Of all the micronutrients essential to human health, few are as versatile—or garner as much attention—as sodium. It plays an essential role not only in the biological function of cells and fluid balance in the body, but also as a food ingredient—adding taste, texture, flavor, and antimicrobial functions.
History of Sodium in Food
Sodium, the predominant mineral in salt (or sodium chloride) has been used as a food ingredient for centuries. Medieval civilizations used salt to preserve foods, which guaranteed a source of food during periods of food scarcity. Ancient Romans and Greeks valued salt as currency and a means to economic stability by ensuring food provisions were available when access to fresh food was limited. Salt remained a primary means of preservation until the late 19th and 20th centuries when other methods, such as refrigeration, freezing, canning, and in some cases, irradiation, came into play. Though consumers in today’s industrial society think of salt as being used primarily for taste and flavor, its value as a preservative in many of the foods we consume is of considerable public health benefit. Indeed, salt is still used as a primary means of preservation, particularly in geographically remote areas of the world with limited or no refrigeration.
Sodium in Food Preservation and Safety
The primary way sodium acts as a food preservative is by inhibiting microbial growth. Many foods contain enough water to encourage growth of microorganisms (such as yeast, bacteria, or mold), especially at room temperature. When microorganisms overgrow in foods (spoilage), both flavor and nutrition are compromised and the food may actually become dangerous to eat. Foods with high water content, such as fresh meat and fish, some cheeses, and sauces made with vegetables or fruits, are susceptible to spoilage by the microorganisms, which can grow rapidly in an abundance of water. Salt, an added ingredient in these and other foods draws water out of the cells of both the food and the microorganism in a process known as osmosis. Microorganisms that do not have enough access to water will not grow and reproduce as fast as those with ample access to water. In this manner, added salt helps to prevent spoilage of the food.
In addition to salt, sodium nitrate and sodium nitrite are often used to prevent spoilage by bacterial growth in meat and fish. Bacteria growth that produces toxins, such as C. botulinum, can have serious health consequences (in this case, botulism) when that specific food is consumed. Other compounds such as sodium lactate, sodium diacetate or sodium benzoate are added to deli-style meat, hotdogs, and poultry products to inhibit microbial growth of L. monocytogenes, a type of bacteria that can cause the foodborne illness listeriosis.
Implications of Sodium Reduction in Foods
Recently, academicians and government agencies are recommending broad reduction of sodium in the food supply due to the possible adverse effects of excess sodium on cardiovascular health. The 2010 Dietary Guidelines Advisory Committee report advocates a goal of 1,500 milligrams of sodium per day for the general population, consistent with Institute of Medicine (IOM) Adequate Intake level for healthy adults 19 to 50 years of age. This is less than half the average amount currently consumed by individuals in the U.S. Indeed, evidence has linked excessive sodium consumption to high blood pressure and related cardiovascular issues. However, a less-known fact is that consuming too little sodium poses its own risks by interfering with fluid regulation, muscle contraction, and the cellular exchange of nutrients and waste.
The IOM’s recently released report, “Strategies to Reduce Sodium Intake in the United States,” is consistent with food industry efforts, underway for many years to reduce sodium in foods. Small changes over time are necessary to allow the American palate to adjust to new flavors, as well as allow industry an ongoing evaluation of the impact of these changes on food safety and public health. In fact, one recent review argues that not enough research has been done to determine the potential impact on food safety of removing or reducing salt in foods, and suggests that consideration be given to reducing other sodium-containing compounds, or reducing sodium content in foods less susceptible to bacterial growth, like boxed prepared foods, dry snacks, and some frozen items.
Another review discusses the possibility of increasing concentrations of other preservative agents, for example potassium chloride or other chemical acids (benzoate, lactate, sorbate), to balance the potential decrease in salt. Though all of these have been found to be effective in preventing bacterial growth, some impart their own flavors to food, which may limit their use. Herbs and spices like garlic, onion, and oregano have been shown to inhibit bacterial growth and may eventually provide alternatives for both preservation and flavor enhancement.
Sodium helps support food quality, safety, and flavor. As efforts continue to reduce sodium in the diet, maintaining a focus on food flavor and product quality will also allow the consumer palate to adjust. A focus the safety role of sodium is critical for public health.