Food salt & health
Salt is ubiquitous in foods and consumed in relatively constant amounts in our diets; it is essential to our health and development. Most of our salt comes from foods, some from water. The universal, consistent appetite for salt, public authorities agree, makes it the ideal vehicle for iodine fortification to prevent mental retardation.
Salt is essential not only to life, but to good health. It's always been that way. The body's salt/water ratio is critical to metabolism. Human blood contains 0.9% salt (sodium chloride) -- the same concentration as found in United States Pharmacopeia (USP) sodium chloride irrigant commonly used to cleanse wounds. Salt maintains the electrolyte balance inside and outside of cells. Routine physical examinations measure blood sodium for clues to personal health. Testing the salinity of perspiration is a good test for cystic fibrosis; scientists suspect that cystic fibrosis is caused by a deformed protein that prevents chloride outside cells from attracting needed moisture.
Salt is important to hydration in our bodies. After exercise, it is critical to replace both water and salt lost through perspiration during exercise. When diarrhea dehydrates the body, we use oral rehydration therapy (ORT) to restore fluids (and health); ORT uses salt, sugar and water and, because of the prevalence in many societies due to inadequate public health, has been termed by the British Medical Journal to be “the most important medical advance of (the 20th) century.”
Expectant mothers and older persons, in particular, need to guard against under-consumption of salt and high-salt diets have been used successfully to combat chronic fatigue syndrome. Asthma sufferers, particularly in Eastern Europe, are often treated by having them live in salt mines because of their unique microclimate, inhospitable to airborne contaminants. Salt, in fact, has been termed “the first antibiotic.”
Though humans tolerate wide variations in salt intake, most Americans consume sodium in the “hygienic safety range:” 1,150 – 5,750 mg/day. Americans average about 3,500 mg/day, just about the worldwide average. The National Academy of Science recommends a sodium intake level at least 500 mg/day, but less than 2,300 mg/day based on its expert group consensus.
Consumption of “excess” amounts of salt, as in Japan with significantly higher salt intake levels compared with North America, may be problematic; high concentrations of salt irritate the stomach lining and may trigger stomach cancer, though studies are more suggestive than definitive.
Medical evidence proves salt is related to blood pressure and several other important risk factors for cardiovascular health. Overall, however, the evidence suggests that low-salt diets may be more problematic than current consumption levels. No evidence demonstrates that current salt intake levels lead to worse health outcomes such as more heart attacks or higher cardiovascular mortality. A careful evidence-based study is needed to determine whether a population salt-reduction advisory would improve health or actually raise the risk of heart attacks. Adoption of true “evidence-based” decision-making should replace the current system for developing dietary guidance by polling expert committees.
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“Evidence-based” recommendations and why they are important. Data quality is the foundational consideraton when considering any medical or public health intervention. Actual data should trump the opinion of experts.
Human salt requirements . As we consider whether a broad public health advisory is appropriate for salt, we must keep in mind that salt is an essential nutrient. By definition, "too much" -- or "too little" -- salt can have important health consequences that must be weighed with care.
How the human body handles salt . Just as salt has many functions, so are there many systems in the body that handle salt. All are affected when salt intake levels vary. Often these changes run counter to each other. That is why it is important to consider the "net health outcome" for any intervention. In addition, because salt is so important to human health, the human body is engineered with a powerful "hard wired" salt appetite that unconsciously directs food choice preferences.
Salt intake and cardiovascular health . The most important outcomes of changes in dietary salt are considered to be the impacts on cardiovascular health (mortality, incidence of heart attacks and strokes, for example). Surprisingly, salt reduction recommendations avoid considering health outcomes studies.
Salt and other health concerns . Just as salt intake level impacts multiple systems in the body, so do changes in salt intake affect such things as glucose metabolism, lung function, etc. which also need to be considered in making recommendations to adjust salt intake levels.
Why we rely on iodized salt . Iodizing salt is arguably the greatest public health achievement of the 20th century and its universal adoption remains a major public health priorty. Nearly a third of our global population lacks acess to iodized salt. This is important, but not for the reason most people think. If you think goiter prevention is the reason we iodize salt, please read further .
How we should resolve the issues of salt and health . Scientists themselves disagree. Judge for yourself whether governments should be encouraging all their citizens to reduce dietary sodium (salt).