Welcome to the April 2019 edition of Thorne’s Research Extracts. This is Thorne’s monthly research update on diet, nutrient, botanical, and lifestyle approaches to good health. Knowing that busy practitioners can’t always focus on the latest research, our medical team of NDs, MDs, PhDs, RDs, and MS (Biol) has summarized the essence of the most interesting studies.

In this issue: (1) aerobic exercise for concussion, (2) blueberries and blood pressure, (3) body composition and bone density, and (4) the microbiome’s effect on glycemic response to food.

Carefully regulated aerobic exercise can be beneficial following sports concussion in adolescents

Although standard of care for sport-related concussion (SRC) has historically included avoidance of physical activity during recovery, recent evidence suggests the potential value of sub-symptom-threshold aerobic exercise to support recovery.

To study this, adolescent participants (ages 13-18 years) who had experienced SRC within 10 days prior to study intake were randomized into aerobic exercise (n=52) or stretching exercise (n=51) groups. Aerobic exercise was walking or stationary cycling at 80% of heart rate (HR) measured at symptom exacerbation during the first study visit and weekly thereafter.

Stretching included gentle, whole-body stretching exercises that also progressed weekly and did not raise HR. Both groups were instructed to exercise for 20 minutes daily. The aerobic exercise group was also instructed to stop early if symptoms worsened during exercise.

Participants reported symptoms and compliance daily and were evaluated weekly by a physician until recovery up to 30 days. Participants who did not recover within 30 days were considered to have delayed recovery. Recovery in the aerobic exercise group was significantly shorter than in the stretching group (median 13 versus 17 days, respectively).

A trend was observed for fewer participants with delayed recovery in the aerobic group (2 aerobic versus 7 stretching). Lower symptom scores were also observed in the aerobic group, although statistical significance was only achieved on 3 of 21 days reported.

The authors suggest that early, sub-threshold aerobic exercise is safe and beneficial for many adolescents with sports-related concussions, but caution this does not generalize to younger or older individuals or those who have sustained head injury via other means.

Contributed by Sheena Smith, MS (Biol)

References

  • Leddy J, Haider M, Ellis M, et al. Early sub-threshold aerobic exercise for sport-related concussion: a randomized clinical trial. JAMA Pediatr 2019 Feb 4. doi: 10.1001/jamapediatrics.2018.4397. [Epub ahead of print]

Blueberries can lower blood pressure and improve endothelial function

Four related small clinical trials looked at the effect of blueberries on endothelial function measured by flow mediated dilations (FMD) and blood pressure in healthy male volunteers.

Study 1: In a crossover trial, five healthy volunteers were given 11 grams of freeze-dried wild blueberry powder (equivalent to 100 grams of blueberries) or one of four other drinks, in random order, with a one-week washout in between. The purpose was to identify the active component or components in the beverage.

The other drinks included control (water matched for color and flavor), control with vitamins and minerals mirroring what would be found in the blueberry powder, control with fiber matched to the amount in the blueberry powder, and control with 160 mg of anthocyanins – active polyphenols found in blueberries. FMD was measured at 1, 2, and 6 hours after drink consumption. Both wild blueberry and pure anthocyanins significantly improved FMD.

Study 2: Ten healthy male volunteers participated in a dose-response study of several anthocyanin concentrations (80, 160, 240, 320, 480 mg) on six days with one-week washouts. FMD was tested at 2 and 6 hours. Higher concentrations resulted in dose-dependent improvements in FMD.

Study 3: Five healthy male volunteers took 11 grams of wild blueberry powder equal to 100 grams of blueberries twice daily for 28 days and FMD was measured once a week for the four weeks. FMD improved after one week, continued to improve by the end of the second week, and then plateaued.

Study 4: Twenty healthy male volunteers took 11 grams of wild blueberry powder equal to 100 grams of blueberries twice daily for 28 days, and were compared to 20 other healthy male volunteers who drank a control drink matched for color and flavor.

In the blueberry group, systolic blood pressure improved an average of 5.8 mmHg between day 1 and day 28 of the study, compared to no differences in the control group; no significant difference in diastolic pressure occurred in either group. In the blueberry group, FMD improved 2.3% after 28 days.

According to the researchers, this should be clinically significant as a decrease as small as 1% has been shown to decrease cardiovascular disease (CVD) risk by 10%. Although both wild blueberry and pure anthocyanins improved FMD – the blueberry juice was more effective, indicating there are other components at play than just the anthocyanins.

The nutrigenomic effect of blueberries was also analyzed in 10 of the volunteers. Between day 1 and day 28, 357 genes were up-regulated and 251 were down-regulated. The authors conclude: “Taken together, our nutrigenomic data showed that blueberry consumption can modulate the expression of genes and miRNA toward an anti-inflammatory and CVD protective profile, revealing new molecular targets that may be underlying the health properties of berries.”

Contributed by Kathi Head, ND 

References

  • Rodriguez-Mateos A, Istas G, Boschek L, et al. Circulating anthocyanin metabolites mediate vascular benefits of blueberries: insights from randomized controlled trials, metabolomics, and nutrigenomics. J Gerontol A Biol Sci Med Sci2019 Feb 16. pii: glz047. doi: 10.1093/gerona/glz047.

The impact of body composition on bone mineral density in childhood

Peak bone mass density is established primarily during childhood and adolescence. Because the rates of childhood obesity are rising, researchers at the Chan School of Public Health at Harvard University examined the role of body composition on bone mineral density (BMD).

While existing research shows a higher total body mass and fat-free mass linked to higher areal bone mineral density (aBMD) z-scores, this study attempted to quantify the impact that percent body fat had on bone quality.

A cohort of 876 school-aged children in Boston were examined via dual-energy X-ray absorptiometry (DXA), as well as anthropometric measures, to assess total body mass, fat-free mass, and fat distribution (truncal/abdominal versus non-truncal). Results confirmed that, overall, higher total body mass and fat-free mass measurements are associated with higher aBMD z-scores.

When fat-free mass was standardized, the researchers noted that in children who fell below the 85th percentile, fat mass was associated positively with aBMD z-score. However, the study identified the 85th percentile as the threshold above which adipose tissue may be more metabolically active, thus adversely affecting bone.

In children above the 85th percentile, fat mass was negatively associated with aBMD scores. In these subjects, central adiposity (abdominal fat) was associated with lower aBMD z-score.

This study adds to recent NHANES data that shows that children with body fat percentages above the mean had lower BMD scores. Further research is expected in the field of childhood body composition and bone health.

Contributed by Joel Totoro, RD

References

  • Rokoff L, Rifas-Shiman S, Switkowski K, et al. Body composition and bone mineral density in childhood. Bone 2019;121:9-15.

Individual glycemic responses not just dictated by food composition

Controlling glycemic response is an important aspect of managing both diabetes and cardiovascular disease. Standard of care often relies on food composition, especially carbohydrates, to estimate glycemic response and inform management decisions.

However, these same foods can generate vastly different glycemic responses in different individuals. Scientists have recently begun to develop models with significantly improved predictive power that utilize individual patient parameters, including gut microbiome data, to account for this diversity.

In a recent study conducted by Mayo Clinic researchers in collaboration with an Israeli company, 293 healthy U.S. adults provided a fecal microbiome sample prior to study start, logged food and activity on a mobile app, and provided constant glucose monitoring data and manual glucose monitoring (4 times/day for calibration) for six days.1

During the study, participants ate normally except for four standardized study meals (bagel and cream cheese). Data from approximately 90% of the participants was combined with a subset of data from a previous study2 to revise and train the predictive model. The remaining 10% was used to test the model. The complex model that was developed successfully predicted individual glycemic responses more accurately than standard predictive models that use only calorie or carbohydrate factors.

The model also accounted for much of the variance between individuals and generated very few predictions that were too high or low. The authors note that many of the factors included in their model were related to the fecal microbiome, suggesting the microbiome’s importance in helping identify individual responses to specific foods.

Contributed by Sheena Smith, MS (Biol)

References

  • Mendes-Soares H, Raveh-Sadka T, Azulay S, et al. Assessment of a personalized approach to predicting postprandial glycemic responses to food among individuals without diabetes. JAMA Netw Open 2019;2(2):e188102. doi:10.1001/jamanetworkopen.2018.8102
  • Zeevi D, Korem T, Zmora N, et al. Personalized nutrition by prediction of glycemic responses. Cell 2015;163(5): 1079-1094. doi:10.1016/j.cell.2015.11.001