The Sobering Potassium

The DRI for potassium(K) is 4.7g/day for men and women ages 14 and up - this recommendations is set as an Adequate Intake (AI), because an RDA (meeting 99% of the population needs) could not be established. The official recommendation is as follows:

"Adults should consume at least 4.7 grams of potassium per day to lower blood pressure, blunt the effects of salt, and reduce the risk of kidney stones and bone loss. However, most American women 31 to 50 years old consume no more than half of the recommended amount of potassium, and men's intake is only moderately higher."

The reality is much dimmer than this - less than 2% of the population is reaching the potassium DRI, as of 2003-2008 NHANES data (5). This is likely exacerbating the issue of hypertension in America, where 1/3 of Americans have high blood pressure. Worse than not getting enough potassium is the unbalanced potassium:sodium ratio, which should be kept around 2:1 (2). Leving's had a really great discussion on the issue of the Na:K ratio in the most recent issue of JAND(4). Many tend to dismiss potassium because they have good blood pressure - it should be noted that higher potassium intake is associated with a 20% decrease in all cause mortality as well (6). Higher potassium intake has also been proposed as being preventative against muscle wasting in older adults (7). Potassium's role in bone health has a lot of mixed literature (and is plagued by the alkaline diet pushers), but there's decent evidence to suggest it has a beneficial effect on bone density and fracture risk (8).

I wanted to write up a post on potassium*, not just because it's something that everyone needs to increase their intake of more, but because of the notion lately that saturated fat is irrelevant and we should all be on low-carbohydrate diets (these aren't necessarily new but for me, their presence has seemed to scale up lately). I'm not particularly against lower carb diets, and I think the metabolic state of ketosis is scientifically quite interesting, deserving further research. However, people often only look at lowcarb/higher saturated fat diets from the perspective of weight loss and metabolic biomarkers (LDL-C, HBA1C, etc). One of the things I think is problematic about liberalizing intake of saturated fat (almost inherently meaning sourcing a lot of your calories from fatty animal meats), and going lower carb, is that you tend to cut out some of the top sources of potassium in your diet (if you're thinking "oh but I eat a lot of vegetables", see discussion below). It's quite difficult to hit 4700mg of Potassium per day, and doing so requires (especially while hitting the fiber recommendations) ingesting a lot of plant foods, almost inherently lower in saturated (cocoa being an exception) and higher in carbohydrates. *this is one of the only times you'll catch me being a reductionist/just focusing on one nutrient

Using the USDA Nutrient Data(3), I downloaded their list of potassium food sources to excel, and created a column that was mgK/kcals, so I could sort out the sources of potassium where you get the most bang for your caloric buck (if you want the excel sheet lemme know):

1. Baking powder, low-sodium - 101mgK/kcal

**2. Clams, mixed species, canned, liquid - 64mgK/kcal

3. Cream of Tartar - 62mgK/kcal

4. Bamboo shoots, cooked, boiled, drained, with salt - 49mgK/kcal

5. Fortified low kcal fruit juice beverage - 48mgK/Kcal

**see clams, raw - I'm not sure what the liquid is but that appears to be where the K is coming from.

Not exactly your most common foods... So i went through and picked out things you'd see normally in a supermarket:

Water cress: 28mgK/kcal
Swiss chard: 27mgK/kcal
Parsley, freeze dried: 25mgK/kcal
Zucchini,baby,raw: 24mgK/kcal
Spinach, raw: 24mg/kcal
Instant tea powder: 21mgK/kcal
Cilantro, raw: 21mgK/kcal
Mushrooms, brown, italian or crimini, raw: 21mgK/kcal
Radishes, white icicle, raw: 20mgK/kcal
Campbell's V8 juice, low sodium, spicy hot: 20mgK/kcal
Chinese cabbage, raw: 20mgK/kcal
Endive, raw: 20mgK/kcal
Swiss Chard, raw: 19mg/kcal
Tomato Juice, low sodium: 18mgK/kcal
Portabella mushrooms, raw: 16mgK/kcal
Celery, raw: 16mgK/kcal
Cowpeas, cooked, boiled: 16mgK/kcal
Romaine lettuce, raw: 15mgK/kcal
Soup, stock, beef, home-prepared: 14mgK/kcal
Taro, tahitian, cooked: 14mgK/kcal
Radicchio, raw: 13mgK/kcal
Fennel, bulb, raw: 13mgK/kcal
Sun-dried Tomatoes: 13mgK/kcal
Pumpkin, raw: 13mgK/kcal
Coconut water: 13mgK/kcal
Wine, non-alc: 13mgK/kcal
Broccoli, stalks, raw: 12mgK/kcal
Cocoa, dry, unsweet, proc w/ alkali: 11mgK/kcal
Espresso: 11mgK/kcal
Kale, raw: 11mgK/kcal
Seaweed, raw: 10mgK/kcal
Iceberg lettuce: 10mgK/kcal
Brussel sprouts: 8mgK/kcal
Beans, snap, green, microwaved: 8mgK/kcal
Carrots, raw: 8mgK/kcal
Cantaloupe, raw: 8mgK/kcal
Soy meal, defatted, raw: 7mgK/kcal
Potatoes, red,flesh and skin: 7mgK/kcal
Whey, acid, dried: 7mg/kcal
Kidney beans, sprouted, raw: 6mgK/kcal
Banana, 1 medium: 4mgK/kcal (honey I shrunk the kids -syndrome)
Molasses: 3mgK/kcal
Pineapple: 3mgK/kcal
Salami, pork, beef, less sodium: 3mgK/kcal
Beef, shoulder pot roast/loin,steak, top sirloin, steak: 3mgK/kcal
Chicken, broilers or fryers, skinless, boneless: 3mgK/kcal
Chicken, breast: 3mgK/kcal
Prunes: 3mgK/kcal
Fish, salmon, Atlantic, wild, raw: 3mgK/kcal
Silk soymilk: 3mgK/kcal
Milk, reduced fat, fluid, 2% milkfat/whole milk: 3mgK/kcal
Yogurt, plain, whole milk: 3mgK/kcal
Avocado, raw: 3mgK/kcal
Wheat, durum, whole wheat, white,: 1mgK/kcal
Almonds/peanuts: 1mgK/kcal
Chickpeas: 1mgK/kcal
Blueberries: 1mgK/kcal

**Clams, mixed species, raw: 1mgK/kcal

If there's one thing that sticks out pretty distinctly here, plant foods are our best sources of potassium, per calorie - some of these being relatively higher carbohydrate contents, like pumpkin, coconut water, carrots, cowpeas, cantaloupe, and potatoes. 

 Many will probably read this and think to themselves "Oh but I eat a lot of vegetables". 4700mg is a lot of potassium. Spinach may look like one of the highest sources, but consider that a cup has 7 calories. Given that there are about 167mg to a cup of spinach, you'd need to be eating 14 cups of spinach to get half of your potassium requirements. Alternatively, you could eat 10 medium red bell peppers and get just short of half the requirements. If that sounds like too much, you can also eat 7 cups of brussel sprouts and get just over half of the DRI (note these latter two options give 40-50g carbs). You may be eating a lot of vegetables, but I don't know anyone eating 28 cups of spinach, 10 red bells peppers, or 7 cups of brussel sprouts a day, let alone everyday. I think we can pretty much all agree that no one is going to be eating enough vegetables to get all of their potassium from these sources. While eating vegetables will certainly increase your potassium intake, we likely have to rely on more calorically dense sources of food to hit these needs. Let's look at some of these options:

Potato, with skin: 163kcal,897mgK -(for my Paleo'ers,Australopithecines knew what they were doing #tubers)

Acorn Squash, 1 cup: 56kcal, 486mgK

Lentils, 1 cup: 230kcal, 731mg K

Edamame, 1 cup: 189kcal, 676mg K 

Prunes, 100g: 240kcal, 732mgK

Non-fat Skim milk, 1 cup: 100kcal, 366mgK

Avocado, 1cup, sliced: 234kcal, 708mgK
Banana, 1 medium: 105kcal, 422mgK

Tuna, canned, 3oz: 100kcal,  201mg K

Salmon, 3oz: 177kcals, 309mg K

Beef, 3oz, 15% fat: 213kcals, 270mg K

Chicken breast, 100g: 172kcal, 220mgK

Almonds, 1oz: 163kcal, 200mgK

Coconut, shredded, 1cup: 283kcal, 285mg

Cottage Cheese, 2% milk fat, 1 cup: 195kcal, 190mg

Swiss Cheese, 1 slice: 70kcal, 45mg K

Quinoa, 100g: 368kcal, 563mg

Whole wheat Bread, 1 slice: 68kcal, 68mgK

Coffee, 1 cup: 1kcal, 116mgK
Dark chocolate, 70-85% cocao solids, 1oz: 168kcal, 200mgK 

1 egg: 78kcal, 63mgK

Butter, 1 tbsp: 102kcal, 3mgK

Oils, coconut, soy, olive, 1tbsp: 120kcal, 0mgK

Sugar: 0mgK

It's hard to generalize about low-carb diets - saying you're on a low-carb diet is like saying you're a Christian: that could mean 1 of 100 denominations, all with their own minor nuances. When we think of low-carb diets, however, if we're trying to generalize, they tend to include meats, eggs, cheeses, nuts, and seeds as their main sources of calories. This ends up limiting a lot of the best sources of Potassium (potatoes, beans/legumes, skim dairy, squash, prunes, bananas, cantaloupe, carrots, pumpkin, coconut water) - these foods also boast a nice potassium:sodium ratio, and a high fiber content. I'm not saying it's impossible to be on a low-carb diet and hit the potassium DRI, but even assuming you hit half of it with intake of low-kcal vegetables (remember those 14cups of spinach...), that leaves a lot of potassium leftover to hit within a specific calorie range.  It should also be noted that, the more individuals rely on meat sources as a source of kcals/potassium (beef/fish boast a decent potassium content), the more they will need to consume vegetables to hit the recommended intakes of fiber (around 30+ grams/day, depending on sex/age/height/weight - note that a cup of spinach only has 1g of fiber, and 2.5g per red bell pepper). 

As always, a diet by any name isn't nutritionally complete (so Shakespearean). If one is trying to go on a low carb diet, depending on which style and brand you choose, this will require extra planning to ensure adequate potassium intake. Apart from copious amounts of dark leafy greens, peppers, radishes, zucchini, brussel sprouts and other vegetables (I'm not as well versed in dogmatic low-carb, but I imagine eating too many vegetables might get carbs too high??), regular food sources should include foods like avocados, sun-dried tomatoes, nuts/seeds, high cocoa % dark chocolate, fish like tuna and salmon, and some beef/chicken.

I don't meant to just pick on low-carb - I just don't like that they cut out beans/legumes and tubers, and with the advent of Paleo low-carb, cut out dairy. And I meet a lot of people who claim to be low carb/Paleo that just end up eating an absurd amount of meat, a cup of almonds, and have a couple salads a day and think they're good to go. Very high grain diets will have just as much an issue with potassium if they're not supplemented with absurd amounts of vegetables. Any largely animal product diet (AKA high saturated fat) without absurd amounts of vegetables will not hit this DRI. Any diet getting a lot of its kcals from added oils/butter without absurd amounts of vegetables will not hit the DRI (i'm also looking at you, bulletproof coffee). There's been a call lately that "butter's back in" - but if you're aiming to hit the DRI for potassium, it's no more back in that it was before: Use sparingly/in moderation, in the preparation of nutrient dense foods. 

We teach it on the first day of nutrition 101 - a varied diet tends to hit all of ones nutrient recommendations. It's one thing if you don't want to eat grains, but if being low-carb removes all starch, you've got some intense planning to do to hit that potassium recommendation. 

1. http://www.iom.edu/~/media/Files/Activity%20Files/Nutrition/DRIs/DRI_Electrolytes_Water.pdf
2.http://www.nih.gov/researchmatters/january2009/01262009hypertension.htm
3. http://ndb.nal.usda.gov/ndb/nutrients/report/nutrientsfrm?max=25&offset=0&totCount=0&nutrient1=306&nutrient2=&nutrient3=&subset=0&fg=&sort=c&measureby=m
4. http://www.ncbi.nlm.nih.gov/pubmed/24742901
5.http://ajcn.nutrition.org/content/early/2012/07/31/ajcn.112.034413.abstract
6. http://www.ncbi.nlm.nih.gov/pubmed/21747015
7. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2597402/
8.http://www.ncbi.nlm.nih.gov/pubmed/23162100