms. Bacterial infections typically cause symptoms that last 1 to 7 days. Viral infections often resolve within 1 to 3 days.
Are organic blueberries safer than regular?
Not for food poisoning risk. Frozen organic blueberries are being recalled over Listeria concerns. Both organic and conventional blueberries can carry harmful germs. Wash all blueberries regardless of how they were grown.
Should you wash blueberries in vinegar?
A vinegar wash can help reduce bacteria and mold. For an even deeper clean, soak them in a vinegar solution of one part vinegar to three parts water. Rinse well under cold water after soaking to remove the vinegar taste.
Can frozen blueberries have listeria?
Yes. Frozen blueberries have the potential to be contaminated with Listeria monocytogenes, an organism which can cause serious and sometimes fatal infections. Listeria can grow even at refrigerator temperatures.
Is it safe to eat blueberries every day?
Yes, blueberries are very healthy and safe for daily eating when properly washed. Eating a serving of blueberries every day can provide you with a good source of vitamin C, vitamin K, manganese, and fiber. These nutrients can support your immune system, bone health, and digestion.
What does hepatitis A from berries feel like?
Symptoms include fever, nausea, abdominal discomfort, diarrhoea, dark urine and jaundice which is yellow skin and eyes. The illness can be quite severe, particularly in people who are already unwell. Most people recover within several weeks.
Do you need to wash pre washed blueberries?
Yes. It is important to rinse your berries under running water before eating them, even if they are labeled pre washed. Use a colander to let water flow over every crevice, rubbing gently to remove contaminants.
Food safety is an important part of a healthy diet, and so is understanding the bigger picture — like whether eating less or exercising more is better for weight loss. If you’re motivated to see rapid results, you may also want to know whether losing 4kg in two weeks is realistic. A Maribyrnong personal trainer can help you build a safe, effective nutrition and training plan.
