Depending on gender and age, adult Americans consume between 2,395 mg and 4,476 mg of sodium per day. As a frame of reference, 2,300 mg of sodium is the equivalent of 5.84 g of sodium chloride or about 1 teaspoon of table salt. The 2010 Dietary Guidelines Advisory Committee set a long-term goal for sodium consumption to be reduced to 1,500 mg per person per day.
Sodium across the food supply
Compliance with the 2010 DGA will require major shifts in consumer behavior and a profound modification of the US food supply. At this time, there is no specific guidance as to whether sodium reduction targets should apply to specific food categories or to the entire food supply as a whole. Several studies, based on the sodium content of Australian foods, noted that the food groups highest in sodium content were sauces and spreads and processed meats. Cereals and cereal products as well as vegetables and fruits were lowest in sodium. However, measuring sodium content in milligrams per 100 g does not take into account either portion size or the likely frequency of consumption. Among food products targeted for reformulation by the UK Food Standards Agency were brown table sauces, such as Worcestershire sauce.
Measures and metrics used to assess sodium sources in the everyday diet must be weighted by purchases or by frequency of consumption. An analysis of the sodium content of foods in the United Kingdom obtained sodium values (mg/100 g) weighted by annual purchases for all food categories known to be major contributors to sodium intake. Using this purchase-weighted approach, researchers concluded that the major sources of dietary sodium to food purchases were table salt, processed meats, breads and bakery products, dairy products, and only then sauces and spreads. They concluded that sodium reduction ought to be targeted to a small number of food categories and to the products sold in the highest volumes. Along these lines, a 2012 report presents a model for reducing salt intake by 0.6 to 1.0 g/d in Europe through sodium reductions in bread. In this model, sodium is replaced with potassium salts, reducing sodium by 30% and lowering the sodium/potassium ratio as well.
Sodium and food intake
An analysis of the chief sodium sources in American diets was conducted for a presentation titled “Sodium, potassium and calories: Can we successfully meet dietary guidelines?” delivered at the American Dietetic Association 2011 Food and Nutrition Conference and Expo (Drewnowski A, unpublished data). It was performed using two federal databases: the US Department of Agriculture (USDA) Food and Nutrition Database for Dietary Studies (FNDDS 1.0) and the National Health and Nutrition Examination Survey (NHANES) database. Analyses were conducted on 4,176 foods and beverages aggregated into 9 food groups, 48 subgroups, and 197 categories. The mean, median, standard deviation, and range of sodium values were calculated for food groups based on USDA food code prefixes (1, 2, and 3 digits). Foods not consumed by NHANES participants, duplicated foods, and baby/toddler foods were excluded.
Based on sodium content per 100 g, items that were highest in sodium were as follows: processed meats, seafood, bacon, processed cheese, and salad dressings (Figure 1). However, many such foods are typically consumed in portion sizes well below 100 g. The FDA definition of portion size is based on reference amounts customarily consumed, and these vary from 15 g for bacon to 240 g for milk. Values for frozen dinners are higher still. When sodium content was converted from 100 g to serving size, different food groups were at the top of the list (Figure 2). Meats, vegetables, grains, and beans were then placed above sauces and spreads.
The frequency of consumption of different sodium-containing foods is vastly unequal, resulting in some foods with high sodium content that are infrequently consumed, being only minor contributors of sodium to the diet, and vice versa. Therefore, the total sodium load, weighted by frequency of consumption, ought to be taken into account. Such an analysis was performed using dietary intake data for 4,413 adults (aged ≥ 20 years) from NHANES 2001–2002 with complete 24-h recall information. Children and adolescents, pregnant women, and individuals reporting low/high energy intake were excluded. The estimated amounts of sodium contributed by the different food groups were calculated based on reported frequency of consumption (Drewnowski A, unpublished data).
The chief sources of sodium in the US food supply were as follows: grain mixtures, mainly grain, pasta, or bread; processed meats, including frankfurters, sausages, and lunchmeats; white breads and rolls; and dishes made with meat, poultry, and fish. In general, breads and meats were the principal contributors of dietary sodium, which is a different picture than the one obtained using sodium content per 100 g.
The 2010 proposed US guidelines for sodium are 1,500 mg per person per day for vulnerable population segments (people ≥ 51 years, African Americans of all ages, and anyone with hypertension, diabetes, or chronic kidney disease), and 2,300 mg for all others. There is some question as to whether the 2010 DGA can even be met at that level of sodium restriction. For example, the guidelines may not be feasible for persons <50 years of age or those with high energy intakes. Food pattern modeling analyses based on linear programming will help determine whether the low-sodium dietary guidelines can be met using any combination of foods in the current US food supply. Another question is whether the low-sodium dietary guidelines will require drastic changes in consumer behavior. For example, diets that are adequate in nutrients yet low in sodium can be achieved, in principle, using high amounts of fruit juices, nuts, and seeds and virtually no grains and meats. Compliance with the proposed guidelines may require not only major behavioral changes but also a profound modification of the US food supply.
Further analyses are required to determine whether the sodium target is compatible with the USDA food plans, which are the mainstay of food assistance. Future analyses also must determine whether the sodium target goals will be more readily achieved given a 10% across-the-board reduction of sodium content in the US food supply.