Salt, or sodium chloride, is a compound that has a significant impact on kidney health. While sodium is an essential nutrient, the amount needed by the body can be obtained from natural foods such as vegetables. The typical modern diet, however, includes excessive amounts of salt, which can be detrimental to kidney function.
The Role of Sodium in the Body
Sodium is a component of salt, making up about 40 percent of the compound, with chloride making up the remaining 60 percent.
Small amounts of sodium are necessary for the body, and can be found in natural foods.
Excessive sodium intake, however, leads to water retention. The body may respond by raising blood pressure to expel the extra fluid and salt.
How Excess Salt Harms the Kidneys
High Blood Pressure: The primary danger of excessive salt consumption is its effect on blood pressure. The kidneys are highly vascular organs, meaning they are packed with blood vessels. High blood pressure damages the blood vessels in the kidneys.
Arterial Stiffening: A single salty meal can cause the arteries to stiffen.
Reduced Artery Function: A single typically salted meal can suppress artery function within thirty minutes.
Oxidative Stress: High sodium intake is a pro-oxidant, suppressing a critical antioxidant enzyme called superoxide dismutase. This enzyme usually detoxifies a million free radicals per second.
Hyperfiltration: The kidneys may go into hyperfiltration mode to process excess sodium. This puts extra stress on the kidneys.
Recommended Sodium Intake
The American Heart Association recommends consuming less than 1,500 mg of sodium daily. This is about three-quarters of a teaspoon of salt.
The average American adult consumes more than double that amount, about 3,500 mg daily.
Reducing sodium consumption by just 15 percent worldwide could save millions of lives every year.
Most Americans Exceed Recommendations: An incredible 99.4 percent of Americans exceed the recommended daily limit of 1,500 mg of sodium a day.
Sources of Excess Sodium
Processed Foods: The primary source of excess sodium in the modern diet comes from processed foods.
Restaurant Meals: A significant portion of sodium consumption occurs when eating out.
Specific Foods:
For American kids and teens, the number-one source of sodium is pizza. A single slice of Pizza Hut pepperoni pizza can contain half of the daily recommended sodium intake.
For adults over fifty, bread is the greatest contributor of sodium in the diet.
For adults between twenty and fifty, chicken is the greatest source of sodium, not canned soups, pretzels, or potato chips.
A single chicken breast can have more than a full day's worth of sodium.
Hidden Sodium: Processed meats often have added phosphates and other additives that increase sodium levels.
Sodium Reduction Strategies
Avoid Adding Salt: Do not add salt when cooking and avoid adding it to food at the table.
Reduce Processed Foods: Limiting processed foods can significantly decrease sodium intake.
Taste Bud Adjustment: Taste buds can adjust to lower salt levels in a matter of weeks. As the taste buds become acclimated to healthier levels of salt, the preference for salty foods decreases.
Use Flavor Enhancers: Replace salt with other flavor enhancers, such as pepper, lime, onions, basil, garlic, tomatoes, thyme, sweet peppers, parsley, celery, chili powder, lemon, rosemary, smoked paprika, curry, and coriander.
The Impact of Reducing Salt Intake
Blood Pressure: Reducing salt intake lowers blood pressure.
Stroke and Heart Attacks: Cutting salt intake by about half a teaspoon a day could prevent 22 percent of stroke deaths and 16 percent of fatal heart attacks.
Endothelial Function: Reducing dietary sodium intake can reverse vascular endothelial dysfunction.
Artery Function: Reducing sodium intake can help improve artery function.
Kidney Disease: Reducing salt intake may help to prevent kidney disease.
Sodium and Kidney Disease
Kidney Damage: High sodium intake can damage the blood vessels in the kidneys.
Proteinuria: Higher dietary acid load was associated with a significantly higher risk of protein leakage into the urine, an indicator of kidney damage.
Chronic Kidney Disease: A diet high in salt is a risk factor for kidney disease.
Kidney Stones: High sodium intake is associated with increased risk of kidney stones.
Sodium and Other Health Conditions
Multiple Sclerosis: High sodium intake can increase disease activity in multiple sclerosis.
Psoriasis: High salt diets can cause oxidative stress, which can worsen skin inflammation and endothelial dysfunction in psoriasis.
Systemic Lupus Erythematosus: Tissue sodium content is associated with disease activity and markers of inflammation.
Arthritis: Sodium chloride can aggravate arthritis.
The Role of Potassium
Balance with Sodium: Maintaining a balance between sodium and potassium is essential for blood pressure and kidney health.
Potassium Intake: Most U.S. adults do not consume enough potassium.
Evolutionary Diet: Humans likely evolved eating a diet with high levels of potassium, around 10,000 mg a day.
Recommended Intake: The recommended daily minimum for potassium is about half of what our ancestors consumed.
Potassium and Sodium Goals: Less than 0.015 percent of the U.S. population meets both the sodium and potassium guidelines.
Potassium Chloride: Using potassium chloride as a salt substitute can help lower blood pressure.
Switching to half potassium salt can effectively make people more than a decade younger when it comes to the risk of death.
Potassium chloride is generally considered safe by the FDA, but people with kidney disease, diabetes, heart failure, or adrenal insufficiency, and those on certain medications should be careful.
Sodium in Miso
Miso and Blood Pressure: Miso is high in sodium, but it may not have the same negative effects as other salty foods. The soy protein in miso may counter the negative effects of salt.
Miso and Hypertension: People with stage 1 or 2 hypertension who ate miso soup had lower nighttime blood pressure than those who ate soybeans with no added salt. Miso may have a diuretic effect, increasing sodium excretion through the kidneys.
Salt and Thirst
Nocturia: Salt intake can be associated with nocturia frequency due to increased thirst-driven fluid intake.
Sodium Restriction: Cutting back on salt may reduce nighttime episodes of nocturia.
The Food Industry and Salt Reduction
Industry Opposition: The now-defunct Salt Institute challenged public health recommendations to reduce sodium intake.
Healthcare Costs: The processed food industry has argued that healthier diets would increase health care costs.
Conclusion
Excessive salt consumption is a significant risk factor for kidney damage and other health problems. A high salt intake can lead to high blood pressure, stiff arteries, and reduced kidney function. Reducing sodium intake, primarily by limiting processed foods, and increasing potassium intake can have a positive effect on blood pressure, kidney health, and overall well-being. The key is to be aware of the sources of sodium in the diet and take steps to reduce them, while incorporating potassium rich plant foods.
References
Greger, M., & Stone, G. (2015). How not to die: Discover the foods scientifically proven to prevent and reverse disease. Flatiron Books.
Greger, M. (2023). How not to age: The scientific approach to getting healthier as you get older. Flatiron Books.
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