Séverine Stragier

Nitrate Supplementation, Exercise, and Kidney Function: Are There Detrimental Effects?

PURPOSE Recently, dietary supplementation with inorganic nitrate (NO3) has been proposed to endurance athletes to increase their performance. However, it has been suggested that an excess of NO3 might be harmful. The present study analyzed the effect of NO3 supplementation on kidney function. METHODS Thirteen young male subjects performed a 20-min cycling exercise at 85% of the maximal oxygen capacity. Seven days before exercise, the subjects ingested either a placebo (Pl) or 450 mg of potassium nitrate (PN) per day. Venous blood samples and urine collections were collected before and immediately after exercise and after 60 min of recovery. Glomerular filtration rates (GFR) and clearances (Cl) were calculated from serum content and urine output for creatinine (Crn), albumin (Alb), and urea. RESULTS Under resting conditions, GFR and all clearance measures did not differ between Pl and PN. Immediately after exercise, GFR remained stable in both Pl and PN, whereas Cl-urea decreased significantly (P < 0.05) in Pl (-44%) and PN (-49%). Alb urine outputs were enhanced by 18- to 20-fold in Pl and PN, respectively (P < 0.05). After the recovery period, GFR remained enhanced under Pl conditions, whereas Cl-urea returned to initial values in placebo and nitrate supplementation. Alb output and Cl-Alb remained enhanced under PN conditions. CONCLUSION These results mainly indicate that dietary nitrate supplementation over a week does not induce any specific kidney function modifications either at rest or during sustained submaximal exercise as compared with Pl.

Contribution of muscle hypertrophy to strength gain after training in elderly adults.

Ageing is associated with a progressive decrease in maximal strength (Clark & Manini 2012), with the loss of muscle mass being proposed as the main contributor of such a decrease. However, muscular...

Potential Benefit of Inorganic Nitrate in Acute Kidney Injury and Renal Cell Cancer Response

We thank our colleagues for their reaction toward our currentpublication related to the use of nitrate salts byexercising humans.In our introduction, our colleagues were surprised by thestatement ‘‘A few publications pointed out that nitrate andnitric salts excess exposure is associated with increased risk ofrenal cell carcinoma and acute injury’’ (9,10). However, in thatsame introduction, we pointed out several references fromspecific publications (1,5,7,8) proposing caution for thoseusing nitrate salts. In addition, Gilchrist et al. (4) cited adeclaration of the Food and Agriculture Organization/WorldHealth Organization showing ‘‘nonconsistently increased riskfor cancer,’’ but the European Food Safety Authority (3)stated that ‘‘nitrate and nitric oxide raised concern.’’ This iswhy some researchers proposed that caution should be appliedwhile exercising under nitrate salts supplementation(2,7,8). Moreover, Jones et al. (6) agreed to ‘‘remain alert tothe risk/benefit quotient when studying the effects of nitrateingestion on human physiology.’’Facing different opposite statements on this matterand no real information related to renal physiology inexercising humans under nitrate supplementation, we decidedto look at the effect of nitrate salts upon differentkidney functions such as glomerular filtration rate (creatinine),glomerular membrane permeability (albumin excretionrate), and tubular reabsorption (urea rate). For certain,we still believe proven evidence is better than unprovenexpectation.