If you eat spinach every day in excessive amounts (more than a bowl) there can be adverse health effects. Most commonly these include gas, bloating and cramps due to its high fiber content.
Eating too much spinach can also interfere with the body’s ability to absorb nutrients. This is because the Oxalic acid present in spinach binds with zinc, magnesium, and calcium, hindering the body’s ability to absorb the nutrients.
Individuals who are on blood thinning medications should be careful not to suddenly increase their consumption of spinach (as well as other leafy greens). This is because spinach is high in vitamin K, which can reverse the effects of anticoagulant drugs if it is suddenly increased in the body. That does not mean these individuals should cut out vitamin K completely, it just means they should be smart and consistent about how much spinach and vitamin K they consume.
Eating too much spinach can also be harmful if you have kidney problems. The oxalic acid in spinach can bind with excess calcium in your kidneys and create kidney stones. If you know you are prone to developing kidney stones, you should eat spinach in moderation.
Spinach is also high in potassium, which can be dangerous for people who already have severe kidney disease. The reduced function of the kidneys causes potassium to build up in the bloodstream, which can then interrupt your normal heart rhythm.
While it’s important to know the risks if you have certain health conditions, for the average person spinach is a healthy dietary addition. When consumed in moderate amounts, the health benefits of eating spinach far outweigh the negative effects for most people.