The Inuit in Canada's North have long been known as a people with virtually no hypertension.
Their largely fish-based diet with an almost total absence of salt consumption is the likely explanation, though genetics may also play a part.
Now, researchers are finding that blood-pressure rates are soaring among the Inuit, as they move away from a traditional diet toward a salt-laden Western diet.
"If the Inuit are developing hypertension, that should be a warning sign to all of us," said Marie-Ludivine Chateau-Degat of the public-health research unit of the Laval University Hospital Research Centre in Quebec City.
Her research, presented yesterday at the Canadian Cardiovascular Congress, showed that the rate of hypertension among the Inuit of northern Quebec has doubled, to 12 per cent from 6 per cent.
Just as important, Dr. Chateau-Degat and her team found that, even among those without hypertension, blood-pressure rates are rising steadily. "The Inuit now have levels almost identical to other Canadians," she said.
Blood pressure is a measure of the force of the blood against blood-vessel walls. It is expressed in two numbers: Systolic, the upper number, is the pressure when the heart contracts; diastolic, the lower number, is the pressure when the heart is relaxed.
A person is considered hypertensive when a blood pressure reading is 140/90 millimetres of mercury (mmHg) or higher. In healthy adults, the reading should be in the range of 120/80 mmHg, although that target varies with age and health.
Dr. Chateau-Degat's research shows that about 16 per cent of the food consumed by Inuit adults in 2004 was traditional fare such as fish and marine mammals, down from 21 per cent in 1992.
Increasingly, they are eating store-bought, processed foods. These packaged foods now account for 95 per cent of salt in the diet of the Inuit. "There was no salt in their traditional diet. This is something new," Dr. Chateau-Degat said.
Her research showed that, in addition to processed foods, 40 per cent of Inuit adults now salt the foods they consume at home because they have developed a taste for it.
The findings are derived from a large, on-going study called Qanuippitaa, which is examining the health of Inuit living in 14 communities in Nunavik (the name given to the territories in Northern Quebec).
The study notes that salt consumption and related rises in blood pressure are only one of the many cardiovascular health challenges in the North.
Three in every four adults in Nunavik smoke, three times the rate in the rest of Canada. And three in five adults are either overweight or obese. While cardiovascular disease was largely unheard of among the Inuit, rates of heart attack, stroke and heart failure are all increasing, the research notes.
Canadians ingest, on average, 3,092 milligrams of sodium daily - about two teaspoons - according to Statistics Canada. Men consume markedly more sodium than women - 4,100 milligrams a day, compared with 2,900 milligrams.
The U.S. Institute of Medicine has established that the adequate daily intake for a healthy adult is between 1,200 and 1,500 milligrams of sodium - about three-quarters of a teaspoon - and it should be lower for people with cardiovascular conditions such as high blood pressure and heart failure, and for those who have had a heart attack or stroke.
