Welcome to the September 2020 edition of Research Extracts. “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.

In this issue you will find studies on (1) the most protective face masks for COVID-19, (2) green tea as a prebiotic, (3) milk thistle for menopausal hot flashes, and (4) PharmaGABA® for cognitive support.

New study sheds light on the most effective face masks

The COVID-19 pandemic has caused widespread mandates for face mask usage across the United States. Due to shortages in supply and access to commercial supplies, as well as concerns for cost and comfort and social movements, there has been an increase in the utilization of homemade face masks and mask alternatives. Most homemade and mask alternatives have not been tested to ensure efficacy.

A recent study evaluated the efficacy of various masks to reduce the transmission of respiratory droplets during regular speech. Researchers at Duke University used a simple optical method to measure droplets transmitted through various mask types. They tested 14 commonly available masks/mask alternatives, one patch of a mask material, and an N95 mask. Some of the “masks” tested included knitted, cotton with pleats, cotton without pleats, bandana, neck fleece, and surgical. Recordings were collected during a 40-second time frame while users repeated the sentence, “stay healthy, people,” to measure droplet transmission during speaking, as well as time after speaking. Final droplet transmission rate measured in a range from below 0.1-percent transmission with an N95 mask, to 110-percent transmission with a fleece mask, relative to the control trials of maskless transmission.

Although the N95 mask clearly offered the most reduction in respiratory droplet transmission, with this type typically reserved for professional medical settings, the surgical and homemade masks provided a significant reduction in transmission. The bandana only reduced transmission by half, and the fleece mask actually increased transmission, which is likely due to the fabric causing dispersion of larger droplets without blocking transmission of smaller droplets.

Looking for a new face mask?

Contributed by Amanda Frick, ND, LAc


  • Fischer E, Fischer M, Grass D, et al. Low-cost measurement of facemask efficacy for filtering expelled droplets during speech. Epidemiology 2020. doi:10.1101/2020.06.19.20132969
  • Click here for full-text

Does green tea encourage growth of beneficial intestinal microorganisms?

Intestinal microorganisms are closely associated with many aspects of health. Lean individuals often have a different microbiome composition compared to obese individuals, specific changes in gut microbes are associated with metabolic syndrome, and infectious diseases can be directly caused by microorganisms.

A species of bacteria known as Akkermansia muciniphila benefits the immune health of the intestinal tract by decreasing chronic inflammation that can lead to metabolic disorders. Green tea has also been studied for its health benefits, particularly those related to obesity and metabolic disorders, and has been correlated with healthy gut bacteria in previous studies.*

A research team recently investigated whether green tea might be a catalyst for Akkermansia growth in the digestive tract of mice. The animals were fed a normal diet or a high-fat diet, with each group subdivided into those receiving green tea or placebo.

Study findings included various improvements in obesity-related conditions following green tea supplementation in the mice fed the high-fat diet, including increasing Akkermansia.* This study adds further evidence that green tea acts as a prebiotic to support the health of the microbiome.*

Explore Thorne’s new, unique non-fiber prebiotic that includes green tea. Or looking for a fiber prebiotic that also contains green tea?

Contributed by Jennifer L. Greer, ND, MEd


  • Jeong H, Kim J, Kim A, et al. Green tea encourages growth of Akkermansia muciniphila. J Med Food 2020;23(8):841-851.

Milk thistle might help women with common menopausal hot flashes*

Milk thistle (Silybum marianum) is a botanical commonly used to support liver health.* A recent study suggests it is also useful for providing relief from menopausal hot flashes.* A randomized, double-blind study2 compared 40 women who took a 200-mg capsule twice daily of a standardized extract of milk thistle (80% silymarin, 47.7% silibinin) to 40 women who took a placebo. The women took the capsules for eight weeks and recorded the frequency and severity of hot flashes for 12 weeks (four weeks beyond the time they took the capsules).

After 12 weeks, hot flash frequency decreased from an average of 4.3 per day to 1.3 per day for the women taking milk thistle, and the severity of hot flashes, which was assessed with a visual analog scale, decreased from 5.25 to 1.62 during the same time period.* In addition, assessing quality of life using the Hot Flash Related Daily Interference Scale, the women taking milk thistle extract reported significant decreases in their scores, reflecting an improved quality of life and lesser impact of hot flashes on their daily life.*

The mechanism for how milk thistle can reduce hot flashes is not known, so further research is required to understand what is responsible for this effect. However, given its ready availability and excellent safety profile, milk thistle extract might be an option for women seeking relief.

Contributed by Jacqueline Jacques, ND


  1. Bansal R, Aggarwal N. Menopausal hot flashes: A concise review. J Midlife Health 2019;10(1):6-13. 
  2. Saberi Z, Gorji N, Memariani Z, et al. Evaluation of the effect of Silybum marianum extract on menopausal symptoms: A randomized, double-blind placebo-controlled trial. Phytother Res 2020 Aug 6. doi:10.1002/ptr.6789

Looking for nutritional support for metabolic syndrome or weight management?

Two studies show PharmaGABA® has cognitive benefits in healthy adults*

PharmaGABA, a natural-sourced form of the inhibitory/calming neurotransmitter GABA, has been shown in numerous studies to offset the effects of stress and to support restful sleep.* Two new studies now suggest its possible support for cognitive function.*

In the first double-blind, placebo-controlled study, 60 healthy participants ages 40 and above were randomly assigned to take 100 mg of PharmaGABA or placebo daily for 12 weeks.1 Cognitive function was assessed using Cognitrax and the Repeatable Battery for Assessing Neuropsychological Status (RBRANS), while quality of life was measured via MOS 36-item Short Form Health Survey (SF-36).

After 12 weeks, the PharmaGABA group experienced significantly higher scores than the placebo group for motor speed (Cognitrax), visuospatial/constructional function and delayed memory (RBRANS), and physical functioning (SF-36). Visuospatial/constructional function is the ability to understand the relationship between shapes, copy them, and select the matching spatial relationship objects. The researchers concluded that even at 100 mg per day, GABA supported good cognitive function in over-40 adults.*

The second study evaluated the effect of a higher daily dose (200 mg) of PharmaGABA for cognitive support.The researchers used the exact same study design, number of participants, and methods of evaluation as the first study.

After 12 weeks, the PharmaGABA group demonstrated significant improvements compared to placebo in non-verbal reasoning, sustained attention, and working memory (Cognitrax); visuospatial/constructional function and delayed memory (RBRANS) – the same categories as the 100-mg dose; and the physical, vitality, and mental health category (SF-36) for quality of life.

Overall, the 200-mg dose of PharmaGABA yielded a significantly wider range of cognitive benefits in middle-aged and older adults than did the 100-mg dose.* The higher-dose PharmaGABA also increased insulin-like growth factor 1, which could be one mechanism by which GABA supports cognitive function.*

Contributed by Kathi Head, ND 

Explore Thorne products containing PharmaGABA


  1. Yamatsu A, Nakamura U, Saddam HM, et al. Improvement of memory and spatial cognitive function by continuous ingestion of 100 mg/day of gamma-aminobutyric acid (GABA) – a randomized, double-blind, placebo-controlled, parallel-group clinical trial. Jpn Pharmacol Thera 2020;4(3):475-486. 
  2. Yamatsu A, Nakamura U, Saddam HM, et al. Intake of 200 mg/day gamma-aminobutyric acid (GABA) improves a wide range of cognitive functions – a randomized, double-blind, placebo-controlled, parallel-group clinical trial. Jpn Pharmacol Thera 2020;4(3):461-474.