The Effects of Short-term Strawberry Supplementation in Reducing Oxidative Stress

 The Effects of Short-term Strawberry Supplementation in Reducing Oxidative Stress

To help further characterize the biological mechanisms underlying the health-promoting effects associated with strawberry consumption, researchers examined the anti-oxidative effects of a diet rich in strawberries in a group of 18 healthy men and women (age 35 ± 10 years; BMI 23 ± 3 kg/m2) by adding about three and a half cups (500 grams) of fresh strawberries to their daily diets for 2 weeks.  Analyses included measures of blood antioxidant status as well as biomarkers of resistance to endogenous and exogenous oxidative stress in red and mononuclear blood cells.  Findings following the 2-week strawberry intervention included a moderate increase in fasting plasma antioxidant status and vitamin C, together with a significant increase in the lag phase preceding the formation of plasma lipid oxidation products.   A significantly enhanced resistance to oxidative hemolysis was noted in red blood cells, with no significant reduction in ghost lipid peroxidation, a measure of the actions of strawberry phytochemicals in biomembranes.   The researchers conclude that regular consumption of strawberries may play a protective role by enhancing the body’s defenses against oxidative challenges, and suggest conducting larger intervention studies with reduced serving sizes of strawberries to confirm these findings.

Tulipani S, Armeni T, Giampieri F, et al.  Strawberry intake increases blood fluid, erythrocyte and mononuclear cell defenses against oxidative challenge.  Food Chemistry.2014;156:87-93.

Strawberries May Help Lower Cholesterol and Cardiovascular Disease Risk Factors

Research suggests that anthocyanins—the most prominent flavonoid in the diet—and the consumption of anthocyanin-rich foods such as strawberries may play an important role in helping reduce the risk of cardiovascular disease.  To evaluate the effects of specific amounts of strawberries on cardiovascular risk factors, researchers at Oklahoma State University conducted a 12-week, randomized controlled study of a strawberry-supplemented diet in a group of overweight/obese adults with abdominal adiposity and elevated lipid levels.  Daily strawberry supplementation (as freeze-dried strawberries (FDS)) was evaluated in two amounts:  a low dose (25 g FDS) equivalent to about one and three-fourths cup (250 g) of fresh strawberries, and a high dose (50 g FDS) equivalent to about three and one-half cups (500 g) of fresh strawberries.  Sixty participants were randomly assigned to consume a strawberry beverage (low-dose (LD-FDS), high-dose (HD-FDS)) or a calorie- and fiber-matched control beverage (LD-C, HD-C) daily for 12 weeks as a snack to their usual diet.

After 12 weeks, high-dose strawberry supplementation (HD-FDS) was shown to significantly reduce total and LDL cholesterol levels and NMR-derived small LDL particle concentrations as compared with the lower-dose strawberry group.  Both the low- and high-dose strawberry supplementation were shown to be equally effective in decreasing lipid peroxidation compared with the control groups, as measured by malondialdehyde (MDA), a well-established marker of oxidative stress.  As the first 12-week study to report the total and LDL cholesterol-lowering effects of a higher amount of strawberries in obese adults, the researchers suggest that a strawberry-supplemented diet may be of clinical significance as a nutritional strategy to help reduce cardiovascular disease risk.

Basu A, Betts NM, Nguyen A, Newman ED, Fu D, Lyons TJ.  Freeze-dried strawberries lower serum cholesterol and lipid peroxidation in adults with abdominal adiposity and elevated serum lipids. J Nutr. Published ahead of print March 26, 2014 as doi: 10.3945/jn.113.188169.

Strawberries Help Lower Risk Factors for Cardiovascular Disease and Improve Biomarkers of Oxidative Stress

Researchers from the Università Politecnica delle Marche (UNIVPM) in Italy and the Universities of Salamanca, Granada and Seville in Spain evaluated the protective effects of strawberries on cardiovascular health by adding about three and a half cups (500 grams) of fresh strawberries to the daily diets of 23 healthy men and women for one month.  Results showed that strawberry consumption positively impacted lipid profiles by significantly reducing total cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides levels by 8.78 percent, 13.72 percent and 20.80 percent, respectively. High-density lipoprotein (HDL) cholesterol remained unchanged. The strawberry intervention also improved antioxidant biomarkers and had a positive effect on antihemolytic defenses and platelet function.  The results suggest a protective role of a strawberry-supplemented diet to significantly improve biomarkers of oxidative stress and cardiovascular disease, which may in part be explained by the fruit’s high anthocyanin content and antioxidant capacity.

Alvarez-Suarez MJ, Giampieri F, Tulipani S, et al.  One-month strawberry-rich anthocyanin supplementation ameliorates cardiovascular risk, oxidative stress markers and platelet activation in humans.  J Nutr Biochem. 2014;25:289-294.


Study Finds Strawberries May Inhibit Oral Cancer Formation in an Animal Model

Strawberries contain a wide array of components that have been studied for their chemopreventive potential, including vitamins C and E, dietary fiber and phytochemicals such as ellagic acid, shown in laboratory studies to exhibit the ability to prevent cancers of the skin, bladder, lung, esophagus and breast.

Researchers from The Ohio State University investigated the effects of strawberries on tumor formation in an animal model of oral cancer developed to mimic conditions found in human oral mucosa after exposure to carcinogens such as tobacco and alcoholic beverages.  Hamsters were given 5% or 10% lyophilized strawberries (LS) in their diet prior to, during and following or only following 12 weeks of carcinogen treatment.  After 12 weeks of treatment, there were significantly fewer tumors found in the LS-treated groups as compared with the carcinogen controls, and histological examination revealed a significant reduction in the number of early lesions.  The fact that little or no reduction in the size of large tumors was seen suggests that the maximum effect of LS was on early-developing tumors.  Also, adding LS following 12 weeks of carcinogen treatment did not result in the reduction of any pre-existing dysplastic lesions, suggesting that the progression to malignancy of both pre-existing and newly-arising dysplasia was inhibited by LS. Researchers also noted a modification in gene expression related to the development of oral cancer.

These data show for the first time that incorporating strawberries (as LS) in the diet is effective in inhibiting the development of oral cancer in an experimental model.

Casto BC, Knobloch TH, Galioto RL, Yu Z, Accurso BT, Warner BM. Chemoprevention of oral cancer by lyophilized strawberries. Anticancer Res. 2013;33(11): 4757-4766.

Berries and Health: A Critical Review of Berry Fruit Bioactives

Berries are nutrient-rich fruits known to have health-promoting benefits related to their high levels of polyphenols, antioxidants, vitamins, minerals and dietary fiber.  A new article provides a comprehensive review of recent in vitro and in vivo studies that focus on the diverse range of berry phytochemicals and their associated biological effects and mechanisms of action.   Berry fruits are popular and widely consumed in the diet, and some, like strawberries, are recognized as functional foods.

Specifically, strawberries are noted by the authors as the richest source of vitamin C among berry fruits, and for their high concentration of anthocyanins, associated with a lower risk for certain cancers, improved memory and normal aging; and ellagic acid, a phenolic compound reported to have antiviral, antimicrobial and antioxidant activity as well as to provide protection against certain cancers.   Strawberries are also an example of an ellagitannin-rich fruit, which may contribute to its unique biological effects in neuronal function and behavior as reported in animal models.

The authors conclude that a number of studies—both human and animal—support the positive role of berry fruits in human health, offering potential for  protection against various diseases and from the damaging effects of free radicals based on specific biological activities, including anticancer, antimutagenic, antimicrobial, anti-inflammatory and neuroprotective properties.

Nile SH, Park SW, Edible berries: Review on bioactive components and their effect on human health, Nutrition (2013),

The Role of Berries in Type 2 Diabetes Prevention: Improving Insulin Response after Meals

The additive and synergistic combinations of plant phytochemicals have been identified to provide health benefits associated with chronic disease risk reduction, including type 2 diabetes and cardiovascular disease. Attenuating insulin resistance, along with oxidative stress and inflammation, has been identified as a mechanism that underlies this protective effect. Studies have documented favorable postprandial (post-meal) effects of strawberries, a polyphenol-rich fruit, on glucose and lipid profiles as well as on mediating the inflammatory response and improving insulin action.

To build upon their previous research findings that whole berries optimize postprandial glucose and insulin responses to sucrose in healthy adults, researchers from the University of Eastern Finland conducted a series of three meal studies to identify the effects of berries on postprandial metabolic responses to starch. The three randomized, controlled crossover studies were conducted with 13 to 20 healthy female subjects who consumed reference meals that provided 50g of starch as white wheat bread (WB) or rye bread (RB), meals with WB and RB served with 6 different berries, or meals with WB or RB served with a mixture of four berries (strawberries, bilberries, cranberries and black currents).

Among berries rich in the ellagitannin polyphenols, only strawberries were found to have a significant effect on insulin response to WB, which suggests that total ellagitannin content is not a driving factor in lowering insulin response. The berry mixture was shown to have a similar insulin-lowering effect on both breads, despite the known differences in insulin responses between WB and RB. Finding no association of the insulin-lowering capacity and the polyphenol composition of the berries, the researchers suggest that the role of acidity and organic acid content of berries be addressed in future studies.

They concluded that consuming foods and food combinations that elicit a lower postprandial insulin response—such as the bread and berry pairings—may offer short- and long-term metabolic benefit for the prevention of type 2 diabetes, particularly for those high risk of developing the disease. Torronen R, Kolehmainen M, Sarkkinen E, Poutanen K, Mykkanen H, Niskanen L. Berries reduce postprandial insulin responses to wheat and rye breads in healthy women. J Nutr. 2013; 143: 430-436.

Berries show anti-diabetes potential: Human data

Strawberries, bilberries, lingonberries, and chokeberries may blunt the insulin response to the starch-rich bread, and offer a means of reducing the risk of diabetes, says a new study from Finland.

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Berries May Protect Brain Functioning, Rat Study Suggests

A diet supplemented with berries could help to protect brain functioning during aging, according to new animal data.

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The Health Benefits of Strawberries: A Functional Food

A new comprehensive literature review by researchers at Oklahoma State University and the University of Oklahoma Health Sciences Center, Strawberries as a Functional Food:  An evidence-based review,” examines research to support the health-promoting benefits associated with strawberry consumption, and discusses the fruit’s nutrient and phytochemical composition and bioavailability.  A popular fruit that is available throughout the year, strawberries are a rich source of phytochemicals (anthocyanins, catechins, the flavonols quercetin and kaempferol, and ellagic acid) and an important source of essential nutrients (ascorbic acid, potassium, folic acid, carotenoids, B-vitamins).  Strawberries are consistently ranked among the top food sources of polyphenols and antioxidant capacity; the preventive and therapeutic health benefits of strawberries may be attributed to the synergistic effects of these bioactives and the nutrients contained in the fruit.

The article reports results of epidemiological studies that support the protective effects of strawberries against a variety of chronic diseases and conditions, including hypertension, inflammation, cancer and cardiovascular mortality. In addition, clinical studies are reviewed that examine the health benefits of strawberries in healthy or overweight subjects and in individuals with mild to moderate elevations in serum cholesterol and with metabolic syndrome, showing favorable postprandial effects on glucose and lipid profiles.

The researchers identify emerging research in animal and cell models that provides evidence for the mechanisms of action of strawberries and their phytochemicals to ameliorate obesity, hyperglycemia, hyperlipidemia, hypertension and oxidative stress, as well as exert anti-carcinogenic effects.  Results of emerging research are also reviewed that support the role of strawberries in reversing age-related neurodegenerative disorders, with the mechanisms of action having potential implications in the reversal of Alzheimer’s or Parkinson’s disease.

Based on the review of several lines of evidence, the authors conclude strawberries satisfy the definition of a functional food, and that the consumption of strawberries—either fresh or frozen—can be an effective disease management and health-promoting dietary strategy.

Published online in Critical Reviews in Food Science and Nutrition, February 19, 2013.

Strawberries and Blueberries Reduce Risk of Heart Attack in Young and Middle-Aged Women

A new study by researchers from the Harvard School of Public Health found that women consuming more than 3 servings of anthocyanin-rich strawberries and blueberries weekly had a lower risk of heart attack than women who did not consume berries.

In the study, published in the American Heart Association Journal Circulation, over 93,000 women age 25-42 from the Nurse’s Health Study, who were healthy at the start, were followed for 18 years to determine the relationship between intake of anthocyanins and other flavonoids and incidence of heart attack. Higher consumption of anthocyanin- rich foods was associated with a 32 percent lower risk of heart attack in women in their mid-40s to age 60.

Food-based analyses for the main dietary sources of anthocyanins were conducted and strawberries and blueberries were identified as the main sources within this population.  A reduced risk was not found for other food sources of flavonoids, except onions, which were protective if consumed more than 5 times per week. Previous research has demonstrated the beneficial effects of strawberries and berry anthocyanins on factors that contribute to heart disease, including cholesterol levels, endothelial function, and blood pressure.  This study provides more evidence that consuming just a few more servings of strawberries and blueberries per week helps prevent heart disease in women.

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