Influence of Ingesting a Flavonoid‐Rich Supplement On the Human Metabolome and Concentration of Urine Phenolics

Abstract

A variety of polyphenol‐rich supplements (juices, extracts, purified flavonoids) have been tested at low to high doses for varying lengths of time, typically with study participants at high disease risk. Results have been mixed, perhaps because of short dosing periods, low subject numbers, and the lack of focus on whole body metabolic responses. This study evaluated the effect of ingesting a flavonoid‐rich supplement (329 mg/d) on total urine phenolics and shifts in plasma metabolites in overweight/obese female adults using untargeted, global metabolomics procedures. Participants (N=103, 18–65 y, BMI ≥ 25 kg/m2) were randomized to flavonoid or placebo groups for 12 weeks, with blood and 24‐h urine samples collected pre‐study, 4‐ and 12‐weeks in a parallel design. Supplements were prepared as chewable tablets, and included vitamin C, wild bilberry fruit extract, green tea leaf extract, quercetin, caffeine, and omega 3 fatty acids. One serving (4 chewable tablets) contained 50 kilocalories, 100 mg vitamin C, 60 mg n3‐PUFA (24 mg docosahexaenoic acid, 36 mg eicosapentaenoic acid), 107 mg caffeine, and 329 mg total flavonoids. Analysis of pre‐ and post‐study 3‐day food records revealed the flavonoid supplement increased dietary intake by 217% (138±23.0 to 437±20.1 mg/day) compared to placebo (interaction effect, p<0.001). At 4‐weeks, urine total phenolics increased 24% in the flavonoid group above placebo, with similar changes at 12‐weeks (interaction effect, P=0.041). Groups did not differ in traditional markers of inflammation (IL‐6, MCP‐1, CRP) or oxidative stress (oxLDL, FRAP). Metabolomics data indicated shifts in 63 plasma metabolites in the flavonoid versus placebo group, with 70% of these from the lipid and xenobiotics super pathways. The largest fold changes were measured for three gut‐derived phenolics including 3‐methoxycatechol sulfate, 3‐(3‐hydroxyphenyl)propanoic acid sulfate, and 1,2,3‐benzenetriol sulfate (interaction effects, p≤0.050). Small group differences in 29 metabolites from the lipid super pathway were more than likely related to the combined influence of green tea extract and caffeine. This randomized clinical trial of overweight/obese women showed that 12‐weeks ingestion of a mixed flavonoid‐nutrient supplement was associated with a corresponding increase in urine total phenolics and gut‐derived phenolic metabolites. The lack of change in traditional measures of inflammation and oxidative stress in this study is consistent with other 10‐ to 12‐week polyphenol supplementation investigations, and supports the strategy of using metabolomics procedures to better define physiological responses in humans.Support or Funding InformationSupported by funding from Reoxcyn Innovation Group LLC, Salt Lake City, UT