What do beans, dried fruit and seeds have in common?  Well, each contains a myriad of health-promoting phytonutrients, but the one of focus for this article is fiber. According to the American Association of Cereal Chemists International, fiber is defined as

“the edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine. Dietary fiber includes polysaccharides, oligosaccharides, lignin, and associated plant substances. Dietary fibers promote beneficial physiological effects including laxation, and/or blood cholesterol attenuation, and/or blood glucose attenuation." 

The 2010 Dietary Guidelines recommend consuming 25g of fiber per day.  Typically, however, Americans consume around 12-18g per day, making fiber incorporation a challenge for food scientists.  This article takes a look at beans, dried fruits and selected seeds as opportunities to enhance the fiber content of foods.

Beans

A number of bean varieties are available to food scientists for use in food products.  Examples include such favorites as black beans, pinto beans, white beans, and kidney beans. Table 1 shows the average fiber content per 100g.  These offer potential application in a range of products including appetizers, soups, salads, and main dishes.        

Table 1: Nutrient Content of Selected Beans, Dried Fruits and Dried Seeds (g/100g edible portion)¹

¹Source: USDA National Nutrient Database

A host of studies reflects the beneficial effects of bean consumption. For example, Winham and her colleagues at Arizona State University examined the effect of consuming ½ cup pinto beans, black-eyed peas, or carrots (control) over eight weeks on blood lipids, C-reactive protein, glucose, insulin and hemoglobin A1c in mildly insulin-resistant adults.  Per the study, pinto beans significantly reduced total serum cholesterol and LDL cholesterol.  The authors suggested that pinto bean intake should be encouraged to help manage cholesterol.

In 2008, Papanikolaou and Fulgoni undertook a secondary analysis of data from the National Health and Nutrition Examination Survey (NHANES), conducted in 1999-2002, to determine nutrient intake and physiological values between bean consumers and non- consumers.  Based on data from 1,475 subjects, the results showed that consumption of a serving of dry beans per day resulted in higher intakes of dietary fiber, potassium, magnesium, iron, and copper compared to non-consumers.  Further analysis indicated that relative to non-consumers, bean consumers had a lower body weight, smaller waist size, and a reduced risk of being obese.  Consumption of baked beans was also associated with a lower systolic blood pressure. 

Therefore, although beans have gotten a “bum rap” in the media for their potential to cause flatulence, their high content of dietary fiber accords them a greater respect as nutritional powerhouses. 

Dried Fruits

With their origin dating back thousands of years ago to the Middle East, dried fruits are consumed today throughout the world in a wide range of foods and food occasions, from salads to desserts and from snacks to main meals.  California is the leading U.S. producer of dried fruits with raisins, dried plums, dates, figs, apricots, and peaches claiming the largest to smallest shares. 

American consumed, on average, a little over 2 lbs of dried fruit per person in 2006. Although better-known for their inherent sweetness and flavor, dried fruits are a rich source of fiber, as shown in Table 1.

In addition to fiber, dried fruits are rich in phytonutrients, particularly antioxidants such as polyphenols.  Raisins contain the flavanols, quercetin and kaempferol, and the phenolic acids, caftaric and coutaric acids.  Dates also contain quercetin, along with apigenin and luteolin.  Dried plums are high in chlorogenic and neochlorogenic acids.  Cranberries and blueberries are sources of anthocyanins  Another group of antioxidants, carotenoids are found in dried apricots and peaches.

Consumption of as little as 1/8 cup of dried fruit per day provides positive health benefits.  Keast and collaborators did a secondary analysis of data from the 1999-2004 NHANE survey.  They found that compared to non-consumers, those consuming 1/8 cup or more of dried fruit had a higher intake of dietary fiber, vitamins A, E, C, and K, and increased consumption of calcium, phosphorus, magnesium and potassium.  Dried fruit consumption was also associated with a higher overall diet quality score, a lower body weight/adiposity measure, and a smaller waist size.

Seeds

Interestingly, common seeds such as flax, pumpkin, sesame, sunflower and poppy are often overlooked as fiber sources.  Table 1 presents the fiber content of selected seeds.

Besides being good sources of fiber, seeds provide a wealth of health benefits.  For example, lignans are found abundantly in flax and sesame seeds.  Lignans act as antioxidants and are one of the major classes of phytoestrogens.  Because lignans are capable of binding to estrogen receptors and interfering with the cancer-promoting effects of estrogen on breast tissue, lignans have been studied for their effects on breast, prostate and colon cancer.

So, fellow food scientists, consider this a clarion call to look to beans, dried fruit and seeds as not just another way of boosting fiber, but as a way to further enhance a food product’s healthful image. 

References

Winham, D.M. Hutchins, A.M., and Johnston, C.S. (2007) “Pinto bean consumption reduces biomarkers for heart disease risk”. J. Am. Coll. Nutr. 26:23-249

Papanikolaou, Y. and Fulgoni, V.L. (2008) “Bean consumption is associated with greater nutrient intake, reduced systolic blood pressure, lower body weight and a smaller waist circumference in adult: Results from the National Health and Nutritional Examination Survey 1999-2002”. J. Am. Coll. Nutr. 27:569-576

Keast, D. R., O’Neil, C.E. and Jones, J. M. (2011) “Dried fruit consumption is associated with improved diet quality and reduced obesity in US adults: National Health and Nutrition Examination Survey, 1999-2002”. Nutr. Res. 31:460-467