Patients with high blood pressure rely on medication over salt reduction, study finds

Lack of adherence to recommended lifestyle changes is leading to higher salt intake for hypertensive patients, more medications needed to treat their condition and more side effects from those medications, according to lead author Dr. Kazuto Ohno of the Enshu Hospital, Hamamatsu, Japan.

“Blood pressure does see decreases due to medication and treatment. However, it is necessary not only to rely on medication alone but also to reduce salt intake to improve adherence of oral administration and to prevent side effects caused by drugs,” Dr. Ohno tells NutritionInsight.

“Patients may be able to improve this vicious cycle by restricting salt intake,” Dr. Ohno adds. “In consequence, they may avoid diseases caused by hypertension, such as heart attacks, stroke, and heart failure. Moreover, they may be able to avoid side effects from antihypertensive drugs, such as dizziness and fainting.”

Excess salt intake is one of the most important causes of hypertension and salt restriction is a key strategy to manage it, but few studies have been done on the relationship between salt intake and blood pressure in hypertensive patients undergoing antihypertensive drug treatment.

The study
Study authors enrolled 12,422 patients taking medication for hypertension who visited the hospital for a physical checkup from 2010-2016. Individual salt intake was estimated in grams per day using a spot urine calculation formula shown to be effective in previous studies.

Blood pressure levels and patients maintaining the target blood pressure of less than 140/90mmHg improved during the seven-year study among all groups, but individual salt intake increased across all groups as well.

“Although blood pressure values in hypertensive patients had lowered, salt intake was gradually increased,” says Dr. Ohno. “We think improvement in blood pressure control is not due to salt restriction but due to drug treatment.”

Guidelines for the Management of Hypertension 2014 published by the Japanese Society of Hypertension, recommend less than six grams of salt intake per day, but less than four percent of study participants were following those recommendations.

Patients in the study were divided into three groups according to whether they were currently prescribed one, two, three or more antihypertensive drugs.

“The observational study in hypertensive patients with antihypertensive drugs found two comparative facts: an improvement of blood pressure levels and an increase in salt intake,” explains Dr. Ohno. “In particular, in hypertensive patients with multiple antihypertensive drugs, salt intake was higher than those taking only one antihypertensive drug.”

Salt intake for healthy people was targeted less than 8 g/day for men and less than 7 g/day for women in Dietary Reference Intakes for Japanese, 2015, published by the Ministry of Health, Labor and Welfare.

“However, the National Health and Nutrition Examination Survey 2016 5 reported 10.8 g/day in men, 9.2 g/day in women,” Dr. Ohno says. “More awareness about the harms of higher salt intake is needed in both hypertensive patients and healthy people. We can check the amount of salt in a lot of food and seasoning, such as soy sauce, miso paste, mayonnaise and so on, which are printed on the food labels. It is impossible to measure salt intake in every meal, so all of us should try to take food with reduced salt by referring to food labels.”

Dr. Ohno says that future research should consider whether nutritional guidance can improve the accomplishment rate of the target blood pressure and decrease the number of antihypertensive drug prescriptions.

“As a new attempt, we have explained their estimated salt intake value and gave nutritional guidance including salt, calories and so on to participants since 2017. We think salt restriction is an important modifiable factor of lifestyle to treat and prevent high blood pressure,” he concluded.

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