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Who doesn't love strawberries? And you don't need any reason other than the pleasure of their sweetness to eat them every day. But according to researchers from Oklahoma State University, there's lots more to strawberries than the flavor.[i]
Their study was published in the journal Critical Reviews in Food Science and Nutrition with funding from the NIH and the California Strawberry Commission. In it the researchers review over 130 studies attesting to the strawberry's status as a "functional food."
There is no regulated meaning for the term "functional food." But it usually refers to a food that provides some benefit in addition to calories that may reduce disease risk or promote general health. That can be said of every fresh, organic whole food. But functional food is also a term that has become a marketing tool for food manufacturers who "enrich" their processed foods with vitamins, minerals, herbs and other supplements.
But strawberries don't need any enriching. They consistently rank among the top fruits and vegetables for health benefits. They are full of powerful natural compounds that include:
- Antioxidants – Strawberries were found to have higher oxygen radical absorbance capacity (ORAC) activity than black raspberries, blackberries or red raspberries.[ii] One study even found strawberries have the highest antioxidant capacity of ALL fruits and vegetables commonly available in the UK as measured by the trolox equivalent antioxidant capacity (TEAC) assay.[iii]
- Polyphenols – Strawberries have been listed among the 100 richest sources of dietary polyphenols.[iv] They contain flavonoids like catechin, epicatechin, quercetin, kaempferol, cyanidins, naringenin, hesperadin, pelargonidin, ellagic acid and ellagitannins. Flavonoids are free radical scavengers, and have anti-inflammatory effects. They also dilate blood vessels and slow tumor growth.
- Vitamins and Minerals – Strawberries are high in vitamin C (ascorbic acid), B vitamins, vitamin E, folate, carotenoids and potassium.
- Anthocyanins – These are water-soluble compounds responsible for the deep colors of berries and are among the principal bioactives in strawberries.
- Phytosterols - These plant-derived sterols have structures and functions similar to cholesterol.
All of those natural components translate to a broad range of health benefits. Animal and cell culture studies show strawberries may be effective in reducing risk factors for cardiovascular disease including obesity, hyperglycemia, hyperlipidemia, hypertension, and oxidative stress.
Here are eight scientifically proven reasons to eat more strawberries:
1. Strawberries Lower Heart Attack Risk
In an analysis of data from over 93,000 subjects in the famous Nurses' Health Study I and the Nurses' Health Study II, researchers looked at the effects of eating strawberries and blueberries on cardiovascular health. They found that over a 14-year period, women eating just three servings weekly of blueberries or strawberries reduced their risk of heart attack by 33% compared to those eating berries once monthly or less.[v]
In addition, in an analysis of data from over 34,489 postmenopausal women in the Iowa Women's Health Study, eating strawberries was associated with a significant reduction in deaths from cardiovascular disease over a 16-year follow-up period.[vi]
2. Strawberries Reduce Hypertension
Researchers again used the data from the two Nurses Studies as well as data from the Health Professionals Follow-Up Study to measure cardiovascular health benefits of strawberry and blueberry anthocyanins. They found that higher intakes of strawberry and blueberry anthocyanins (16–22 mg/day) were associated with a significant 8% reduction in the risk of hypertension. That was compared to those consuming only 5–7 mg/day of berry anthocyanins.[vii]
3. Strawberries Lower Inflammation and C-Reactive Protein (CRP)
In a study of 38,176 female US health professionals enrolled in the Women's Health Study participants were asked whether they ate fresh, frozen, or canned strawberries "never," or "less than one serving per month," or up to "6+ servings per day." Over an 11-year follow-up period, cardiovascular disease was lower among those consuming more strawberries.
CRP levels were significantly reduced among women consuming just two or more servings of strawberries per week.[viii] Elevated CRP is strongly associated with inflammation and is a high-risk factor for cardiovascular disease.
4. Strawberries Reduce Cancer Risk
In a prospective five-year cohort study in an elderly population, higher consumption of fresh strawberries and other fruits and vegetables was associated with significantly reduced cancer mortality. The authors attribute these observations to the carotenoid content of fruits and vegetables known to exert anti-carcinogenic effects.[ix]
In another larger five-year prospective cohort study, eating more foods from the Rosaceae botanical subgroup, including strawberries, was associated with a protective effect against esophageal squamous cell carcinoma compared to eating less of this fruit group.[x] The same cohort also reported reduced rates of head and neck cancer among those consuming more servings of the Rosaceae botanical subgroup including strawberries.[xi]
Other studies show that strawberries can even reverse early stage esophageal cancer.
5. Strawberries Reduce Oxidized Cholesterol
Studies show strawberries increase plasma antioxidant capacity helping to reduce oxidized LDL cholesterol. In human trials fresh, frozen, or freeze-dried strawberries were shown to reduce oxidative stress associated with metabolic syndrome or eating high-fat meals.[xii]
6. Strawberries Lower LDL Cholesterol and Raise HDL Cholesterol
The fiber, phytosterols, and polyphenols in strawberries have been shown to lower serum total and LDL cholesterol.[xiii] It's also been shown to raise serum high-density lipoprotein (HDL)-cholesterol.[xiv]
7. Strawberries Help Control Blood Glucose Levels
Polypenols in a berry mixture that included strawberries produced a lower glucose response after eating a meal.[xv]
8. Strawberries May Help Reverse Age-Related Neurodegenerative Disorders
In an animal study researchers at the USDA Human Nutrition Research Center on Aging at Tufts found that strawberry extracts significantly reversed signs of age-related neuronal deficits.[xvi]
And animals eating a diet including 2% strawberries for two months showed significant protection from radiation damage to neurons.[xvii] Researchers suggest that strawberries and other berries may have a role in reversing Alzheimer's disease or Parkinson's disease.[xviii]
Are Fresh or Frozen Strawberries Better?
Studies show benefits to all forms of strawberries whether fresh, frozen, dried, pureed, or made into juices or jams. But the more they're processed the more strawberries can lose some of their active compounds.
Frozen strawberries have significantly higher vitamin C (ascorbic acid) and polyphenols than freeze-dried or air-dried.[xix] Processing strawberries into juices and purees also results in a loss of ascorbic acid, polyphenols, and antioxidant capacity.[xx] And canning strawberries or making them into jams can significantly reduce the levels of anthocyanins and total phenolic compounds.[xxi]
Fresh or frozen are the best choices for health benefits when it comes to strawberries. But processed strawberry products still have some benefits and are a good choice when the real things aren't in season.
Just remember to buy organic berries. Most conventionally grown strawberries are heavily sprayed with pesticides.
For more studies visit GreenMedInfo's page on strawberries.
[i] Arpita Basu , Angel Nguyen , Nancy M. Betts & Timothy J. Lyons "Strawberry As a Functional Food: An Evidence-Based Review." Critical Reviews in Food Science and Nutrition, (2014) 54:6, 790-806.
[ii] Wang, S. Y., and Lin, H. S. (2000). "Antioxidant activity in fruits and leaves of blackberry, raspberry, and strawberry varies with cultivar and developmental stage." J. Agric. Food Chem. 48:140–146.
[iii] Proteggente, A. R., Pannala, A. S., Paganga, G., Van Buren, L., Wagner, E., Wiseman, S., Van De Put, F., Dacombe, C., and Rice-Evans, C. A. (2002). The antioxidant activity of regularly consumed fruit and vegetables reflects their phenolic and vitamin c composition. Free Radic. Res. 36:217–233.
[iv] P´erez-Jim´enez, J., Neveu, V., Vos, F., and Scalbert, A. (2010). "Identification of the 100 richest dietary sources of polyphenols: An application of the phenolexplorer database." Eur. J. Clin. Nutr. 64:S112–S120.
[v] Aedín Cassidy, Kenneth J Mukamal, Lydia Liu, Mary Franz, A Heather Eliassen, Eric B Rimm. High anthocyanin intake is associated with a reduced risk of myocardial infarction in young and middle-aged women. Circulation. 2013 Jan 15 ;127(2):188-96.
[vi] Mink, P. J., Scrafford, C. G., Barraj, L. M.,Harnack, L., Hong, C. P.,Nettleton, J. A., and Jacobs, D. R., Jr. (2007). Flavonoid intake and cardiovascular disease mortality: A prospective study in postmenopausal women. Am. J. Clin. Nutr. 85:895–909.
[vii] Cassidy, A., O'Reilly, E. J., Kay, C., Sampson, L., Franz, M., Forman, J. P., Curhan, G., and Rimm, E. B. (2010). Habitual intake of flavonoid subclasses and incident hypertension in adults. Am. J. Clin. Nutr. 93:338–347.
[viii] Sesso, H. D., Gaziano, J. M., Jenkins, D. J., and Buring, J. E. (2007). Strawberry intake, lipids, c-reactive protein, and the risk of cardiovascular disease in women. J. Am. Coll. Nutr. 26:303–310.
[ix] Colditz, G. A., Branch, L. G., Lipnick, R. J.,Willett,W. C., Rosner, B., Posner, B. M., and Hennekens, C. H. (1985). Increased green and yellow vegetable intake and lowered cancer deaths in an elderly population. Am. J. Clin. Nutr. 41:32–36.
[x] Freedman, N. D., Park, Y., Subar, A. F., Hollenbeck, A. R., Leitzmann, M. F., Schatzkin, A., and Abnet, C. C. (2007). Fruit and vegetable intake and esophageal cancer in a large prospective cohort study. Int. J. Cancer. 121:2753–2760.
[xi] Freedman, N. D., Park, Y., Subar, A. F., Hollenbeck, A. R., Leitzmann, M. F., Schatzkin, A., and Abnet, C. C. (2008). Fruit and vegetable intake and head and neck cancer risk in a large United States prospective cohort study. Int. J.Cancer. 122:2330–2336.
[xii] Paiva, S. A., Yeum, K. J., Cao, G., Prior, R. L., and Russell, R. M. (1998). Postprandial plasma carotenoid responses following consumption of strawberries, red wine, vitamin c or spinach by elderly women. J. Nutr. 128:2391–2394.
[xiii] Basu, A., Fu, D. X., Wilkinson, M., Simmons, B., Wu, M., Betts, N. M., Du, M., and Lyons, T. J. (2010). Strawberries decrease atherosclerotic markers in subjects with metabolic syndrome. Nutr. Res. 30:462–469.
[xiv] Erlund, I., Koli, R., Alfthan, G., Marniemi, J., Puukka, P., Mustonen, P.,Mattila, P., and Jula, A. (2008). Favorable effects of berry consumption on platelet function, blood pressure, and hdl cholesterol. Am. J. Clin. Nutr. 87:323–331.
[xv] T¨orr¨onen, R., Sarkkinen, E., Tapola, N., Hautaniemi, E.,Kilpi, K., andNiskanen, L. (2010). Berries modify the postprandial plasma glucose response to sucrose in healthy subjects. Br. J. Nutr. 103:1094–1097
[xvi] Joseph, J. A., Shukitt-Hale, B., Denisova, N. A., Prior, R. L., Cao, G., Martin, A., Taglialatela, G., and Bickford, P. C. (1998). Long-term dietary strawberry, spinach, or vitamin e supplementation retards the onset of age-related neuronal signal-transduction and cognitive behavioral deficits. J. Neurosci. 18:8047–8055.
[xvii] Rabin, B. M., Joseph, J. A., and Shukitt-Hale, B. (2005). Effects of age and diet on the heavy particle-induced disruption of operant responding produced by a ground-based model for exposure to cosmic rays. Brain Res. 1036:122–129.
[xviii] Joseph, J. A., Shukitt-Hale, B., and Willis, L. M. (2009). Grape juice, berries, and walnuts affect brain aging and behavior. J. Nutr. 139:1813S–1817S.
[xix] Asami, D. K., Hong,Y. J.,Barrett, D. M., and Mitchell, A. E. (2003).Comparison of the total phenolic and ascorbic acid content of freeze-dried and air-dried marionberry, strawberry, and corn grown using conventional, organic, and sustainable agricultural practices. J. Agric. Food Chem. 51:1237–1241.
[xx] Klopotek,Y., Otto, K., and B¨ohm,V. (2005). Processing strawberries to different products alters contents of vitamin c, total phenolics, total anthocyanins, and antioxidant capacity. J. Agric. Food Chem. 53:5640–5646.
[xxi] Ngo, T., Wrolstad, R. E., and Zhao, Y. (2007). Color quality of Oregon strawberries–impact of genotype, composition, and processing. J. Food Sci. 72:C025–C032.