Why Does Lettuce Turn Pink? An Expert Explains

For many, lettuce is a diet staple. As the main ingredient in a leafy green salad, lettuce is also often a welcome addition to hearty sandwiches and wraps—or, how about a lettuce wrap? And, depending on the type of lettuce, it may be used in stir-fries or soups too. Grilled lettuce, topped with a buttermilk-blue cheese dressing, is yet another way for the vegetable to shine.

But what do you do when lettuce turns pink, and why does lettuce turn pink? Southern Living consulted with Dr. Steven Sargent, professor and associate chair of the Horticultural Sciences Department at University of Florida to get to the bottom of this.

What Causes Lettuce To Turn Pink?

When lettuce turns pink, it is known as pink rib or pinking since it generally appears on the mid-rib of the lettuce leaf, explains Dr. Sargent.

“It is important to remember that the plant is typically cut from the roots, creating a wound,” says Dr. Sargent. Often the middle rib or ribs of lettuce will turn pink due to a lack of proper nutrients received during the growing season, but Dr. Sargent says that even “so-called ‘living lettuce’ in which the green-house grown plant is harvested with the roots attached, can develop pink rib.”

Post-harvest, mechanical damage from careless handling of the lettuce head is a common stressor leading lettuce to turn pink, explains Dr. Sargent, who says delayed or inadequate cooling is also a culprit. 

Think about when you bring a head of lettuce home, you might immediately see pink on the cut end, and the same is sometimes true of pre-washed salad greens—“pink rib can develop on the cut surfaces if not properly handled,” notes Dr. Sargent.

Is There A Health Risk In Consuming Pink Lettuce?

There’s no harm in eating pink lettuce, though if there’s a lot of pink, the flavor of the lettuce may be more bitter, says Dr. Sargent. The pink to reddish-brown pigments that develop on pieces of lettuce or the tips of lettuce occur when the plant is stressed, but the pigments, known as anthocyanins, don’t pose a health risk. “Other than being unsightly, they are edible,” says the professor.

What Kinds Of Lettuce Are Affected By This Color Change?

All lettuce, endives, and escaroles are susceptible to pink rib, says Dr. Sargent. And all are fine to eat, though again, if you’re seeing a lot of pink on your lettuce, you may discover that the taste is too bitter for your liking.

Can You Prevent Or Slow Down The Pink Coloring? 

While the primary parties responsible for lettuce turning pink—it’s up to commercial growers to carefully manage the lettuce fields and oversee careful harvesting and packing and cooling post-harvest, says Dr. Sargent—consumers can play a role in keeping lettuce from turning pink too. 

Dr. Sargent stresses: “Cold, cold, cold.” You don’t want to delay getting the lettuce home and placed in your fridge, preferably in a crisper drawer set to high humidity. Don’t leave lettuce in a hot car, advises Dr. Sargent, and try to choose good-looking lettuce by checking out both its appearance and feel—if the leaves are wilting in the store, there’s not much you can do to save them back home. 

How Can You Tell If Lettuce Has Gone Bad Or Has Spoiled?

Lettuce, says Dr. Sargent is living tissue and as such, it begins to age as soon as it’s removed from the root system. This inevitably leads to leaf yellowing and lettuce wilting. When bacterial decays develop on cut surfaces, “turning the normally turgid tissue into black mush,” then it’s time to toss it.