In the local Trader Joe’s, I often find myself holding up an organic and non-organic cucumber, deciding whether it’s worth the extra $1.99 to buy the organic one.  Organic means no synthetic pesticides, herbicides, or fertilizers, while the cheaper cucumber beside it may have been treated with all three. And I can’t stop thinking about what those chemicals might be doing inside my body.

After taking the UMD course “The Microbiology of Fresh Produce,” I learned about even more chemicals I hadn’t even known were being used on most industry-grown produce. Not just in the fields, but after harvest. Hypochlorite, a chemical in the same family as household bleach, and peracetic acid, an alternative to chlorine used for water treatment, are routinely used to wash produce in commercial facilities to prevent cross-contamination and comply with federal food safety regulations under the Food Safety Modernization Act.

Suddenly, I wasn’t just thinking about pesticides anymore. I found myself standing in the produce aisle, wondering whether everything I was looking at, oranges, lettuce, potatoes, organic and non-organic alike, had been soaked in chemicals that were now making their way into my gut. I used to think the healthiest way to eat was loading up on fresh, raw produce and whole foods to diversify my microbiome and flood my body with antioxidants. Now I wasn’t so sure.

I wasn’t willing to just accept the uncertainty. So I went to my professor, Dr. Shirley Micallef, and asked directly: Are these post-harvest washes breaking down the antioxidants and vitamins that make fresh produce worth eating in the first place? Are they degrading the very nutritional quality we’re attempting to gain when we reach for a salad instead of a bag of chips? She suggested I design an experiment and find out. And so I did.

The Experiment:

I grew three varieties of leafy greens: kale and two types of lettuce, in a controlled growth chamber right here at UMD. After harvest, I washed them with either plain tap water or one of the two sanitizers used in the commercial produce industry, at the exact concentrations manufacturers recommend. I then analyzed health-promoting compounds called phenolics, carotenoids, and chlorophylls, the antioxidants and pigments that give leafy greens their nutritional punch. I took these measurements immediately after washing, and again after two and seven days in the refrigerator to mimic what happens between the processing facility and your plate.

The Good News:

Here’s what I found, and honestly, it surprised me: the sanitizers did not meaningfully destroy the nutritional quality of the leafy greens. The antioxidant compounds I measured were largely preserved across all three varieties, regardless of which sanitizer was used. The food safety measures that keep us from getting sick from Salmonella and E. coli in our salads are not, as it turns out, quietly robbing our lettuce of its vitamins in the process.

The biggest factor determining how nutritious your greens are? The variety. The type of lettuce or kale matters far more than anything that happens in the wash. ‘Red Salad Bowl’ lettuce had the highest concentrations of health-promoting compounds across the board, more than the kale, and more than the other lettuce variety I tested. If you want the most nutritious salad, your best lever is choosing the right variety, not stressing about whether it was washed with a sanitizer.

The Complicated News:

That said, it wasn’t entirely straightforward. ‘Red Salad Bowl’ lettuce started losing some of its beneficial compounds within just two days of refrigerated storage. This decay displays how, by the time it travels from a processing facility to a distribution center to your grocery store and finally into your fridge at home, some of that nutritional value may already be on its way out. Kale, on the other hand, actually accumulated more beneficial metabolites over seven days in the fridge. If shelf life and nutrition both matter to you, kale is a remarkably resilient choice.

I also found that one of the sanitizers, peracetic acid, was associated with lower levels of carotenoids and chlorophyll, the compounds that give produce its deep green and orange pigments, specifically in ‘Red Salad Bowl’. Nonetheless, it didn’t affect the other varieties the same way. The relationship between produce and the chemicals used to wash it, is more complicated and variety-specific than a simple “safe” or “not safe” verdict.

So, Is Your Salad Safe?

Yes, and it’s probably more nutritious than you’ve been giving it credit for. The sanitizers being used in the produce industry exist because the alternative is serious. According to the FDA, contaminated fresh produce sickens approximately 48 million Americans every year, sends 128,000 to the hospital, and kills around 3,000, and leafy greens are one of the most common culprits. That trip to the bathroom can turn into an emergency room visit, and for vulnerable populations, a foodborne illness from contaminated salad can be fatal. Sanitizers are the frontline defense against that outcome. They are not perfect, and more research is needed, but the evidence from my experiment suggests these sanitizers are doing their job without undermining the reason we eat salad in the first place.

I still pick up the organic cucumber sometimes. But I feel a little less anxious about what’s happening to my greens between the farm and my fork, and I feel a lot more curious about the science that happens in between.