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.
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. 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. 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.
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.
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.
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.
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.