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Q #1: Potassium and Exercise/Heat
Is potassium gluconate good to take when working outside in the extreme heat? (July, 2001)
A: Charlie Smilgelski, RD responds:
I vaguely recall that potassium chloride is a more effective potassium supplement than any other form, but that is for helping to replace lost potassium caused by "fluid pills" used in the treatment of high blood pressure. There the key still seems to be getting about 40 mEq of potassium, about 1600 milligrams I think...roughly 3 bananas.
Potassium supplements are notoriously nauseating anyway.
As for potassium losses in hot working or athletic environment.... In exercise, there is generally a shift of more potassium into the blood, from inside cells, and so blood tests show higher potassium levels during exertion in heated conditions. Blood levels usually return to normal in about an hour. Why the change occurs, I am not sure, but nerves control potassium reabsorpion in kidneys, and are under the influence of noradrenaline. Also, muscle cell damage causes leakage of potassium out of cells and into blood. There may be other mechanisms too.
Adding potassium to a sports beverage does not really change blood levels much I think, the kidneys just have a little less work to do. If you remember, the drink "Exceed" (from Mead Johnson) had more potassium than sodium as compared to Gatorade, which is more sodium than potassium. One drink survived!!! You know which one. Exceed was quite nauseating for most people. (I can tell you the story of 300 people in my bike club riding the 130 miles from Boston to Provincetown on a warm June Saturday who were quite annoyed about my trying Exceed one day instead of Gatorade at the refreshment stations.)
All in all, hot weather would warrant a few extra oranges and bananas for snacks, and more sweet and white potatoes than rice and pasta at supper. But potassium supplements of any kind offer no benefit that I see, and supplements risk nausea as well.
Here are some potassium levels in common foods:
1 cup cooked mushrooms 555 mg potassium
1 cup grated carrot 355 mg
1 cup spinach, cooked 566 mg
1 medium raw tomato 573 mg
1 cup cooked mashed parsnips 844 mg
1 cup mashed sweet potato 1206 mg
1 Tblsp black stra molasses 511 mg
1 cup plain, no fat yogurt 625 mg
2500 mg is minimum; 3000 to 4000 mg is better. No need for pills.
Q #2: Potassium in Food
I would just like to know what foods are a good source of potassium. Thank you. (August, 2000)
A: Barbara J. Scott, MPH, RD responds:
Potassium is found in a very wide variety of foods in our typical diet. Excellent sources include dried fruits, avocado, melon, orange juice, wheat germ, clams, most types of fish, almonds, peanuts, sunflower seeds, all kinds of cooked dry beans (kidney, pinto, garbanzo, etc.), most leafy greens, potatoes, mushrooms, squash, tomato paste. Other good sources include almost all fresh fruit and vegetables, fruit juice, red meats, and dairy products.
In addition, many salt substitutes are made with potassium chloride and can add considerable amounts of potassium to your diet.
Q #3: Potassium in Heart Disease
What effect do high potassium levels have on heart disease patients? (August, 2000)
A: Donna Tinnerello, MS, RD, CD/N responds:
Potassium is a mineral (a micronutrient that is found in fruits and vegetables) that is an indispensable dietary constituent. Among its many roles in the body, it is essential for normal muscular function. The heart is a muscle. Too little potassium interrupts the activity of the heart, as does potassium overload. Excess potassium causes an increased fibrillation of the heart and death in extreme cases.
In heart disease high potassium is likely to be due to medications used to treat high blood pressure. These medications tend to conserve potassium in the blood. The medications in question are classified as ACE inhibitors and include Accupril, Altace, Capoten, Lotensin, Monopril, Prinivil, Vasotec and Zestril. We usually counsel patients taking these medications to go on a low potassium diet if the MD agrees. Sometimes people taking these medications take other drugs that cancel out the effect - they might take water pills, for example, that cause potassium losses. People taking these medications should not take potassium supplements or potassium based salt substitutes without the permission of their MDs.
The main reason for potassium overload in disease is when there is an inability to rid the body of the excess in the urine e.g. kidney failure. The normal kidney is capable of excretion - exceptions are cases of severe burns or crushing injuries, severe infections or overtreatment with potassium salts and potassium-sparing medications such as those mentioned above.
Q #4: Potassium Absorption
Do you see any differences in the different types of potassium, i.e., in absorption, etc., once they are in water? (December, 1998)
A: Chester Myers, PhD, MS responds:
I'm not sure of all the different forms of potassium used for supplements, rehydration formulations, etc. There are numerous candidates - pretty well anywhere one finds sodium, there is likely to be the corresponding potassium compound. Potassium chloride seems the most common in supplements, but there are others. I think there are some studies, which I am not 'up on', that suggest potassium absorption may vary somewhat with variation in polymers such as polysaccharides in a formulation - this may have to do with intestinal transit time as a function of those polymers.
If the compound is slow dissolving, this may not be a serious issue since potassium absorption occurs mainly in the colon, i.e., late in the gut's digestive processes. However, if the compound has a very low solubility/dissociation constant, then the potassium may not become available for absorption. I would be surprised if anyone uses compounds that would not dissolve in the gut. I don't know what role the stomach acid and its subsequent neutralization might have on all this. Suppliers should provide such information for any form of potassium that is not the standard chloride or other readily dissociable salt.
"Chelation" is used as a bit of a buzzword, but whether this is any advantage likely depends on WHAT the chelating agent is. Certainly for divalent cations such as calcium or zinc, there are chelates that make them unavailable for absorption, other chelates that may aid absorption. I'm not aware of any particular chelate that is an advantage for potassium, but I've not made a point of collecting info on this topic. Colloidal mineral forms have also been promoted, but these have been seriously questioned as to efficacy. Personally, I think some of these are nothing more than marketing ploys that enable individual companies to simply distinguish their products from others' products, with a bit of "sabre rattling" along the way.
While not relevant to absorption per se (or at least I don't think so), of current interest re fat redistribution issues associated with declining viral loads, the action of the steroidal hormone aldosterone is affiliated with potassium. Aldosterone is formed from cholesterol by the action of the higher numbered cytochrome P450 enzymes (CYP11 & CYP21). This occurs in a discrete section of the adrenals. There is good reason to believe that, just as many of the lower numbered P450 enzymes are altered by food components, drugs and other chemicals, there may also be alteration of the higher numbered enzymes so that aldosterone function could be altered. In this group of compounds, current thinking focuses more on another steroidal hormone, cortisol (as well as on the non-steroidal hormone, insulin). However, a role by aldosterone has not been ruled out. It may yet be interesting to see if there are any clinical observations that might point the finger at potassium problems as a result of quircks in aldosterone function, when in fact a more likely culprit would be the P450 enzymes and their interfering substances.
