Wednesday, March 30, 2011

nutrition homework week 11 Electrolytes and Sports Drinks vs Coconut Water

1. Electrolytes: how/where do electrolytes fit with water and cellular balance, as well as regulation of blood pH? For athletes and those who are very active, electrolytes play an important role. From what you have learned about water, cellular balance and blood pH in relation to electrolytes, discuss this relationship with exercise. After explaining the above process, choose one electrolyte and describe how it is affected during the same process when heavy activity and sweating is involved.

Wikipedia gives a great explanation: “A sports drink is a beverage designed to help athletes rehydrate, as well as restore electrolytes, carbohydrates, and other nutrients, which can be depleted after training or competition. Electrolyte replacement promotes proper rehydration, which is important in delaying the onset of fatigue during exercise.”

Electrolytes include sodium, potassium, chloride, calcium and other minerals vital to proper body function. When you sweat you lose these minerals along with water, which is why it is so important to replace them when rehydrating from prolonged intense exercise. Drinking water alone will not replace these electrolytes and can lead to muscle cramps, increased fatigue and in extreme cases death. In healthy mammals, large amounts of water are regularly secreted into the small intestine to help digest and absorb nutrients. Most of the water is recovered as the nutrients are digested and absorbed. Nearly twice the total volume of water in an mammal’s bloodstream cycles into and out of its digestive tract each day.

The mucosa, or lining of the small intestine, is made up of villi and crypts. Villi project into the open space, or lumen, of the small intestine and are mainly involved in nutrient absorption. Each villi is well supplied with blood and lymph vessels that rapidly move absorbed nutrients away from the digestive tract and into the body. Crypt cells, on the other hand, are primarily concerned with secretion of substances, including water, into the intestinal lumen. As food enters the small intestine, water readily “leaks” between the mucosa cells of the upper small intestine into the lumen. During digestion large food particles are broken down to small absorbable nutrients, increasing the concentration of particles inside the intestine. This concentration, referred to as osmotic pressure, is much greater inside the intestine than it is in the cells and fluids of the body surrounding the digestive tract. Since water flows toward areas of high osmotic pressure, water moves from the body into the intestinal lumen. Water can also be moved into the intestine through specific action of crypt cells. By pumping chloride ions (Cl-) into the crypt space of the lumen, crypt cells actively draw water into the intestine. These Cl- ions attract sodium ions (Na+) into the crypt space, increasing the local osmotic pressure. As the osmotic pressure increases, water is pulled into the intestine Some bacteria produce enterotoxins that trigger this pumping mechanism causing hyper-secretion of water. Cholera, which has resulted in the deaths of millions of humans, is perhaps the most infamous of these organisms that lock this pump system in the “ON” position.

Water is reabsorbed from the digestive tract as a result of nutrient absorption, with sodium (Na+) playing an important role in this process. As a rule: water follows sodium. Sodium is free to move across mucosa cell membranes in response to osmotic difference. Although this passive diffusion of Na+ results in water movement out of the digestive tract, it is insufficient for adequate water reabsorption. Sodium is also actively moved across the mucosa cell membrane along with other nutrients, moving from areas of higher osmotic pressure to areas of lower osmotic pressure. Once inside the cell, Na+ is rapidly pumped into the extracellular fluid surrounding the cell, away from the intestinal lumen. As a result of these nutrient movements, a series of osmotic gradients are created which move water from the lumen into the cell, and then from the cell into the extracellular fluid. The Na+ and water then diffuse into the bloodstream. The ability to concentrate Na+ in the extracellular fluid surrounding mucosa cells, drawing water from the digestive tract, increases as food particles move through the small intestine. By the time food reaches the large intestine, about 80% of the water has been reabsorbed.

I searched for a natural alternative to commercial sports drinks and found; that coconut water is so close to natural blood plasma that soldiers in WWII were given direct infusions of coconut water when supplies of blood were low. It has been touted as nature’s sports drink for its balance of electrolytes and natural carbohydrates. One serving of coconut water has about the same amount of potassium and much less sugar than a banana. When compared to Gatorade, coconut water packs a staggering 13x the potassium. You lose quite a bit of sodium through sweat. It is important to replace that sodium because of its importance in proper nerve conduction. In extreme cases of sodium deficiency a person can develop hyponatremia, a serious acute condition in which nerve impulses are interrupted all around the body which can result in death. Coconut water has a little over twice the sodium as Gatorade. Carbohydrate supplementation is more important in higher intensity cardiovascular exercise lasting longer than 60 minutes. For less intense or shorter duration exercise, there is not much benefit to glucose supplementation. When it comes to fat loss goals, limiting the amount of sugar that you ingest is an important step in decreasing body fat. With that in mind, coconut water has far less sugar than regular Gatorade and the sugar it does contain is natural unlike the artifical sweeteners in sugar free or low carb sports drinks. Nothing is perfect however and neither is coconut water. While most sports drinks are heavy on the sodium and light on the potassium, coconut water is the exact opposite. It is traditionally thought that you lose more sodium while sweating and therefore need more sodium after a longer vigorous workout.

While coconut water is getting lots of attention recently with Pepsi Co. producing O.N.E. coconut water with all sorts of added flavors from mango to aci! Minnie Driver's two year old sons birthday party being sponsored by the same (yes, seriously), it is hard not to think of it as a passing fad. Well, maybe it is in Hollywood but in countries where coconuts are plentiful, people have been drinking it for years and have certainly noticed great health benefits from it. I think it is definitely better than Gatorade especially for shorter less intense workouts. I also think most of us get way too much sodium in our diets anyway so the average American shouldn't worry too much about not getting enough sodium after our workouts if we are supplementing with coconut water.

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