5 Serious Side Effects of Spinach Although spinach is one of the healthiest vegetables to eat, an excessive intake of this plant can be dangerous. Here are five serious side effects that can occur when you eat too much spinach. 1. Poor Mineral Absorption This prevents the body from properly absorbing these minerals and can hamper its functionality. 2. Teeth Coarseness These crystals may cause your teeth to become temporarily coarse or gritty after consumption. 3. Stomach Disorders While dietary fiber is good for healthy digestion, an excess can cause bloating, cramps and gas. 4. Anemia A lack of iron causes a lower red blood cell count, preventing your body from getting enough oxygen. 5. Kidney Stones Uric acid causes an increased buildup of calcium in the kidneys which then leads to the formation of kidney stones.