Welcome to the November 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 very most interesting studies. 

In this issue: (1) quercetin phytosome absorption, (2) branched-chain amino acids and exercise recovery, (3) link between psoriasis and inflammatory bowel disease, and (4) obesity and colorectal cancer risk.

Quercetin in a phytosome complex results in as much as 20-times higher blood levels than non-complexed quercetin.

Contributed by Kathi Head, ND

Although the flavonoid quercetin is known to confer numerous health benefits, it is also known to be very insoluble and poorly absorbed. Researchers in Italy studied the effects of binding quercetin to phospholipids from sunflower oil (a complex known as a phytosome) to determine if complexed quercetin is better absorbed. In a double-blind, three-arm, crossover trial, 12 healthy volunteers were given one dose of three preparations of quercetin with a one-week washout period in between each arm. The three preparations were: 500 mg non-complexed quercetin, 250 mg quercetin phytosome, and 500 mg quercetin phytosome. Blood samples were taken before consuming the quercetin, and at 15, 30, 45, and 60 minutes, and 2, 3, 4 6, 8, 12, and 24 hours after taking each preparation.

The maximum concentration (Cmax) achieved with the 500-mg quercetin phytosome preparation was 223 ng/mL – about 20 times higher than the non-complexed quercetin preparation. The area under the curve (AUC) for the 500-mg quercetin phytosome preparation was 18 times higher than the non-complexed quercetin. The 250-mg quercetin phytosome preparation mirrored the 500-mg quercetin phytosome preparation, at about half the Cmax and AUC.


BCAA supplementation following eccentric exercise.

Contributed by Laura Kunces, PhD

This randomized, placebo-controlled study examined the effects of a pre- and post-exercise branched-chain amino acid (BCAA) drink compared to a placebo maltodextrin drink on various markers of muscle damage and recovery of muscle function in 20 resistance-trained male subjects completing a muscle-damaging protocol. Subjects ingested 0.22 g/kg/day of BCAA (average 7.16 g = 3 g leucine, 1 g isoleucine, 2 g valine) for eight days, while adhering to a dietary protein intake slightly lower than the recommended range (1.2 g/kg/day).

On day five, subjects performed the exercise protocol. Results showed creatine kinase (CK) was elevated from pre (p<0.001) in BCAA and placebo at 4, 24, 48, and 72 hours post-exercise, but was lower (p = 0.02) in BCAA at 48 hours compared to placebo. Soreness increased significantly from baseline (p < 0.01) in both groups at all time points; however, the BCAA group reported less soreness (p < 0.01) at 48- and 72-hour time-points. Maximal voluntary isometric contraction (MVIC) force output returned to baseline levels (p > 0.05) at 24, 48, and 72 hours for the BCAA group.

Researchers report BCAA supplementation pre- and post-exercise can mitigate muscle soreness following muscle-damaging exercise. However, when consumed as part of a diet with lower than recommended protein intake (1.2 g/kg/day), the attenuation of muscular performance decrements or CK levels are likely negligible.

Note:  1.4 to 2.0 g protein/kg body weight/day is a typical recommendation of protein intake for most exercising individuals. Protein intake above 2 g/kg/day can be efficacious in hypocaloric exercising adults.*


Individuals who have psoriasis are at increased risk for inflammatory bowel disease.

Contributed by Sheena Smith, MS (Biol) 

A large meta-analysis involving nine studies, including nearly eight million participants, recently identified a correlation between psoriasis and an increased risk for inflammatory bowel disease (IBD). IBD occurs in various forms, with Crohn’s disease (CD) and ulcerative colitis (UC) being the most common. Psoriasis is associated with numerous comorbidities and both psoriasis and IBD are chronic, relapsing, immune-mediated diseases with similar genetic and immunologic landscapes. 

Of the eight million individuals included in the nine studies, one-fourth were in one cross-sectional and four case-control studies. Patients who had psoriasis had a risk for CD that was 1.7 times higher, and for UC it was 1.75 times higher than patients who did not have psoriasis. For the nearly six million participants in the four cohort studies included in the meta-analysis, the risk for CD was 2.53 times higher, and for UC it was 1.71 times higher, when psoriasis was present.  Similar increased risk was found in a subgroup with psoriatic arthritis. 

Obesity increases the risk of early-onset colorectal cancer in women.

Contributed by Mario Roxas, ND

The incidence of, and mortality from, colorectal cancer (CRC) among individuals younger than age 50 (early-onset CRC) are on the rise. Although the reason for this increase is unknown, it is suspected that the prevalence of obesity might be partially responsible. This study investigated the association between obesity and weight gain since early adulthood with the risk of early-onset CRC.

Data was collected and analyzed from 85,256 women, ages 25 to 42, who had enrolled in the Nurses’ Health Study II in 1989, who had all been free of cancer and inflammatory bowel disease at that time, and who had been followed through December 31, 2011. Validated body mass index (BMI) measures and lifestyle information were self-reported biennially. The data included current BMI (calculated as weight in kilograms divided by height in meters squared), BMI at 18 years of age, and weight gain since age 18. Statistical analysis was performed from June 12, 2017 to June 28, 2018.

Of the 85,256 participants, there were 114 documented cases of early-onset CRC (median age at diagnosis: 45 years). Compared with women with a current BMI of 18.5-22.9, the relative risk (RR) was 1.37 for overweight women (BMI, 25.0-29.9) and 1.93 for obese women (BMI, ≥30.0). Both BMI at age 18 and weight gain since then contributed to this observation. Compared with women with a BMI at age 18 of 18.5-20.9, the RR of early-onset CRC was 1.32 for women with a BMI of 21.0-22.9 at age 18 and 1.63 for women with a BMI ≥23.0 at age 18. Compared with women who had gained less than 5.0 kg or had lost weight, the RR of early-onset CRC was 1.65 for women gaining 20.0-39.9 kg and 2.15 for women gaining 40.0 kg or more.

The study therefore suggests that obesity might very well be associated with an increased risk of early-onset CRC among women. Further investigation is needed to identify the underlying biological mechanisms. In addition, the researchers suggest a similar study be conducted among men.