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[[File:salad 20189577 s.jpg|right|thumb|500px|Fruit and veg are the best sources of potassium.]]Potassium is a vital, but widely misunderstood nutrient. The This is partly because recommended intake of potassium is remarkably high, but this is not because of the potassium itself, but rather because of the health benefits of the potassium containing foods. Potassium deficiency (hypokalemia) is extremely rare in healthy people, even athletes who train in hot environments. However, care must be taken when training with or after some illnesses such as those that include cause vomiting or diarrhea.

Potassium is an abundant nutrient in most fruit and vegetable. Most of this potassium is in the form of potassium bicarbonate, not potassium chloride. This is important, as the bicarbonate has a number of health benefits in itself, including regulating the blood acidity. If there is not sufficient bicarbonate, calcium will be leached from the bones to maintain the correct acidity level. The fruit and veg that contain potassium also typically contain other nutrients including [[Fiber]].

For adults the recommended daily intake of potassium is 4700 mg, but this is not set to prevent potassium deficiency (hypokalemia). Instead, "This this level of dietary intake (i.e., from foods) should maintain lower blood pressure levels, reduce the adverse effects of sodium chloride intake on blood pressure, reduce the risk of recurrent kidney stones, and possibly decrease bone loss<ref name="RDA"/>." These benefits are largely from the bicarbonate and the other vegetable matter rather than than from the potassium.

All adults should aim to get sufficient fruit and vegetables to ensure that they get the recommended intake of 4700 mg of potassium. However, as little as 580mg/day can prevent hypokalemia, though might cause insulin resistance<ref name="Norbiato-1984"/>. Healthy A study showed that healthy patients could maintain their potassium balance on 1600 mg per day, though they were at the lower end of the acceptable range<ref name="Sebastian-1971"/>.

Sweat losses can be as high as 1800mg/day on the initial introduction to hot conditions, but this drops to around 600-800 mg/day with adaptation<ref name="CONSOLAZIO-1963"/>. This is equivalent to around 850 mg/L in the first few days of heat exposure, rapidly dropping to around 250 mg/L. Therefore, if you get close to the RDA of 4700 mg, and need ~1600 mg/day, that would leave ~3000 mg that could be lost in the sweat without creating a deficiency. This would be around 7.5 pints (3.75l75L) initially, or around 24 pints (12l12L) after heat adaptation. Therefore, potassium is probably not necessary for sports drinks if you are healthy. It won't do any harm, and you could add a little salt substitute ([http://www.amazon.com/No-Salt-Substitute-11-Ounce-Can/dp/B000H185N6 No Salt]) to your sports drink if you find this is an effective placebo. However, don't count potassium from salt substitute towards your recommended daily intake of potassium from natural sources.

* '''Diarrhea'''. Severe diarrhea can be a problem on ultramarathons, so additional potassium may be warranted. Be careful returning to training or competition after a serious bout of diarrhea.

* '''Antibiotics'''. Antibiotics such as penicillin, nafcillin, carbenicillin, gentamicin, amphotericin B, foscarnet, can all have been associated with potassium deficiencyexcretion.* '''Kidney disease.''' Diseases that affect the kidneys' ability to retain potassium (such as Liddle syndrome, Cushing syndrome, hyperaldosteronism, Bartter syndrome, or Fanconi syndrome), are risk factors for potassium deficiency.

There Most fruits and vegetables are many sources of potassium, and it's one of the most widely available plant nutrients. However, but it's worth making sure you include a few foods that are particularly high in potassium, mostly for the associated bicarbonate. Here are a few some that I think are particularly noteworthy:* Spinach has a number of health benefits, and has even been associated with improved muscle growth. It is a great source of potassium and fiber. Hundred grams of , and 100g spinach contains 558 mg of potassium.* The average avocado (200g) contains 975 mg (16% DV) of potassium as well is plenty of fiber and some healthy oiloils.* A 3 ounce fillet of salmon contains 534 mg (15% DV) of potassium along with healthy oil and protein. Other fish that are good sources of potassium include Halibut (13% DV), Yellowfin Tuna (13% DV), Anchovies (12% DV), and other fish are about 10% DV.

* Be careful when recovering from a bout of nausea or diarrhea. This as this can cause life-threatening potassium deficiency. I have seen an ultrarunner need urgent medical attention because they attempted to complete 100 mile race soon after a serious digestive tract upset.