Vitamin K is responsible for activating certain clotting factors in the blood. Those who are prescribed a blood thinner, such as Coumadin, are told to avoid foods high in Vitamin K because this will counteract the effects of the blood thinner. Leafy vegetables (e.g. kale, collards, turnip greens, Swiss chard, salad greens, parsley, spinach) are the highest sources of vitamin K. Other vegetables, egg yolk, soybeans, soybean and canola oils, and some nuts also provide vitamin K at lower levels. Fruit is not a significant source of vitamin K. Abrupt increases or decreases in the intake of vitamin K-rich foods should be avoided, as might occur with seasonal food choices. We know of nothing that will “counteract” eating leafy greens. However, there is some evidence that patients with diets higher in vitamin K do well with a higher dose of the anticoagulant, while those with lower vitamin K intakes have lower doses of the anticoagulant.
It is most important to follow the instructions of your physician and closely monitor the diet and medicine levels to find the right balance.