The Benefits of Strawberries, the Richest Dietary Source of Fisetin

At least in mice, fie-setin is a rejuvenating senotherapeutic that extends lifespan, and also kills of those senescent, pro-inflammatory zombie cells in human tissue too. Though first isolated from Venetian sumac, fisetin is concentrated in strawberries, the richest dietary source. A pint of strawberries has 57 mg of fisetin. In contrast, a large apple could have up to 8 mg, a persimmon 2 mg, an onion or cup of grapes 1 mg, and kiwi fruit, cucumbers, and peaches have less than 1 mg. The total average daily intake of fisetin may only be about 1 mg, mostly from apples, but only because people don’t eat a lot of strawberries.

Although fisetin is considered safe, toxicity studies have been largely confined to in vitro or laboratory animal analyses. Caution should be exercised in taking any kind of flavonoid, wrote a toxicology professor, at “levels above that which would be obtained from a typical vegetarian diet,” by which they presumably mean a plant-rich diet (some vegetarians only average barely two more servings of fruits and vegetables compared to nonvegetarians). If you do choose to take supplements, note that both quercetin and fisetin can inhibit a specific type of drug-metabolizing enzyme in your body, so if you’re on any medications, make sure you first ask your prescribing physician before you start taking any supplements.

The life-extending dose of fisetin used in mice would be equivalent to around 500 mg in people, nearly 8 pints of strawberries worth. Given the hit-and-run nature of clearing the slate with senolytics, though, one could potentially reserve a berry binge to once a month or even once a year, but there have been benefits tied to more reasonable strawberry doses.

It is no surprise that the consumption of fresh or frozen strawberries can increase the antioxidant capacity of our bloodstream, but the impacts of strawberry consumption may go beyond just mopping up free radicals. For example strawberries, but not blueberries (which have even more antioxidants), were able to more effectively rescue rats exposed to radiation in experiments funded by NASA to protect astronauts from cosmic rays in space.

The consumption of either blueberries or strawberries was associated with slower cognitive decline in the Harvard Nurses’ Health Study. Researchers found that women who consumed at least one serving of blueberries and two servings of strawberries each week had slower rates of cognitive decline—by as much as two and a half years—compared with those who didn’t eat berries. These results suggest that simply eating a handful of berries every day, one easy and delicious dietary tweak, may slow your brain’s aging by more than two years. But you don’t know if it’s cause-and-effect, until you put it to the test.

Strawberry extracts reverse age-related deficits and improved memory in rats, but we didn’t know about humans until 2021 when researchers at Tufts published “Dietary Strawberry Improves Cognition in a Randomised, Double-Blind, Placebo-Controlled Trial in Older Adults.” Men and women ages 60 through 75 were randomized to 4 tablespoons a day of freeze-dried strawberry powder, equivalent to two cups of fresh strawberries, providing about 50 mg of fisetin. The control group placebo powder was designed to look and taste like the real thing but without any actual strawberries. After three months the strawberry group experienced a significant improvement in some, but not all, aspects of cognition.

Randomized controlled trials show similar amount of strawberries can also help lower high cholesterol and reduced CRP levels, a marker of systemic inflammation. Even just a single meal can help. Have people eat a largely unhealthy breakfast and the level of inflammatory markers goes up over the next 6 hours, but less so if you added just 5 large strawberries to the meal. No wonder strawberries can help with arthritis.

Osteoarthritis patients randomized to get around a pint and a half of strawberries a day for 12 weeks didn’t just see inflammatory markers drop, but experienced a significant improvement in pain and overall quality of life. Strawberries decrease the levels circulating in the blood of an inflammatory mediator known as tumor necrosis factor (TNF). There are TNF inhibitor drugs on the market available now for the low-low cost of about $40,000 a year. For that kind of money you’d want some really juicy side effects, and they do not disappoint, linked to, in rare cases, an especially fatal lymphoma. I think, I’ll try to stick with the strawberries.

The antioxidant phytonutrients thought responsible for some of the benefits hold up well to freezing and freeze-drying but not to cooking, so jellies and jams would appear to be poor substitutes for fresh, frozen, or powdered strawberries. As with creamer in coffee, having strawberries with cream may block some of the berry benefits. A strawberry beverage made with milk cuts the bioavailability of strawberry phytonutrients by as much as half compared to the same beverage made with water. But strawberries may be able to improve our health even if they don’t make it into our system.

In 2021 a study was published entitled “California Strawberry Consumption Increased the Abundance of Gut Microorganisms Related to Lean Body Weight, Health and Longevity in Healthy Subjects.” Researchers took people eating typical low fiber, low fruit and vegetable diets (what they refer to as “beige diets”) and added about an ounce of powdered strawberries to their daily diets for a month. Not only did they experience a boost of typical good gut bugs like Bifidobacteria, but also a significant increase in Christensenellaceae.

This newly discovered bacterial family comprises only about 0.01% of the human gut microbiome, but has been associated with longevity. Studies of centenarians and supercentenarians have found to have a greater relative abundance of Christensenella bacteria in populations in China, Italy, and Korea, though we don’t yet know if this is cause or effect. Note: I highly doubt the state of origin has any significance beyond funding bias….