Research Extracts: UVB light can improve the microbiome; the timing of exercise in relation to eating; and other January research summaries
Welcome to the first Research Extracts – blog edition – of 2020. “The Extracts” is designed to keep busy practitioners and savvy consumers up-to-date on the latest research on diet, nutrients, botanicals, the microbiome, the environment, and lifestyle approaches to good health. Our medical team, which includes NDs, MDs, PhDs, RDs, an MS, and an LAc, has summarized the essence of several of the most interesting studies.
Research summaries in this issue include: (1) Acid blockers might contribute to gastroenteritis, (2) UVB light can improve the microbiome, (3) the timing of exercise in relation to eating, and (4) the effect of various caffeine sources on fat metabolism.
Proton pump inhibitors might increase vulnerability to GI viruses in winter
The prevalence of gastroenteritis due to viruses in the GI tract is elevated in winter. Chronic use of proton pump inhibitors (PPIs) is associated with an increased risk of intestinal bacterial infection. A French matched cohort study sought to evaluate whether chronic PPI use is also associated with an increased risk of viral infections in the GI tract.
Anonymous data was included in the study for 850,000 individuals from a national drug dispensing database encompassing the winter of 2015-2016. Prescriptions analysis identified chronic PPI use and incidence of acute gastroenteritis (AGE) during the study period.
Approximately 25 percent of participants were identified as chronic PPI users, while approximately 40 percent of AGE cases occurred in PPI users, which represented a significantly higher AGE incidence among PPI users than non-users. Adjustment for confounders yielded a 66-percent higher risk for 45-64 year-olds, a 119-percent higher risk for 65-74 year-olds, and a 98-percent higher risk for those 75 and older.
While there was no correlation in younger groups, these age groups represented less than five percent of the included population and are not typical users of PPIs.
Although this study did not specifically assess a causative relationship, the authors suggest that known effects of chronic PPI use, including changes to the gastrointestinal microbiome, make the biological link plausible and recommend reassessment of long-term PPI therapy in light of this possibility.
Contributed by Sheena Smith, MS (Biol)
- Vilcu A, Sabatte L, Blanchon T, et al. Association between acute gastroenteritis and continuous use of proton pump inhibitors during winter periods of highest circulation of enteric viruses. enteric viruses. JAMA Netw Open 2019;2(11):e1916205-e1916205
Does UVB light affect the microbiome?
You’ve probably heard a lot about the gut-brain axis. Is there a gut-skin axis?
Twenty-one Caucasian females, ages 19 to 40, were recruited for this study, which took place at the end of winter (February-April) in Vancouver, BC, Canada. During these months at this latitude there is minimal vitamin D-promoting UV light available. Participants had also not been exposed to UV light from outside Canada or from a tanning bed in the three months prior to the start of the study.
The women were divided into two groups – those who had been taking supplemental vitamin D (n=9) during the previous months and those who had not (n=12).
On testing vitamin D blood levels prior to the beginning of the study, most in the vitamin D group had serum levels above 30 ng/mL; whereas, all but one outlier in the no-supplement group measured as insufficient (10-30 ng/mL).
Stool samples were collected before and after UVB exposure – two samples during the three days prior to UVB exposure and two samples during the three days after the exposure. Participants were exposed to full-body UVB light for three sessions in one week.
After UVB exposure most women in both groups experienced a 10-percent average increase in serum vitamin D levels, with the most significant increases seen in the low-vitamin D status group.
In terms of the microbiota, women in the low-vitamin D group at the beginning of the study demonstrated significantly less microbial diversity than women in the vitamin D-sufficient group. After exposure to UVB light for one week, microbial diversity in the low-vitamin D group increased significantly – to levels similar to the vitamin D-sufficient group. Microbial diversity is an important sign of a healthy gut microbiome.
A couple of important take-aways: The health of the gut microbiome as measured by microbial diversity can be significantly improved by exposure to UVB light – which in turn relates to increased vitamin D levels. And, if you live in Canada, then you are likely vitamin D-deficient unless you take a supplement, particularly during winter months.
Contributed by Kathi Head, ND
- Bosman E, Albert A, Lui H, et al. Sun exposure to narrow band ultraviolet (UVB) light modulates the human intestinal microbiome. Front Microbiol 2019 Oct 24;10:2410 doi: 10.3389/fmicb.2019.02410
- To access full text, click here
- Test vitamin D levels for yourself or your patients.
- How healthy is your microbiome? Test for microbial diversity and much more.
Exercise fasted improves insulin sensitivity and lipid metabolism
Regular exercise improves many aspects of health – from mental health to weight management – as well as improvements in laboratory metrics like blood lipids, glucose, and insulin. Opinions vary in the literature and in practice regarding whether best results are achieved when exercising in a fasted versus a fed state.
This study assessed the effect of acute and chronic manipulation of nutrient timing around exercise on lipid metabolism and insulin sensitivity in overweight/obese men. The end goal was to evaluate whether exercising in a fasted state or a fed state would increase insulin sensitivity most efficiently.
The study was comprised of two different experiments – an acute and a training (chronic) component. The acute portion was a randomized crossover study, and the training experiment was a 6-week randomized, controlled study.
In the acute study, 12 sedentary men classified as overweight or obese, without hypertension or diabetes, were assessed at two different visits. At one visit, the participants consumed a standardized breakfast including 25 percent of the estimated daily caloric requirement, followed by 90 minutes of rest, then 60 minutes of cycling exercise.
At the other visit, the participants consumed the same breakfast immediately after the exercise session. Expired gas samples were collected during exercise, blood samples were collected at multiple intervals prior to, during, and after the exercise session, and muscle samples were taken immediately prior to and after the exercise session to assess intramuscular triglyceride utilization.
To assess longer term responses to nutrient timing, the training study recruited 30 sedentary men classified as overweight or obese. Participants were allocated to a no-exercise control group, a breakfast before exercise group, or an exercise before breakfast group, all for six weeks. The exercise session included moderate intensity cycling, three times per week.
Expired gas samples were collected every 10 minutes and ratings of perceived exertion were recorded during exercise sessions. Pre- and post-intervention, an oral glucose tolerance test was conducted and muscle samples were collected.
In the acute study, exercise before breakfast consumption significantly increased intramuscular triglyceride utilization. In the training study, postprandial glucose levels were not affected after six weeks, although postprandial insulin was reduced with exercise performed before, but not after, breakfast consumption.
This resulted in increased insulin sensitivity and lipid utilization during exercise. Exercise before breakfast also contributed to the remodeling of skeletal muscle content of glucose transport protein.
Fasted-state exercise versus fed-state exercise increased intramuscular and whole-body lipid use, translating into increased muscle adaptation and insulin sensitivity when regularly performed over six weeks.
Contributed by Amanda Frick, ND, LAc
- Edinburgh R, Bradley H, Abdullah N-F, et al. Lipid metabolism links nutrient-exercise timing to insulin sensitivity in men classified as overweight or obese. J Clin Endocrinol Metab October 2019. doi:10.1210/clinem/dgz104
Caffeine from all sources shows similar effects on metabolism
Most people know that caffeine gives you an extra burst of energy, but caffeine has also attracted interest lately for its potential to benefit metabolism and body weight. Caffeine can be found from many sources. It can be made in a lab (synthetic caffeine) or it can occur naturally in plants like coffee beans, tea leaves, and the South American shrub called yerba maté. Many of these plants also contain other health-supportive compounds like polyphenols, so researchers have wondered if these compounds have their own benefits on body weight that would give them an advantage over caffeine alone.
A study conducted by researchers in the United States and Spain explored this idea with a specific focus on yerba maté.1 Researchers used synthetic caffeine, caffeine from coffee, caffeine from maté, maté tea, and decaffeinated maté tea, and looked at their effects in mice (in vivo), on fat cells (in vitro), and in a computer model (in silico) to understand how they might differently impact fat accumulation and fat breakdown.
They found that caffeine from all sources had a beneficial effect on body fat accumulation in animals fed with a high-fat-high-sucrose diet, and that in all models, caffeine appears to be most responsible for the beneficial effects observed on body weight and metabolism. Further studies are needed to determine if these results can be reproduced in humans, although some data already exists that supports caffeine as a potential weight management aid.2
Although not everyone can tolerate caffeine, it might also have other health-supportive benefits for things like brain health and possibly digestive health, so adding some to your routine could be doing more than helping you feel energized.
Contributed by Jacqueline Jacques, ND
- Zapata F, Rebollo-Hernanz M, Novakofski J, et al. Caffeine, but not other phytochemicals, in mate tea (Ilex paraguariensis St. Hilaire) attenuates high-fat-high-sucrose-diet-driven lipogenesis and body fat accumulation. J Funct Foods 2020;64:103646. doi:10.1016/j.jff.2019.103646
- Tabrizi R, Saneei P, Lankarani K, et al. The effects of caffeine intake on weight loss: a systematic review and dose-response meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr 2019;59(16):2688-2696.