My first post from the National Kidney Foundation Spring Clinical Meeting! Writing from Long Beach California, this morning I attended a presentation on potassium and fibre! Below are the points and some of the references presented by the speaker. Hope you enjoy!

Speaker: Dr Yoko Narasaki, PhD RD

Objectives:

1. Risk of hyperkalemia, related outcomes, impact of potassium intake and potassium restriction on clinical outcomes.
2. Describe role of dietary fibre
3. Practical Implications of dietary potassium/fibre

Who is at risk of hyperkalemia?

• In the general population risk is very low.
• Older age, eGFR, DM, MI, HF or RAASi increases risk
• Linear relationship between eGFR and HyperK

Review of potassium homeostasis

Most potassium is in the Intercellular fluid. Only 2% is in the extracellular fluid. Homeostasis is maintained by intentional absorption, colonic excretion sweat loss, renal excretion and tissue distribution. Incretins (e.g. insulin and GLP-1) influence transport of potassium into target organs.

Example: 70mEq/day of potassium intake

• Step 1: Intestinal absorption = 60mEq per day, 10mEq per day excreted through feces and sweat
• Step 2: Tissue distribution: uptake promoted by insulin and release into blood stream as needed
• Step 3: Renal excretion of 60mEq

In general population about 10% of potassium is excreted in the GI tract, but in CKD the potassium excretion increases to 50%.

What causes hyperkalemia?

• Group 1: Excess intake
• Group 2: Intracellular potassium shifts (metabolic acidosis, insulin deficiency or DKA, cell lysis or injury, Channelopathies, Medications)
• Group 3: Impaired excretion: CKD, AKI

What’s wrong with having hyperkalemia?

Heart, Muscle dysfunction, neuropathy, osmotic imbalance and metabolic acidosis.

Increases the risk of all cause mortality and arrhythmia mortality. Increases the risk of ischemic stroke.

High potassium foods can have high fibre

Every 1 g increase in dietary potassium increases 5.1g higher intake of fibre.  But it’s not all fruits and vegetables: milk contributes 11% and meat contributes 10%, grain based mixed dishes contribute 10%.

Food additives can also contribute sources of potassium.  Highlights acesulfame potassium. 

How much potassium is needed for health and how much do we eat?

Different organizations recommend different amounts – between 2700-4700mg, but very few countries meet the recommended intake.  And most Americans consume less potassium than is recommended. 

Clinical practice guidelines for CKD recommend altering potassium. In earlier guidelines the recommendations were more strict with regards to how much potassium to target in this population.

Outdated guidelines is a low potassium diet for everyone.  Updated guidelines recommend potassium liberalization and individualization. 

Why has this change occurred?

1. Correlation between serum levels and intake: There is not clear evidence that intake is closely related to serum potassium levels.  In the general population potassium supplementation increased potassium by 0.14mmol/L. NHANES cohort confirms that there is low correlations with intake and serum levels in the general population. In Stage 3b-4 CKD potassium supplements increased potassium by 0.4mmol/L, this was statistically significant.  Though most stayed within the normal range.  In HD KCl 0.25mmol/kg supplement increased levels but this effect was blunted by glucose (1993 study).  BalanceWise study in HD showed low correlation between measured potassium intake and serum potassium levels.
2. Not all dietary potassium sources are the same: Factors associated with low bioavailability is fibre, carbohydrates by stimulating insulin secretion and alkalinizing effect. Narasaki et al 2023 in Nutrients.  Highlights Naismith Article.
3. Unclear that dietary restriction improves outcomes Narasaki et al 2020 in JRN. Low K and Low Fibre group had a lower hazard ratio for mortality risk.  While those with high potassium, low fibre group also had higher mortality risk.  Check this reference Narasaki et al 2022 AJCN. Also looked at HRQOL and reported that plant based diets had higher physical QOL and mental QOL.  Though what types of people are eating these diet patterns and what cause what?

What benefits of plant-based diets in CKD?

Narasaki et al Nutrients 2024 – lower risk factors for CKD (HTN, DM, Obesity), decreases CKD complications (inflammation) and reduced progression. While being higher in Vitamins, Healthy fats.

What is the role of dietary fibre in CKD?

Fibre is a non-digestible form of carbohydrate.  Fibre is water soluble or insoluble.  Can be from plant cell walls or gel-forming. Food sources tend to contain a combination of soluble and insoluble fibre.

How much fibre is recommended and how much do we eat?

Recommendation is 25-35g. Most people eat about half of this recommendation.  Recommendations in CKD is lacking, though ASN and NJEM publication recommends the 25-35g target.  Studies have confirmed that CKD patients do not tend to eat that much and eat less than the general population.

Benefits of fibre:

1. Bulk to both the diet and stool which promotes satiety and prevent constipation
2. Viscosity – inhibits glucose and cholesterol absorption improving glucose and lipids and cancer prevention
3. Fermentability – intestinal microbiota.

Higher fibre has been associated with a lower incidence of CKD and CVD in the general population.  In HD and PD patients higher fibre intake is associated with lower CVD risk and mortality. High fibre through supplementation reduces uremic toxins and inflammation. Higher fibre also helps with constipation.

To reduce hyperkalemia risk:

• Step 1: Address non dietary causes – hyperglycemia, acidosis, constipation, medication changes or potassium-sparing diuretics
• Step 2: Avoid processed foods – reduce lower nutrition value potassium foods
• Step 3: Use cooking techniques to lower potassium content, then lower potassium foods. Cooking techniques that lower potassium – cooking in water, steaming or using a pressure cooker.  Batista et al J Hum Nutr Diet 2021.

My Take Aways

I thought this presentation gave a nice general overview of potassium homeostasis and dietary factors. I didn’t feel like I learned too much in this presentation but I will take a look at some of the newer studies the presenter discussed.