Newsletter #203 - Strawberries & Cardiometabolic Health 🍓
Hey guys! This week, I decided to look into some of the clinical evidence linking strawberries to improvements in markers related to cardiovascular and metabolic health (think cholesterol, triglycerides, blood sugar, insulin, etc).
In general, strawberries have a lot going for them from a nutritional standpoint. They’re a good source of vitamin C, folate, potassium, magnesium, manganese, fiber, and various B vitamins. They’re pretty inexpensive, easy to find, and are low in calories relative to volume. Not too surprising that they are among the four most commonly consumed fruits in the US.
But perhaps most importantly, strawberries are a rich source of bioactive phytochemicals, especially flavonoids, which appear to have impressive health-promoting effects when we eat them.
This may be why epidemiological studies suggest that strawberries and other berries are linked to better heart and metabolic health. For instance, an analysis of data from the massive Nurses’ Health Study found that middle-aged women who consumed three or more servings of blueberries and strawberries per week had a 34% reduced risk of heart attack, compared with the women who infrequently consumed berries. This was primarily attributed to these berries’ anthocyanins, which are also responsible for the deep pigmentation of strawberries.
To learn more, scroll on down 👇🏻
This Week's Research Highlights
🍓 Strawberries can improve blood lipids.
Researchers supplemented volunteers daily with 500 grams of strawberries. Plasma lipid profile and other blood markers were measured at baseline, after 30 days of strawberry consumption, and finally 15 days after the end of the study. After one month of consuming the strawberries, the subjects showed, on average, an 8.78% drop in total cholesterol, 13.72% decrease in LDL cholesterol, and a 20.80% decrease in triglycerides. This was accompanied by substantial improvements in biomarkers related to oxidative stress (-31.40% serum malondialdehyde, -29.67% urinary 8-OHdG, and -27.90% isoprostanes), as well as increases in total antioxidant capacity.
🫀 Strawberries may improve vascular health.
Researchers recruited 34 adults and had them go through two different study sequences, each separated by a 4-week washout period. In one segment of the study, they drank beverages containing 25 grams of freeze-dried strawberry powder twice daily for 4 weeks. In the other, they consumed a beverage with a matched control powder twice daily. Unlike the previous study, no changes in LDL cholesterol were observed after the 4-week interventions. However, subjects consuming strawberries did experience improvements in flow-mediated dilation (+1.5%), which is basically a measurement of the capacity of an artery to widen in response to increased blood flow. They also developed lower systolic blood pressure (-3.1 mmHg). The researchers attribute these improvements in vascular health to phenolic metabolites generated by the gut microbiota, which boost endothelial function.
🍓 Strawberries may improve insulin resistance.
Researchers recruited 33 obese participants with elevated serum LDL cholesterol, and put them through three different arms for four weeks, each separated by a one-week washout period: 1) a low dose of strawberries (13 g freeze-dried strawberry powder/day), 2) a high dose of strawberries (32 g strawberry powder/day), 3) a control powder. After consuming the higher dose of strawberries for one month, the subjects showed significantly lower fasting insulin, suggesting that their body was becoming more sensitive to the hormone. And indeed, after the higher dose of strawberries, participants showed significant reductions in insulin resistance, measured via HOMA-IR (Homeostatic Model Assessment of Insulin Resistance). This demands a bit more context: HOMA-IR is an indirect measure of insulin resistance, calculated from fasting glucose and fasting insulin. If you’re below 1, you have good insulin sensitivity; a level above 1.9 signals early insulin resistance, and above 2.9 means significant insulin resistance. So to put this into perspective, these subjects started the study with an average HOMA-IR of 3.6, indicating pretty serious insulin resistance. After the high dose of strawberries, they reached a HOMA-IR of 2.1, which would generally be characterized as mild insulin resistance. Pretty impressive, for just eating a couple servings of strawberries every day.
Random Trivia & Weird News
🐬 Almost a quarter of the US nuclear stockpile is protected by militarized dolphins.
The largest single nuclear weapons site on Earth is situated in Bangor, Washington. To defend the seaward side of this extremely high-security location, the Navy uses trained dolphins, whose remarkable sonar capabilities can pick up on dangers lurking below the surface of the water.
Podcasts We Loved This Week
- Danny Lennon & Alan Flanagan: Soy − yes, no, maybe? Via Sigma Nutrition Radio.
- Michael Hiller: How vampire bats evolved to drink blood. Via Science Friday.
Products We Are Enjoying
This container has a colander built into it, so you can wash your berries (or whatever produce you happen to have) and then stick them in the fruit keeper. This way, they stay dry and fresh for longer. It’s also a pretty decent size (50 ounces).
humanOS Catalog Feature of the Week
Optimizing Nutrition with Smoothies
This week, we’d like to highlight our course on smoothies and phytochemicals. One thing to keep in mind, when talking about the impact of ultra-processed food, is that altering the structure of food isn’t necessarily a bad thing per se. In fact, certain forms of processing can actually enhance the health-promoting properties of whole foods in some cases. Smoothies are a great example. For instance, a recent study found that an apple and blueberry smoothie elicited a reduced glycemic response compared to an equal portion of whole apples and blueberries!
The course takes a deep dive into phytochemicals in plants, where they are found, their powerful health effects, and how intelligently-devised smoothies can help optimize our intake of these compounds. For more practical information on using smoothies to enhance nutrition, please refer to our How-to Guide for smoothies.
Thanks for reading! If you're looking for more health research, be sure to visit with us on Twitter on@humanOS_me.