Newsletter #048: Heart Rate Variability, Berries for Good Health 🫐
Welcome to the latest edition of the humanOS newsletter! Here is where we share our work, and the various studies and media that captured our attention this week. 🤓
This Week’s Research Highlights
Researchers assessed independent associations between sleep duration, sleep disturbances, and social jetlag with variables related to adiposity in a cross-sectional study of 341 kids aged 8-10 years. Following adjustment for confounders, sleep duration was not associated with any adiposity variable. However, just one hour of social jetlag was associated with a 3% increase in body fat, 1.73 kg increase in fat mass, 0.89 kg/m2 increase in BMI, and 0.13 (ratio) increase in waist-to-hip ratio.
Researchers randomly assigned 40 participants to receive either a drink containing 200 grams of blueberries, or matched control beverages. The subjects who consumed blueberry drinks daily showed rapid and sustained improvements in blood vessel function. Over the course of a month, they experienced a reduction in blood pressure by 5 mmHg. Most effects were attributable to anthocyanins - control drinks containing similar levels of fiber, vitamins, and minerals did not have a significant impact on blood vessel function.
Researchers randomly assigned adults with type 2 diabetes to consume a high-fat, fast-food-style breakfast, either with or without raspberries. Subjects who ate the meal with the additional 250 grams of raspberries showed lower serum blood glucose and reduced markers of inflammation. Participants who consumed raspberries daily for four weeks also exhibited lower inflammation (IL-6 and hsTNF-α) compared to controls.
Infants (mean age of 10 months) were randomly assigned to receive either placebo or a daily mixture of Lactobacillus rhamnosus and Bifidobacterium animalis subsp lactis. At follow-up (about six months later on average) the incidence of eczema was 4.2% in the probiotic group and 11.5% in the placebo group.
Researchers analyzed data from 81233 individuals with pre-diabetes, 29.7% of whom had insomnia at some point during the 4.3-year (average) observation period. After adjustment for traditional risk factors, those with insomnia were 28% more likely to go on to develop type 2 diabetes. This suggests that insomnia may impart an increase in risk of type 2 diabetes comparable to that conferred by traditional risk factors, such as being overweight.
Podcasts We Loved This Week
- Matthew Walker: Dangers of poor sleep, Alzheimer’s risk, mental health, memory consolidation, and more (Part I of III). Via The Peter Attia Drive Podcast.
- Nanci Guest: Caffeine, Your Genes, and Performance Effects. Via Dr. Bubbs Performance Podcast.
Products We Are Enjoying
Ginny says: This apparatus efficiently combines the best attributes of gymnastic rings and typical suspension trainers. The Jungle Gym has a split anchor design, meaning that you can easily adjust the length and separation of both of the straps - you can even do pullups with it if you just shorten each of the straps enough. This makes it a more versatile device than the TRX (while also being much less expensive). It also has little molded foot cradles so you can easily perform knee tucks, pikes, and other exercises without worrying about your feet becoming disengaged from the trainer. Very lightweight and portable, would be a good addition to a basic home gym setup.
New humanOS Content
Stress is something that all of us experience. Even those of us who live relatively safe and comfortable lives in industrialized countries are subject to the effects of chronic stress. As Robert Sapolsky documents in his well-known book on the subject, prolonged exposure to these sorts of psychological stressors ultimately increases our risk of a host of physical ailments, ranging anywhere from mood disorders to gastrointestinal issues to cardiovascular disease.
The problem, of course, is that it is difficult to objectively measure this kind of stress, and how our body is responding to it. Growing interest in better managing physiological stress has led to the release of a number of wearable devices that purport to monitor how we are handling stress on a day-to-day basis - generally through measuring heart rate variability (HRV). But what does that really mean? And does it work?
This week on humanOS Radio, Greg interviewed Professor Phyllis Stein, director of the Heart Rate Variability Lab at Washington University School of Medicine in St Louis. As an undeniable expert on the subject, we felt she could provide useful and objective info on this much-hyped topic. In the podcast, she and Greg discuss:
- What HRV is
- Why people measure HRV
- Using HRV to stratify people according to risk of disease
- Whether higher HRV is always better
- Circadian and ultradian rhythms in heart rate and HRV
- What HRV can tell us about sleep
- The utility of consumer devices designed to assess HRV or pulse rate variability
- What people should standardize when measuring their own HRV
Check out the blog to learn more!