The goal of this study is to compare the possible beneficial effect of beetroot juice supplementation versus the usual management during hospitalization to prevent contrast-induced nephropathy after cardiac catheterizations. The study includes patients diagnosed with non-ST elevation acute coronary syndrome with a possible indication for catheterism and high risk of kidney injury related to iodinated contrast. The intervention group will drink 500 mL (2 glasses daily, at breakfast and dinner) of beetroot juice added to the usual diet for 7 days or until hospital discharge and will receive the recommendation to maintain a diet rich in inorganic nitrates. The control group will receive the usual diet and recommendations. In both cases, other therapies will be prescribed to prevent contrast-induced nephropathy (hydration and statins) if there is no contraindication. Our hypothesis is that a compound present in beetroot juice, inorganic nitrates, can prevent the deterioration of kidney function related to contrast due to its vasodilatory effect, in addition to improving the subsequent prognosis of coronary heart disease due to its anti-inflammatory and antiproliferative effects, protector of the endothelium and inhibitor of platelet aggregation. Beetroot juice could also be beneficial in this context due to the antioxidant effect of the betalains it contains.