Sodium/Potassium (Na+/K+) nexus: key to Geriatric health

Ageing is a natural process that encounters changes in physical wellbeing due to cellular malfunctions. In senior adults over 50s to late 80s, observational changes occur which are manifested phenotypically, while cellular changes require periodical monitoring to evaluate physiological parameters that indicate any disease or requirement of surgical intervention. Over 15-35% of hospitalized patients and about 25.98% of elderly patients suffer from low sodium levels which is a disorder of water homeostasis rather than a disease, medically termed as Hyponatremia. This loss of electrolyte is fatal to the older patients and deaths have been reported who do not respond to treatment with sudden drop in blood pressure and other comorbidities. Low potassium level is known as Hypokalemia. Potassium is responsible for nerve excitation, muscular contractility and functioning of heart rhythm. The balance of Na and K is therefore vital to geriatric health and is often unnoticed in public and the clinical settings.

The Na⁺/K⁺ pump

The Na/K pump is a transmembrane protein in the cell membrane that effectively transports Na⁺ ions out of the cell into the extracellular fluid and K⁺ ions into the cellular compartment which are essential for regulating membrane potential, nerve impulse transmission and in the maintenance of cell volume. A single cycle of the Na/K pump actively effluxes 3 Na⁺ ions and takes in 2 K⁺ ions. This creates a concentration gradient across the membrane and is mediated by the binding of an ATP (the energy molecule) to the protein pump which releases a phosphate group causing a conformational change aiding active transport of the Na⁺ and K⁺ ions in and out of the cell and the native conformation of the pump is restored and the next cycle continues. This is a very important phenomenon in muscle cell and nerve functions. Any repair in this cellular balance would lead to disruption of the membrane potential and causing impaired homeostasis.

Deficiency & Symptoms

The normal sodium levels are between 135-145 mmol/L of blood sample. Hyponatremia is a condition when sodium level is below 135 mmol/L. Drop in sodium levels can be severe such as disorientation, confusion, dizziness, seizures, muscle cramps, irritability and even coma. Patients need immediate medical attention which can be lifesaving. Increasing the sodium levels would include electrolyte supplementation by IV (intravenous) fluids and medications to treat the symptoms caused.

Normal potassium levels in blood are between 3.5-5.2 mmol/L in adults. Levels below 3.5 mmol/L indicate Hypokalemia which causes mild to severe symptoms such as fatigue, nausea, vomiting, diarrhoea, palpitations, irregular heartbeats or arrythmia.

Recommended Dietary Allowance (RDA)

In India, the RDA for sodium intake is about 2000 mg/day which is equivalent to 5 g salt per day, while in the USA, RDA is 2300 mg sodium per day for age 14 and older. However, most people consume much higher levels of sodium due to processed foods and restaurant food styles. Although this has been of much concern, low sodium salt substitutes have been introduced in the market such as low sodium salt manufactured by the Tata group and in the pharmaceutical market. Low sodium substitutes replace sodium chloride in part with potassium chloride which further require taste-improving ingredients. Limiting water intake will also help to stabilize sodium levels.

The RDA of potassium per day are 3400 mg for the male population while it is 2600 g for females. This limit is recommended to help maintain normal blood pressure and prevent stroke.

Impact on Geriatric health

Above age 50 in both men and women, a low-salt diet is a common prescription to be followed for healthy individuals or patients with any terminal illness such as CVDs (cardiovascular diseases), cancer, hypertension, diabetes, liver cirrhosis, renal dysfunctions, and other pathological conditions. This is because salt as sodium ions affect a number of physiological processes such as renin-angiotensin cycle, muscular contractility, salt retention during renal clearance, nerve excitation and nutrient transport across plasma membrane. The low salt diets offer manageable load for the functioning of organs in response to age-related atrophies. Low salt diets may tend to lower the Na levels in the extracellular fluid (ECF). Low Na increases risk of mortality and morbidity, and this occurs in senior adults. Low potassium levels also lead to physiological disturbances such as fluid imbalance, muscular dystrophy, severe constipation, respiratory failure, arrythmia of heart function and eventually death.

Role of Nutrition in Na/K balance

The Greek physician and philosopher, Hippocrates, ‘Father of Medicine has quoted,’ Let food be thy medicine and medicine be thy food.” This shows the remarkable role where nutrition must play in maintaining good health, during a disease condition and convalescence period. Nutritious food/diet is a strong determinant of a person’s health and helps in slowing or prevention of a number of lifestyle diseases. There are different types of nutrition based on plant and animal sources. Human nutrition includes vegetables and fruits, meat and meat products, dairy, seafood, bakery foods and include vegan, organic, keto and weight loss diets. Each kind of diet is personalized according to the individual’s weight, age, type of disease and severity of the disease. Nutrition is also very important for a healthy individual which keep them fit and immune. Nutrition is also specific for cancer, heart health, diabetes, brain health and allergies. Some foods are beneficial during summers and some for winters. Nutrition is therefore a vital component of a person’s growth and physical wellbeing.

In the case of Na/K imbalance, nutrition can manage the disorder and restore the sodium and potassium levels. Sodium levels can also be raised from consuming processed meats, canned vegetables, vegetable juice, soft drinks, cheese, salty biscuits and chips, soups, and pickles. Olives, gooseberries, passion fruit and seaweeds are higher in sodium content. Bananas are a rich source of potassium which can also balance sodium level. A balanced diet is the fundamental requirement to maintain a normal level of these ions and includes adequate portions of vegetables and fruits in all meals. Dairy products and Coconut water contain high potassium levels. Kiwi fruits are a rich source of potassium. Dried fruits of apricots, dates, prunes, figs and oranges, pears, papaya, and mangoes are high in potassium. Nutritional sources are a remedy to hypokalemia by intake of a low salt diet and suitable portions of fruits and veggies a day. While consumption of tea is not effective for hyponatremia, it can help to increase potassium levels.

Conclusion

Na and K ions in blood act as electrolytes that assist in several physiological processes. Low levels of Na and K in blood often occur in senior adults in the age group of 50-80+ because of impaired metabolism and/or restricted diets. This calls for immediate medical attention which if left undiagnosed may lead to death. Prevention of loss of Na and K ions can be attained through proper diet/nutrition. Awareness of the Na/K balance is a need of the hour in geriatric health and this can increase life expectancy of the older population with sufficient medical advice and following a balanced nutrition.