A well-formulated ketogenic diet (WFKD) requires real food choices and preparation to maintain an optimum potassium intake.
The sodium and potassium management by the kidneys and the changes in sodium handling during nutritional ketosis is makes this especially important.
Potassium and Mortality in the Balance
Potassium is the positively charged ion (aka electrolyte) that is predominate in the fluid inside all of the body’s cells, while sodium plays a matching role in the fluid surrounding our cells – including blood plasma. Keeping the two of them in balance is involves multiple hormones and organs, particularly the kidneys.
In order for nerves and muscles to function, the concentrations of positively charged potassium (K+) and sodium (Na+) have to be essentially equal across the cell membranes. If either this balance, or the in-and-out flow of these two electrolytes is impaired, nerves and muscles don’t work properly, endangering health and even life itself.
Because part of sodium’s role in the plasma is to maintain adequate circulation, it has been well characterized as necessary for normal blood flow. And in the case of high blood pressure, it is tempting to conclude that one just needs to restrict sodium intake to get it to come back down. While there is some truth to this (for people with salt-sensitive hypertension), for most people with high blood pressure, it involves the appropriate balance between these two electrolytes rather than a focus on the intake of sodium in isolation.
Recently, large studies have measured the actual amounts of sodium in a person’s urine. The most definitive results to date are from the massive international PURE study reported by O’Donnell et al. In this study, they collected urine from 102,000 people in 17 countries and then monitored health and mortality for 4 years. The lowest mortality was seen in people consuming 5 grams per day, which is about twice the current US recommended guideline for healthy adults. For sodium intakes substantially above or below this value, the associated mortality rates rise, generating a U-shaped curve.
See The Estimated Sodium Excretion chart below. *
But the urinary potassium data from the PURE Study (See The Roles of Vegetables and Broth in Reducing Risk of Death chart below) tell a very different story. While low levels of potassium excretion are clearly associated with increased mortality risk, increasing levels in the urine up to 3-4 grams per day correlate with reduced risk. And in particular, the associated mortality at 1 gram per day is about double that seen at 3 grams per day. For this reason, we recommend incorporating real foods into a WFKD providing 3-4 grams per day of potassium.
See the Roles Of Vegetables And Broth In Reducing Risk Of Death chart below **
The Relationship Between Sodium and Potassium Intakes and Urinary Excretion
Almost all of the sodium we eat gets absorbed, and then about 90% of that comes out in our urine. Therefore, urinary sodium is an accurate reflection of our dietary intake.
However, this relationship between dietary intake and urinary output is not quite as good for potassium. In most people, about 75% of dietary potassium is excreted in the urine. Thus, in the studies linking urinary potassium excretion to health a correction factor of about 1.3 should be applied. This means that in order to have 2 grams of potassium come out in the urine, one would need to consume 2.6 grams in the diet, and similarly to have 3 grams in the urine would require about 4 grams of dietary intake.
Practical Health Implications of Dietary Potassium
An important point to note here is that processing of meat to create luncheon meat, hot dogs, or bacon removes much of the potassium originally associated with that protein source and therefore should be restricted. In addition, if unprocessed protein sources are boiled or stewed, some of the potassium they contain comes out in the broth. Thus they should be prepared and served such that the broth or sauce is consumed to get the full benefit of their electrolytes and minerals.
Official Dietary Potassium Guidelines
The great majority of the population eats far less than the current estimated Adequate Intake value of 4.7 grams.
The reason it is only an estimate is because when dietary sodium is restricted, the kidneys tend to excrete more potassium to maintain the balance. This process is regulated by a series of hormones, with the main one being the stress hormone aldosterone. On average a sodium-restricted diet given to people with normal blood pressure increases this stress hormone more than 3-fold.
Getting Enough Potassium with a WFKD
From what we currently know about potassium needs for someone getting adequate sodium on a WFKD, 3 to 4 grams per day, appears to be an appropriate target to provide the necessary amount of potassium for health-related benefits.
This is an amount that is achievable with real foods.To begin, the right choices of protein that are prepared correctly will provide the first gram. On average, non-starchy vegetables that are consumed raw, sautéed or steamed contain about 200 mg per standard serving, so 4-5 servings of vegetables per day will provide the second gram. Nuts and seeds vary in their potassium content but range from 100-300 mg per ounce (oz), so 2 oz per day moves the scale closer to the 3 g per day optimum target.
The amount of potassium in home-made broth will vary depending upon how much meat remains on the bones used to prepare the broth. Typically, a pound of chicken carcass or meaty beef bones used to make a quart of broth will contain 200-300 mg of potassium per cup.
Technical Information on the Regulation of Electrolyte Balance
It is known that both total fasting and a ketogenic diet lead to an accelerated sodium excretion that increases water and salt loss through the urine. If this lost sodium is not replaced, the kidneys will reabsorb sodium. This process comes at the price of increased potassium excretion.
With consistent loss of potassium and/or chronically low intake of potassium the body will attempt to correct via the release of intracellular potassium from skeletal muscle.
It is clear that maintaining sufficient sodium and potassium intakes from the diet serves a number of important functions: potential mitigation of risk for cardiac events, preservation of plasma volume and muscle mass, and prevention or reduction of symptoms of the ‘keto- flu’.
The fail-safe endocrine system responsible for the tight regulation of electrolytes is commonly referred to as the renin-angiotensin-aldosterone system (RAAS). When plasma sodium levels are low (an intake of less than 3 grams per day), when blood potassium levels are significantly elevated (hyperkalemia), or when there is a notable reduction in blood pressure, RAAS is activated.
The cost for frequent RAAS activation is increased oxidative stress, increased vascular damage, measurable dyslipidemia * and potential sleep and mood disturbances.
Dyslipidemia * is elevation of plasma cholesterol, triglycerides (TGs), or both, or a low HDL cholesterol level that contributes to the development of atherosclerosis. Sourcehttps://www.merckmanuals.com/en-ca/professional/endocrine-and-metabolic-disorders/lipid-disorders/dyslipidemia
This compensatory activity of RAAS as well as increased sympathetic nervous system activity that together work to maintain electrolyte levels helps explain why we typically do not see a large decrease in blood pressure when sodium is restricted in most patients. In those who do not have salt-sensitive hypertension, these systems appear to adjust to dietary intake and manipulate sodium, potassium and fluid levels in order to maintain a person’s blood pressure.
The important role of potassium in muscle function and sodium in maintaining plasma volume are added considerations for individuals who exercise or engage in activity that results in a large volume of sweat loss. Due to the loss of Na+ and K+ in sweat, these circumstances may require additional electrolyte replacement in order to maintain performance, especially for those following a ketogenic way of eating. A good rule of thumb is about ½ tsp of salt 30 minutes prior to exercise and if exercise is performed at a relatively-high intensity in a hot environment, an additional ½ tsp of salt each hour may be warranted.
For better health and well-being on a WFKD consume the recommended amounts of the electrolytes, sodium 3-5 g and potassium 3-4 g per day, will help support overall health as well as the success and sustainability of nutritional ketosis.
Talk to your doctor about your sodium and potassium needs, if you are taking a diuretic medication (aka, a water pill), if you have high blood pressure, if you have any impairment in kidney function, or if you have limited heart function (such as congestive heart failure).
This Post has been condensed fromThe Importance of Managing Potassium and Sodium as Part of a Ketogenic Diet by Stephen Phinney, MD, PhD, Jeff Volek, PhD, RD. Please see the original post for the scientific citations.
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