Newsletter #150: The First Day of Spring & The Power of Polyphenols 🌼
Welcome to the Spring edition of the humanOS newsletter! ☀️ I don’t know about you, but we are definitely ready for winter to end, and for longer days with more sunshine.
This week, we looked at how food-derived bioactive compounds, like polyphenols, affect human health. However, it is worth noting that many of these notable benefits do not come directly from the phytochemicals themselves.
Rather, it is from metabolites resulting from the biotransformation of these compounds through the gut microbiota. This matters because people vary in their capacity to convert polyphenols to their bioactive metabolites, perhaps due to differences in the microbiota. Does this mean that some people don’t benefit as much from fruits, vegetables, tea, etc, due to the composition of their gut bugs? And if so, is there anything that can be done about it?
Scroll down to learn more! 👇🏼
This Week’s Research Highlights
🍵 Catechins found in tea may lower blood pressure by relaxing blood vessels.
A number of studies have shown that tea consumption is linked to reduced hypertension and cardiovascular disease. One such study found that people who drank at least 120 mL of tea daily experienced a 46% lower risk of developing hypertension, compared to non-drinkers. This is thought to be mediated by catechins - flavonoid compounds that are found abundantly in tea. However, precise mechanisms that underlie these benefits remain uncertain. Researchers in Copenhagen determined that several different herbs that lower blood pressure all share a propensity to activate a specific potassium channel protein called KCNQ5, which is found in the smooth muscle that lines blood vessels. They suspected that green tea might work by the same means, and did indeed find that green tea catechins augmented KCNQ5 activity in vitro. Somewhat alarmingly, the addition of milk, commonly consumed with tea, inhibited this process. However, the researchers do not believe that milk would likely have this effect in vivo, due to how the human stomach separates catechins from molecules in milk that block their beneficial effects. This is supported by prior studies showing that drinking tea with milk does not affect plasma antioxidant activity.
🫐 Consuming blueberries and soluble fiber may improve cardiometabolic health in pregnant women at high risk.
Researchers recruited women in early pregnancy deemed at high risk for developing gestational diabetes (n = 34; BMI 35.5 on average), the majority of whom had a previous history of GDM. These participants were randomly assigned to either standard prenatal care (control) or to a dietary intervention of 280 grams of whole blueberries and 12 grams of soluble fiber every day. Subjects in both groups received nutritional education and maintained food logs. At the end of the trial, the intervention group gained significantly less weight than the controls (6.8 ± 3.2 kg versus 12.0 ± 4.1 kg), and their blood sugar levels were also lower (100 ± 33 mg/dL versus 131 ± 40 mg/dL). The women consuming the berries and fiber also had reduced inflammation, suggested by lower C-reactive protein levels.
🍓 Increased intestinal permeability due to age may impair the bioavailability of polyphenols - and in turn blunt their biological activity.
Previous research has shown that diets rich in polyphenols can improve intestinal permeability, likely through the generation of secondary metabolites like butyrate. However, it is known that there is significant variability between individuals that affects the bioavailability of these polyphenols, as well as the conversion of these compounds into bioactive metabolites. To examine the impact of this interindividual variability, researchers recruited older adults living in a residential care setting (n = 55) and divided them into two subgroups based on their intestinal permeability (determined by serum zonulin levels). They then randomly assigned the subjects to consume either a polyphenol-rich diet or a control diet for eight weeks, followed by an eight week washout period, then a crossover to the opposite condition. At baseline and after each intervention period, subjects provided urine samples, which were subjected to metabolomics analysis to assess how well the polyphenols in the diet were being absorbed and transformed into active metabolites. And indeed, levels of metabolites were significantly different between subjects with healthier intestinal barrier integrity and those with increased intestinal permeability. This is important because these metabolites are thought to be largely responsible for the health benefits associated with polyphenols, and they may be especially useful for addressing age-related conditions. What can be done about this dilemma? Julie Andersen and colleagues at the Buck Institute have been experimenting with rejuvenating the gut microbiota of older animals with probiotics to boost their ability to produce these bioactive metabolites - check out this podcast to learn more about that.
Question of the Week
🤔 Serotonin is a neurotransmitter best known for mediating mood, as well as regulating sleep and appetite. Where is most of the serotonin in your body generated?
💡 Answer
Podcasts We Loved This Week
- Kevin Hall: Plant-based diet vs ketogenic diet - Impact on calorie intake. Via Sigma Nutrition Radio.
- Anna Rothschild and Sinduja Srinivasan: Turning the COVID-19 pandemic into the COVID-19 endemic. Via Podcast-19 from FiveThirtyEight.
- Ashish Ja: How America’s COVID-19 nightmare ends. Via The Ezra Klein Show.
Products We Are Enjoying
Oat fiber
If you are looking for an efficient way to boost your fiber intake and feed your gut bugs, this is a good option (obviously in conjunction with a healthy fiber-rich diet). This fiber blends easily into beverages, smoothies, sauces, baked goods, etc with no discernible flavor, and it also appears to be keto-friendly for those of you who are doing that.
Importantly, oat fiber is one of the richest, if not the richest, sources of beta-glucan, a soluble fiber that has been shown to lower blood lipids as well as help regulate blood sugar. Interestingly, beta glucan may also stimulate the immune system (much of this research is in fungal beta-glucans, though there is reason to believe that cereal-derived beta-glucans share this intriguing property).