August 2015 Issue
Top 10 High-Fiber Foods
By Judith C. Thalheimer, RD, LDN
Today's Dietitian
Vol. 17 No. 8 P. 34
These surprising sources have unexpected nutrient profiles that make them fantastic additions to a healthful diet.
High-fiber foods provide more than just roughage. Many also are an excellent source of healthful, disease-fighting nutrients and phytochemicals.
In this article, Today's Dietitian looks at 10 foods with surprising amounts of fiber and unexpected nutrient profiles that demonstrate the health-promoting power of choosing naturally high-fiber foods.
Fabulous Fiber
A 2014 meta-analysis concluded that higher fiber intake was associated with a lower risk of death from all causes. In fact, for every additional 10 g of fiber subjects ate, their risk of death decreased by 10%.1 Fiber has long been known for its usefulness in treating constipation, but higher fiber diets also are linked to a decreased risk of breast cancer and stroke, and may reduce systemic inflammation.2-5 The American Heart Association recommends high-fiber foods for weight management and reduction of cardiovascular disease (CVD) risk.6 The American Diabetes Association recommends them for blood glucose control.7 On the face of it, fiber appears to be the magic bullet the public is looking for.
The truth is that "there's no one food or food component that will reduce disease risk," says Colleen Doyle, MS, RD, managing director of nutrition and physical activity for the American Cancer Society. "It's likely that it's the synergy between many nutrients—fiber, vitamins, minerals, phytochemicals, and antioxidants—that give you the most protection." It's known that antioxidants work together to protect plants from oxidative damage. When humans consume plant foods, they ingest this same mix of antioxidants—along with the plant fiber.8 This cooperative effect may contribute to the impressive health benefits researchers find when examining the health effects of fiber intake.
The 2010 Dietary Guidelines for Americans recommend 25 g of fiber per day for women and 38 g per day for men, and encourage a dietary pattern with plenty of fiber-rich plant foods.9 "These foods are the foundation of healthful diets like the Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and Therapeutic Lifestyle Changes (TLC) that are recognized for their ability to combat disease and promote health," says Ximena Jimenez, MS, RDN, LD, a national spokesperson for the Academy of Nutrition and Dietetics (the Academy).
Increasing fiber improves the overall quality of a diet because naturally high-fiber foods are packed with vitamins, minerals, and phytochemicals. "They're the best sources of vitamins, minerals, and flavonoids and have plenty of vitamin C, [vitamin] E, beta carotene, zinc, selenium, and copper—powerful antioxidants that may play a crucial role in the management or prevention of diseases such as macular degeneration, some forms of arthritis, heart disease, and some cancers," Jimenez says.
High Fiber … and More
In addition to helping people reach daily fiber-intake goals, eating a variety of naturally high-fiber foods such as the ones discussed in this article can dramatically improve diet quality. There are plenty of fiber- and nutrient-packed choices for all plates and palates. Here are 10 surprising sources with unexpected nutrient profiles that illustrate just how healthful fiber-rich foods can be.
1. Almonds
Almonds aren't only the highest fiber nut in the USDA's nutrient database but they also have the most calcium and antioxidant vitamin E.10 A 1-oz serving of almonds (about 23 nuts) provides 3 g of fiber, or 12% of the recommended DV for a 2,000 kcal diet.10 One recent randomized controlled trial concluded that substituting almonds for a high-carbohydrate snack could help prevent the onset of CVD in healthy individuals by reducing LDL cholesterol and central adiposity while maintaining HDL cholesterol levels.11 Another study found that overweight and obese women lost more weight and had greater improvement in CVD risk factors if almonds were a part of their weight-loss diet.12
"Almonds are a good source of vitamins, minerals, and antioxidants, including potassium, magnesium, vitamin E, and phosphorous," says Jessica Crandall, RD, CDE, a national spokesperson for the Academy. "They can help lower total and LDL cholesterol and have been shown to help lower blood glucose impact of carbohydrates with which they are eaten." A small study in the March 2007 issue of Metabolism found that the more almonds eaten with a white-bread meal, the less blood sugar levels rose in the two hours following that meal.13
A palmful of almonds makes an easy and satisfying snack, or, Crandall suggests, "try tossing chopped almonds on salads or yogurt, or adding them into muffins or breads."
2. Artichokes
Topping the vegetable list for fiber content is the artichoke. One medium artichoke has 10.3 g of fiber, or 41% DV.10 Moreover, artichokes are an excellent source of vitamin C and a good source of folate and magnesium.10 "Artichokes have extremely high levels of antioxidants," Crandall says. A 2006 study of antioxidant levels in various foods ranked artichokes the highest of all vegetables studied, and in the top 10 of the 1,120 foods tested based on typical serving size.8
Since human cells are unable to produce high levels of antioxidants on their own, dietary antioxidants such as those in artichokes may reduce oxidative damage known to contribute to aging and many diseases and conditions.8
Canned artichoke hearts are available, but preparing and eating fresh artichokes can be a fun option. For information on preparing, cooking, and eating artichokes, visit www.oceanmist.com.
3. Avocados
The rich, creamy texture of avocados hides an average of 54% DV for fiber.14 This nutrient-dense fruit also provides plenty of vitamins C, E, K, and B6, as well as folate, potassium, and magnesium, and significant amounts of beta-carotene and lutein.15
Beyond the fiber content, the biggest surprise about avocados is their fat profile. Only olives rival avocados for monounsaturated fat content in a fruit or vegetable.10
Nearly 67% of the fat in avocados is heart-healthy monounsaturated, and another 12% is polyunsaturated.10 What's more, the fats in avocado increase the absorption of the fat-soluble vitamins (A, D, E, and K) and also may help the body absorb phytochemicals.15
Dice some avocado into salads or add a few slices to a breakfast sandwich. Crandall recommends using mashed avocados in place of condiments such as mayonnaise. "They add good nutritional properties as well as a creamy texture," Crandall says.
4. Cloud Ear Fungus
An edible fungus often used in Asian dishes such as Chinese hot and sour soup, cloud ears pack a whopping 78% DV of fiber per cup.10 They're also an excellent source of manganese and a good source of selenium and riboflavin.10 While the mechanism of action is still unknown, preliminary research in rabbits indicated this black tree fungus may help prevent atherosclerosis and coronary heart disease by protecting against plaque buildup and arterial stenosis with an effect better than aspirin.16
The cloud ear is known for its crunchy texture and ability to soak up the flavor of the ingredients around it.17 While uncommon in Western cooking, the cloud ear fungus is a surprising source of fiber that illustrates the diversity of fiber sources available in the plant kingdom.
5. Collard Greens
Although its close cousin kale gets all the press, collard greens are at least as health promoting. One cup of boiled, chopped collards provides 30% DV of fiber—three times the fiber of kale.10,18 Collards also have three times as much calcium, and twice as much protein, iron, and riboflavin as kale.18
Collard greens bind bile acids at the same rate as kale, potentially reducing CVD and cancer risk.19 Furthermore, one cup of boiled collards has close to three times the DV of vitamin A and is packed with phytochemicals.10 Cruciferous vegetables such as collard greens are known for their antioxidant phytochemicals called phenolic compounds. One of the most important groups of antioxidants, phenolics are believed to protect against cancer and heart disease.20 "Cruciferous vegetables like collard greens contain sulforaphane, a phytochemical that may reduce the risk of stomach, breast, and skin cancers," Doyle says.
After washing the collard greens, removing the spines, and slicing them into strips to speed cooking, they can be sautéed, steamed, baked, fried, blanched, or added to soups, stews, or bean dishes.21
6. Dates
A staple food in the Arab world for centuries, dates are a sweet source of fiber.22 Just one Medjool date provides 6% DV for dietary fiber, but this sweet treat also contains nearly four teaspoons of naturally occurring sugar.10 Despite being sugar-packed, many date varieties have a low-glycemic index, which means they raise blood glucose relatively slowly.23
Studies have shown that dates have antioxidant properties and may protect against cancer and inflammation, stimulate the immune system, and have a protective effect on the stomach, liver, and nerves.24 A 2013 study on the chemical composition of date fruits found the main chemical components include phenolic acids and carotenoids.22 Dates also have plenty of vitamin B6, magnesium, potassium, copper, and manganese.14
Crandall recommends adding chopped dates to muffins or salads, or simply eating a date as part of a balanced snack.
7. Lentils
Beans are a well-known source of fiber, but their fellow legumes, lentils, often don't get the attention they deserve. One cup of boiled lentils has 15.6 g of fiber—that's more than 62% DV.10 A 2012 randomized controlled trial compared the effect of a low-glycemic-index diet high in wheat fiber with one high in legumes such as lentils and beans in subjects with type 2 diabetes. The study found that, while both diets reduced A1c, weight, waist circumference, total cholesterol, triglycerides, blood pressure, heart rate, and absolute coronary heart disease risk, the diet that included 1 cup of legumes per day had a greater effect than the wheat-fiber diet.25
"Besides being low in calories and packed with fiber and phytochemicals, beans and lentils are a great source of protein," Doyle says. One cup of cooked lentils provides 18 g of protein and is an exceptional source of folate and an excellent source of thiamin, iron, phosphorus, potassium, copper, and manganese.14
"Lentils can be easily added to soups and stews as well as mixed into salads and sauces," Crandall says.
8. Potatoes
Often demonized as a low-value starchy vegetable, potatoes actually are quite healthful. For example, one large Russet potato eaten with the skin provides 6.9 g of fiber (nearly 28% DV).10 It also has 64% DV of vitamin C and 47% DV of potassium, and is an excellent source of B6, manganese, magnesium, and niacin, and a good source of folate, copper, phosphorous, iron, thiamin, and pantothenic acid.14
As one of the top five crops consumed worldwide, the potato is one of the most important sources of antioxidants in the human diet.26 Yellow and purple varieties have higher concentrations of antioxidants such as phenolic acids and carotenoids (yellow) or anthocyanins (purple). Consumption of these pigmented potatoes may reduce inflammation and DNA damage and affect the expression of immune cells.27
The 2010 Dietary Guidelines for Americans identified both potassium and fiber as nutrients of concern for underconsumption.9 Potatoes and beans are the least expensive sources of potassium and fiber commonly consumed in the American diet.28
Potatoes are a versatile choice. Baking, roasting, sautéing, and boiling all are preferable cooking methods to deep frying, but eating potatoes with the skin on is essential, since most of the fiber is in the skin.29
9. Quinoa
Although quinoa typically is considered a whole grain, it's actually the seed of a grainlike crop closely related to beets.30 With 5.2 g of fiber in one cup cooked, quinoa provides more than 20% DV (more fiber than one cup of cooked brown rice).10 This gluten-free option is a good source of magnesium and phosphorus and a very good source of manganese, and quinoa provides complete high-quality protein.14,31
There are whole grains that have more protein than quinoa, but only amaranth is equal to quinoa in providing all of the essential amino acids in the ideal amounts.31 While it isn't necessary to make every meal a source of complete protein, quinoa's protein quality sets it apart from most other whole grains.
Be sure to rinse quinoa to remove the bitter outer coating. After boiling the quinoa, drain off any excess water, and return the cooked quinoa to the pan to rest for 15 minutes to avoid watering down dishes.30 Grain or seed, this little powerhouse works well alone, or in a wide variety of hot or cold dishes.
10. Raspberries
Raspberries may seem like they're mostly juice, but actually they have twice the fiber of blueberries or strawberries. The 8 g of fiber in one cup of raspberries provides 32% DV.10 Raspberries also are an excellent source of vitamin C (54% DV in one cup) and manganese, and a good source of vitamin K.14 Like other berries, raspberries are a potent source of cancer-fighting antioxidants, and fermentation of raspberry seeds by gut bacteria may help lower serum triglycerides and CVD risk.32,33
"Berries are thought to offer particularly powerful cancer-preventive effects," Doyle says, "because they contain antioxidants like polyphenols, including ellagic acid and anthocyanins that counteract, reduce, and repair damage to cells."
Plant Sources Reign
From fruits to fungi, and from grains to greens, roots, nuts, and seeds, plant foods are a nutrient-dense source of natural dietary fiber. Encouraging clients to consume plant foods (whether it's berries at breakfast, quinoa salad for lunch, or dried fruit and nuts for a snack) will increase fiber intake, while simultaneously providing a whole host of health-promoting and disease-fighting nutrients and phytochemicals.
— Judith C. Thalheimer, RD, LDN, is a freelance nutrition writer, a community educator, and the principal of JTRD Nutrition Education Services.
References
1. Yang Y, Zhao LG, Wu QJ, Ma X, Xiang YB. Association between dietary fiber and lower risk of all-cause mortality: a meta-analysis of cohort studies. Am J Epidemiol. 2015;181(2):83-91.
2. Yang J, Wang HP, Zhou L, Xu CF. Effect of dietary fiber on constipation: a meta analysis. World J Gastroenterol. 2012;18(48):7378-7383.
3. Dong JY, He K, Wang P, and Qin LQ. Dietary fiber intake and risk of breast cancer: a meta-analysis of prospective cohort studies. Am J Clin Nutr. 2011;94(3):900-905.
4. Chen GC, Lv DB, Pang Z, Dong JY, Liu QF. Dietary fiber intake and stroke risk: a meta-analysis of prospective cohort studies. Eur J Clin Nutr. 2013;67(1):96-100.
5. Jiao J, Xu JY, Zhang W, Han S, Qin LQ. Effect of dietary fiber on circulating C-reactive protein in overweight and obese adults: a meta-analysis of randomized controlled trials. Int J Food Sci Nutr. 2015;66(1):114-119.
6. Fiber up, slim down. American Heart Association website. http://www.heart.org/HEARTORG/GettingHealthy/WeightManagement/LosingWeight/Fiber-Up-Slim-Down_UCM_322704_Article.jsp. Updated May 5, 2015.
7. Diabetes superfoods. American Diabetes Association website. http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/making-healthy-food-choices/diabetes-superfoods.html#sthash.yKUZ90aB.dpuf. Updated February 2, 2015.
8. Halvorsen BL, Carlsen MH, Phillips KM, et al. Content of redox-active compounds (ie, antioxidants) in foods consumed in the United States. Am J Clin Nutr. 2006;84(1):95-135.
9. US Department of Agriculture, US Department of Health and Human Services. Dietary Guidelines for Americans, 2010. 7th ed. Washington, DC: US Government Printing Office; 2010.
10. United States Department of Agriculture. National Nutrient Database for Standard Reference, Release 27. http://ndb.nal.usda.gov/ndb/foods
11. Berryman CE, West SG, Fleming JA, Bordi PL, Kris-Etherton PM. Effects of daily almond consumption on cardiometabolic risk and abdominal adiposity in healthy adults with elevated LDL-cholesterol: a randomized controlled trial. J Am Heart Assoc. 2015;4(1)e000993.
12. Abazarfard Z, Salehi M, Keshavarzi S. The effect of almonds on anthropometric measurements and lipid profile in overweight and obese females in a weight reduction program: a randomized controlled clinical trial. J Res Med Sci. 2014;19(5):457-464.
13. Josse AR, Kendall CW, Augustin LS, Ellis PR, Jenkins DJ. Almonds and postprandial glycemia—a dose-response study. Metabolism. 2007;56(3):400-404.
14. Nutrition facts. SELF Nutrition Data website. http://nutritiondata.self.com
15. Nutrition facts. California Avocado Commission website. http://www.californiaavocado.com/nutrition/nutrients
16. Fan YM, Xu MY, Wang LY, et al. The effect of edible black tree fungus (Auricuaria auricula) on experimental atherosclerosis in rabbits. Chin Med J (Engl). 1989;102(2):100-105.
17. Cloud ears and wood ears. About.com website. http://chinesefood.about.com/library/blchineseing3.htm
18. Engelmann L. Move over, kale! Collard greens, the new super food. AtlantiCare Well4Life website. http://www.atlanticarewell4life.org/Blog/Move-over-kale-Collard-greens-the-new-super-food
19. Kahlon TS, Chiu MC, Chapman MH. Steam cooking significantly improves in vitro bile acid binding of collard greens, kale, mustard greens, broccoli, green bell pepper, and cabbage. Nutr Res. 2008;28(6):351-357.
20. Cartea ME, Francisco M, Soengas P, Velasco P. Phenolic compounds in Brassica vegetables. Molecules. 2011;16(1):251-280.
21. How to cook collard greens. WikiHow website. http://www.wikihow.com/Cook-Collard-Greens
22. Tang ZX, Shi LE, Aleid SM. Date fruit: chemical composition, nutritional and medicinal values, products. J Sci Food Agric. 2013;93(10):2351-2361.
23. Glycemic index and diabetes. American Diabetes Association website. http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/understanding-carbohydrates/glycemic-index-and-diabetes.html. Updated May 14, 2014.
24. Vayalil PK. Date fruits (Phoenix dactylifera Linn): an emerging medicinal food. Crit Rev Food Sci Nutr. 2012;52(3):249-271.
25. Jenkins DJA, Kendall CWC, Augustin LSA, et al. Effect of legumes as part of a low glycemic index diet on glycemic control and cardiovascular risk factors in type 2 diabetes mellitus: a randomized controlled trial. Arch Intern Med. 2012;172(21):1653-1660.
26. Lovat C, Nassar AM, Kubow S, Li XQ, Donnelly DJ. Metabolic biosynthesis of potato (Solanum tuberosum L.) antioxidants and implications for human health [published online February 12, 2015]. Crit Rev Food Sci Nutr. doi: 10.1080/10408398.2013.830208.
27. Kaspar KL, Park JS, Brown CR, Mathison BD, Navarre DA, Chew BP. Pigmented potato consumption alters oxidative stress and inflammatory damage in men. J Nutr. 2011;141(1):108-111.
28. Drewnowski A, Rehm CD. Vegetable cost metrics show that potatoes and beans provide most nutrients per penny. PLoS One. 2013;8(5):e63277.
29. Are potatoes healthy? Yes they are! Potatoes Goodness Unearthed website. http://www.potatogoodness.com/nutrition/
30. Walsh D. 5 most common mistakes when cooking quinoa. Bon Appétit website. http://www.bonappetit.com/test-kitchen/common-mistakes/article/5-most-common-mistakes-when-cooking-quinoa. Updated February 23, 2012.
31. Whole grain protein power! Whole Grains Council website. http://wholegrainscouncil.org/newsroom/blog/2014/02/whole-grain-protein-power. Updated February 18, 2014.
32. Fact sheets. Berry Health Benefits Network website. http://berryhealth.fst.oregonstate.edu/health_healing/fact_sheets/
33. Kosmala M, Zdunczyk Z, Juskiewicz J, et al. Chemical composition of defatted strawberry and raspberry seeds and the effect of these dietary ingredients on polyphenol metabolites, intestinal function, and selected serum parameters in rats. J Agric Food Chem. 2015;63(11):2989-2996.
Recipes
Quinoa and Grape Curry Salad
Serves 6
Ingredients
21/2 cups water
1 tsp kosher salt
1 cup brown or red quinoa, well-rinsed
2 cups green and red seedless California grapes, halved
2 stalks celery, thinly sliced
1/2 cup chopped toasted walnuts
3 large radishes, thinly sliced
3 scallions (white and green parts), thinly sliced
2 T chopped fresh dill
1 jalapeño, seeded and minced
Curry Vinaigrette
1 garlic clove, minced
1 tsp kosher salt
2 tsp curry powder
3 T white wine vinegar
1/3 cup extra-virgin olive oil
1/4 tsp freshly ground black pepper
Directions
1. In a medium saucepan, bring water and salt to a boil. Stir in quinoa. Lower heat, cover, and simmer until quinoa is tender, about 12 to 15 minutes. Drain any excess water.
2. Transfer quinoa to a large bowl and stir in grapes, celery, walnuts, radishes, scallions, dill, and jalapeño.
3. To make vinaigrette: In a small bowl, mash garlic and salt together until it becomes a paste. Add curry powder, vinegar, olive oil, and pepper; mix well and pour over quinoa salad.
Nutrient Analysis per serving
Calories: 389; Total fat: 17 g; Sat fat: 2 g; Trans fat: 0 g; Cholesterol: 0 mg; Sodium: 658 mg; Total carbohydrate 27 g; Dietary fiber 4 g; Sugar: 9 g; Protein 6 g.
— RECIPE COURTESY OF CALIFORNIA TABLE GRAPE COMMISSION, WWW.GRAPESFROMCALIFORINA.COM
Easy Baked Artichokes
Serves 2
Ingredients
2 medium or large artichokes, rinsed and trimmed
1 lemon, halved
4 T extra-virgin olive oil
4 cloves garlic, slivered
Sea salt to taste
4 sheets heavy duty foil wrap
Directions
1. Preheat oven to 425˚ F.
2. Squeeze one-half lemon over each trimmed artichoke.
3. Drizzle each artichoke with 2 T olive oil (allowing oil to go in between artichoke leaves).
4. Stuff two cloves of slivered garlic between leaves of each artichoke. Sprinkle with salt.
5. Double wrap each artichoke with two layers of heavy duty foil, sealing well on top by twisting and pinching foil packets.
6. Place foil packets in oven and bake 1 hour and 20 minutes for jumbo- to large-size artichokes, or 1 hour for medium-size artichokes.
7. Remove artichokes from oven. When cool enough to handle, unwrap and enjoy with additional lemon, or scoop out the fuzzy center and use artichoke as an edible bowl filled with your favorite soup, stew, or dip.
Nutrient Analysis per serving
Calories: 237; Total fat: 20 g; Sat fat: 2 g; Trans fat: 0 g; Cholesterol: 0 mg; Sodium: 73 mg; Total carbohydrate: 17 g; Dietary fiber: 10 g; Sugar: 2 g; Protein: 4 g
— RECIPE COURTESY OF OCEAN MIST FARMS