Do you have a salty tooth?
|Dr. Bruce Van Vliet holds up a three-kilogram container of salt, enough for more than five years “adequate intake” of sodium.|
Even if you never use a salt shaker, the chances are your daily diet contains too much sodium. From bread to canned vegetables to pizza, the average person’s diet is rich in sodium, most of it added during the industrial preparation and processing of foods. While much of this sodium is added as salt (sodium chloride), it can also sneak into food in a number of other forms such as monosodium glutamate and baking soda.
Biomedical researcher Dr. Bruce Van Vliet is an expert on the effect of sodium on blood pressure and its relationship to cardiovascular disease, the number one cause of death in Canada. He is particularly concerned about the exposure children have to a high sodium diet and its contribution to a “slow and insidious” rise in our blood pressure during aging.
"There are a growing number of studies which show that the earlier in life you are exposed to salt, the more profound the effect will be,” said Dr. Van Vliet. “Starting to eat a high sodium diet early in life is a terrible thing.”
This raises the question of whether sodium consumed by a mother when she is breastfeeding, or even pregnant, could increase her child’s risk of hypertension later in life. Dr. Van Vliet's findings could eventually influence the dietary recommendations for pregnant women.
“The maternal nutritional environment during pregnancy seems to alter the offspring in a long-term way. It can't change the offspring’s genetic code, but it can change the manner in which the offspring’s genes are used,” explained Dr. Van Vliet. “We want to find out if the sodium a mother consumes during her pregnancy can have this kind of reprogramming influence on her baby’s genes.”
Like a sweet tooth, we all have a salty tooth, said Dr. Van Vliet. The good news is that you can re-program your palate – but it takes some effort and close attention to what you eat.
“Three-quarters of the sodium in food is added by the food industry. Only 10 per cent occurs in food naturally. If companies weren’t adding salt to food we could control it more easily,” said the researcher.
Even if you carefully add up the amount of sodium listed in purchased food, and try to keep within a reasonable daily limit, you may still be eating too much sodium.
“The number on, for example, a can of soup is stated as a percentage of the maximum daily limit,” said Dr. Van Vliet. “The daily limit of 2,300 milligrams is the most you should be consuming – an adequate intake would be about 65 per cent of this or 1,500 milligrams.”
Dr. Van Vliet’s research is helping us to understand precisely how a lifetime exposure to salty foods affects our blood pressure, and the underlying mechanisms. In societies where sodium consumption is high, such as North America, blood pressure rises as a person ages. This is a slower phenomenon that isn’t necessarily reversible with medication or dietary changes.
“The more sodium the society eats, the more the blood pressure rises with age," explained Dr. Van Vliet. “And when I say with age, I mean over decades. You can't see it in an individual very easily, so it's hard to investigate. But what we can do is look at it in animals.”
With the help of funding from the Canadian Institutes of Health Research, Dr. Van Vliet and his colleagues performed experiments in salt-sensitive rats, known as Dahl rats, to illustrate that salt-induced hypertension has both rapid and slow phases, with varying levels of reversibility.
Next, he plans to look at the impact of high-salt diets on pregnant mice and rats and their offspring. This research could help reveal whether or not the sodium a mother eats during her pregnancy affects her offspring’s blood pressure later in life.
For more details on sodium and health, check out www.sodium101.ca.