Editor’s note: This article was originally published on The Conversation and was picked up by the National Post.
Salt is the universal flavour enhancer, and we can’t seem to get enough of it.
While preparing food at home, or while buying prepared food from grocery stores and restaurants, salt tends to find its way onto our plates.
Does our love for salt come at a cost? How much salt is too much, and should we be concerned? These are the questions that not enough people are asking.
As a PhD candidate in human health and nutritional sciences at the University of Guelph, I study how the genetics of taste affects taste perception, taste preference, dietary intake and metabolism in the Guelph Family Health Study.
Part of this research examines how genetics can cause some people to be less sensitive to the taste of salt than others, leading them to prefer higher amounts in their food.
Identifying genetic markers can help us understand who may be more at risk of developing the adverse consequences of excessive salt intake, such as high blood pressure, the silent killer.
Salt, heart disease and hypertension
In 2012, about 48,000 lives were claimed by heart disease, the second leading cause of death in Canada.
One of the major silent risk factors for heart disease is high blood pressure or hypertension. While it cannot be seen or felt, high blood pressure puts an enormous strain on blood vessels and weakens the body’s organs, including the heart and kidneys.
In 2014, almost one in five Canadian teens and adults reported being diagnosed with high blood pressure. Because this condition has such a widespread influence on the health of Canadians, researchers and government have been working to identify and address this growing concern.
While the complex solution to lowering blood pressure in Canadians continues to evade us, it is well known that we don’t need to look further than our dinner tables to find a culprit.
A certain amount of salt is essential to health. But most Canadians are consuming double and sometimes even triple the daily adequate intake (AI).
In fact, more than 85 per cent of men and between 60 to 80 per cent of women had sodium intakes exceeding 2,300 mg per day — the Tolerable Upper Intake Level (UL) set by Health Canada — according to the 2004 Canadian Community Health Survey.
Children exceed tolerable salt levels
In children aged one to three years and four to eight years, the ULs for sodium are 1,500 mg and 1,900 mg, respectively.
With these adjusted guidelines, even young children are not exempt from this striking pattern. Seventy-seven per cent of children aged one to three years and 93 per cent of children aged four to eight years exceed the UL for sodium, according to the 2004 Canadian Community Health Survey.
At these excessive levels, sodium in salt causes the kidneys to retain water in the blood vessels.
An increased amount of blood in the vessels puts pressure on the walls of the arteries, similar to how pumping gas into an inflating balloon puts pressure on its walls.
Over time and in combination with lifestyle factors, including an overall poor diet and lack of exercise, high blood pressure increases the risk of heart disease.
A food industry fail
We know Canadians are eating too much salt, but why is there so much in the diet?
While Canadians love the taste of salt in their food, intake of sodium is not mainly a problem in terms of how food is being prepared in the home.
Health Canada identified that commercially prepared foods account for 77 per cent of sodium intake in Canada. With the dependence of many Canadians on readily available prepared foods at grocery stores and restaurants, part of the solution must be for manufacturers to reduce the amount of sodium in their products.
In 2012, Health Canada published its Guidance for the Food Industry on Reducing Sodium in Processed Foods. This challenged the food industry to reduce sodium in a variety of food products, to targeted levels, by the end of 2016.
With this plan, Canadians would meet sodium targets without even having to reduce the amount of salt used at home.
These guidelines were mostly unmet by the food industry by the end of the program. Forty-eight per cent of food categories tested did not make any progress and 86 per cent of food categories did not meet their final sodium reduction goals.
While it is tempting to fault the food industry entirely for this shortcoming, we must keep in mind that reducing sodium is more difficult in some products as it helps with food preservation and safety.
Consumer awareness and purchasing actions are also important for reducing sodium in food products.
This is a challenge to Canadians — to read nutrition labels on food products and make informed purchasing decisions.
Are we ready to choose products with less sodium? With increased pressure on the food industry, perhaps we can improve blood pressure in Canadians.
The genetics of taste
Even if the goal of sodium reduction should be a collective effort by Canadians, not everyone responds to dietary sodium in the same way.
From the way that we taste salt to the way our kidneys process sodium, there are important differences in sodium sensitivity between individuals, caused in part by genetics.
The Heart and Stroke Foundation estimates that one in three people are sodium-sensitive.
One important underlying reason for sodium sensitivity is the way we taste salt. Genetics may lead some individuals to require more salt on their tongues to taste it; this is called low oral sensitivity. These individuals may need to consume higher amounts of salt in their food to taste it.
Genetics also plays a role in the way sodium is handled by the kidneys. For some unlucky people, genetic differences in kidney function lead to higher sodium retention and therefore higher water retention in the blood vessels.
Know what you eat
Whether sodium sensitivity affects the amount of salt we need for tasting or how the kidney handles sodium, these circumstances present special risks for certain individuals to develop high blood pressure.
Understanding the genetics behind these individual risks and being able to inform individuals of their sodium sensitivity are important steps in fighting the rise of hypertension in Canada.
Of course, while genetics is an important piece of the puzzle, non-genetic factors also predispose individuals to high blood pressure or hypertension.
Regardless of sodium sensitivity, it’s important for Canadians to know that eating a poor, calorie-dense diet that includes processed and refined foods is an independent risk factor for hypertension.
Dietary sodium reduction remains the most promising preventive approach to avoiding the silent killer — even for individuals without sodium sensitivity.
If asked today whether you consume too much salt, would you know the answer?
Knowledge is power. Knowing what you eat offers the power to take control of your health.