Beet supplementation mitigates post-exercise inflammation

Abstract

Objectives: This study investigated the efficacy of a mixed beet-based supplement (BEET) versus placebo (PL) in countering inflammation during recovery from 2.25 h of intensive cycling in 20 male and female cyclists. A multi-omics approach was used that included untargeted proteomics and a targeted oxylipin panel.

Methods: A randomized, placebo-controlled, double-blind, crossover design was used with two 2-week supplementation periods and a 2-week washout period. Supplementation periods were followed by a 2.25 h cycling bout at close to 70%VO_2max. The BEET supplement provided 212 mg of nitrates per day, 200 mg caffeine from green tea extract, 44 mg vitamin C from Camu Camu berry, B-vitamins from quinoa sprouts (40% Daily Value for thiamin, riboflavin, niacin, and vitamin B6), and 2.5 g of a mushroom blend containing Cordyceps sinensis and Inonotus obliquus. Six blood samples were collected before and after supplementation (overnight fasted state), immediately post-exercise, and at 1.5 h-, 3 h-, and 24 h-post-exercise.

Results: The 2.25 h cycling bout increased plasma levels of 41 of 67 oxylipins detected. BEET supplementation significantly increased plasma nitrate (NO₃ ^-) and nitrite (NO₂ ^-) (sum, NO₃ ^- + NO₂ ^-) concentrations (interaction effect, p < 0.001) and two anti-inflammatory oxylipins [18-hydroxyeicosapentaenoic acid (18-HEPE) and 4-hydroxy-docosahexanoic acid (4-HDoHE)]. The untargeted proteomics analysis identified 616 proteins (458 across all times points), and 2-way ANOVA revealed a cluster of 45 proteins that were decreased and a cluster of 21 that were increased in the BEET versus PL trials. Functional enrichment supported significant BEET-related reductions in inflammation-related proteins including several proteins related to complement activation, the acute phase response, and immune cell adhesion, migration, and differentiation.

Discussion: Intake of a BEET-based supplement during a 2-week period was linked to higher plasma levels of NO₃ ^- + NO₂ ^-, elevated post-exercise levels of two anti-inflammatory oxylipins, and a significant decrease in a cluster of proteins involved in complement activation and inflammation. These data support that 2-weeks intake of nitrate from a mixed beet-based supplement moderated protein biomarkers of exercise-induced inflammation in athletes.

Keywords: beets; exercise; inflammation; oxylipins; proteomics.

Figure 1

Study participant flow diagram.

Figure 2

Change in the sum of plasma nitrate and nitrite after 2-weeks BEET and placebo supplementation and during 24 h recovery from 2.25 h cycling in n = 20 cyclists. Time and interaction effects, both p < 0.001.

Figure 3

Change in (A) plasma HEPE-18 and (B) 4-HDoHE in BEET and placebo trials during 24 h recovery from 2.25 h cycling in n = 20 cyclists. Interaction effect, p = 0.016 and 0.010, respectively.

Figure 4

Heatmap and line graphs of clustered proteins in the BEET and placebo trials. T1, pre-study; T2, 2-weeks supplementation, pre-exercise; T3, immediately post-exercise (2.25 h cycling bout); T4, 1.5 h post-exercise; T5, 3 h post-exercise; T6, 24 h post-exercise.

Figure 5

Protein–protein interaction networks and functional enrichments of (A) cluster 1 (45 proteins) that were lower and (B) cluster 2 (21 proteins) that were higher in the BEET compared to placebo trials.