It is well known that the Japanese have the longest life expectancy rates in the world. It is less known however, that they also have the highest rates of salt consumption.
Salt is essential to the health, and is one of the five basic taste sensations. Sodium ions are vital for generation of nerve impulses, for maintenance of electrolyte balance and fluid balance, for heart activity and certain metabolic functions. It helps your muscles stay strong, and keeps your cells and brain functioning. Actually, no mineral is more essential to human survival than sodium. However, our body cannot produce it, and therefore it must be consumed with our diet.
Low salt diet myths
Far from being harmful, salt is actually is of vital importance, but in many developed countries salt has been considered as a primary cause of high blood pressure and heart disease. Now lots of studies are shaking up the salt myth and warning about the dangers of salt restriction that pose a serious threat to human health.
Salt daily intake
According to the new guidelines of the World Health Organization, salt daily intake is 5g (1 teaspoon) for adults. It is recommended that adults should consume less than 2,000mg of sodium (which is contained in 5g of salt) and at least 3,510 mg of potassium per day. 
A low salt diet reduces the intake of sodium by the careful selection of food. The human minimum requirement for sodium in the diet is about 500mg per day, which is typically less than one-sixth as much as many diets “seasoned to taste”. 
Health risks of a low salt diet
The researchers from McMaster University and Hamilton Health Sciences have found that, contrary to popular belief, low-salt diets may not be beneficial and may actually increase the risk of cardiovascular disease and death compared to average salt consumption. A large worldwide study that involved more than 130,000 people from 49 countries showed that regardless of whether people have high blood pressure, low-sodium intake is associated with more heart attacks, strokes and deaths compared to average intake. They looked specifically at whether the relationship between sodium (salt) intake and death, heart disease and stroke differs in people with high blood pressure compared to those with normal blood pressure. 
Studies also show that excessively low salt intake (below three grams of salt per day) is associated with an increased mortality and higher risk for cardiovascular disease [2, 3].
The study published in the Journal of the American Medical Association revealed the results of eight years of investigation of 3,681 middle-aged healthy Europeans that were divided into three groups: low salt, moderate salt, and high salt consumption. It was found that the less sodium excreted in the urine (a marker of salt consumption), the greater the risk of dying from heart disease. The risk for heart disease was 56% higher for the low-salt group than for the group who ate the most salt! 
The minimum physiological requirement for sodium is 500 milligrams per day.
Sodium is the most prominent cation in extracellular fluid: the 15 liters of it in a 70kg human have around 50grams of sodium, 90% of the body’s total sodium content.
The distribution of sodium ions are mediated by Na+/K+-ATPase, which is an active transporter pumping ions against the gradient, and sodium/potassium channels. By means of this enzyme, living human cells pump three sodium ions out of the cell in exchange for two potassium ions pumped in; comparing ion concentrations across the cell membrane, inside to outside, potassium measures about 40:1, and sodium, about 1:10. In nerve cells, the electrical charge across the cell membrane enables transmission of the nerve impulse – an action potential – when the charge is dissipated; sodium plays a key role in that activity. [5, 6, 7]
The problem is that currently most people consume too much sodium and not enough potassium. Processing reduces the amount of potassium in many food products.
Potassium-rich foods include: beans and peas (1,300mg of potassium per 100g), nuts (600mg/100g), vegetables such as spinach, cabbage and parsley (550mg/100 g) and fruits such as bananas, papayas and dates (300mg/100g).
Salt in food
In very small quantities, salt naturally occurs in a variety of foods, including meats, milk, vegetables and fruit, for instance:
- milk and cream – 50mg of sodium per 100g
- eggs – 80mg/100g
Salt is often added to processed foods, such as canned foods and especially salted foods, pickled foods, and snack foods or other convenience foods, where it functions as both a preservative and a flavoring. Here are some examples:
- bread – 250mg/100g
- bacon – 1,500mg/100g
- snack foods such as pretzels, cheese puffs and popcorn – 1,500mg/100g
- soy sauce – 7,000mg/100g
- bouillon cubes – 20,000mg/100g
Before modern refrigerating, salting was one of the main methods of food preservation. Thus:
- herring contains 67mg of sodium per 100g, while kipper, its preserved form, contains 990mg;
- pork typically contains 63mg while bacon contains 1,480mg;
- potatoes contain 7mg but potato crisps 800mg per 100g
The main sources of salt in the diet, apart from direct use of sodium chloride, are bread and cereal products, meat products and milk and dairy products. The high level of sodium in many processed foods has a major impact on the total amount consumed. In the United States, 75% of the sodium eaten comes from processed and restaurant foods, 11% from cooking and table use and the rest from what can be found naturally in foods.
Most of the sodium in the Western diet comes from salt. In many East Asian cultures, salt is not traditionally used as a condiment. In its place, condiments such as soy sauce, fish sauce and oyster sauce tend to have high sodium content and fill a similar role to table salt in western cultures.
Foods that are low in sodium include:
- Seasonings: black, cayenne, or lemon pepper, mustard, some chili or hot sauces
- Herbs: dried or fresh garlic, garlic/onion powder (no salt), dill, parsley, rosemary, basil, cinnamon, cloves, paprika, oregano, ginger, vinegar, cumin, nutmeg
- Most fresh fruits and vegetables, exceptions include celery, carrots, beets, and spinach
- Dried beans, peas, rice, lentils
- Macaroni, pasta, noodles, rice, barley (cooked in unsalted water)
- Honey, sugar
- Unsalted butter
- Unsalted dry curd cottage cheese
- Fresh beef, pork, lamb, fish, shrimp, egg
- Milk, yogurt
- Hot cereals
- Club soda, coffee, seltzer water, soy milk, tea
- “Global study finds low salt diets not beneficial” – http://fhs.mcmaster.ca/main/news/news_2016/low_salt_diet_study.html
- “Eating half the recommended amount of salt per day could increase the risk of heart attacks, scientists warn”, The Telegraph, 21 May 2016 – http://www.telegraph.co.uk/news/2016/05/21/eating-half-the-recommended-amount-of-salt-per-day-could-increas/
- Graudal, Niels; Jürgens, Gesche; Baslund, Bo; Alderman, Michael H. (1 April 2014). “Compared With Usual Sodium Intake, Low- and Excessive-Sodium Diets Are Associated With Increased Mortality: A Meta-Analysis”. American Journal of Hypertension.
- “Fatal and Nonfatal Outcomes, Incidence of Hypertension, and Blood Pressure Changes in Relation to Urinary Sodium Excretion”, The Journal of the American Medical Association, May 4, 2011, Vol 305, No. 17 – http://jama.jamanetwork.com/article.aspx?articleid=899663
- “WHO issues new guidance on dietary salt and potassium”. World Health Organization. 31 January 2013. – http://www.who.int/mediacentre/news/notes/2013/salt_potassium_20130131/en/