title: Plasma potassium concentration and content changes after banana ingestion in exercised men.
abstract: BACKGROUND
  Individuals prone to exercise-associated muscle cramps (EAMCs) are instructed to eat bananas because of their high potassium (K(+)) concentration and carbohydrate content and the perception that K(+) imbalances and fatigue contribute to the genesis  of EAMCs. No data exist about the effect of bananas on plasma K(+) concentration ([K(+)](p)) or plasma glucose concentration ([glucose](p)) after exercise in the heat.
  
  
  OBJECTIVE
  To determine whether ingesting 0, 1, or 2 servings of bananas  after 60 minutes of moderate to vigorous exercise in the heat alters [K(+)](p) or [glucose](p) and whether changes in [K(+)](p) result from hypotonic fluid effluxes or K(+) ion changes.
  
  
  METHODS
  Crossover study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Nine euhydrated men (age = 27 ± 4 years, height = 180.3 ± 8.4 cm, mass = 84.9 ± 26.1 kg, urine specific gravity ≤ 1.006) without EAMCs volunteered.
  
  
  METHODS
  On 3 separate days, participants completed 60 minutes of moderate to vigorous cycling (temperature = 36.4°C ± 1.1°C, relative humidity = 19.4% ± 2.5%) and then ate 0 g (0 servings), 150 g (1 serving), or 300 g (2 servings) of bananas. Blood samples were collected at 3,  5, 15, 30, and 60 minutes postingestion.
  
  
  METHODS
  The [K(+)](p), changes in plasma K(+) content, plasma volume changes, and [glucose](p).
  
  
  RESULTS
  The [K(+)](p)  differed between conditions at 60 minutes; 2 servings (4.6 ± 0.3 mmol/L [conventional unit = 4.6 ± 0.3 mEq/L]) was greater than 1 serving (4.5 ± 0.2 mmol/L [conventional unit = 4.5 ± 0.2 mEq/L]) and 0 servings (4.4 ± 0.3 mmol/L [conventional unit = 4.4 ±  0.3 mEq/L]) (P < .05). The [K(+)](p) was greater at 60 minutes than at 3 and 5 minutes in the 1-serving condition and was greater at 30 and 60 minutes than at 3 and 5 minutes in the 2-servings condition (P < .05). Percentage change in K(+) content  was greater only at 30 and 60 minutes postingestion than at baseline in the 2-servings condition (4.4% ± 3.7% and 5.8% ± 2.3% increase, respectively) (P < .05). The plasma volume changes among conditions were unremarkable. The [glucose](p) was greater in the  2-servings condition than in all other conditions at 15, 30, and 60 minutes (P < .05).
  
  
  CONCLUSIONS
  The effect of banana ingestion on EAMCs is unknown; however, these data suggested bananas are unlikely to relieve EAMCs by increasing extracellular [K(+)]  or [glucose](p). The increases in [K(+)](p) were marginal and within normal clinical values. The changes in [K(+)](p), plasma K(+) content, and [glucose](p) do not occur quickly enough to treat acute EAMCs, especially if they develop  near the end of competition.
authors.affiliation: Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, PO Box 6050, Department 2620, Fargo, ND 58108, USA. Kevin.C.Miller@ndsu.edu
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Miller
mesh_terms: D000328:Adult; D001786:Blood Glucose; D018592:Cross-Over Studies; D004435:Eating; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D028521:Musa; D009120:Muscle Cramp / Q000178:diet therapy*; D011188:Potassium / Q000097:blood*
chemical_list: D001786:Blood Glucose; D011188:Potassium