Newsletter #049: Why You Shouldn’t Use Your iPad in Bed, and the Power of Vitamin D ☀️
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 assigned mice to four different diets. One was a standard diet with 4.6% soy-based fiber (healthy controls); the other three were high-fat diets containing no fiber, 10% cellulose fiber, or 10% flaxseed fiber respectively. After 12 weeks, the mice given flaxseed fiber were more physically active, gained less weight, and exhibited better glucose control than other high-fat groups. This may be due to how flaxseed fiber modulates the gut microbiota - the flaxseed group had levels of beneficial metabolites in the gut that was comparable to healthy controls.
Researchers recruited 24 non-obese women who normally slept 7-9 hours per night. The women were randomly assigned to two different sleep conditions: a normal night of sleep, and one night wherein sleep was curtailed by 33%. Hunger and food cravings were assessed, and participants were allowed to select as much food as they wanted at a buffet. Food reward was tested using a progressive ratio task that offered chocolate as a reinforcer. When the women got less sleep, they reported increased hunger, selected larger portion sizes with more total calories at lunch, and consumed more chocolate, compared to when they got a full night of sleep.
☀️ High-dose vitamin D improves insulin sensitivity and slows the progression to diabetes in deficient patients.
Adults diagnosed with prediabetes and vitamin D deficiency were randomly assigned to either vitamin D3 or placebo. After six months, serum 25-hydroxyvitamin D levels were higher in the intervention group (as you would expect). In addition, a measure of insulin resistance (HOMA-IR) was significantly reduced (2.6 versus 3.1 in placebo), and the rate of progression to full-blown diabetes was significantly lowered (3%, versus 28% in the placebo group).
A recent review showed that magnesium plays a crucial role in the activation of vitamin D - in fact, all of the enzymes that metabolize vitamin D appear to require magnesium. Without enough magnesium, not only are the benefits of vitamin D significantly attenuated, but vitamin D without magnesium may disrupt calcium balance, leading to vascular calcification. Surveys suggest that as much as 50% of the population is failing to meet the recommended daily intakes for magnesium, and magnesium content has been declining in commonly consumed food over the past few decades.
Researchers compared the microbiome of children with autism to typically developing children, and observed that those with autism showed lower diversity and an absence of beneficial bacteria. They then treated a group of children with autism with antibiotics, then fecal microbiota transfer daily for 7-8 weeks. The fecal transfer increased microbial diversity and helpful bacteria in the gut. After two years, diversity was even higher, and improvements in gut health persisted. Even more remarkably, a professional evaluator found a 45% reduction in core behavioral symptoms associated with autism spectrum disorder two years post-treatment.
Videos We Loved This Week
- Rachel Herz: Smell, Your Least Appreciated Sense. Via TEDxNatick.
- James Hill: National Weight Control Registry - Common Behaviors in Weight Maintenance. Via Obesity Action Coalition.
- Mikael Ryden: The Role of Adipose Tissue in Weight Loss and Weight Maintenance. Via EASO Obesity.
Products We Are Enjoying
Ginny says: Nutritional yeast is a powdered deactivated yeast that is impressively nutrient rich: relatively high in fiber, B vitamins, and amino acids. It also has a sort of savory, cheesy flavor that is kinda hard to describe. I frequently use it in soups, or to make tasty dips. I prefer this brand (Whole Foods) because it is not fortified - I’m generally not a fan of ultra-high dose vitamins - but there are tons of options out there if you look around.
New humanOS Content
Most people living in Western countries are not getting as much sleep as they need. Not surprising, I know, but research suggests that the situation may be pretty dire. One study that examined 669 American adults found the average sleep duration in that group was just 6.1 hours, which is, um, not great. 😬 Short sleep is associated with a plethora of problems, ranging from impaired immune function to worse glucose tolerance, to increased risk of traffic accidents. Needless to say, this is a really big deal!
So why do we struggle to get enough sleep? Well, we know that the most powerful cue for our biological rhythms is bright light. Visible light regulates circadian rhythms by interacting with light-sensitive neurons in the eye. And our patterns of light exposure have changed dramatically in the modern era, due in large part to technological advances like electricity and consumer electronics. Even when it is pitch black outside, we are often bathed in light. It’s not hard to see how this might constitute an evolutionary mismatch, and how it might have important implications for our health.
This week on humanOS Radio, Dan spoke with Jeanne Duffy. Jeanne is an associate professor of medicine at Harvard Medical School and a sleep researcher at Brigham and Women’s Hospital. She has worked on some compelling lab experiments that explore precisely how alterations in the light environment impact sleep and circadian rhythms. In one recent study, she and colleagues examined how using iPads at night affected melatonin secretion and sleep patterns, and the results are pretty enlightening. To learn about what they found, and what you can do yourself to improve circadian alignment, please check out the podcast!