Most dark leafy greens are rich in vitamin K. Trista Best, MPH, RD, LDN, tells Eat This, Not That!, “Vitamin K, which is found in abundance in leafy greens, is fat-soluble. This means it can become toxic when too much is consumed or supplemented.” While a vitamin K deficiency can cause bleeding issues, a vitamin K overdose can cause toxicity in the body as it also acts as a blood thickener, explains Best.
Diana Gariglio–Clelland, RD, CDCES, is a certified diabetes care and education specialist. She shares her expertise with Eat This, Not That! Blood thinner patients should be extra cautious with their vitamin K intake as they are more prone to bleeding.
The Daily Meal reports that gastrointestinal symptoms are another uncomfortable effect of eating too many leafy greens. Gas, bloating, and constipation may occur when you eat more fiber than your body can handle, and some leafy greens, like kale and collard greens, do contain high amounts (via Medical News Today).
It is possible that eating enough leafy greens can be beneficial rather than harmful. If you have any gastrointestinal problems or are suffering from a medical condition, you should discuss your diet with your doctor.