Strawberries – 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.