Gut microflora dysbiosis affects the majority of individuals after COVID-19, contributing to both gastro-intestinal (GI) and non-GI symptoms. Natural phytochemicals have reported anti-viral properties and favourable effects on inflammatory and oxidative pathways, both important for tissue damage post-viral pneumonia. This study involved 147 participants with symptomatic COVID-19, randomised to receive a placebo (P) or a phytochemical-rich concentrated food capsule (PC) in addition to a pre/probiotic lactobacillus capsule. Participants taking the PC had an almost two-fold reduction in mean fatigue scores compared to P [p = 0.02], a three-fold reduction in cough score and more than a double improvement in overall well-being scores [p = 0.02]. Two (1.5%) participants reported mild, increased bloating which they felt was attributable to the capsules, although GI symptoms improved in 25 of 31 participants (82%) who reported them at baseline. Sedentary, older, previously hospitalised men with GI symptoms had a statistically significantly improvement among those given the probiotic. Although some participants with early disease would have improved spontaneously, such a rapid improvement observed in the majority of participants, who had been suffering for an average of 108 days, was clinically relevant and welcomed, especially among those more likely to have pre-existing gut dysbiosis. We are now evaluating whether this blend could also enhance antibody titres post-COVID-19 vaccination.

Natural phytochemicals (PCs) are responsible for the taste, colour, and aroma of many edible plants. Cohort studies have linked higher intake to a reduced risk of chronic degenerative diseases and premature ageing. The ability of foods rich in PCs, such as phytanthocyanins, apigenin, flavonols, flavonoids, bioflavonoids, gallic acid, ellagic acid, quercetin, and ellagitannins, to support physical activity has also been highlighted in a number of published pre-clinical and prospective clinical studies. This literature mostly emphasises the ability of PCs to enhance the adaptive upregulation of antioxidant enzymes (AEs), which reduces exercise-associated oxidative stress, but there are several other mechanisms of benefit that this narrative review addresses. These mechanisms include; protecting joints and tendons from physical trauma during exercise; mitigating delayed-onset muscle symptoms (DOMS) and muscle damage; improving muscle and tissue oxygenation during training; cultivating a healthy gut microbiome hence lowering excess inflammation; cutting the incidence of upper respiratory tract viral infections which disrupt training programmes; and helping to restore circadian rhythm which improves sleep recovery and reduces daytime fatigue, which in turn elevates mood and motivation to train.