Strawberries
Health Benefits
(Source: World's Healthiest Foods, George Mateljan)
Antioxidant and Anti-Inflammatory Benefits of Strawberries
As our 5th best source of vitamin C among all 100 WHFoods, strawberries might logically be expected to provide antioxidant benefits. But the scope of strawberry antioxidants extends far beyond vitamin C. What we're talking about in the case of strawberries is a collection of polyphenol antioxidants that includes flavonoids, phenolic acids, lignans, tannins, and stilbenes. Each one of the polyphenol categories contains an enormous variety of antioxidants, most of which have also been shown to have anti-inflammatory properties. We have compiled the list of polyphenols below to give you a better idea about the antioxidant and anti-inflammatory phytonutrients present in strawberries.
Antioxidant and Anti-Inflammatory Polyphenols in Strawberries
FlavonoidsPhenolic AcidsTanninsStilbenesAnthocyaninsCaffeic acidEllagitanninsPterostilbeneCatechinsCinnamic acidGallotanninsResveratrolCyanidinsEllagic acidSangulin H-6EpicatchinsFerulic acidGallotcatechinsGallic acidKaempferolHomovanillic acidPelargonidinsVanillic acidPetunidinsQuercetin
Alongside of vitamin C and their diverse polyphenol content, strawberries provide us with other key antioxidants and anti-inflammatory nutrients. Strawberries are an excellent source of manganese—a mineral which plays a key antioxidant role as a cofactor for the enzyme superoxide dismutase. And while strawberries are not a high-fat food, they do contain seeds and those seeds serve as a good source of the omega-3 fatty acid alpha-linolenic acid. You are also going to find small amounts of carotenoids in strawberries, especially lutein and zeaxanthin.
We would like to add a special note here about the ellagitannins in strawberries. These beneficial antioxidant and anti-inflammatory polyphenols change in concentration along with the ripening of the berries. In research studies on strawberries, four stages of ripening are usually taken into account: (1) the green stage, which is the least ripe; (2) the veraison stage, in which the berries are basically pinkish in appearance with some yellowish and greenish hues; (3) the ripe stage, which we are quite familiar with because of its bright anthocyanin reds; and (4) the overripe stage. While it can be difficult to see color differences in the ripe versus overripe stage, overripe strawberries are more mushy to the touch (at least in spots) and duller in appearance. Their vibrant reds have "lost their shine." Interestingly, the ellagitannin content of strawberries appears to decrease from stage to stage across the lifespan of the strawberries. While this is not a reason to choose unripe strawberries (since some of their health-benefitting qualities do not develop until they increase in ripeness, and also because they also have yet to develop their full delicious taste and aroma), it is a reason not to choose overripe strawberries in order to preserve as many ellagitannin benefits as possible.
Cardiovascular Benefits of Strawberries
Not surprisingly, the rich antioxidant and anti-inflammatory content of strawberries can pave the way for impressive cardiovascular benefits. Research on the antioxidant content of strawberries is providing us with more and more evidence about decreased lipid peroxidation in our blood vessel linings following strawberry consumption, and less malondialdehyde formation as well. Strawberry intake has also been shown to result in better free radical scavenging activity. Of special interest in this area of research has been the effect of strawberry consumption on the activity of an enzyme called paraoxonase-1 (PON-1). This enzyme is able to help break down lipid hydroperoxides (LOOH), and this process can help protect our blood vessels since excessive presence of LOOH can increase our risk of blood vessel damage due to the highly reactive nature of LOOH. In studies to date, strawberry intake has ranged from 2–4 cups per day over a period of 10–30 days. Within this context, it can also be helpful to know that about eight whole large strawberries will fit into one measuring cup. In terms of pint containers, you will usually find roughly 3 cups of whole large strawberries per pint, or 24 large strawberries. While these amounts are obviously not precise, they can give you a ballpark for understanding the amounts used in studies of strawberries and cardiovascular health.
Other Health Benefits of Strawberries
In this "other" category we would like to mention two other areas of ongoing health research on strawberries. The first area involves regulation of blood sugar, and the second area involves cognitive processes, especially as they can change during later life.
Improved regulation of blood sugar is a health benefit that appears more and more likely based on the findings from recent studies on strawberry consumption. Especially following consumption of a meal, researchers are finding better regulation of insulin and blood sugar levels in connection with strawberry intake. Numerous mechanisms are under investigation here, including release of incretin hormones like GLP-1 (glucagon-like peptide 1) and GIP (glucose-dependent insulinotropic polypeptide) and alterations in the activity of carb-related enzymes like alpha-glucosidase and alpha-amylase. At this point in time, however, much of the research on strawberries and blood sugar regulation has been conducted on animals only, and we have yet to see any large-scale human studies on these aspects of strawberry intake.
Most assessments of strawberries show a glycemic index (GI) value of approximately 40. This GI for strawberries would not only be considered low, but is also considerably lower than the GI for many other fresh fruits, including apricots, bananas, cantaloupe, pineapple, and watermelon (and, of course, dried fruits like figs which have a more concentrated sugar content after being dried). The low GI of strawberries seems to match up well with new research studies on their blood sugar impact. We would also like to note that among our Top 25 food sources for folate at WHFoods, there are only two fruits: papaya and strawberries. The fact that 1 cup of these berries provide roughly 10% of our daily recommended folate (400 micrograms) might play an important role in their blood sugar impact since folate deficiency has been associated with increased risk of type 2 diabetes and since improvements in type 2 diabetes have been shown with increased intake of folate. Coupled with the substantial number of animal studies that show improved blood sugar regulation following strawberry intake, as well as the low GI value for strawberries and their provision of nutrients like folate, we expect to see future studies that document the benefits of strawberries for lowering risk of type 2 diabetes in humans, and also perhaps also for improved blood sugar regulation in persons already diagnosed with this condition.
The strong antioxidant and anti-inflammatory benefits provided by strawberries make this fruit a natural candidate for research in the area of cognitive function. Research on female participants 70 years and older in the Nurses Health Study (conducted jointly by Brigham and Women's Hospital, Harvard Medical School, and Harvard School of Public Health) has shown reduced cognitive loss in women who consumed at least 1–2 servings of strawberries per week. This finding is encouraging, especially due to the very feasible amount of strawberries involved. (At 8 large strawberries per cup, we are talking about 8–16 strawberries during the course of an entire week.) Research on rats in the area of cognitive function and strawberry intake has demonstrated a phenomenon technically referred to as "hippocampal neurogenesis." This term refers to new nerve generation in the area of the brain known as the hippocampus, which is often involved in the learning and recall of new information. Researchers have hypothesized that the benefits of strawberries in this regard might be due to increased expression of the gene for insulin-like growth factor 1 (IGF-1), a peptide (protein-based) hormone involved in growth and tissue building. More research is needed before we can draw any firm conclusions about strawberries and cognitive function. However, these preliminary study findings suggest that the benefits of strawberry intake extend into this area of our health.
Contacts
mail@doforothers.org
Socials
Subscribe to our newsletter
(203) 545-7857