Revision as of 10:55, 25 August 2013

Potassium is a vital, but widely misunderstood nutrient. The 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 vomiting or diarrhea.

1 What is potassium?

Potassium and sodium of the two major positive electrolytes, with potassium concentrated inside our cells and sodium concentrated on the outside. The primary negative electrolyte is chloride, along with some bicarbonate (HCO3) that maintains the pH level (acidity).

2 Where do we get potassium from?

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.

3 How much potassium is recommended?

For adults the recommended daily intake of potassium is 4700 mg, but this is not set to prevent potassium deficiency (hypokalemia). Instead, "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^[1]." These benefits are largely from the bicarbonate and the other vegetable matter rather than than from the potassium.

4 How much potassium do we need?

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^[2]. Healthy patients could maintain their potassium balance on 1600 mg per day, though they were at the lower end of the acceptable range^[3].

5 Do you need potassium in your sports drink?

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^[4]. 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, that would leave ~3000 mg that could be lost in the sweat without creating a deficiency. This would be around 7.5 pints (3.75l) initially, or around 24 pints (12l) 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 (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.

6 Running, illness, and potassium deficiency

While potassium deficiency is rare in healthy people, there are a number of conditions, many that affect runners, which could cause this deficiency^[5]:

• Eating disorders. There is reason to believe that eating disorders are more common amongst both male and female athletes than the general population^[6]. These eating disorders can easily result in potassium deficiency, especially if they involve induced vomiting and laxative abuse.
• Diarrhea. Severe diarrhea can be a problem on ultramarathons, so additional potassium may be warranted.
• Vomiting. Many ultrarunners have issues with nausea and vomiting, and this is another situation where additional potassium might be advisable.
• Magnesium deficiency. Athletes should ensure they have an adequate intake of magnesium, as magnesium has many health benefits in addition to its synergy with potassium.
• Antibiotics. Antibiotics such as penicillin, nafcillin, carbenicillin, gentamicin, amphotericin B, foscarnet, can all have been associated potassium deficiency.
• Kidney disease. Diseases that affect the kidneys' ability to retain potassium (Liddle syndrome, Cushing syndrome, hyperaldosteronism, Bartter syndrome, Fanconi syndrome).
• Diuretic medications. Medications intended to increase urine output will also flush out potassium.
• Glycyrrhetinic acid. Eating large amounts of licorice or products that contain licorice made with glycyrrhetinic acid can cause potassium deficiency. Note that glycyrrhetinic acid is no longer used in licorice made in the United States.

The symptoms of potassium deficiency include:

• Abnormal heart rhythms (dysrhythmias), especially in people with heart disease.
• Constipation.
• Fatigue.
• Muscle damage (rhabdomyolysis).
• Muscle weakness or spasms.
• Paralysis (which can include the lungs).

7 Sources of potassium

There are many sources of potassium, and it's one of the most widely available plant nutrients. However, 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 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 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 oil.
• A 3 ounce fillet of salmon contains 534 mg (15% DV) of potassium along with healthy oil and protein. Other fish include Halibut (13% DV), Yellowfin Tuna (13% DV), Anchovies (12% DV), and other fish are about 10% DV.
• While people tend to think that bananas are the best source of potassium, the average banana contains 422mg (12% DV). This is pretty good, but far from the best.

8 Summary and recommendations

My personal recommendations based on my study of the literature are:

• You should aim to eat fruit and vegetables that provide you with 4700 mg or more of potassium each day.
• Don't worry about potassium in your sports drink. It's far more important to get plenty of sodium, but a little potassium won't do any harm.
• Be careful when recovering from a bout of nausea or diarrhea. 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.
• If you or someone you know is suffering from an eating disorder, please seek professional help.

9 References

1. ↑ Accessed on 25 August 2013
2. ↑ G. Norbiato, M. Bevilacqua, R. Meroni, U. Raggi, R. Dagani, D. Scorza, G. Frigeni, T. Vago, Effects of potassium supplementation on insulin binding and insulin action in human obesity: protein-modified fast and refeeding., Eur J Clin Invest, volume 14, issue 6, pages 414-9, Dec 1984, PMID 6441716
3. ↑ A. Sebastian, E. McSherry, RC. Morris, Renal potassium wasting in renal tubular acidosis (RTA): its occurrence in types 1 and 2 RTA despite sustained correction of systemic acidosis., J Clin Invest, volume 50, issue 3, pages 667-78, Mar 1971, doi 10.1172/JCI106537, PMID 5101785
4. ↑ CF. CONSOLAZIO, LO. MATOUSH, RA. NELSON, RS. HARDING, JE. CANHAM, Excretion of sodium, potassium, magnesium and iron in human sweat and the relation of each to balance and requirements., J Nutr, volume 79, pages 407-15, Apr 1963, PMID 14022653
5. ↑ Hypokalemia: MedlinePlus Medical Encyclopedia, http://www.nlm.nih.gov/medlineplus/ency/article/000479.htm, Accessed on 25 August 2013
6. ↑ J. Sundgot-Borgen, MK. Torstveit, Prevalence of eating disorders in elite athletes is higher than in the general population., Clin J Sport Med, volume 14, issue 1, pages 25-32, Jan 2004, PMID 14712163