Potassium doses
November 4, 2005 7:17 PM   Subscribe

Why do supplements with potassium often contain relatively low amounts of potassium? A common per-capsule dosage is 99mg, which is only 3% of the USRDA. Multi-minerals often contain impressive doses of other mins, but not of K.
posted by O Blitiri to Science & Nature (12 answers total)
Probably because a multimineral with 100% RDA of all the minerals would be so big it would easily get lodged in your throat.

And, actually, most minerals are only required in microgram quantities.
posted by shoos at 7:44 PM on November 4, 2005

Too much potassium can kill you. It would be better to get this mineral naturally rather than with pills.
posted by caddis at 8:14 PM on November 4, 2005

Thus, if you sold potassium supplements which allowed people to easily and inadvertently get their potassium levels up into dangerous territory you could be facing a lot of lawsuits.
posted by caddis at 8:17 PM on November 4, 2005

You can get plenty of potassium (Km) from Km®, as long as you don't mind the predatory cultist sales culture.

"When we first started taking Km®, We were instant winners."
posted by StickyCarpet at 8:47 PM on November 4, 2005

The UK gov't has an interesting PDF on supplementary potassium. "UK food supplements can contain up to 200 mg potassium per tablet as potassium chloride." Since the recommended amount is 3500 mg, that won't get you very far.

Also, this bit:
Overall, for guidance purposes, it can be concluded that supplemental doses of up to 3700 mg potassium/day appear to be without overt adverse effects, but may be associated with gastrointestinal lesions diagnosed by endoscopy.
Given the tendency of people to take multiple times the recommended daily value of vitamins, I can see the health risk.
posted by smackfu at 9:13 PM on November 4, 2005

Yes, this underscores the fault with trying to get nutrition from pills. No natural food we eat has potassium in lethal concentrations. A pill with 100% might make you sick or worse. A lot of that has to do with the potassium in a banana, say, being surrounded by other natural sugars, proteins, and enzymes which facilitate and pace its absorption. You can't just swallow X grams of element K and expect it to do everything that real food will do in your body.

Vitamins are, in a word, kind of bullshit. At the very least you need to take them with food, over the course of a day (not just once a day) and the way they are derived, dosed, and composed can be good or bad in terms of absorption & time release.

Treat them skeptically. Don't rely on them.
posted by scarabic at 9:14 PM on November 4, 2005

On a related note, people who are doing weight training out often comment about consuming potassium after a workout (typically from a banana or other natural source). Assuming that the potassium-after-weight-training adage is true for a moment (is it?), how many mg of pill-based potassium should an average weight-training person take if he doesn' t like the taste of bananas or milk?
posted by Handcoding at 9:57 PM on November 4, 2005

Pill form of minerals and cofactors (vitamins/"vital amines") may not be absorbed into your body as similar minerals and cofactors if they were injested as part of one's diet. (ie., minerals - you can swallow a penny; how much zinc and how much copper do you think you'll absorb from it? But.. but... it has zilllions of times more mineral than recommended daily intake!)

It is very difficult to determine one's "supplement" intake. Basing it on the label of something you bought at the drugstore is just lying to yourself.
posted by PurplePorpoise at 10:27 PM on November 4, 2005

The potassium in supplements is generally potassium gluconate, which the body will absorb.
posted by kindall at 10:44 PM on November 4, 2005

The potassium in supplements is generally potassium gluconate, which the body will absorb.

With or without food. What kinds of foods? What percentage will be absorbed?

I'm not denying that the gluconate salt of potassium is more easily absorbed than other forms, but it's very diffifult to determine exactly how much.

If you're worried about K deficiency, eat a banana. Sorry, I'm (currently a little) beligerent and feel that pill-form supplements are overly relied upon.

As for why there's low K - it's possible that it's cost-ineffective. Other, more reasonable reaons, suggest that since it's abundant in plants - especially roots (tubers) - that it's not something that someone on a North American diet will be lacking, so there's no need to supplement it.

Eat balanced (and varied) meals, and unless you have alergies to certain classes of food, you shouldn't have to worry about supplements. If you're an older person, you can adjust your diet to include foods that are rich in things that you need. Supplements = more free whatevers circulating around in your system that can help bacteria/viruses that want to take advantage of your body.
posted by PurplePorpoise at 11:05 PM on November 4, 2005

Potassium overdose kills. If you made a pill with 100% of the RDA, and put in huge letters on the bottle, "DO NOT TAKE MORE THAN ONE OF THESE PER DAY - DEADLY!", somebody would take 10 "because they read you need a lot of potassium", die, and their heirs would sue you.

It's a lot harder to overdose if you have to consume a whole bottle of pills to do it.
posted by jellicle at 7:14 AM on November 5, 2005

Best answer: A little physiology should answer your question. All cells rely on a "battery" type mechanism which involves a relatively high concentration of K inside the cell with a relatively low concentration of Sodium (Na). The opposite of this exists in the fluid outside the cells (high Na, low K). This chemical gradient across the cell wall maintains a small voltage (measured in millivolts) which acts like a battery to power the metabolism of the cell.

About 30 years ago, there were three independent studies that demonstrated that high blood pressure could be dramatically reduced by supplements of K. (This is another topic for another time.) When people rushed out and bought Potassium Chloride tablets, they soon developed gastric ulcers. The reason was that as the tablet settled next to the stomach lining and slowly dissolved, the high local concentration of K outside the cells stopped the "battery" and the cells died. The cluster of dead cells soon became infected and formed an ulcer. In fact, surgeons reported that one could see many, random spots of ulceration, corresponding to each tablet consumed. Accordingly, Potassium supplementation developed a very bad reputation.

Clearly, taking a liquid form of K would solve the ulceration problem, but as has been noted several times above, a sudden influx of potassium (such as several times the RDA) could have the general effect of lowering the "battery" voltage throughout the body. Some heart conditions are particularly susceptible to such a lowering, resulting in sudden heart failure.

Since it is somewhat risky to take concentrated K in any form, the prudent approach has been to limit its dosage. It is worth noting that the cells of fruits and roots are quite good sources of K, and in a format that is easily digested. The juices of these foods (carrot, celery, apples.....) taken on a daily basis are a very good source of the K we need.

One of the reasons that North American and European diets require large amounts of K is because so much Na (table salt) is added, especially to processed and snack foods. The "battery" derives its power from the gradient of these elements across the cell membrane, so a salty diet will need extra K to keep the cells healthy.
posted by RMALCOLM at 8:23 AM on November 5, 2005 [1 favorite]

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