Dried fruits retain most of the nutritional value of fresh fruits, and so are included with fresh fruit in dietary recommendations by U.S. and world health agencies. The specific nutrient content of the different dried fruits reflect their fresh counterpart and the processing method (e.g., traditional dried fruits versus sugar infused dried fruit). In general, all dried fruits provide essential nutrients and an array of health protective bioactive ingredients, making them valuable tools to both increase diet quality and help reduce the risk of chronic disease. The combination of nutritional value and enjoyable taste is the reason dried fruits have been popularly considered a healthy food for millennia. Because they are naturally resistant to spoilage, easy to store and transport and relatively low in cost, dried fruits are a convenient way to increase the number of servings of fruit in the diet. The following are basic nutritional facts on dried fruits:
Like fresh fruits, dried fruits have very low sodium content.
Dried fruits are a particularly significant source of dietary fiber and potassium. On a per serving basis (1/4 cup)
dried fruits are among the top 50 contributors of these nutrients among all foods in the American diet. Amongst all fruits, they are among the top 5 contributors of potassium and fiber.
Dried fruits also provide essential nutrients that are otherwise low in today's diets, such as vitamin A (apricots and peaches), calcium (figs), vitamin K (dried plums), iron, and copper. Raisins and dried plums are among the 50 major contributors of boron in the American diet raisins having the highest concentration at 2.2 mg per 100 g.Boron, a putative trace element is important for the growth and maintenance of healthy bones and joints.
Traditional dried fruits have no added sugars. Drying removes some of the fruits' water and so concentrates their natural sugars. This, however, is normalized by a smaller serving size (e.g. 40 g for raisins versus 126 g for grapes, Nutrition Labeling and Education Act).For this reason, total sugar and energy values are similar between dried and fresh fruit. Most traditional dried fruits have minimal amounts of sucrose, their sugar is in the form of fructose and glucose.
Health
Protective components
Dried fruits are not only important sources of vitamins, minerals and fiber in the diet but also provide a wide array of bioactive components or phytochemicals. These plant compounds are not designated as traditional nutrients since they are not essential to sustain life, but play a role in health and longevity and have been linked to a reduction in the risk of major chronic disease. Convincing evidence suggest that the benefits of phytochemicals may be even greater than is currently understood, since they affect metabolic pathways and cellular reactions believed to be involved in the etiology of a wide range of chronic disease. However, the precise mechanisms by which specific compounds exert their biological effect remains largely hypothetical and are thus subject of intense investigation. The following are some of these health protective components in dried fruits:
Dried fruits are an excellent source of polyphenols and phenolic acids.These compounds make up the largest group of phytochemicals in the diet and appear to be, at least in part, responsible for the potential benefit associated with the consumption of diets abundant in fruits and vegetables. Different dried fruits have unique phenolic profiles. For example, the most abundant in raisins are the flavonols quercetin and kaempferol and the phenolic acids caftaric and coutaric acid. Dates contain quercetin, apigenin and luteolin; dried plums are very high in chlorogenic and neochlorogenic acids; cranberries and blueberries are high in anthocyanins and anthocyanidins.
By virtue of their high polyphenol content, dried fruits are an important source of antioxidants in the diet. These phytochemicals are believed to account for a major portion of antioxidant capacity in plant foods. Antioxidants can lower oxidative stress and so prevent oxidative damage to critical cellular components. Dried apricots and peaches are also important sources of carotenoids. These compounds not only are precursors of vitamin A but they also have antioxidant activity.
Dried fruits such as dried plums provide pectin, a soluble fiber that may lower blood cholesterol levels.
Dried fruits such as raisins are a source of prebiotic compounds in the diet. They contain fructooligosacharides like inulin, naturally occurring fiber-like carbohydrates that contribute to colon health.
Dried fruits contain organic acids such as tartaric acid (raisins) and sorbitol (dried plums). These organic acids and fiber appear to work synergistically to maintain a healthy digestive system. They may also help increase the bioavailability of minerals in the diet, such as calcium and iron
Glycemic Index
Traditional dried fruit have a low to moderate Glycemic Index (GI) – a measure of how a food affects blood sugar levels. GI measures an individual's response to eating a carbohydrate-containing food (usually 50 grams of available carbohydrates) compared to the individual's response to the same amount of carbohydrates from either white bread or glucose. Carbohydrate containing foods are classified as high (above 70), moderate (56–69), or low (0–55) GI.Foods with high fiber content generally have a low GI. However, other factors also contribute to a food's glycemic response, such as the type of carbohydrate or sugar present, the physical characteristic of the food matrix and the presence of organic acids. All studies assessing the GI of dried fruit show that they are low to moderate GI foods and that the insulin response is proportional to their GI. Factors thought to contribute to this glycemic response include the viscous texture of dried fruits when chewed; their whole food matrix; the presence of phenolic compounds and organic acids and the type of sugar present (about 50% fructose in most traditional dried fruit).
Oral health
Dried fruit may promote healthy teeth and gums. Contrary to longstanding popular perception that dried fruits such as raisins promote cavities, recent studies indicate that they may benefit oral health. Bioactive compounds found in dried fruit appear to have antimicrobial properties that inhibit the growth of bacteria that cause cavities and gum disease. For example, oleanolic acid, oleanolic aldehyde and 5-(hydroxymethyl)-2-furfural found in raisins have been shown to inhibit the growth of two species of oral bacteria: Streptococcus mutans, which cause cavities, and Porphyromonas gingivitis, which causes periodontal disease. Oleanolic acid also blocks in vitro biofilm formation by S. mutans and the adherence of S. mutans to experimental surfaces. This quality is significant because adherence is bacteria's first step in forming dental plaque, the film that accumulates on teeth.
Raisins have been thought of as cariogenic foods because they are sweet and sticky. However, it has been shown that perceived "stickiness" bears little relationship to the actual retention of food particles on tooth surfaces or to the clearance of food-derived sugars from saliva. In these studies, raisins have been shown to exhibit rapid clearing rates, placing them among the least retentive foods within a sample of 21 commercially available snack foods. Investigators showed that raisins were almost completely cleared from tooth surfaces five minutes after chewing and swallowing. It is probable that these properties also apply to other traditional dried fruit because they have similar fiber content and physical matrix as raisins.
A recent clinical study investigated raisins and oral health in 7–11 year old children. Researchers measured dental plaque acidogenicity after the children ate raisins, raisin-containing cereal and cereal alone. The plaque pH was measured prior to and 2, 5, 10, 15 and 30 minutes after consumption of each food. Eating raisins alone did not lower plaque pH below pH 6 over the 30-minute test. This indicates that they did not lower plaque pH to the critical level that would increase the risk of caries. Addition of raisins to bran flakes promoted less plaque pH drop beyond 10 minutes when compared to bran flakes alone. Raisins were less acidogenic than a raisin bran cereal, bran flakes or a 10% sucrose solution. This shows that raisins were less retentive on tooth surfaces and were rapidly cleared after chewing. They also enhanced clearance rate of the chewed cereal particles so that they lowered the acidogenicity when added to bran flakes.While this research has been conducted on raisins, preliminary evidence indicates that these findings may also be replicated using other traditional dried fruit.
Finally, the predominant sugars in traditional dried fruit are fructose and glucose, with trace amounts of sucrose. It is sucrose that serves as a substrate for the synthesis of adherent compounds in dental plaque, the causal agent in tooth decay and gum disease. Studies comparing the cariogenicity of different sugars (sucrose, maltose, lactose, fructose and glucose) invariably demonstrate that sucrose, more than any other type of sugar, induces the most smooth-surface-type and fissure-type caries.
Bone health
Dried fruits, particularly dried plums, may promote bone health. Research conducted with dried plums indicates that they have a role in supporting bone health. This may be because they are rich in phenolic compounds, such as phenolic acids and lignans, which may stimulate bone formation and enhance osteoblast activity. Animal studies have shown that dried plums protect, and even reverse, bone loss in models of osteopemia (low bone mineral density, a precursor to osteoporosis). For example, feeding dried plums reduced loss of bone in ovariectomized rats in a dose-dependent fashion. It also increased circulating insulin-like growth factor (IGF-1). Serum IGF-1 is known to stimulate bone formation, osteoblast activity, and collagen synthesis and has a role in bone remodeling.A follow-up study showed that dried plums restored loss of tibial and femoral density in an osteopenic rat model of osteoporosis. Various doses of dried plums were also able to significantly improve trabecular bone structure and increase tibial bone volume and connectivity. These observations are unique because it is believed that once bone volume and connectivity are lost they cannot be brought back to normal. In studies where bone loss was produced by skeletal unloading, a diet containing dried plums also enhanced bone recovery by increasing bone mineral density and trabecular bone structure. The effect was similar to parathyroid hormone treatment.
In vitro studies have shown that dried plum polyphenols suppress osteoclast differentiation and activity under normal, oxidative stress and inflammatory conditions. These studies also show that dried plum enhances osteoblast ALP activity, calcified nodule formation and type I collagen cross-linking. These changes may be mediated by up regulating transcription and growth factors.In addition to animal studies, the findings of a short-term (three month) clinical trial showed that the consumption of dried plums (100 grams per day) by postmenopausal women significantly increased markers of bone formation including serum total alkaline phosphatase (ALP) activity, bone-specific ALP activity and IGF-1.Currently, a one-year comparative control randomized study is being conducted to confirm these findings and to determine whether dried plum increases bone mass or prevents further bone loss in osteopemic postmenopausal women. While the mechanism of action of dried plums remains to be elucidated, researchers believe that phenolic compounds may be the major bone protective agents. However, essential nutrients like vitamin K and minerals like potassium and the trace element boron may contribute to their beneficial effect. Dried plums are also high in copper, which is essential for bone building processes as it is a co-factor of lysyl oxidase. This enzyme promotes cross-linking of lysine residues in collagen and elastin.
Intestinal health
Dried fruits promote digestive health. There is considerable research supporting the role of dried fruit in regulating bowel function and maintaining a healthy digestive system.Dried plums are well known in common experience to alleviate constipation. Some researchers ascribe it to their high fiber content: the combination of soluble (49%) and insoluble fiber (51%) in dried plums probably acts in a gentle way in the lower intestines, softening stool increasing bulk and promoting intestinal motility. More recent research indicates that they also provide prebiotic compounds such as fructans, which help to maintain intestinal balance and colonic health.
Weight management
Dried fruits may contribute to healthy body weights. Emerging data suggests that dried fruit intake is not associated with higher body weight. On the contrary, recent analysis of NHANES (1999–2004) data indicates that diets high in dried fruits are associated with lower Body Mass Index (BMI), reduced overweight and obesity and improved diet quality.Moreover, after adjusting for potential cofounders (socioeconomic status, education, exercise), these data show that prevalence of overweight/obesity and prevalence of abdominal obesity are lower for those who consume dried fruits than for those who did not. Finally, emerging data suggest that dried fruit promotes satiety by affecting the levels of hormones such as leptin that regulate appetite.
Healthy diet
Dried fruits meet dietary guidelines for daily fruit servings and address barriers to fruit intake. The greatest benefit of including dried fruits regularly in the diet is that it is a means to expand overall consumption of fruit and the critical nutrients they contain. Dried fruits have the advantage of being very easy to store and distribute, they are readily incorporated into other foods and recipes, relatively low cost and present a healthy alternative to sugary snacks. The scientific basis for the recommendations to increase fruit consumption in the diet by health authorities is the epidemiological evidence that individuals who regularly eat generous amounts of these foods have lower rates of cardiovascular disease, obesity, several cancers, diabetes and other chronic diseases. Dried fruits, with their unique combination of essential nutrients, fiber and bioactive compounds are a convenient step toward healthier eating and a means to bridge the gap between recommended intake of fruits and the amount Americans actually consume.
