California Raisins Health and Nutrition Research
Updated August 2015
Harold Bays MD, FACP, FACE, FNLA
This new 12-week study among 51 individuals with T2DM found that regular consumption of raisins — as compared to a variety of snack crackers — positively impacted both glucose levels and systolic blood pressure. The research, published in The Physician and Sportsmedicine journal, revealed study participants who consumed one ounce of raisins three times a day for the duration of the study, as compared to a group that ate a comparable amount of snack crackers, were shown to have:
- 23 percent reduction in postprandial (post-meal) glucose levels
- 19 percent reduction in fasting glucose
- A significant reduction (8.7 mmHg) in systolic blood pressure
These recent findings build on previous research announced at the American College of Cardiology’s Annual Scientific Session in 2012. In the early study, 46 men and women with pre-hypertension were randomly assigned to snack on raisins or pre-packaged commercial snacks that did not contain raisins or other fruits or vegetables, three times a day for 12 weeks. The results indicated that eating raisins three times per day:
- May significantly lower blood pressure among individuals with pre-hypertension when compared to other popular snacks.4
- May significantly lower postprandial (post-meal) glucose levels when compared to other popular snacks of equal caloric value.5
Both studies were conducted at the Louisville Metabolic and Atherosclerotic Research Center (L-MARC) by Harold Bays, MD, medical director and president of L-MARC.
2. “A Randomized, Un-blinded,Single Research Site, Comparator Study of Raisins Versus Alternative Snacks on
Cardiovascular Risk Factors In Generally Healthy Subjects”
Harold Bays MD, FACP, FACE, FNLA
This was a randomized,un-blinded, single research site, comparator study of raisins versus
alternative snacks on cardiovascular risk factors in generally healthy
subjects. Study participants were instructed to orally consume one prepackaged
serving of raisins (90 kcal/serving), or one prepackaged comparator snack (100
kcal/serving) orally administered three times daily before breakfast, lunch,
and dinner with 8 oz. of non-caloric fluid (preferably water) over 12 weeks.
Hypothesis of this study was that routine raisin consumption over 12 weeks would improve cardiovascular risk
factors compared to generally equal calorie alternative snacks.
The objective of this study was to compare the effects of raisins three times per day versus alternative snacks
three times per day on cardiovascular risk factors in generally healthy
Primary objective/endpoints were
change at week 12 for raisin versus control snacks regarding:
- Fasting plasma glucose
- Plasma glucose levels
2 hours after administration of 75 g oral glucose
- Body weight
Secondary objective/endpoints were change at week 12 for raisin versus control snacks regarding:
- Hemoglobin A1c
- Blood pressure
(systolic and diastolic)
- Body mass index
Other endpoints included laboratory of special interest
- Alkaline phosphatase
- Fasting serum insulin
(Insulin was not an apriori “endpoint of special interest” in the protocol. It
was added at time of study analysis due to its potential relevance to other
measured metabolic parameters.)
Overall, this study supports regular consumption of raisins as reducing the important
cardiovascular risk factors of postprandial plasma glucose and blood pressure,
which may help account for the favorable effects of grapes (and thus
potentially raisins) on possibly reducing the risk for cardiovascular disease.
3. “Raisin Effects on Biomarkers of Coronary Heart Disease in Elderly Men and Women”
Maria Luz Fernandez, PhD, University of Connecticut
A randomized, controlled study with 17 men and women aged 50-70 years were involved in the study. They were encouraged to walk or to walk and eat 1 cup of raisins per day or just eat 1 cup of raisins per day. The intervention improved the lipid risk profile for all groups by resulting in a reduction in both total cholesterol and LDL-C. The authors suggested that the increase in fiber intake was a likely contributor to the reduction in LDL-C for RAISIN and RAISIN + WALK. The reduction in blood pressure for RAISIN and RAISIN + WALK may have resulted from antioxidant effects of the raisin polyphenols. In conclusion, risk factors for CVD were affected significantly by consuming raisins or increasing steps walked. Blood pressure, plasma total cholesterol and LDL-C were significantly decreased by all interventions, while walking lowered plasma TG. Raisins lowered the risk for inflammatory damage by decreasing one of the markers of inflammation associated with diabetes and coronary heart disease (tumor necrosis factor – alpha -TNF-α.).
4. Raisins Deliver Antioxidants
Raisins rank among the top antioxidant foods, according to tests conducted by the U.S. Department of Agriculture (USDA). Antioxidants are important because they protect cells and their components from oxidative damage – a little like “rust prevention” for the body. Early findings suggest that eating plenty of fruits and vegetables high in antioxidants, such as raisins and spinach, may help slow the processes associated with aging in both body and brain and may help protect cell components from changes that lead to diseases such as cancer and coronary heart disease. Antioxidants protect cholesterol and other fats in the blood from oxidizing. This is critical because oxidized fats in the bloodstream are much more likely to be deposited on the artery wall or form clots which may lead to heart attack or stroke. Raisins are among the top contenders for convenient, accessible, affordable, all-season antioxidant foods.
5. “Raisins, Cyclo-oxygenase – 2 and Cancer Prevention”
Andrew J. Dannenberg, M.D., NewYork-Presbyterian Hospital/ Weill Medical College of Cornell University, New York, NY.
One of the antioxidant compounds in raisins and some other fruits and vegetables is catechin. When catechins were fed to tumor-prone mice by the noted cancer researcher Dr. Andrew Dannenberg and his colleagues, there was a 70 percent reduction in the number of tumors compared to control animals (not fed additional catechin). This type of study adds to the body of evidence linking phytochemical components of fruits and vegetables to reduction in the risk of colorectal cancer, colorectal adenomas and other gastrointestinal tumors.
6. “Antioxidant Capacity and Cholesterol Concentration in Human Subjects”
Carl L. Keen, Ph.D., Professor and Chair, Department of Nutrition, University of California – Davis, Davis, California.
Subjects eating raisins (4 servings) daily for 4 weeks increased the plasma antioxidant capacity. This in turn decreased the level of circulating oxidized low-density lipoprotein (LDL), so-called bad cholesterol, in subjects. High levels of LDL cholesterol are associated with increased cardiovascular disease. Oxidized LDL is especially problematic because the oxidized particles in the bloodstream are more likely to add to plaque on the artery wall. These data clearly show raisins are an important part of a diet that encourages 8 to 13 servings of fruit and vegetables loaded with important phytochemicals and antioxidants.
7.”Value of Raisins for Reduction of Oxidative Stress, Endothelial
Dysfunction, and Inflammation in Obesity”
Janet Walberg Rankin, Ph.D., Professor in Human Nutrition, Foods, and Exercise,
Virginia Tech., Blacksburg, Virginia.
Research expert on oxidative stress and disease, Janet Walberg Rankin, studied theeffect of raisins with their important antioxidant contribution on oxidative stress and inflammation in overweight subjects. It is well known that oxidative
stress triggers an inflammatory response that increases disease risk. Together with graduate student Mary Whitlock, Dr. Rankin looked at whether the modest, easily accessible raisin can benefit obese individuals. They showed lowered levels of markers of inflammation, C-reactive peptide (CRP) and interleukin-6 (IL-6). These findings are important because those eating high fat meals or who are obese have elevated levels of CRP and IL-6. High levels of these components adversely affect proper blood vessel functioning. Thus, those with high oxidative stress tend to have blood vessels that do not appropriately dilate and relax.Foods, such as raisins, that are good sources of antioxidants, especially flavonoids and phenolics,can be helpful in fighting oxidation stress and improving blood vessel function.
Clifton Carey, PhD, Director of Administration, American Dental Association – Paffenbarger Research Center
Strong evidence exists that food particles retained on the teeth will lead to Demineralization of the tooth enamel and dental caries. (caries) (Kashket et al, 1996). This led to the idea that foods which are perceived as ‘sticky’ will be more cariogenic than non-sticky snack foods. Raisins have been perceived bythe general public and by pediatric dentists as the ninth stickiest food out of a list of twenty-one popular snacks. Despite this, there is no evidence that raisins contribute to the demineralization of teeth. In fact measurement of food that is on the tooth 5 minutes after swallowing showed that foods that are less soluble in oral fluids are retained for longer times. Specifically, raisins although perceived as quite sticky, they are easily cleared from the oral cavity. These observations suggest that raisins may not contribute to tooth demineralization significantly because the sugars areremoved from the dentition before the plaque mass has the opportunity to generate sufficient acid to lower the pH below 5.5. There is also research that shows that raisins contain compounds that inhibit the in vitro growth of S. mutans, thus making raisins less cariogenic than other foods. However, the in vitro research with 10% raisin juice showed that it had the potential to demineralize tooth enamel but that this was less than orange juice with its citric acid.
9. “Raisins as a Functional Food for Oral Health”
Christine D. Wu, M.S., Ph.D., Professor, Department of Periodontics, University of Illinois, College of Dentistry, Chicago, Illinois.
Raisins contain compounds including oleanolic acid that inhibit in vitro growth of Streptococcus mutans, one of the major bacteria in the mouth responsible for tooth decay. Oleanolic acid and other compounds in raisins also inhibit organisms associated with periodontal disease, including Porphyromonas gingivalis and Fusobacterium nucleatum. Oleanolic acid is effective in suppressing in vitro plaque formation by Streptococcus mutans. Prevention of plaque formation on the tooth surface is critical both for preventing tooth decay and promoting healthy gums.
Harold E. Bays, Kathy Schmitz, Amber Christian, Michelle Ritchey, James Anderson, Louisville Metabolic and Atherosclerosis Research Center, Louisville, KY, USA, University of Kentucky, Lexington, KY, USA. Raisins are high in potassium content, and have fiber, polyphenols, phenolic acid, tannins, and antioxidants which may help account for their often cited, yet unproven BP lowering effects.
11. “Phenolic Content, Antioxidant Activity and Antimicrobial Properties of Raisins in Food Systems”
Luis Cisneros-Zevallos, Ph.D., Assistant Professor, Department of Horticultural Sciences, Texas A&M University, College Station, Texas.
Raisins have a considerable concentration of phenolic compounds. This analysis showed that they were quinic and gallic acid, chlorogenic and caffeic acids, catechin, and epicatechin. Golden raisins have more of many of these compounds because the antioxidant effect of the sulfite used in golden raisins inhibits the loss of these compounds. Raisin juice extracts and concentrates also have significantly increased numbers of these compounds, so they have the potential to reduce the growth of harmful microorganisms and prevent browning of cut produce. According to studies conducted by Luis Cisneros-Zevallos and his team at Texas A&M, raisin extracts were shown to reduce the growth of known food pathogens such as Listeria monocytogenes and Escherichia coli 0157:H7 in a variety of model food systems. This has great importance to food safety and to the produce industry as a non-food additive solution to help extend the shelf life of food and reduce food-borne disease.
12.”Inhibition of Lipid Oxidation by Raisin Paste in Cooked Ground Meat”
Daren Cornforth, Ph.D., Professor, Nutrition & Food Sciences, Utah State
University, Logan, Utah.
Raisins are recognized as a good source of dietary antioxidants. Adding raisin paste or extract to cooked ground beef or pork at just 1% to 2% of the weight improved its flavor after storage due to inhibition of rancidity by the antioxidants. Addition of the raisin extract to chicken at the same levels was also effective but did cause the meat to darken. In all cases the addition of the small amount of raisins did not affect the flavor of the meat.
13. “Evaluation of the Potential Anti-Microbial Properties of Raisins and Their Application in Food Safety and Preservation”
Mark A. Daeschel, Ph.D., Professor, Food Microbiology and Safety, Oregon State University, Corvallis, Oregon.
Pathogenic bacteria, including Escherichia coli 0157:H7, Staphylococcus aureus and Listeria monocytogenes, were inhibited in jerky systems containing 25% or 50% raisins. Raisins were shown to have the same preservative properties as sodium nitrite in meat systems. Raisins’ innate combination of antioxidants, sugar and acids were shown to be as effective as the sodium nitrite in inhibiting organisms that cause food- borne disease and in maintaining food safety. This is good news because producers of jerky, sausages, hot dogs and other cured meats may be able to reduce or eliminate the use of nitrite additives.
Use of raisins to replace sodium nitrite in cured meats has many health benefits. First, the nitrite may form cancer-causing nitrosamines during digestion. Second, unlike the sodium nitrite, raisins add no sodium. This is important for those on sodium-restricted diets. Third, addition of raisins may improve the overall nutritional profile of cured meats, such as jerky, since the raisins provide antioxidants and make it possible to produce a palatable product that is lower in fat.
14. “Raisin Dietary Fiber: Composition and Characteristics”
Mary Ellen Camire, Ph.D., Professor, Department of Food Science and Human Nutrition, University of Maine, Orono, Maine.
Dietary fiber and other components may reduce the risk of heart disease and cancer by binding bile acids and causing their elimination from the body. Camire’s study confirms that eating fibrous foods, such as raisins, caused the elimination of bile acids. This in turn stimulates the body to replace the excreted bile acids using its own cholesterol, thus potentially lowering serum cholesterol and the risk of coronary heart disease. Furthermore, bile acids that are bound by fibers such as those in raisins will not be metabolized in the gut to a more toxic form that can cause harmful changes on the colonic wall, and this may potentially reduce cancer risk.
15. “Raisins as a Source of Inulin”
Medallion Labs, Minneapolis, Minnesota.
California raisins are a good source of inulin, a naturally occurring fiber-like carbohydrate that helps keep the colon healthy. Independent laboratory analysis by Medallion Labs, a laboratory known for their analytical work for nutrition labeling in the U.S., showed that a standard 1/4-cup serving of California raisins contains 1.5 grams of inulin. Recommended daily intake levels of inulin have yet to be established. However, inulin is one of the soluble fibers. Health benefits of inulin are the subject of active research and new functions are being documented. Some of these include its effects on cholesterol levels and gut health. Its role as a prebiotic has received much attention because prebiotics are important to support immune function both in the gut and in the body.
16. “Beneficial Effects of Raisins on Colonic Function with Possible Implications for the Prevention of Colon Cancer”
Gene A. Spiller, Ph.D., Head, Sphera Foundation and Health Research Studies Center, Los Altos, California.
The combination of dietary fiber and tartaric acid in sun-dried raisins plays an important role in colon function and health. The study was designed to test the hypothesis that eating 2 to 4 servings of raisins per day may improve colonic health. Research by Dr. Spiller found a positive correlation between consuming sun-dried raisins and a reduction in some colon cancer risk factors. For example, raisins increased fecal weight and caused material to move through the colon faster (called faster transit time). Increased transit time and increased fecal weight is important not only to have a properly functioning gastrointestinal tract and to reduce constipation and hemorrhoids, it also means that any toxic materials that might be in the diet or produced by metabolism in the gut will have little time to adversely affect the colon wall. Raisins reduced the alkalinity in the colon. Both the faster transit and lowered pH are associated with reduced colon cancer risk. The authors concluded that 2 servings of raisins per day caused moderate but beneficial changes in colon function.
17. “The Impact of Pre-exercise Snacks on Exercise Intensity, Stress, and Fatigue in Children”
Debra R. Keast, PhD; Carol E. O’Neil, PhD, MPH, RD; Julie M. Jones, PhD, CNS, LN
Objective: This study examined the association of dried fruit consumption with nutrient intake, diet quality, and anthropometric indicators of overweight/obesity.
Design: Analyses of dietary and anthropometric data collected from adult (19+ years) participants (n=13,292) of the 1999-2004 National Health and Nutrition Examination Survey were conducted. Dried fruit consumers were defined as those consuming amounts ≥⅛ cup-equivalent fruit/day and identified using 24-hour recalls. Diet quality was measured using the Healthy Eating Index-2005 (HEI-2005). Covariate-adjusted means, standard errors, prevalence rates and odds ratios were determined to conduct statistical tests for differences between dried fruit consumers and non-consumers.
Results: Seven percent of the population consumed dried fruit. Adult shortfall nutrients for which there were mean intake differences (p<0.01) between consumers and non-consumers were: fiber (+6.6 g/d), vitamin A (+173µg RAE/d), vitamin E (+1.5 mg AT/d), vitamin C (+20 mg/d), calcium (+103 mg/d), magnesium (+72 mg/d), and potassium (+432 mg/d). Dried fruit consumers had improved MyPyramid food intake, including lower SoFAAS intake, and a higher SoFAAS score (11.1±0.2 vs 8.2±0.1) than non-consumers. The total HEI-2005 score was significantly higher (p<0.01) in consumers (59.3±0.5) than non-consumers (49.4±0.3). Covariate-adjusted weight (78.2±0.6 kg vs 80.7±0.3 kg), body mass index (27.1±0.2 vs 28.1±0.2), and waist circumference (94.0±0.5 vs 96.5±0.2) were lower (p<0.01) in consumers than non-consumers, respectively.
Conclusions: Dried fruit consumption was associated with improved nutrient intakes, a higher overall diet quality score, and lower body weight/adiposity measures.
Glycemic Effects, Sustainable Energy and Healthy Snacks
18. “Effects of Carbohydrate Supplementation Form on Gastrointestinal Tolerance and Running Performance”
Brandon Too, Sarah Cicai, Kali Hockett, Elizabeth Applegate, Brian A. Davis and Gretchen A. Casazza
Purpose: We examined the effects of raisins and sport chews on running performance and gastrointestinal (GI) tolerance.
Methods: This study recruited 11 competitive male (29.3 ± 2.4 yrs) endurance runners and triathletes to complete an 80-min sub-maximal (75% VO2peak) running bout followed immediately by a 5K time trial and a 10K time trial 24 hours later. Subjects ingested 3 randomized treatments (raisins, sport chews, and water only) with each treatment separated by 7 days. Heart rate (HR), respiratory exchange ratio (RER), blood glucose, lactate, free fatty acids (FFA), glycerol, insulin, electrolytes and creatine kinase, GI symptoms and rating of perceived exertion (RPE) were recorded every 20 minutes during the sub-maximal exercise test and at the end of the 5K. We also measured whole body muscle soreness and fatigue and mood disturbance via questionnaires.
Results: VO2, HR, body weight changes, muscle soreness and fatigue, total mood disturbance and RPE during the submaximal exercise bout did not differ due to treatment. However, RER was highest during the sport chews treatment, followed by the raisins and water was the lowest (0.92 ± 0.01, 0.91 ± 0.01, 0.89 ± 0.01 for raisin, chews and water respectively). FFA and glycerol were higher with water than both CHO treatments. Blood glucose was higher for both carbohydrate treatments compared to water. Plasma creatine kinase was higher for all exercise time points with raisins versus chews and water. Time to complete the 5K time trial was faster for both carbohydrate treatments (20.6 ± .8, 20.7 ± .8, 21.6 ± .8 min for raisin, chews and water respectively). GI disturbance was mild (less than 1 out of 6) for all treatments with only belching higher in both CHO treatments compared to water.
Conclusion: Both the raisins and sport chews maintained high blood glucose levels and improved running performance compared to water only. Running performance between the raisins and sport chews were similar and their GI tolerance was good. Raisins provided a good, natural carbohydrate source that had similar physiological and performance benefits as a commercially available product.
19. “Comparing Nutrient Density of Raisins to Sports Chews”
Apfel, K., Painter, J. 2013. Journal of the Academy of Nutrition and Dietetics. October 2013. In press.
Purpose: Participants will understand the nutrient difference between an all-natural carbohydrate source (raisins) to a commercially available sports chew.
Methods: A published study examined the performance levels of male athletes (n=11) who underwent each of three randomized nutrition treatments (raisins, sports chews, and water) while performing an 80-minute treadmill run at 75% VO2 max, followed by a 5 kilometer timed trial. The study showed that performance levels were similar when athletes consumed 400 kcals of raisins and 400 kcals of sports chews in comparison to water (20.6 ± 2.6, 20.7 ± 2.5, 21.6 ± 2.7 min for raisin, sports chews, and water) respectively. IRB was granted.
Conclusion: Although raisins and sports chews may provide similar performance results, raisins provide a nutrient dense all-natural carbohydrate source which contains more vitamins and minerals overall.
20. “The Impact of Pre-exercise Snacks on Exercise Intensity, Stress, and Fatigue in Children”
Jennifer M. Sacheck, Tamar Kafka, Helen Rasmussen, Jeffrey B. Blumberg, and Christina D. Economos
Purpose: Few studies have examined how the composition of snacks affects athletic performance in children. We investigated whether the macronutrient and flavonoid content of 3 pre-exercise snacks differentially affected exercise intensity, stress, and postgame fatigue in young soccer players.
Methods: At 1 h prior to a 50-min soccer game, 115 children (9.1 ± 0.9 y) were randomly assigned to consume 1 of 3 isocaloric snacks: 1) nutrient dense/high flavonoid (HF) raisin/nut bar; 2) low flavonoid (LF) peanut butter graham bar; or 3) low flavonoid/high sugar (LF/HS) rice cereal bar. Blood glucose and salivary cortisol and IgA were measured before consuming the snack and immediately following the game. Game exercise intensity was measured by accelerometry. Self-administered questionnaires were used to assess diet quality and physical and mental fatigue after the game.
Results: The children spent approximately 33% of the game in moderate to vigorous activity and 49% of the game in sedentary activity. The snack consumed was not related to exercise intensity. Mean post-exercise blood glucose (P<0.001) and cortisol (P<0.05) increased and IgA levels decreased (P<0.001) from pre-game values. The pre-exercise snack did not predict the post-exercise outcome for any of these parameters after controlling for pre-exercise values of the biomarkers, age, gender, BMI, exercise intensity, game-time water consumption, and diet quality. Children who reported symptoms of fatigue were more likely to have consumed the LF/HS snack (P<0.05).
Conclusion: The pre-exercise snacks formulated for this study did not affect blood sugar or salivary biomarkers of stress following a soccer game in young children. The nutrient content of the single snack did not differentially influence these biomarkers or the exercise intensity; however subjective feelings of fatigue may be associated with low flavonoid/high sugar snacks. Future investigations are warranted to further explore the effects of pre-exercise snacks on exercise, performance, stress and fatigue in children.
21.“Glycemic Index in the Management of Type 2 Diabetes Mellitus”
Carla Miller, PhD, RD, Ohio State University
The glycemic index of the diet decreased following a 9-week intervention in which 109 diabetics were instructed to increase their intake of fruit and dried fruit, total dietary fiber (including soluble and insoluble fiber) and the percentages of energy from protein and total fat (including saturated and monounsaturated fat) improved. IN addition to a changed GI of the diet, there was a significant reduction in body weight and body mass index (weight (kg)/height (m2)) in both men and women and a significant reduction in waist circumference in men. More fruit including raisins and other dried fruit was consumed following the intervention, which is consistent with the dietary pattern recommended in the Dietary Guidelines 2005. These studies show the importance of fruit, including dried fruit, and dietary fiber in the diet of diabetics. Thus, a carbohydrate-controlled portion of raisins can readily be incorporated into a well-constructed diabetic diet.
22. “Determination of the Glycemic and Insulinemic Responses to Raisins and the Application of Raisins as a Pre-exercise Snack for Persons with Impaired Glucose Tolerance”
Craig Mattern, Assistant Professor, State University of New York at Brockport
Raisins fed as a pre-exercise food to 22 exercisers (approximately half with normal and abnormal glucose tolerance) resulted in similar increases in blood glucose to those observed with a popular energy bar. These observed increases in blood glucose for raisins and energy bar were less than a standardized glucodex solution. The blood insulin response to the pre-exercise meal with raisins, especially in a sedentary population, produced statistically lower insulin values than the standardized glucose solution or the energy bar. All three test substances including Raisins resulted in similar mobilization of free fatty acids from adipose tissue during exercise. Thus, raisins resulted in a similar glucose response during exercise when compared to an energy bar and were less than the standardized glucose solution. The good news is that the insulin responses to raisin ingestion prior to, and in the early phases of exercise, were more favorable than those observed with the energy bar. Thus, raisins can be an excellent food for use by exercisers to help deliver the right kind of carbohydrates.
23. “Determination of the Glycemic and Insulinemic Indexes of Raisins in Three Populations”
Steve Hertzler, Ph.D., Assistant Professor of Nutrition, The Ohio State University, Columbus, Ohio.
The glycemic index (G.I.) and insulin index (I.I.) of raisins was determined on three different populations. In 10 sedentary adults, the G.I. of raisins was determined to be an average of 49.4. A nearly identical G.I. value for raisins was found for 10 prediabetic individuals. In the 11 endurance athletes, the G.I. of raisins was 62.3. As expected, the highest insulin index was found in prediabetic subjects (I.I. = 54.4) and the lowest was found in sedentary subjects (I.I. = 47.3). While the I.I. for athletes was 51.9, the overall insulin excursion in trained athletes was not nearly as great, showing the effects of training on insulin sensitivity and glucose utilization.
Interestingly, California raisins in this study came in as a moderate glycemic food, which is different from the ‘high’ classification they are given in published tables. Data for published tables have not been collected on California raisins, and the population studied is not from the United States.
24. “Raisin Consumption and Exercise Performance of Endurance Athletes”
Mark Kern, Ph.D., Department of Exercise and Nutritional Sciences, University of California – San Diego, San Diego, California.
Raisins were shown to be a good alternative to sports gels in a study conducted with endurance athletes under two different conditions. In studies by Mark Kern, San Diego State professor and author of the CRC Desk Reference on Sports Nutrition (2005, CRC Press), endurance-trained cyclists (4 males and 4 females) completed two feeding-performance trials where changes in metabolism and cycling performance were compared after consumption of raisins (a moderate to low glycemic index food) versus a commercial sports gel (a high glycemic index food). There were no differences in performance in the 45 minute cycling trial (at 75% VO2max). No gastrointestinal discomfort was reported with either the gel or raisins. Measures of metabolic substrates after exercise were the same with both the sports gel and raisins except there were more free fatty acids after the pre-exercise ingestion of raisins. This increase in the free fatty acids indicates that raisins subtly, but favorably, improved metabolism. The authors concluded that raisins have similar performance effects to commercial sports gel products, but raisins are a better alternative since they provide more micronutrients, an acid-neutralizing load to the kidneys and are a more cost-effective and convenient food for use during exercise.
25. “The Effects of a Raisin-Peanut Pre-Event Meal on Indices of Energy and Fatigue in Young, Trained Soccer Players (10-12 Years of Age) Playing a Standard Game”
Gene A. Spiller, Ph.D., Head, Sphera Foundation and Health Research and Studies Center, Los Altos, California.
Feeding raisins along with peanuts and water to 10 to 12 year old children prior to a soccer game resulted in lower increases in blood glucose and insulin than a snack of a white bagel and lemonade. This is important because it means a more steady fuel supply to the exercising muscle of the young players. Lower insulin levels are advantageous because high levels of circulating insulin can promote the laying down of fat and may lead to insulin resistance, a concern among U.S. children today, where rates of obesity and type-2 diabetes are increasing dramatically.
26. “The Effects of a Pre-Meal Raisin Snack on Satiety and Food Intake in Children”
Dr. G. Harvey Anderson, Professor, Nutritional Sciences and Physiology. Department of Nutritional Sciences,UniversityofToronto.
Three experiments were conducted to determine how raisin snacks influences appetite and calorie intake in 8-11 year old children.
First Experiment Children were asked to visit the lab for three times and during each visit they were asked to eat until comfortably full one of three snacks: (1) raisins, (2) grapes or (3) a mix of almonds with raisins. In a half an hour, a lunch meal with pizza was provided to kids and again they were asked to eat it until they felt comfortably full. The results of this experiment indicated that after the raisin snack, kids consumed about 21% less pizza compared with other snacks. The total calories received from the snack and lunch meal were lower after raisins compared to other snacks.
Second Experiment The equicaloric (150 kcal) snacks were provided to children and food intake was measured with a pizza meal in 30 min, similarly as in the first experiment. When total calories consumed were calculated after the snack and pizza meal, the calories after the snack with raisins were similar to those after just water, while other snacks led to higher calorie intake when compared with water. It was concluded that raisins was the only snack that does not increase calorie intake when provided before a lunch meal.
Third Experiment All children received the same breakfast (skim milk, cereals and orange juice), morning snack (medium apple) and the lunch (turkey sandwich with a cup of 2% milk). Then in the afternoon (between 3:30 and 4 pm in the lab) they ate, until comfortably full, one of the four after-school snacks: (1) raisins, (2) grapes, (3) potato chips and (4) chocolate chip cookies. The results of this experiment demonstrated that calorie intake after raisins was the lowest compared to other snacks. Thus, children consumed about 1.5 times more calories with grapes or potato chips, and about twice more calories with cookies.
Conclusion The results of this project indicate that raisins compared to other popular snacks reduce appetite and provide the lowest energy intake.