Americans consume an average of 5 to 14 g of fiber daily, according to the National Digestive Diseases Information Clearinghouse. This is well below the recommended 20 to 35 g per day. A low-fiber diet is a major cause of constipation. Constipation can also result from hypothyroidism, a disease in which your thyroid gland produces too few hormones. Although fiber does not directly affect thyroid function, consuming enough may help manage thyroid disease symptoms.
Benefits
As an indigestible carbohydrate, fiber promotes digestive function and positive cholesterol without contributing calories to your diet. Because fiber has a positive impact on your blood sugar and requires more chewing than low-fiber foods, fiber-rich foods keep you fuller longer between meals. These attributes are particularly important if you have hypothyroidism, according to Patricia Vasconcellos, a registered dietitian at Falmouth Hospital in Cape Cod, Massachusetts. This is because a reduced metabolism, weight gain and infrequent bowel movements are common complications. Maintaining positive cholesterol levels is important if you have gained excess weight, which increases your risk for heart disease.
Best Sources
In an interview with "Today's Dietitian," published in Oct. 2004, Vasconcellos listed fruits and vegetables as valuable fiber-rich dietary options for people with an underactive thyroid. Fruits particularly rich in fiber include raspberries, which supply 8 g per cup, and pears; one medium pear provides 5.5 grams. One medium, cooked artichoke contains 10 g of fiber. One cup of cooked lentils or split peas provides 15.5 to 16.5 grams. Other fiber-rich foods include oatmeal, barley, beans, air-popped popcorn and 100 percent whole-grain bread.
Foods to Avoid
Some fiber-rich foods contain goitrogens -- substances that interfere with thyroid function. If you have thyroid disease, the University of Maryland Medical Center recommends avoiding cruciferous vegetables, such as broccoli, brussels sprouts and kale, soybeans, mustard greens and millet. Avoiding refined foods, such as white bread, sugary sweets and white flour-based snack foods, such as pretzels and soda crackers, leaves more room in your diet for fiber-rich fare, guarding against weight gain and constipation. If you are intolerant to gluten -- a storage protein in wheat, barley and rye -- which may coexist with thyroid disease, avoid all breads, cereals, pasta and snack foods prepared with whole wheat flour, white flour, baking flour, pastry flour, rye, barley or gluten.
Additional Diet Suggestions
Regardless of whether your thyroid gland functions normally, fiber is a vital part of most healthy diets. To ensure ample fiber intake from commercially-prepared breads, cereals and pasta, choose items that list whole grains as main ingredients. If you have a thyroid condition, Vasconcellos recommends limiting soy to no more than one serving per day, which is equal to 8 oz. of soy milk or 4 oz. of tofu, and cruciferous vegetables to no more than one cup, two to three times per week. Low-fluid intake can also trigger constipation, so stay well hydrated by drinking water or other hydrating fluids, such as caffeine-free herbal tea, throughout each day.
References
- National Digestive Diseases Information Clearinghouse: Constipation
- "Today's Dietitian"; Thyroid Disease in Women -- Diagnostic Conundrum; Jennifer Sisk; Oct. 2004
- MayoClinic.com: Dietary Fiber: Essential for a Healthy Diet
- MayoClinic.com: High-Fiber Foods
- University of Maryland Medical Center: Hypothyroidism
- Johns Hopkins Medicine: Could You Have Celiac Disease and Not Know It?
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