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Nutrition and Metabolism

Sodium

What is sodium?

Sodium is an essential mineral for human body. The most common form of sodium is sodium chloride (NaCl), which is table salt. As an added ingredient to most foods for curing meat, masking off-flavors, retaining moisture, and enhancing flavors, sodium is typically over consumed in very high amounts in modern society. Mostly sodium the Americans consume comes from processed food.  Salt added at the table and in cooking provides only a small pro­portion.

Too much sodium normally leads to hypertension and kidney damage.  In special population such as salt sensitive people, too much salt can lead to heart attack and other forms of cardiovascular diseases.

How is sodium used in human body?

Sodium plays important roles in the body fluid balance maintenance, nerve impulse transmission and muscle contraction. 

What is the normal sodium level in human body?

The normal range for blood sodium is between 135 and 145 mEq/L (3.10 mg/ml to 3.34 mg/ml).

Higher level is normally associated with hypertension. A level of 150 mEq/L (3.45 mg/ml) or more is considered as hypernatremia, a condition that is commonly caused by dehydration or eating too much salt, but can also be caused by other conditions such as diabetes or hormonal imbalances.  Hypernatremia shows the symptoms of lethargy, agitation, restlessness, irrational behavior, and in extremely cases a seizer or a coma.

Low blood sodium can occur due to certain diseases such as kidney failure or certain cancer, or excessive sweating.  A level of 125 mEq/L (2.88 mg/ml) or less is considered as hyponatremia. Symptoms of hyponatremia include fatigue, lethargy, confusion, muscle cramps and nausea, and in extreme case a seizure.

How much Sodium do I need in my diet?

Natural foods contain enough dietary sodium for human health. The challenge is to cut it down from diet. The Institute of Medicine of the National Academies recommends no more than 2,300mg of sodium (about 1 teaspoon of table salt) per day for people of 14 years and older. The American Heart Association recommends that people with high blood pressure eat less that 1,500mg per day.

According to USDA, all Americans currently consume more sodium than they need. The estimated average intake of sodium for all Americans ages 2 years and older is approxi­mately 3,400 mg per day.

Why low-salt diet is more important for people carrying certain gene variants?

People with certain genetic variants are more sensitive for sodium levels. For example, a genetic variant in the ACE gene renders its carriers more likely to develop hypertension when they consume high sodium diet.  Over 50% of Africans and Caucasians and about 40% of Asians carry this genetic variant. Three genetic variants of the NOS3 gene, distributed from 20-50% in different ethnic populations, making their carriers more sensitive to sodium. Diet sodium restriction has been proven to reduce hypertension in these people more effectively. Therefore, limiting sodium intake is more important for these populations.

Which foods contain high level of sodium?

The highest amount of sodium is available from table salt and other cooking ingredients (Table 1).  However, these ingredients are not the major sources of sodium we consume, which are shown in Table 2.  In general, highly processed foods tend to have high level of added salt for a longer shelf life although some processed foods also have lower or reduced sodium versions, such as the unsalted potato chips shown in Table 2.

Table 1. Sodium levels in common cooking ingredients.

Sodium Sources Per 100 grams Per serving Serving Size
Table salt 40,000 mg 2325 mg 1 teaspoon
Baking soda 27,360 mg 1368 mg 1 teaspoon
Bouillon cubes 24,000 mg 1200 mg 1 cube (5 g)
Baking powder 10,600 mg 530 mg 1 teaspoon
Soy sauce 5,700 mg 340 mg 1 teaspoon

Table 2. Sodium levels in common foods.

Junk Foods
Bacon
Per 100 g (mg) 2425
Per Serving (mg) 194
Serving Size 1 slice (8 g)
 
Salami
Per 100 g (mg) 2260
Per Serving (mg) 226
Serving Size 1 slice (10 g)
 
Pretzels
Per 100 g (mg) 1357
Per Serving (mg) 611
Serving Size 1 cup
 
Potato chips (salted)
Per 100 g (mg) 525
Per Serving (mg) 149
Serving Size 1 oz
 
Potato chips (unsalted)
Per 100 g (mg) 8
Per Serving (mg) 2
Serving Size 1 oz
Cheese
Cheese, Cheddar
Per 100 g (mg) 1297
Per Serving (mg) 368
Serving Size 1 oz
Fast Foods
Pizza, cheese
Per 100 g (mg) 537
Per Serving (mg) 462
Serving Size 1 piece (1/8 of 12" dia)
 
Hamburger
Per 100 g (mg) 504
Per Serving (mg) 534
Serving Size 1 sandwich
 
French fries
Per 100 g (mg) 491
Per Serving (mg) 570
Serving Size 1 medium order (116 g)
Bakery
Bread, white
Per 100 g (mg) 681
Per Serving (mg) 170
Serving Size 1 slice
   

How to reduce sodium intake?

Most of the sodium consumed in American is from processed food. Some of the low sodium foods, such as bread and pastas, can also lead to high sodium intake if consumed in large quantity.  The good news is that sodium content in most of the foods from grocery store is celery labeled.  And the GB Food Calorie and Nutrition Calculator helps you get the most accurate estimate of your sodium intake amount.

Below are the guidelines for sodium reduction:

  1. When shopping, read the Nutrition Facts label for information on the sodium content of foods and purchase foods that are low in sodium and avoid the ones contain high sodium.  Most processed foods now have low sodium versions available.
  2. Consume more fresh foods and fewer processed foods.  Fresh foods in general contain less added sodium than the foods intended for longer shelf life.
  3. Eat more home-prepared foods and little or no salt-containing ingredients when cooking.
  4. Avoid eating large portion of baked food even when it is fresh.  Many people under estimate the sodium introduced from baking soda or baking powder.
  5. When eating at restaurants, ask that salt not be added to your food or order lower sodium options, if available.

 

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