they can disturb the agni (digestive fire) and imbalance the doshas (energy principles); leading to gas, fermentation, putrefaction, toxins, and indigestion.
NewsBugMedia similarly reported:
[Tomatoes and cucumbers] require different digestive environments and thus, they should be eaten separately. The bad food combination can trigger digestive un-ease, gas, bloating, stomach ache, nausea, fatigue, and problems with elimination. (...) When they reach the stomach and the process of fermentation starts, the acid released in the abdominal cavity for digestion can cause numerous digestive problems.
Another explanation is given by LittleThings:
The tomato/cucumber pairing work against each other in our stomachs. Tomatoes are an excellent source of vitamin C, according to the USDA — in fact, they actually have more of it than an orange. However, cucumber contains an enzyme that interferes with the absorption of vitamin C, making your digestive tract a little angry, and canceling out some of the benefits.
There are other sites with similar claims.
UseYourBrainForScience ridicules the claim:
This is an utterly ridiculous internet rumor. You know you’ve eaten a salad with tomatoes and cucumber in it before and you’ve been just fine. Cucumber/tomato salads are very common. People EAT THESE FOODS TOGETHER ALL THE TIME! How does it make sense that we’ve been poisoning ourselves since the domestication of tomatoes and cucumbers and it took the internet to finally save us? This just doesn’t pass the smell test.
However, it reads more like a rant and does not reference any research data to back up its claims, either.
So, are there any quality sources on whether the cucumber and tomato together in a salad can cause indigestion (or worse)?