Can Eating Expired Butter Make You Sick?

You might feel as if you’re running to the grocery store to buy fridge staples like eggs or milk every other day, but one fridge staple seems to last forever: butter.

However, it definitely expires, and you’ll know about it from its off-color and foul taste. Different guidelines recommend different storage times for butter, so working out exactly how long you can store an unopened or opened chunk of butter might seem confusing.

However, is expired butter dangerous for you or just unpleasant to eat? This article explains the expiry date of butter, how eating expired butter may affect your health, and how to store it.

Can Expired Butter Make You Sick?

Eating old butter won’t make you seriously ill.

“Butter is a special type of food,” says Benjamin Chapman, PhD, a professor and food safety extension specialist at North Carolina State University in Raleigh and the host of the podcast Food Safety Talk.

Dr. Chapman explains that since butter is structured with the fat on the outside and the bulk of water on the inside, the fat serves as a protective layer of sorts, preventing bacteria from forming.

“The microbes that we’re concerned about when it comes to food safety need water to grow,” he says. “It won’t grow on fat.”

If you have salted butter in your fridge, Chapman says you’re even more in the clear. “Microbes don’t like salt,” he says, saying they’re less likely to grow in foods with a high concentration of the mineral.

“There’s actually nothing in the butter that’s causing this, but if you eat something that tastes sour or not like you were expecting it to taste, it might lead to a physical response, such as gagging or wanting to throw up,” he says. In other words, you can literally think yourself sick.

Does Butter Go Rancid?

This brings up an important point: Even though eating old butter can’t make you sick, Chapman says it can go rancid. He explains that while butter doesn’t have an expiration date, it does have a “best sell date.” Once that passes, the taste, color, and texture can change.

If your butter tastes sour, chances are it’s definitely past its sell-by date. “Rancidity has nothing to do with microbes or safety,” Chapman says. “What’s happening is oxygen is binding to the fat and changing the chemical components, which can lead to a terrible taste, but it won’t make you sick.”

As long as butter doesn’t have mold in it, rancid butter may just have an unpleasant flavor or odor.

But if the butter has mold, get rid of it. Molds are fungi, some of which can trigger allergies and cause breathing problems. Certain molds can release harmful toxins (many of these don’t affect butter, though).

How Long Does Butter Take to Expire?

The Takeaway

• Eating expired butter is generally harmless but can cause temporary digestive discomfort, like vomiting or diarrhea, due to its nasty taste.
• Butter is less likely to harbor harmful bacteria due to its high fat content. The salt in salted butter also helps keep out microbes.
• Rancid butter won’t pose long-term health risks but can have unpleasant taste changes.
• For the longest shelf life, store unopened butter in the refrigerator, or freeze butter you don’t plan to use within a few weeks to prevent spoilage.