Impact of Beetroot Juice Supplementation Behaviour on Strength and Physiological | Original Article

ABSTRACT:

Beta vulgaris L. (beetroot) contains high amounts of biologically active substances including betalains and inorganic nitrate. We determined the amounts of various compounds (minerals, betalains, oxalic acid, phenolic acids, and sugars) in juice prepared from seven different beetroot varieties cultivated in Upper Austria. Large differences were found between the varieties for some substances (such as nitrate), whereas others showed only minor variation (certain minerals and sugars). The total betalain content was found to range between 0.8 and 1.3 g/L fresh juice (about 60% betacyanins and 40% betaxanthins) that accounted for 70–100% of the total phenolic content. Other detected phenolic were hydroxycinnamic acids, which accounted for up to 2.6% of total phenolic. Nitrate content varied 10- fold between single varieties. Sugar composition was similar in all varieties with an average total content of about 7.7%, consisting of 95% sucrose. Only minor differences in the concentration of oxalic acid (0.3– 0.5 g/L fresh juice) were found between the varieties. In addition, 16 commercial juices and four powders were analyzed for their nitrate contents, as its metabolic product nitric oxide has been reported to provide cardiovascular benefits. Large variations of the nitrate levels, ranging from 0.01 to 2.4 g/L, were found. Dietary supplementation with beetroot juice (BR) containing ~5-8 mmol of inorganic nitrate (NO3-) increases plasma nitrite concentration ([NO2-]), reduces blood pressure, and may positively influence the physiological responses to exercise. However, the dose-response relationship between the volume of BR ingested and the physiological effects invoked has not been investigated. Following acute BR ingestion, plasma [NO2-] increased in a dose-dependent manner, with the peak changes occurring at ~2-3 h. Compared to PL, 70 ml BR did not alter the physiological responses to exercise.