Perhaps stung by all the criticism, Ortiz has now released a statement clarifying what he meant. In it, he says he only wants to ban unnecessary levels of salt—not salt that is, as he says, “a functional component of the recipe.” That seems like something that’s a bit hard to prove. Who’s to say what level of salt is functional or not?

While sodium is an essential nutrient in man, physiological need in acclimatized adults is only of the order of 8–10 mmol/d (184–230 mg/d) (Dahl, 1972). In contrast to the present day, our predecessors during 70 million years of mammalian and primate evolution, and 4–15 million years of hominoid and hominid evolution leading to Homo sapiens had no exposure to sodium (salt) as a food additive, only to sodium occurring naturally in foods and water (Denton, 1982). This was true also for Homo sapiens during tens of thousands of years of evolution as a nomadic food gatherer and hunter, until about 6000–8000 years ago when agriculture and animal husbandry developed, and for the first time, the need to have a substantial reserve of food. Hence there developed a requirement to preserve food, i.e. by salting of meat, fish, vegetables and dairy products (Stamler, 1993). Our species evolved in the warm climate of Africa (Leakey, 1991), a salt-poor continent, on a low salt diet of no more than 20–40 mmol sodium/day; it became – and remains – exquisitely adapted to the physiological retention and conservation of the limited salt naturally present in foods. We are not optimally adapted to the excretion (via the kidneys) of large quantities of sodium, many times physiological need, that has become necessary with the addition of salt to foods late in human evolution (Denton, 1982; Stamler, 1993).

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Sodium intakes of different populations around the world were vividly brought to the attention of the research community by publication of Louis Dahl’s famous graph in 1960, showing a positive linear relationship between prevalence of hypertension and mean salt intake across five population groups (Dahl, 1960). He noted that daily intakes of sodium (salt) varied considerably across population groups from 4 g salt/d (1.56 g/d, 68 mmol/d sodium) among Alaskan Eskimos to 27 g salt/d (10.6 g/d, 460 mmol/d sodium) in Akita prefecture, north-east Japan (Figure 4). American men had intakes averaging 10 g salt/d (3.91 g/d, 170 mmol/d sodium). He also noted a strong north–south trend in death rates from stroke in Japan. This coincided with differences in sodium intakes ranging from 14 g salt/d (5.47 g/d, 238 mmol/d sodium) in the south up to the 27 g/d salt (10.6 g/d, 459 mmol/d sodium) in the northeast region noted above (Figure 5). The extremely high sodium intakes in north-east Japan reflected the dietary practice of eating rice with miso soup and pickles, and the use of soy sauce as seasoning (Sasaki, 1962)

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The extremely high sodium intakes recorded in some regions, notably northern Japan, in the late 1950s and early 1960s, are no longer apparent. These declines in sodium intakes coincided with public health awareness campaigns about the dangers associated with a high salt intake. More recent data from Japan and other countries suggest that salt intakes are no longer falling and may be on the rise, nor do there appear to be populations with the low sodium intakes previously found, including in the INTERSALT study. More recent data suggest that most populations appear to have mean sodium intakes well in excess of 100 mmol/d (2.30 g/d), and in many (especially the Asian countries) in excess of 200 mmol/d (4.60 g/d). Sodium intakes in men are greater than those in women, most likely reflecting the higher food consumption (energy intake) among men. Sodium intake in adults appears to be slightly lower above the age of 50 years than at younger ages.

An intake of 65 mmol/d (1500 mg/d) has been recommended as adequate intake (AI) in the USA to ensure that the diet provides adequate intakes of other nutrients, and to cover sodium sweat losses in unacclimatized individuals who are exposed to high temperatures, or who are physically active (Institute of Medicine, 2004). The current data suggest that the vast majority of individuals have sodium intakes well in excess of this level.

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In developed country diets, a large proportion of the sodium ingested is added (as sodium chloride) in food manufacture and foods eaten away from the home. James, Ralph & Sanchez-Castillo (1987) and Mattes & Donnelly (1991) estimated that for the United Kingdom and USA, about 75% of sodium intake was from processed or restaurant foods, 10–12% was naturally occurring in foods and the remaining 10–15% was from the discretionary use of salt in home-cooking or at the table.

Figure 17 illustrates the difference in sodium content of two typical developed- country meals, comparing a takeaway or manufactured meal with a home-cooked meal without added salt. Sodium content of a takeaway cheeseburger and chips (French fries) is estimated at 1240 mg (54 mmol) compared with homemade steak and chips at 92 mg (4 mmol); sodium content of a ‘ready-meal’ risotto is estimated at 1200 mg (52 mmol), while that of its homemade equivalent at < 2 mg (< 0.1 mmol). Table 12 lists the sodium content of a number of foods in their natural state and after processing. In some cases, for example chick peas, sweetcorn and peas, which have a naturally very low sodium content, food processing increases the sodium content by 10–100-fold; and foods such as corned beef, bran flakes or smoked salmon, have sodium intakes of 1–2%, equivalent to, or more than, the sodium concentration of Atlantic seawater (MacGregor & de Wardener, 1998).

Table 13 lists the foods that contribute the largest proportions of sodium to the diet in the United Kingdom, based on National Food Survey data for 2000. Cereals and cereal products including bread, breakfast cereals, biscuits and cakes, contribute about 38% of estimated total intake, meat and meat products 21%, and other foods such as soups, pickles, sauces and baked beans a further 13%.

Similar data for the USA are shown in Table 14 (Cotton et al., 2004). Bread, ready-to-eat cereal and cakes, cookies, quick-breads and doughnuts contribute 16-17% of sodium intake; ham, beef, poultry, sausage and cold cuts about 13%; milk and cheese 8–9%; condiments, salad dressing and mayonnaise about 5%; other foods including potato chips, popcorn, crackers and pretzels, margarine, hot dogs, pickles and bacon a further 23–25%. Table 15 shows the sodium content of selected foods available in restaurants in the USA. All the products listed alone contain over 2.3 g (100 mmol) sodium, i.e. the recommended daily tolerable upper intake level (UL) for the USA (Institute of Medicine, 2004); some foods contain twice the recommended UL.

Some children’s foods are extremely high in sodium. For example the estimated salt content of one large slice of pizza or two thin fried pork sausages is around 1 g (391 g, 17 mmol sodium) (Figure 18).

In the United Kingdom, cereals contribute 38–40% of sodium present in the diets of children and young people ages 4–18 years; meats 20–24%; vegetables 14–17%, and dairy products 7–9% (Figure 19). In the USA, girls reporting that they ate fast foods at least four times per week had higher sodium intakes than girls having fast foods < 1–3 times per week (Figure 20) (Schmidt et al., 2005).

A different picture with regard to dietary sources of sodium is apparent in some Asian countries. In China and Japan, a large proportion of sodium in the diet comes from sodium added in cooking and from various sauces, including soy sauce and (in Japan) miso. Table 16 shows the proportions of sodium from different sources contributing to the Chinese diet, based on data from the 2002 Chinese Health and Nutrition Survey (Zhao, personal communication). Overall, some 75% of dietary sodium comes from sodium added as salt in cooking, and a further 8% from soy sauce. The main sources of sodium in the diets of INTERMAP participants from China and Japan are shown in Table 17. Again, the predominant source in China was salt added during cooking (78%). In Japan, the main sources were soy sauce, fish and other sea food, soups and vegetables (66% in total) with a further 10% being contributed by salt added during cooking. Some foods commonly consumed in Malaysia are also very high in sodium (Table 18); for example a bowl of Mee curry and a bowl of Mee soup available from ‘hawker’ markets contain about 2.5 g (109 mmol) and 1.7 g (74 mmol) sodium, respectively (Campbell et al., 2006).

Summary

The amount of sodium in diets in developed countries is dominated by salt added in food manufacture and in foods eaten away from home. Some children’s foods are extremely high in sodium. In some Asian countries, a different pattern is evident, with salt added in cooking and in various sauces (e.g. soy) being predominant.

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