Anticoagulant Therapy
Manual of Clinical Nutrition Management III- 4 Copyright © 2013 Compass Group, Inc.
Table III-3: Foods Rich in Vitamin K (9)
Food Serving Size Vitamin K (mcg)
Kale, cooked ½ cup 531
Spinach, cooked ½ cup 444
Collards, cooked ½ cup 418
Swiss chard, raw 1 cup 299
Swiss chard, cooked ½ cup 287
Mustard greens, raw 1 cup 279
Turnip greens, cooked ½ cup 265
Parsley, raw ¼ cup 246
Broccoli, cooked 1 cup 220
Brussels sprouts, cooked 1 cup 219
Mustard greens, cooked ½ cup 210
Collards, raw 1 cup 184
Spinach, raw 1 cup 145
Turnip greens, raw 1 cup 138
Endive, raw 1 cup 116
Broccoli, raw 1 cup 89
Cabbage, cooked ½ cup 82
Green leaf lettuce 1 cup 71
Prunes, stewed 1 cup 65
Romaine lettuce, raw 1 cup 57
Asparagus 4 spears 48
Avodaco 1 cup(cube, slice, puree) 30 - 48
Tuna, canned in oil 3 ounces 37
Blue/black-berries, raw 1 cup 29
Peas, cooked ½ cup 21
Some evidence suggests that cranberry products interact with anticoagulants to increase their effects (10).
However, a prospective randomized study of patients taking warfarin demonstrated that their INR levels
were not adversely affected by consumption of 1 cup of cranberry juice daily (11). Until further evidence is
available on a variety of cranberry products, patients consuming cranberry juice or products should be
educated, and their INR/PT should be monitored for the potential interaction. Although iceberg lettuce, red
cabbage, asparagus, cauliflower, and soybean oil are often reported as being high in vitamin K, these foods
contain much smaller amounts of vitamin K than the foods listed in Table III-3. Therefore, these foods and
other foods and beverages not listed (including coffee and tea) may be consumed as desired (9).
Special Considerations
Alcohol: Alcohol has shown to adversely affect the PT/INR ratio (5). Consuming more than 3 servings of
alcoholic beverages per day can increase the effect of warfarin (9). Limiting or avoiding alcohol may be
advised, and persons who do consume alcohol should consult with their physician.
High-protein, low-carbohydrate diets: A high-protein, low-carbohydrate diet pattern decreases the
INR/PT ratio (12). Case reports have demonstrated a decrease in the INR/PT ratio after initiation of a high-
protein, low-carbohydrate diet (12). The INR/PT ratio returned to a normal level after the diet was stopped
and the warfarin dose was decreased to the original dose. High-protein diets rapidly increase serum albumin
levels. This increase may result in more warfarin binding to serum albumin, thereby decreasing the
anticoagulant effect of warfarin (12). Patients receiving warfarin therapy should be monitored and educated
about the potential interaction that occurs with warfarin and high-protein, low-carbohydrate diets (12).
Dietary and herbal supplements: Several dietary and herbal supplements can interact with anticoagulants
and alter the INR/PT ratio (9). Dietary supplements that affect the INR/PT ratio include arnica, bilberry,
butcher’s broom, cat’s claw, dong quai, feverfew, forskolin, garlic, ginger, ginkgo, ginseng, horse chestnut,
inositol hexaphosphate, licorice, melilot (sweet clover), pau d’arco, red clover, St. John’s wort, sweet
woodruff, turmeric, willow bark, and wheat grass (9). In addition, persons who take vitamin and mineral
supplements containing vitamin K should be monitored. Vitamin and mineral supplements that are taken
consistently pose less of a problem than supplements that are taken sporadically (9). Vitamin E intakes
greater than 1,000 International Units (IU) may increase the risk of excess bleeding. Research suggests that