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Salt and Edema

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What is the connection between salt consumption and edema?

Foods that you consume have an influence on the chemicals in your body, especially your blood. If the amount of sodium in your blood becomes imbalanced, it may lead to swelling of different parts of the body, particularly your feet. 

Excessive salt consumption is a major cause that contributes to this problem. However, this may be relieved by reducing the salt intake in your diet

If you notice swelling in your feet, legs, ankles or other parts of the body, you may be suffering from a medical condition known as edema. 

Edema can cause the affected swollen areas to look shiny or stretched. A gentle push on the affected areas for 15 seconds may cause a visible indentation, called pitting edema. 

Salt and Sodium

Sodium is an essential nutrient for humans. It is responsible for the regulation of blood volume, blood pressure, other body fluids, pH and osmotic equilibrium.

It is also important for a number of metabolic processes, nerve transmission and the activity of the heart and circulatory system.

Sodium is so essential that it is the reason for the evolutionary preservation of “salty” taste buds on the tongue. Other inorganic salts may trigger this taste but they do not always do for everyone.

While sodium is important for the normal functioning of the body, it can also be harmful if present in high amounts. The human body has a complex mechanism in place for maintaining an optimal sodium balance.

Sodium and Water

There are osmoreceptors in the hypothalamus of the brain responsible for sensing the sodium and water levels in the body.

When a diuretic inhibits the reabsorption of sodium in the kidneys, the sodium is excreted alongside water in urine. The osmoreceptors detect this hyponatremia state and trigger a sensation of thirst to prompt the body to replenish its fluid content through drinking.

Since the osmoreceptors track the balance of water and sodium in the extracellular fluids, they can also detect edema and signal a number of mechanisms to correct the abnormality.

The Renin-Angiotensin System and Vasopressin 

The renin-angiotensin system is also called the renin-angiotensin-aldosterone system. It is a hormonal system which is important for the regulation of water balance and blood pressure.

The cascade reaction starts with the release of renin in the kidney in response to low blood volume. Renin then converts angiotensinogen, which is secreted in the liver, into angiotensin I.

Angiotensin I has only a little biological activity. It is further converted into the more active angiotensin II by the angiotensin converting enzymes present in the lungs.

Angiotensin II is a peptide which stimulates the release of aldosterone from the adrenal cortex. Aldosterone then enters the tubules of the kidney and increases the reabsorption of blood and sodium into the blood.

The overall effect of the renin-angiotensin system is to increase the retention of water and sodium in the body. Drugs which inhibit the production of renin, angiotensin I and II as well as aldosterone can help reduce edema by promoting the excretion of sodium.

Angiotensin II also stimulates the release of vasopressin which is also called anti-diuretic hormone.

Vasopressin is a peptide hormone which increases water reabsorption from the nephrons of the kidney by increasing the water permeability of the collecting ducts.

When the kidney is insensitive to vasopressin, the body cannot efficiently down-regulate the hormone when sodium levels rise. This can easily compound edema as the body keeps reabsorbing sodium and water from the kidney instead of reducing the reabsorption.

Natriuretic Peptide

Natriuretic peptides are a polypeptide secreted by the cells of the muscles of the heart. It is secreted in response to high sodium concentration in the body. It inhibits the production of vasopressin by blocking angiotensin II.

In the kidney, natriuretic peptide acts by

  • Inhibiting the renin-angiotensin system by blocking the secretion of renin
  • Blocking the release of aldosterone from the adrenal cortex
  • Reducing the reabsorption of sodium in the distal convoluted tubule and collecting ducts of the nephrons
  • Increasing blood flow to select parts of the kidney nebula so as to remove sodium into the urine
  • Increasing pressure in the capillaries of the nephron which leads to an increase in glomerular filtration rate (GFR) and an increased excretion of sodium and water.

The renin-angiotensin system is important in the regulation of the sodium and water balance in the body.

It is activated and deactivated in response to the levels of salt and water in the body. In this way, it provides a good balance by preventing edema on one hand and dehydration on the other.

However, when this system cannot effectively regulate salt and water balance, increased sodium intake causes the accumulation of fluids in the spaces between cells. This causes edema.

Diuretics are one way to stimulate the kidneys to act as if prompted by the deactivation of the renin-angiotensin system.

Salt Intake and Edema – What’s the Connection? 

Consuming too much salt may result in mild cases of edema. When you eat too much salt, it increases the amount of sodium in your body. 

As unusually high sodium concentrations may be risky, your body will retain more water to dilute this excess sodium. 

This retention of fluid causes small blood vessels or capillaries to leak the excess fluid into the space between your cells, causing edema. 

How Much Sodium Should I Consume? 

Sodium is a vital nutrient. It is also one of the most abundant electrolytes present in the body. It is also found in a number of body fluids, including intestinal secretions, bile acids, and pancreatic fluids. 

While sodium is a vital nutrient, you only require small amounts to perform the various body functions. Thus, you should limit your daily sodium or salt intake to less than 1,500 mg a day. 

How to Reduce Salt Intake?

You should reduce your sodium intake to reduce water retention. You can start by completely eliminating salt while preparing your food.

Always read food labels and incorporate more low-sodium food products in your diet. The low-sodium foods usually contain less than 140 mg of sodium per serving.

Avoid high sodium foods such as microwave popcorn, instant hot cereals, commercial pancakes and waffles, ready-to-eat bran and oat cereals, salty snack crackers, and pretzels.

Avoid eating canned vegetables as they contain high amounts of sodium. You should carefully read the nutrition facts labels on the can to avoid salty foods.

Canned legumes might also contain high levels of sodium, so prepare your own food using dried beans to limit your sodium consumption.

Convenience foods contain high amounts of sodium and should be avoided by people who are trying to control edema. Furthermore, you should completely avoid fast foods if you have edema and request your food be prepared without salt at restaurants.

Other Treatment Options

You may also benefit from wearing compression stockings and elevating your legs while relaxing or sleeping to help the fluid drain out of the extracellular space.

Diuretics may also be prescribed to eliminate water retention in your body, though they may not be suitable for pregnant women. You may also consider taking Capisette, a fluid retention remedy to treat edema

Next Article: Edema Diet: Foods to Avoid for Edema