Fundamentals of Human Nutrition/Sodium

9.1 Sodium

Sodium is an element that is crucial for the body to function properly. The most common places that sodium can be found is in table salt as well as processed meats, processed foods, and fast food. The main functions for sodium in the body are for control of blood pressure and for correct functioning of the muscles (Chen, Zieve, Ogilvie, 2015). Other functions include the conduction of nerve impulses and proper balance of minerals and water (Harvard School of Public Health). On the molecular level, sodium is used in sodium-potassium pumps which actively transports ions across the cell membrane (Nave). Although sodium is important for proper bodily functions, the body only needs a small amount to function (American Heart Association, 2014). Since sodium is found in many food sources, and it is easy to have too much sodium in the diet. It can also be difficult for people to control how much sodium they are consuming if they are eating out and not cooking their meals. On average, Americans consume about 3400 mg of sodium daily (American Heart Association, 2014). Too much sodium in the diet can lead to high blood pressure. Continuous high pressure can cause congestive heart failure, strokes, and kidney disease. It is recommended that healthy adults should limit their sodium intake to 2300 mg per day (Chen, Zieve, Ogilvie, 2015). For those adults with already high blood pressure, it is recommended that they consume less than 1500 mg per day. Additionally, as people age blood pressure naturally increases, therefore, older adults should be more aware about limiting their sodium intake to prevent further health issues (American Heart Association, 2014). In order to prevent these health issues, it is best to develop healthy eating habits by limiting sodium intake at a young age. These good habits can carry on into adulthood which can help individuals continue to lead healthy lives (Chen, Zieve, Ogilvie, 2015). One way to decrease sodium intake is by eliminating added salt from daily dishes, but this does not expel nearly enough salt from the diet to be considered healthy. Another way to reduce sodium intake includes eating more home-cooked meals instead of at restaurants or fast food, and to be more aware of sodium in processed foods. Reading and understanding the “Nutrition Facts” and the “Percent Daily Value” labels on all processed foods can easily determine whether or not you are consuming too much sodium in one meal (American Heart Association, 2014).

Around 85% of the sodium in your body is found in the blood and lymph fluid (Sodium in Blood). Aldosterone is a hormone secreted by the adrenal gland that is partly responsible for the amount of sodium retained in the body. It tells the kidneys when to keep sodium in the body or excrete it through the urine (Sodium in Blood).

About Sodium (Salt). (2014, April 29). Retrieved December 2, 2015, from http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/HealthyEating/About-Sodium-Salt_UCM_463416_Article.jsp#.Vl6Uid-rTow

Nave, R. (n.d.). The Sodium-Potassium Pump. Retrieved December 2, 2015, from http://hyperphysics.phy-astr.gsu.edu/hbase/biology/nakpump.html

Salt and Sodium. (n.d.). Retrieved December 2, 2015, from http://www.hsph.harvard.edu/nutritionsource/salt-and-sodium/

Sodium (Na) in Blood. (n.d.). Retrieved December 2, 2015, from http://www.webmd.com/a-to-z-guides/sodium-na-in-blood

Sodium in diet: MedlinePlus Medical Encyclopedia. (2015, November 19). Retrieved December 2, 2015, from https://www.nlm.nih.gov/medlineplus/ency/article/002415.html

9.1.1 Sources

Sodium is found in a wide variety of foods consumed by the general population. More often than not, sodium is found in foods that have undergone processing. The top 10 sources of sodium are “breads and rolls, cold cuts and cured meats, pizza, poultry, soups, sandwiches, cheese, pasta dishes, meat dishes, and snacks,” (Center for Disease Control and Prevention.)

The amount of sodium in a given product can be determined from reading the Nutrition Facts panel located on the food product package or box. All nutrients will be listed here. Sodium is measured in milligrams (mg). The amount of sodium can be rounded to the nearest 10 mg measurement for recording purposes. A good rule of thumb for determining whether or not to consume a product containing sodium is to not eat anything with more than 200 mg of sodium per serving (Shepell). Do keep in mind that the serving size listed may be less than what a person would normally consume.

Beyond the label, sodium can be added to meals, especially in fast food chains and restaurant settings. Sodium is thought to enhance flavors, but it also adds unwanted salt to the food product. Sodium can be found in sneaky, hidden places too. Salt, being a large source of sodium in the diet, is not the only source of sodium. Baking soda in the form of sodium bicarbonate adds sodium to many processed foods, especially baked products. Flavor enhancers, for example MSG, as well as many preservatives also add unexpected sodium levels to food. Shepell warns against labels such as “marinated, pickled, smoked or breaded” because they are essentially code names for added salt and high sodium food choices. “A healthy adult should consume no more than 2,300mg of sodium a day (Thomas.) This is the equivalent to about 1 teaspoon. However, most Americans consume a diet that contains much more than the recommended amount. The excessive sodium consumption directly correlates to the increase in blood pressure in the American population. One easy guideline to follow when trying to consume less sodium is to choose foods with less than 5 percent of the daily value as given on the nutrition facts for a 2,000-calorie diet." (The American Heart Association).

Luckily, taste buds in the mouth have a high turnover rate, so they can be “trained” to like new flavors. By gradually lowering the amount of salt added to food, and transitioning to lower sodium alternatives, one can become independent of the amount of salt added to food. Since salt becomes sodium in the body, this would directly decrease the amount of sodium in the blood and decrease blood pressure. Some of the best flavors to substitute in place of sodium are “lemon, ginger, curry, dried herbs (such as bay leaves, basil and rosemary), onion, garlic and dry mustard,” (Thomas).

There are many sources of sodium lurking in our food. In order to combat sodium, we must first know the places it hides. By monitoring sodium content from reading the Nutrition Facts panel to limiting processed foods in the diet, huge cuts in the amount of sodium in our every day diets will have a huge impact on our health overall, especially blood pressure.

American Heart Association. (2015). Retrieved from http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/HealthyEating/Understanding-Food-Nutrition-Labels_UCM_300132_Article.jsp

Centers for Disease Control and Prevention. (2014). Top 10 Sources of Sodium. Retrieved from http://www.c dc.gov/salt/sources.htm

Shepell. (2011). Sodium Overload: Shaking the Salt Habit. Retrieved from http://www.bcit.ca/files/hr/pdf/tba_march_2011.pdf

Thomas, G. (2013). Hidden Salt in Foods. Retrieved from http://health.clevelandclinic.org/2013/07/hidden-salt-in-foods/

9.1.2 Functions

Sodium is one of the key nutrients to hydric balance.

Humans take all the Sodium (Na) that we need in the form of salt. Edible, table salt is composed primarily of sodium chloride (NaCl),

Sodium:

• Principal cation in extracellular fluid.
• Helps to stabilize the potassium/sodium ratio
• Regulates blood volume.
• Regulates blood pressure.
• Regulates osmotic equilibrium.
• Regulates acid-base (pH) equilibrium.
• Essential for nerve impulse transmission
• In animals, sodium ions are used against potassium ions to build up charges on cell membranes, allowing transmission of nerve impulses when the charge is dissipated (Wikipedia).
• Essential for muscle contraction.

In muscle movement, sodium channels open in the muscle cell and sodium ions (positively charged) rush into the muscle fiber (How Ion Channels…). This quick change in charge causes a brief electrical impulse to run throughout the fiber (How Ion Channels…). In nerve impulses, an electric impulse is created in much the same way. A sodium channel allows sodium to enter that had previously built up outside of the cell (The Nervous System) . Sodium plays an important role in pH balance throughout the body. It is part of the compound sodium bicarbonate, more commonly known as baking soda. Sodium bicarbonate acts as a pH buffer and helps to stabilize blood pH. Even though sodium is not active in buffering pH, the sodium binds to the bicarbonate, allowing it to move throughout the body (How Does Sodium…). One important role of sodium is controlling blood volume. Another hormone that is important in balancing sodium levels as well as maintaining adequate amounts of fluid in the body is antidiuretic hormone or ADH. This hormone causes the kidneys to retain water and, as a result, increase blood volume (Overview of Sodium).

How Does Sodium Bicarbonate Affect Blood pH Levels? (2013, August 16). Retrieved December 2, 2015, from http://www.livestrong.com/article/419115-how-does-sodium-bicarbonate-affect-blood-ph-levels/

How Ion Channels Regulate Muscle Contraction Inherited and Endocrine Myopathies. (n.d.). Retrieved December 2, 2015, from http://www.mda.org/disease/inherited-and-endocrine-myopathies/causes-inheritance/ion-channels-muscle-contraction

The Nervous System. (n.d.). Retrieved December 2, 2015, from https://mcb.berkeley.edu/courses/mcb135e/nervous.html

Overview of Sodium - Hormonal and Metabolic Disorders. (n.d.). Retrieved December 2, 2015, from http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/electrolyte-balance/overview-of-sodium

9.1.3 Requirements

The current recommendation for sodium intake is less than 1,500 mg a day. The upper limit for sodium is 2,300 mg a day (American Heart Association). The recommendation is set lower as a safety precaution for people with high blood pressure. People that are at risk for high blood pressure such as people with hypertension, African Americans, and people of middle or older age should be careful not to consume too much sodium (American Heart Association). The average American consumes around 3,400 mg of sodium every day, well above the recommendation and upper limit for sodium intake (The FDA Recommended…). Athletes and very active individuals who may lose a lot of electrolytes through sweat, can consume more sodium than a non-active individual, but even they may not need more than 1,500 mg of sodium a day (The FDA Recommended…). Table salt or sodium chloride is made up of about 40% sodium (Sodium in Diet). One teaspoon of salt contains the upper limit of sodium, or 2,300 mg of sodium (Sodium in Diet).

As of May 2014, it is recommended by the American Heart Association that the average individual should consume less than 1500 mg of sodium per day. Extreme athletes or workers who are exposed to heat for prolonged periods of time should consume the maximum requirement of 1500 mg of sodium each day. This is to replace the large amounts of sodium that are lost with excessive sweating. The requirement is set at 1500 mg/day because this value is the best for maintaining a proper blood pressure.

American Heart Association. (2015). Retrieved from http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/HealthyEating/Understanding-Food-Nutrition-Labels_UCM_300132_Article.jsp

The FDA Recommended Sodium Intake. (n.d.). Retrieved December 2, 2015, from http://healthyeating.sfgate.com/fda-recommended-sodium-intake-1873.html Sodium in diet: MedlinePlus Medical Encyclopedia. (n.d.). Retrieved December 2, 2015, from https://www.nlm.nih.gov/medlineplus/ency/article/002415.htm

American Heart Association. (May 2014). Frequently Asked Questions About Sodium. The American Heart Association Inc. Retrieved from <http://www.heart.org/HEARTORG/ GettingHealthy/NutritionCenter/HealthyEating/Frequently-Asked-Questions-FAQs-About- Sodium_UCM_306840_Article.jsp#.Vl9ImktbzwI>!

9.1.4 Imbalance

When you consume food, you don’t think about the minerals and nutrients that you are consuming. Man was made to eat, in order for the survival of its species. Yet when it comes to cooking foods, it is important to monitor the ingredients added. Salt, otherwise known as sodium, is one of those ingredients that you have to control. A national survey showed that the average daily sodium intake for Americans is 3,400 milligrams per day (Pineo). That is a lot considering that the Recommended Daily Allowance (RDA) is 1,500 milligrams per day (Palacios, 2013). There is even leniency for those that tend to consume more with a limit of no more than 2,300 milligrams of sodium per day (Palacios, 2013).

Hyponatremia occurs when the concentration of sodium in the blood is lower than normal. This can become a problem because sodium is needed for the correct function of nerves and muscles and also to maintain blood pressure. Acute hyponatremia occurs quickly over a few days and is more dangerous than chronic hyponatremia, where the sodium level gradually decreases over time. This is because in chronic hyponatremia, the body’s cells have enough time to adjust to the swelling of water inside them. In extreme cases, hyponatremia can cause hallucinations, brain herniation, and/or death.

Symptoms. Symptoms of hyponatremia include:

• Confusion
• Convulsions
• Headache
• Loss of appetite
• Muscle cramps
• Nausea
• Vomiting
• Weakness

Causes. There are three different types of hyponatremia. These conditions vary depending on how the imbalance of sodium and water within the body occurred. The first type is known as Euvolemic Hyponatremia. This type of imbalance occurs when the amount of water in the body increases, and the amount of sodium stays the same. The next condition is Hypervolemic Hyponatremia. This type occurs when the amount water and salt both increase in the body, but the amount of water increases more. The third and final type is Hypovolemic Hyponatremia. This occurs when the amount of sodium and water in the body both decrease, and the loss of sodium outweighs the loss of water. Any one of these imbalances can be caused by physical factors, such as:

• Large burns
• Diarrhea
• Heart Failure
• Kidney Disease
• Sweating
• Vomiting

Diagnosis. Hyponatremia can be diagnosed through blood and urine tests. The blood tests include running a whole comprehensive metabolic panel, as well as a blood osmolality test. The urine tests include that examination of the concentration of water and sodium in the patient’s urine.

Treatment. In order to treat hyponatremia, the patient may be given an IV that contains sodium to directly correct their fluid imbalance. A patient may also be given medicine to help cure their symptoms. A patient may also be told to be cautious of their amount of water intake. There is an understanding that people partake in different levels of activity and need to consume more or less than average amounts of sodium. There is also an influence of culture and background that can influence opinions and preferences on foods. . Yet you do have to make sure that you do not consume too much, or too little, sodium in order to keep your blood cells from malfunctioning (Benjamin Wedro, 2015). Symptoms can lead to lethargy, swelling, or even a coma (Benjamin Wedro, 2015). There are methods in order to prevent a high or low intake level. Eat more fresh foods, rather than processed products with excessive amounts of sodium (Palacios, 2013). The types of seasoning that you use to cook also can easily be altered. Rather than using sodium based products, use herbs like cilantro, garlic, onions, and lemon juice (Palacios, 2013). We all want to live healthy lives and the first step can be as small as watching the amount of sodium you consume.

Palacios, Anthony Isaac. "What Is the RDA of Sodium?" Live Strong. N.p., 13 Oct. 2013. Web. 2 Dec. 2015. <http://www.livestrong.com/article/482968-what-is-the-rda-of-sodium/>.

Pineo, Cindy. "The FDA Recommended Sodium Intake." Healthy Eating. SFGate, n.d. Web. 02 Dec. 2015. <http://healthyeating.sfgate.com/fda-recommended-sodium-intake-1873.html>.

Wedro, Benjamin. "Electrolytes Causes, Symptoms, Treatment - Symptoms of Sodium Imbalance - EMedicineHealth." EMedicineHealth. N.p., 4 Aug. 2014. Web. 02 Dec. 2015. <http://www.emedicinehealth.com/electrolytes/page4_em.htm#symptoms_of_sodium_imbalance >.

Wedro, Benjamin. (4 August 2015). Electrolytes: Symptoms of sodium imbalance. E medicine health experts for everyday emergencies. Retrieved from <http:// www.emedicinehealth.com/electrolytes/page4_em.htm>

Dugdale III, David C. (14 April 2013). Hyponatremia. Medline Plus: Trusted Health Information For You. Retrieved from <https://www.nlm.nih.gov/medlineplus/ency/article/ 000394.htm>!

HYPONATREMIA AND HYPERNATREMIA

The ideal concentration of sodium in blood plasma, for humans, lies between 135 – 145 mEq/L. (Mayo Clinic Staff, 2015)

Hyponatremia is a electrolyte disorder in which sodium levels, relative to blood plasma, are too low, falling below 136 mEq/L. This condition can be classified under three main categories. (Douglas, 2006) Euvolemic or isotonic hyponatremia occurs when total body water increases however sodium levels stay constant. Hypervolemic or hypertonic hyponatremia is defined as the increase of total sodium and water content in the body, however water levels increase more and at a faster rate. Finally, hypovolemic or hypotonic hyponatremia is defined as both total water and sodium levels dropping, however sodium loss is greater.

Hyponatremia can occur through any form of excess body water to sodium concentration within blood plasma. (Douglas, 2006) One potential cause is through water intoxication, such as by drowning or consuming too quickly, to the point of overwhelming the kidney’s ability to compensate and maintain body water equilibrium. Vomiting and diarrhea can also exacerbate hyponatremia in the case that a subject chooses to replenish his or her lost fluids without replacing lost electrolytes. Additionally, dysfunctional secretion of Antidiuretic Hormone (ADH) can further disorder electrolyte balance. This is one of the most common causes of clinical euvolemic hyponatremia. (Douglas, 2006) Pneumonia, cancer, thyroid complications or certain medications can bring about a syndrome of inappropriate anti-diuretic hormone secretion (SIADH). If the secretion of ADH is not properly regulated, water levels within the human body can build up.

Symptoms of hyponatremia include nausea, vomiting, headaches, fatigue, restlessness, and in extreme cases, nervous dysfunctions ranging from spasms and muscle weakness, to seizure and coma. (Mayo Clinic Staff, 2015)

Hypernatremia is a condition in which sodium levels are too high, reaching above 145 mEq/L. (Parrish & Rosner, 2014) Hypernatremia can occur through any form of unbalancing the water to sodium ratio within blood plasma, with an excess of sodium. One possible cause is dehydration, either by lack of thirst impairment or excessive sweat/water loss. It can also occur as a consequence of consuming too much sodium, or medicinal side-effects. Finally, hypernatremia can occur due to an endocrine disorder, such as diabetes, which causes a body to retain too little water. (Mayo Cinic Staff, 2015) Excessive expulsion of body water will lead to a higher and disordered total concentration of sodium. Clinically, patients will be especially at risk for hypernatremia if their sensation of thirst is altered, they are unconscious, or their water intake is dependent upon a caretaker or physician. (Parrish & Rosner, 2014)

Clinical symptoms of hypernatremia can include dysfunctions of CNS functionality. (Parrish & Rosner, 2014) This can manifest itself into confusion, stupor or in extreme cases, coma.

References

Diabetes insipidus. (n.d.). Retrieved December 11, 2015, from http://www.mayoclinic.org/diseases-conditions/diabetes-insipidus/basics/complications/con-20026841

Douglas, I. (2006). Hyponatremia: Why it matters, how it presents, how we can manage it. Cleveland Clinic Journal of Medicine, S4-S12. Retrieved December 11, 2015, from http://jacobimed.org/public/Ambulatory_files/Educational/hypo%20Na%20eval%20and%20tx.pdf

Hyponatremia. (n.d.). Retrieved December 3, 2015, from http://www.mayoclinic.org/diseases-conditions/hyponatremia/basics/causes/CON-20031445

Parrish, C., & Rosner, M. (2014). Clinical Observations Correcting Hypernatremia: Enteral or Intravenous Hydration? NUTRITION ISSUES IN GASTROENTEROLOGY, SERIES #137, 68-72. Retrieved from https://med.virginia.edu/ginutrition/wp-content/uploads/sites/199/2014/06/Parrish_Rosner-Dec-14.pdf