Diets that contain high fiber can interfere with absorption of levothyroxine. Levothyroxine replaces thyroid hormone and is prescribed to patients with hypothyroidism. Since fiber affects the rate of food absorption in the body, it can affect the amount of medication the body absorbs.
Cabbage, like other high-fiber foods, interferes specifically with iodine uptake. Preventing iodine from being absorbed inhibits the body from producing thyroid hormones.
Walnuts can also interfere with the absorption rate of levothyroxine. Walnuts are a high source of fiber and omega 3, which helps prevent cardiovascular diseases. The daily limit of walnut consumption when taking levothyroxine is 12 grams. Any amount beyond that will interfere with the medication.
St. John’s Wort
St. John’s Wort has traditionally been used for pain relief, anti-diarrhea, and anti-inflammatory treatment. It also has many drug contraindications including levothyroxine. It interferes with absorption time and decreased the activity of levothyroxine in the body.
Other sources of fiber include apples, raspberries, pears, black beans, peas, lentils, artichokes, broccoli, brussels sprouts and soybeans.
Changing the amount of fiber in a daily diet can affect the amount of levothyroxine the body absorbs therefore decreasing the effectiveness of the drug. This is due to the fact that fiber speeds up the absorption process of food in the body. If diet habits fluctuate, check thyroid hormones levels every six to eight weeks to assure normal hormone levels in the body. Maximum absorption of levothyroxine is best when taken early in the morning on an empty stomach one hour before consuming food.