Preliminary Assessment of Red Beetroot Supplementation and Cultivar Effects in Low-Protein-Fed WKY Rats

Background/Objectives: Red beetroot (Beta vulgaris L.) is recognized for its antioxidant, anti-inflammatory, and metabolic properties. This study evaluated the effects of two beetroot cultivars (Boldor and Wodan) on blood serum parameters, body composition, and organ weights in male WKY rats fed a low-protein diet (LPD, 8.8% protein). Methods: Five-week-old male rats were maintained on an LPD for 8 weeks and subsequently continued on the LPD diet supplemented with 4% dried beetroot for 45 days. The experimental diets included beetroot from the Boldor and Wodan cultivars, either treated or untreated with a plant growth stimulator during cultivation. Results: Foliar application of the selenium-based plant growth stimulator did not significantly increase selenium or other element concentrations in beet roots. Elemental analysis showed higher levels of Fe, Zn, Cu, Cr, Pb, As, Cd, and Sb in the Wodan group, while Boldor increased Cr, Pb, and As; Ni and Se remained unchanged. Beetroot supplementation significantly affected 14 of the 30 measured biochemical parameters, including biomarkers of liver function (ALT, ALP, total bilirubin, albumin, and total protein), renal function (uric acid), pancreatic activity (amylase and lipase), electrolyte balance (sodium, potassium, and chloride), mineral metabolism (calcium), inflammatory status (CRP), and nutritional metabolism (iron). Conversely, no significant effects were observed on lipid profile parameters or biomarkers of cardiac and skeletal muscle injury. Among the beetroot cultivars evaluated, Wodan exerted distinct effects relative to Boldor, resulting in higher circulating total bilirubin and potassium concentrations, alongside reduced uric acid and lipase levels in treated rats. Boldor supplementation significantly increased body weight gain and fat mass, with a trend toward higher lean mass, and increased kidney weight. Wodan did not significantly affect body weight but increased kidney and spleen mass. Feed intake was similar across groups. No changes in cardiovascular function were observed ex vivo. Conclusions: Beetroot supplementation modulated multiple metabolic and physiological biomarkers in rats fed a low-protein diet, with distinct cultivar-specific effects, underscoring the importance of cultivar selection for optimizing functional dietary interventions.