Jun 25, 2016
It's summer and these wonderfully bright red morsels of sweetness are everywhere. In this educational article from whfoods.com we find that besides being delicious, amazing strawberries are healthy, too!
- Many foods commonly consumed in the U.S. are valuable sources of antioxidants. But researchers have recently ranked the 50 best antioxidant sources among commonly eaten foods and found strawberries to be quite exceptional. When total antioxidant capacity was measured against a uniform amount of food (100 grams, or about 3.5 ounces), strawberries ranked 27th best among U.S. foods. In addition, when only fruits were considered, strawberries came out 4th among all fruits (behind blackberries, cranberries, and raspberries). However, since many foods (for example, spices and seasonings) are seldom consumed in amounts as large as 3.5 ounces, researchers also looked at common serving sizes for all foods and their total antioxidant capacity. In this evaluation based on common serving sizes, strawberries came out 3rd among all U.S. foods including spices, seasonings, fruits, and vegetables! (In this analysis based on serving size, only blackberries and walnuts scored higher in total antioxidant capacity.) When we hear the word "strawberry," we might think about a very commonplace fruit. But the antioxidant capacity of strawberry is anything but common!
- Recent research has shown strawberries to be a surprisingly fragile, perishable, and delicate fruit. Food scientists recently took a close look at storage time, storage temperature, storage humidity, and degree of strawberry ripeness and found significant differences between different types of strawberry storage. On average, studies show 2 days as the maximal time for strawberry storage without major loss of vitamin C and polyphenol antioxidants. It's not that strawberries become dangerous to eat or invaluable after 2 days. It's just that more storage time brings along with it substantially more nutrient loss. In terms of humidity, 90-95% has been shown optimal. Most refrigerators will average a much lower humidity (between 80-90%). Because air circulation inside the fridge can lower humidity, you may want to give your strawberries more storage humidity by putting them in your refrigerator's cold storage bins (if available). Those cold storage bins will help boost humidity by reducing air circulation. If your fridge does not have storage bins, you can use a sealed container for refrigerator storage of your strawberries. Optimal temperature for strawberry storage over a 2-day period has been found to be relatively cold—36F (2C). All public health organizations recommend refrigerator temperatures of 40F (4.4C) as the maximum safe level for food storage. However, if you are storing sizable amounts of fruits and vegetables—including strawberries—in your refrigerator, you may want to consider setting your refrigerator to a lower-than-maximum temperature setting in the range of 36-38F (2-3C). In terms of ripeness, recent studies have found that both underripeness and overripeness can have an unexpectedly large impact on the phytonutrient content of strawberries, especially their antioxidant polyphenols. Fortunately, optimal strawberry ripeness can be judged by color. You'll want to consume your strawberries when their amazing pinkish-red color is most vibrant and rich in luster.
- Improved blood sugar regulation has been a long-standing area of interest in research on strawberries and health. However, scientists have recently discovered a fascinating relationship between intake of strawberries, table sugar, and blood sugar levels. As you might expect, excess intake of table sugar (in a serving size of 5-6 teaspoons) can result in an unwanted blood sugar spike. But you might not expect this blood sugar spike to be reduced by simultaneous consumption of strawberries! Yet that's exactly what researchers have discovered. With the equivalent of approximately one cup of fresh strawberries (approximately 150 grams), blood sugar elevations from simple sugar intake can be reduced. These health science researchers have further speculated that polyphenols in strawberries played a major role in helping regulate blood sugar response. This finding is great news for healthy persons wanting to maintain healthy blood sugar levels, and also for persons with type 2 diabetes who enjoy fresh strawberries and want to enjoy them on a regular basis.
- Given their amazing combination of phytonutrients—including anthocyanins, ellagitannins, flavonols, terpenoids, and phenolic acids—it's not surprising to find increasing research interest in the anti-inflammatory properties of strawberries. But it's still exciting to see this remarkable fruit lowering levels of inflammatory markers like C-reactive protein (CRP) when consumed several days per week in everyday amounts of approximately one cup. Recent research has shown that several blood markers for chronic, unwanted inflammation can be improved by regular intake of strawberries. Interestingly, in one large-scale study, consumption of strawberries did not show anti-inflammatory benefits until strawberries were consumed at least 3 times per week. This research is one of the reasons we recommend inclusion of berries at least 3-4 times per week in your overall fruit intake.
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WHFoods Recommendations - In our Healthiest Way of Eating Plan, we encourage the consumption of 5-10 servings of fruits-plus-vegetables (combined) each day. We believe that the balance between fruits and vegetables can vary from day to day, depending upon personal health factors, personal taste preferences, and optimal combining of foods in recipes as well as meals. We recognize that our recommendation calls for a more generous amount of fruits and vegetables than the amount recommended by the Centers for Disease Control (CDC) at the U.S. Department of Health and Human Services (DHHS). The CDC recommends between 1.5-2.5 cups of fruit and 2.5-4.0 cups of vegetables per day, as well as a target goal of at least 5 fruit-plus-vegetable servings (combined) per day.
With respect to berries, the CDC approach provides the example of strawberries and explains that 8 large strawberries count as 1 cup. If all fruit for the day were to be obtained from strawberries, the CDC recommendation would translate into 12-20 strawberries for the day as a way of meeting a requirement for 1.5-2.5 cups of fruit.
We recommend that you set your fruit goals higher than these CDC amounts. Based on the scientific research, we believe it's going to take closer to 3 fruit servings per day to provide you with optimum health benefits. With respect to berries in particular, we recommend that you include berries at least 3-4 times per week within your fruit servings.
In several of our sample meal plans, we include berries on a daily basis! It would definitely not be a mistake for you to include a serving of berries in your daily meal plan! At the same time, we recognize that the fruit group contains many outstanding fruit options, and personal preferences (as well as local and seasonal availability) can vary greatly. Also, remember that large strawberries--at about 18 grams per berry and 8 berries per cup--stand at one end of the berry range in terms of size and recommended amount. Most berries are considerably smaller in size and weight, and a one-cup serving allows you to eat a lot more berries! With blueberries, for example, the average weight per berry is closer to 1-2 grams, and a cup's worth of blueberries means about 100-150 berries. For cranberries and raspberries, the amount would be similar.
The fragrantly sweet juiciness and deep red color of strawberries can brighten up both the taste and aesthetics of any meal. Not only do they taste great they are among the fruits and vegetables ranked highest in health-promoting antioxidants. Antioxidants help combat the damaging effects of free radical activity to cellular structures and DNA. Like the other World's Healthiest Fruits, we recommend enjoying strawberries raw (not in baked/cooked desserts) because they provide you with the best flavor and the greatest benefits from their vast array of nutrients and digestion-aiding enzymes. Peoples around the world have long been eating fruit for dessert, not only as a delicious ending to a meal but as a great digestive aid as well. For more on the Healthiest Way of Preparing Strawberries, see below.
Strawberries, fresh, 1.00 cup, (144.00 grams), Calories: 46, GI: low
NutrientDRI/DV
vitamin C113%
manganese28%
fiber12%
iodine9%
folate9%
copper8%
potassium6%
magnesium5%
phosphorus5%
biotin5%
omega-3 fats4%
vitamin B64%
This chart graphically details the %DV that a serving of Strawberries provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Strawberries can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Strawberries, featuring information over 80 nutrients, can be found under the Food Rating System Chart.
Health Benefits - Given their unique combination of antioxidant and anti-inflammatory nutrients, it's not surprising to see strong research support for strawberry health benefits in three major areas: (1) cardiovascular support and prevention of cardiovascular diseases (2) improved regulation of blood sugar, with decreased risk of type 2 diabetes, and (3) prevention of certain cancer types including breast, cervical, colon, and esophageal cancer. In this section, we'll review the outstanding research-based benefits of strawberries in each area.
Cardiovascular Benefits - No area of strawberry health benefits is better documented than benefits for the cardiovascular system. It's also hard to imagine any other research result, since our heart and blood vessels need everyday protection from oxidative and inflammatory damage, and the antioxidant and anti-inflammatory nutrient content of strawberries is simply outstanding. Among all fruits profiled as the World's Healthiest Foods, strawberries come out as the best fruit source of a pivotal antioxidant vitamin: vitamin C in several nationwide studies conducted in different countries. In one study that surveyed 66 different fruits consumed by adults in Iran, strawberries not only emerged as the best fruit source of vitamin C, but a source that provided more than twice as much vitamin C (47 milligrams versus 18 milligrams in 3.5 ounces) than the average for fruits as a group. After raspberries and grapes, strawberries also rank among the best fruit sources of manganese among the World's Healthiest Foods. Because of its key role as a cofactor for antioxidant enzyme activity by the enzyme superoxide dismutase (SOD), manganese is considered to be a key antioxidant mineral. Yet, strawberries "claim to fame" in the antioxidant department is really reserved for their phytonutrient content.
Many of the phytonutrients present in strawberries function not only as antioxidants but also as anti-inflammatory nutrients. The chart below shows several of the more important antioxidant and anti-inflammatory nutrients present in fresh, ripe strawberries:
Antioxidant and Anti-Inflammatory Phytonutrients in Strawberries
(* indicates that these are typically in small or trace amounts)
- Anthocyanins
- Flavonols
- procyanidins
- catechins
- gallocatechins
- epicatechins
- kaempferol
- quercetin
- ellagic acid
- gallic acid
- vanillic acid*
- salicylic acid
- cinnamic acid
- coumaric acid
- caffeic acid
- ferulic acid
- ellagitannins
- gallotannins
- resveratrol
- Hydroxy-benzoic acids
- Hydroxy-cinnamic acids
- Tannins
- Stilbenes
Several research studies have shown that these diverse strawberry phytonutrients actually work together in synergistic fashion to provide their cardiovascular benefits. Decreased oxidation of fats (lipid peroxidation) in the cell membranes of cells that line our blood vessels; decreased levels of circulating fats, including total cholesterol and LDL cholesterol; and decreased activity of angiotensin I-converting enzyme (ACE), an enzyme whose overactivity increases our risk of high blood pressure are results that have all been documented following daily intake of strawberries over 1-3 months period of time. Amounts of strawberries in most studies were equivalent to 1-2 cups of strawberries per day.
Blood Sugar Benefits - One of the more recent areas of health benefit to be documented in strawberry research is the area of blood sugar benefits. Several recent studies have found regular intake of strawberries to be associated with decreased risk of type 2 diabetes. In some of these studies, frequency of strawberry intake definitely seems to matter since an intake frequency of once per week or less is not associated with blood sugar benefits in some studies. In these studies, significant benefits do not emerge until frequency of intake reaches at least 2-3 strawberry servings per week.
Of special interest for blood sugar regulation is the relationship recently documented by researchers between intake of strawberries, intake of table sugar, and resulting blood sugar levels. As you might expect, excess intake of table sugar (in a serving size of 5-6 teaspoons) was able to produce an unwanted blood sugar spike in study participants during this study. But as you might not expect, this blood sugar spike was actually reduced by simultaneous consumption of strawberries. Approximately one cup of fresh strawberries (approximately 150 grams) was able to decrease blood sugar elevations when table sugar was consumed along with strawberries. The investigators speculated that polyphenols in strawberries played a major role in helping regulate blood sugar response. One particular type of polyphenol in strawberries—ellagitannins—might have been especially important for this blood sugar-relating benefit. Ellaginannins are polyphenols that are known to inhibit the activity of an enzyme called alpha-amylase. Since this enzyme is responsible for breaking amylose starches into simple sugars, fewer simple sugars might be released into the blood stream when activity of this enzyme is reduced.
Anti-Cancer Benefits - Since chronic, excessive inflammation and chronic, excessive oxidative stress (lack of antioxidant nutrients and unsupported oxygen metabolism) are often primary factors in the development of cancer, strawberries would definitely be expected to have cancer risk-lowering properties given their outstanding antioxidant and anti-inflammatory nutrient content. Anti-cancer benefits from strawberries are best documented in the case of breast, cervical, colon, and esophageal cancer. Most of the tumor-inhibiting studies on animals have focused on the phytonutrient content of strawberries. Among the strawberry phytonutrients, ellagic acid and ellagitannins in strawberry have emerged as anti-cancer substances of special interest. While the anti-cancer (chemopreventive) properties of these phytonutrients have yet to be fully understood, their ability to lower risk for some forms of cancer may be related to their ability to boost the activity of antioxidant enzymes like catalase or superoxide dismustase, their ability to lessen the activity of pro-inflammatory enzymes like cyclo-oxygenase 2 (COX-2), or their ability to lessen expression of the enzyme inducible nitric oxide synthase (iNOS). Whatever the mechanism or combination of mechanisms, strawberries are likely to bring anti-cancer health benefits to your diet.
Other Health Benefits - A growing area of health research on strawberries is the area of aging and aging-related events. Several preliminary studies on intake of strawberries on aged animals has shown enhanced cognitive function (in the form of better object recognition) following ingestion of a diet with 2% of the calories provided by strawberry extracts. Enhanced motor function (in the form of better balance and coordination of movements) has also been shown in these strawberry extract studies. Some of the strawberry impact in these aging studies has been attributed to the ability of strawberry phytonutrients to lower the presence of pro-inflammatory messaging molecules like nuclear factor kappa-B.
Improvement of inflammatory bowel problems—including ulcerative colitis and Crohn's disease—has also been demonstrated in preliminary studies on animals with daily strawberry extract or strawberry powder intake. Interestingly, even though strawberries contain relatively small amounts of salicylic acid (an anti-inflammatory compound very similar to the acetylsalicylic acid of aspirin), some researchers have suggested that this naturally-occurring anti-inflammatory substance in strawberries might be partly responsible for decreased inflammation in the digestive tract of individuals diagnosed with inflammatory bowel diseases like ulcerative colitis or Crohn's disease.
Inflammation-related arthritis (including rheumatoid arthritis), and inflammation-related diseases of the eye (including macular degeneration) are two additional areas in which strawberries may turn out to provide important health benefits. Even though health research in these areas is in a preliminary stage, the unique combination of anti-inflammatory phytonutrients in strawberries is likely to explain some of the key potential benefits in these areas.
Image: Strawberries - clipartpanda.com
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