Welcome to the September 2019 issue of Thorne’s Research Extracts – 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, and an MS, LAc, and CCN, has summarized the essence of several of the most interesting studies.

Research summaries in this issue include: (1) macular carotenoids for brain health, (2) nutrient deficiencies and frailty in elderly, (3) choline, eggs, and cognition, (4) GABA, whey, and muscle mass, and (5) link to a podcast interview with The Medicine Hunter on ashwagandha.

Macular carotenoids show promise for brain health and cognitive function

Supplementation with the carotenoids lutein and zeaxanthin have been shown to increase pigmentation in the macula, the area of the eye’s retina that is responsible for focus and color vision.* These pigmented nutrients support the function of the macula and can protect it from damage from blue-spectrum light and oxygen.*

Researchers at Duke University and the University of Georgia studied the relationship between supplementing with lutein and zeaxanthin and brain health and cognitive function. In a 6-month study of 59 young individuals given these nutrients or a placebo, supplementation increased pigmentation in the macula and caused an increase in brain-derived neurotrophic factor – a positive indicator of brain function and neuroplasticity (the ability to learn and form new memories).* 

In addition, significant improvements were observed on cognitive tests, including tests related to memory, attention, and processing speed,* which were not seen in the placebo group. This study shows that a modest amount of the carotenoids lutein and zeaxanthin (13 mg total daily) not only supports eye health, but brain function as well.*

Contributed by Alan Miller, ND


  • Stringham N, Holmes P, Stringham J. Effects of macular xanthophyll supplementation on brain-derived neurotrophic factor, pro-inflammatory cytokines, and cognitive performance. Physiol Behav 2019 Aug 16:112650. doi: 10.1016/j.physbeh.2019.112650.

Micronutrients guard against frailty in aging

Frailty, defined as a general decline in physical and physiological wellbeing, is associated with many of the debilitating symptoms associated with advanced age, such as an increased risk of falls, poor ability to adapt to stress, poor ability to recover from common illness, increased cognitive decline, and greater likelihood of institutionalization or hospitalization.

This analysis looked at the association between circulating micronutrients and assessments of frailty in 4,000 adults older than 50. After adjusting for social, lifestyle, health, and seasonal factors, numerous correlations were found. All frailty indicators were associated with low levels of vitamin D and the carotenoids lutein and zeaxanthin.*

Prefrailty, where just one or two risk factors are present, was also evaluated and found to be linked to low levels of vitamin D and lutein (but not zeaxanthin).* No relationship was established with folate and B12 levels, which were also measured in the study.

Based on these findings and other supportive data, the researchers concluded: “Micronutrient supplementation and mandatory food fortification may be cost-effective strategies to both prevent and intervene in the progression of frailty.”*

Contributed by Jacqueline Jacques, ND


  • O’Halloran A, Laird E, Feeney J, et al. Circulating micronutrient biomarkers are associated with 3 measures of frailty: evidence from the Irish Longitudinal Study on Ageing. J Am Med Dir Assoc. August 2019:S1525861019304979. doi:10.1016/j.jamda.2019.06.011
  • Full text of study available here: https://www.jamda.com/article/S1525-8610(19)30497-9/fulltext

Editor’s note: This study adds to the growing body of evidence of cognitive support from macular pigments.* As noted in another study in this Take 5 Daily post, lutein and zeaxanthin also support cognitive function, an important aspect of any nutritional program for an aging population.*

Dietary choline and cognitive function – eat your eggs

Egg intake has been positively associated with improved cognitive performance in previous observational studies.* Eggs are one of the best dietary sources of choline and the best food source of phosphatidylcholine (PC) – nutrients associated with healthy brain function.*

In the Kuopio Ischemic Heart Disease Risk Factor Study (conducted at the University of Eastern Finland), 2,497 Finnish men (ages 42-60) were studied to determine the association between dietary choline/PC intake and cognitive performance.

Four years into the study, a subset of 482 men completed five tests measuring memory and cognitive processing – the Mini-Mental State Exam, Trail Making Test A, Verbal Fluency Test, Selective Reminding Test, and Russell’s adaptation of the Visual Reproduction Test. Choline and PC intake were both associated with improvement in several cognitive functions associated with verbal fluency and memory.*

Increasing dietary choline and PC appear to be a simple way to maintain good cognitive health. Although the jury still seems to be deliberating on whether eggs are an overall health benefit or risk, this study appears to point to the potential cognitive benefits of eating eggs.

Contributed by Danielle Paciera, LDN, RD, CCN


  • Ylilauri M, Voutilainen S, Lönnroos E, et al. Associations of dietary choline intake . . . and . . . cognitive performance: The Kuopio Ischaemic Heart Disease Risk Factor Study. Am J Clin Nutr 2019 Jul; pii: nqz148. doi: 10.1093/ajcn/nqz148.

PharmaGABA® plus whey protein promotes lean muscle mass*

In a recent study on the effect of nutrient supplementation on muscle mass, 21 males (average age, 39) who did not exercise regularly were given 10 grams of whey protein or 10 grams of whey protein plus 100 mg of natural-source GABA (PharmaGABA®) daily for 12 weeks.

Both supplements were taken within 15 minutes of completing exercise training, or before bedtime on non-exercise days. Both groups participated in twice-weekly, 60-minute strength training sessions consisting of leg presses, leg extensions, leg curls, chest presses, and pull-downs.

Total body lean muscle mass increased significantly in th  whey protein plus PharmaGABA group compared to the whey-only group after 12 weeks.* In addition, growth hormone (GH) increased significantly from baseline in the whey protein-plus-GABA group after four and eight weeks; whereas, GH increased in the whey-only group from baseline only after eight weeks.*

Contributed by Kathi Head, ND


  • Sakashita M, Nakamura U, Horie N, et al. Oral supplementation using gamma-aminobutyric acid and whey protein improves whole body fat-free mass in men after resistance training. J Clin Med Res 2019;11(6):423-434.
  • Full text of study available here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6522239/

Listen to Dr. Miller’s interview with The Medicine Hunter

Alan Miller, ND, interviews The Medicine Hunter Chris Kilham. Chris, an expert on many botanicals indigenous to traditional medicine systems around the world, talks about the Ayurvedic botanical ashwagandha in this lively podcast.

Listen Now