What’s the Real Culprit Behind Your Stomach Pain—Food Poisoning or Lactose Intolerance?

Earlier this year, a viral video made the rounds on TikTok about an infamous plate of carbonara served at a theme park in Japan that left the video creator with diarrhea and intense stomach pain. In the video's comment section, multiple viewers shared similar experiences from their vacations, one person referring to it as "the forbidden carbonara." This sparked a debate over whether the stomach issue was a result of a foodborne illness (i.e., food poisoning) or from the high dose of lactose in the dish. But...nobody came to a firm conclusion.

Because the symptoms of food poisoning and lactose intolerance have some overlap, it can be difficult to tell them apart, says Andrew Boxer, MD, a gastroenterologist at Gastroenterology Associates of New Jersey.  Here, gastroenterologists share how to tell if your bout of illness was caused by food poisoning or lactose intolerance.

What is food poisoning?

Food poisoning, or foodborne illness, occurs when you ingest a harmful pathogen, says Dr. Boxer. It can be caused by bacteria or viruses like Escherichia coli (E. coli), Salmonella, Campylobacter, rotavirus, norovirus, hepatitis, or parasites including Giardia and Cryptosporidium. The pathogen produces toxins (substances that are toxic to humans) or multiples itself, making you unwell.

With food poisoning, you’ll typically experience nausea, vomiting, diarrhea, and stomach pain or cramps. But it may also cause you to develop a fever, says Robynne Chutkan, MD, a gastroenterologist and author of The Microbiome Solution. These symptoms can start as soon as 30 minutes to several hours after eating contaminated food or drinks, or it may take days or weeks to make an appearance. “It’s all dependent on the type of pathogen, so there's a lot of variation,” Dr. Chutkan points out.

Food poisoning symptoms usually last several hours or days. But they can take more than a week to resolve for certain pathogens.

What is lactose intolerance? 

Lactose intolerance is defined as the inability to digest lactose, a natural sugar found in dairy. If you have an intolerance, your body doesn't have enough of the enzyme called lactase to break down the lactose. This can lead to symptoms like bloating, cramps, stomach pain, diarrhea, and nausea if you eat more than the amount your body can handle. According to Dr. Boxer, each person’s threshold amount is different and very individualized.

“Typically, lactose intolerance symptoms are going to develop within 30 minutes to a couple hours after eating,” says Dr. Chutkan. Dr. Boxer also says that symptoms “usually resolve within a few hours to a day after lactose consumption, but in some cases, mild discomfort can persist for a bit longer, especially if there was significant irritation to the gut.”

But why does this intolerance happen? As babies, most of us can digest lactose without issues, says Dr. Chutkan. As we hit adulthood, however, we may experience something called lactase nonpersistence, (i.e., where our bodies produce less lactase over time). This means we may not digest lactose as well as we did in childhood.

Another common cause of lactose intolerance is damage to the small intestine. Lactase is stored within our intestinal lining, so "if we're damaging cells on the brush border of the small intestines, where lactase enzyme is present, we're going to diminish the ability to actually break down lactose," Dr. Boxer says. He adds this damage can occur for the following reasons:

• Systemic illnesses like the flu or COVID-19
• Acute gastrointestinal (GI) illness like gastroenteritis (i.e., inflammation of the intestinal lining)
• Radiation or chemotherapy for cancer
• Surgery
• Certain medications like strong antibiotics or NSAIDs (non-steroidal anti-inflammatory drugs like Ibuprofen)
• GI autoimmune diseases like celiac disease, Crohn's disease, or ulcerative colitis

Can you tell whether you have food poisoning or lactose intolerance?

If you recently recovered from a bout of sudden diarrhea and abdominal pain, you might be wondering what the culprit was. Could it have been food poisoning or a sudden case of lactose intolerance from the dairy I ate that day? Here are some tips gastroenterologists provide to their patients to tell them apart.

1. You have a fever

If you were vomiting or had a fever, it was most likely a foodborne illness, says Dr. Chutkan. In saying that though, “many people who have food poisoning don’t have vomiting or fever, they just have diarrhea, cramping and nausea,” she adds.

2. You've had prior dairy sensitivity

If you cast your mind back to "the before times," i.e., before your GI illness, consider whether you’ve ever felt even a tiny bit of bloating, cramping, queasiness, or loose poops every time you had something with dairy in it. (Think: milkshakes, bubble tea, ice cream, gooey soft cheese, feta, chocolate, and milky coffee.) This would tell you that although your body’s reactions to lactose were not extreme, you’ve been living with some level of intolerance, says Dr. Chutkan. This gives you another clue that your recent illness may have been due to lactose intolerance.

3. You feel better on a dairy elimination diet

Though this tip won't help your current predicament, starting a dairy elimination and reintroduction process, as approved by your healthcare provider, may give you some future insight into your lactose intolerance. If you notice uncomfortable stomach issues when you reintroduce dairy, take note of them and bring it up to your provider. They can help you develop a new diet plan to ensure you're still meeting your calcium requirements.

The best way to go about this process? Dr. Chutkan suggests eliminating all dairy foods and drinks for two weeks to see if you feel better. You might discover you're not feeling nauseous or bloated as you did before. After two weeks, "you can reintroduce small amounts," she adds. "Start with yogurt and hard cheese, because those have less lactose, and work your way up [to higher lactose foods and drinks]."

Diagnosing a lactose intolerance may require other tests, such as a breath or blood test, according to Dr. Chutkan, but she believes the elimination diet and reintroduction process gives you a better sense of how intolerant you are. For example, "the breath test tells you that you're "moderately lactose intolerant," but what does that really mean? Does it mean you can eat a portion of lasagna without feeling crummy? It can't really tell you," Dr. Chutkan adds. And as for the blood test, it may not be everyone's cup of tea, as you have to get your blood drawn every 30 minutes for three hours.

“You understand how your body works, and can figure it out by paying attention to the feedback it gives you when you eat certain things," Dr. Chutkan says.

The treatment for both looks similar

While you’re in the throes of diarrhea, nausea, and abdominal pain, you don’t need to worry too much about determining whether what you’re experiencing is food poisoning or lactose intolerance. Focus instead on managing your symptoms and flushing out the lactose or the pathogen from your digestive system. No matter the perpetrator, the treatment process is similar. Here are some options to consider:

1. Check to see if you need medical attention

Typically, both food poisoning and lactose intolerance can be treated at home, says Dr. Boxer, but sometimes, you may develop symptoms that would require medical attention. Watch out for the following signs that might indicate you need to see your provider, per Drs. Boxer and Chutkan:

• Your abdominal pain is severe and persistent
• You’re so nauseous that you’re unable to keep any fluids down for hours
• You’re vomiting often
• You’re dehydrated (which involves dizziness or lightheadedness, weakness, dry mouth, and minimal urination
• You have a fever 
• You see blood in the diarrhea
• You’re vomiting and having diarrhea
• You have diarrhoea for more than three days
• You’re having blurry vision or skin tingling

If you have any of the above, your provider will likely run tests to see if you're dealing with a virus, intolerance, or something else. They may also treat any severe symptoms with medications and intravenous infusion (IV) to rehydrate you. For example, if your issue stems from bacteria, your provider might prescribe an antibiotic, says Dr. Chutkan. (Just keep in mind, some antibiotics can cause diarrhea as a side effect, too.)

And “if your doctor diagnoses you with lactose intolerance, ask about options to ease discomfort,” says Dr. Boxer. “Simethicone (i.e., Gas-X) may help with gas and bloating, while an antispasmodic like dicyclomine is sometimes considered for cramping, though it is more commonly used for irritable bowel syndrome.”

2. Put yourself on 'gut rest'

According to Dr. Chutkan, gut rest¹ means drinking plain water to help flush the lactose out of your digestive system and not eating any food until your stomach feels settled and you’re hungry again. This is a generally safe and helpful option for most adults for up to 24 hours, she adds.

When you’re hungry again, try to eat bland, easy-to-digest foods like bananas, white rice, plain crackers, broth, applesauce, or mashed potatoes (just be sure to avoid ones you make from packaging that could have dairy added to it), which can help firm up your stools and prevent watery diarrhea. Other tips? Take it easy, don’t force yourself to eat if you feel nauseated again, and keep sipping on water.

Once you're able to keep food down, try to reintroduce your normal meals, though it's best to continue avoiding certain things like fatty, greasy, and fried foods, caffeine, alcohol, and dairy for a while (or indefinitely if intolerant) until you’re completely recovered.

If your symptoms persist for more than 48 to 72 hours, Dr. Boxer advises going to your healthcare provider for further examination. 

How to prevent future lactose intolerance symptoms

Unfortunately, lactose intolerance isn't something you can cure. The only way to prevent symptoms is to familiarize yourself with your body's tolerable limit of lactose and try not to go beyond that amount. You can also opt for lactose-free dairy products or foods that are lower in lactose—such as yogurt and hard cheeses—or simply avoid dairy products altogether.

That said, we know it can be tough to completely remove dairy from your life (who doesn't love a good slice of pizza?!). In this case, you have the option to take lactase pills (i.e., Lactaid) before eating, says Dr. Boxer. Just try not to rely on these pills regularly, says Dr. Chutkan. "If it's a special occasion like my kid's birthday, I'm going to use some enzymes so I can have a little bit of cake," he adds.

"It's not something that you can do regularly to keep eating something your body has already told you it doesn't like and cannot digest."

How to lower your risk of food poisoning

There's no guarantee that you can completely eliminate your risk of food poisoning or foodborne illnesses, but there are some things you can do to minimize the risk overall. Experts say this includes the following:

• Wash your hands: The most important thing to do is wash your hands thoroughly with soap and warm water, especially before handling food. This is because your hands pick up germs from whatever they touch and can transfer these germs to your food. For example, pathogens from sick people, the toilet or bathroom, diapers, and raw animal products—like meat, fish, or eggs—can make you unwell.
• Wash your utensils: Similarly, utensils and cutlery can also pick up and transfer pathogens from risky raw foods (like animal products) to ready-to-eat foods. So be sure to wash your utensils with soap and warm water to avoid cross-contamination.
• Keep a separate knife and cutting board for meat: It’s also recommended to have a separate knife and chopping board solely for raw animal products. Do not place ready-to-eat foods together with risky raw foods.
• Stick to recommend food storage conditions: Make sure that all foods are stored at the proper temperature to keep them fresh and that they are packaged properly. Additionally, make sure your foods reach the ideal safe internal temperature before you eat it.
• Rinse your produce well: This will help remove any bugs or bacteria.
• Avoid eating food that's been left out: Especially if the food has been at room temperature for an hour or more and includes raw or undercooked animal products. Make sure all hot food is served hot, and cold foods (like salad) are served cold.
• Take precautions while traveling: When eating out in a country where tap water isn’t treated like it is in the U.S., additional precautions to take include steering clear of raw vegetables, peeling all fruits, and avoiding ice.

The bottom line

Because lactose intolerance and food poisoning symptoms can look very similar, it can be tricky to tell which you are dealing with at any given time. But there are some signs that can help offer clues. For instance, if you have a fever along with vomiting and diarrhea, you more than likely are dealing with a virus or foodborne illness. But if you notice your stomach upset happens after eating dairy products, you could be dealing with a flare from lactose intolerance.

Healing from both conditions will often involve putting yourself on "gut rest" by drinking only plain water and avoiding foods for about 24 hours. From there, introducing bland, easy-to-digest food can help your gut get back on track. If you suspect you have lactose intolerance, starting a dairy elimination diet once you're healed can help narrow down whether dairy is the issue.

Ultimately, if your symptoms—like stomach pain, diarrhea, and vomiting—last longer than a couple of days, reach out to your healthcare provider, who can help diagnose you and prescribe a medication if necessary. They can offer some guidance and gut health management advice.