The available data suggest Western societies consumed between three and 3.3 teaspoons (15-17 grams) of salt per day from the early 1800s until the end of World War II, based on military archives for prisoner-of-war and soldier rations around the world. During the Anglo-American War of 1812, despite its high cost, salt rations amounted to three teaspoons (15 grams) per day. (See: Rations: The History of Rations, Conference Notes, Prepared by The Quartermaster School for the Quartermaster General, January 1949, accessed at http://www.qmfound.com/history_of_rations.htm on 4/19/2014.)
American prisoners of war, incarcerated in Britain’s Dartmoor prison, bitterly complained that the 1.5 teaspoons (8 grams) of salt per day they received was part of a “…scanty and meager diet for men brought up in the land of liberty, and ever used to feast on the luscious fruits of plenty…”(James Adams, Dartmoor Prison, A Faithful Narrative of the Massacre of American Seamen, to Which is added a Sketch of the Treatment of Prisoners During the Late War by the British Government (See: Pittsburgh, S. Engles, 1816), accessed at http://www.archive.org/stream/prisonersmem00andr#page/12/mode/2up/search/salt on 4/19/2014.)
Declassified World War II documents regarding rations fed to American prisoners of war show a ration of one hundred forty grams per week or 3.3 teaspoons (17 grams) per day. (See: American Prisoners of War in Germany, Prepared by Military Intelligence Service War Department, November 1945, Restricted Classification Removed – STALAG 17B (Air Force Non-Commissioned Officers) accessed at http://www.valerosos.com/AMERICANPRISONERSOFWAR.pdf on 4/19/2014.)
After World War II, when refrigeration began to displace salt as the main means of food preservation, salt consumption in the U.S. (and somewhat later in other countries) dropped dramatically to about half that rate, or nine grams (1.8 teaspoons) per day and, based on twenty-four hour urinary sodium data, has remained flat for the last fifty years. (See: Bernstein AM, Willett WC. Trends in 24-h urinary sodium excretion in the United States, 1957-2003: a systematic review. Am J Clin Nutr. 2010;92(5):1172-1180. Epub 2010 Sep 8.)
During that time, rates of hypertension have increased, thus casting doubt on any linkage between the two. (See: Ayala C, Croft JB, Wattigney WA, Mensah GA. Trends in Hypertension-Related Death in the United States: 1980- 1998. J Clin Hypertens. 2004;6(12):675-681.)
It is telling that this sudden drop took place without pressure or influence from any government Dietary Guidelines, public health institutions or strident warnings from salt-reduction advocates. The massive reduction was the result of an effortless shift to a palatable, cold-chain-based food supply. It is further interesting that this abrupt drop halted at one level of consumption fifty years ago and descended no further. It is equally extraordinary that, without guidance or pressure of any kind, the consumption of salt around the world, for more than two centuries has remained in the range of 1.5 to three teaspoons (8-15 grams) per day, which, from all the available data, appears to hold the lowest risk for us. It lends support to the notion of the “wisdom of the body” (Prof. Walter Cannon, Harvard – 1932) at work through a mechanism that may not be as obvious as the typical sodium appetite so common in most other mammalian species, but effective nevertheless.