Salt tied to elevated blood pressure, even with healthy diet

(Reuters Health) - People who eat lots of fruits, veggies, and whole grains may still have an increased risk of elevated blood pressure if they consume a lot of salt, a new study suggests.

Eating high-sodium foods has long been associated with raised blood pressure readings, but some evidence suggests that body weight and other nutrients in the diet may modify or offset the effects of sodium on blood pressure.

To see how diet might influence the connection between salt and blood pressure, researchers examined data from food surveys completed by 4,680 middle-aged adults, and determined the amount of 80 nutrients in each person’s diet.

With the exception of potassium, none of these nutrients appeared to weaken the connection between eating a high-sodium diet and having higher average blood pressure readings over 24 hours than people who ate the least sodium, researchers report in Hypertension.

“This matters because it indicates that the problem of excess salt intake and its adverse effects on blood pressure cannot be solved by augmenting the diet with other nutrients,” said lead study author Dr. Jeremiah Stamler of the Feinberg School of Medicine at Northwestern University in Chicago.

“The solution is reduction in salt intake,” Stamler said by email. “This is difficult since, as a result of commercial food processing, salt is almost everywhere in the food supply.”

Chronic high blood pressure is tied to an increased risk of heart disease, heart attack, stroke and heart failure.

To lower the risk of heart disease, adults should reduce sodium intake to less than 2 grams a day, or the equivalent of about one teaspoon of table salt, according to the World Health Organization (WHO).

Sodium is found not only in salt, but also in a variety of foods such as bread, milk, eggs, meat and shellfish as well as processed items like soup, pretzels, popcorn, soy sauce and bouillon cubes.

Extra sodium in the bloodstream can pull water into the blood vessels and boost blood pressure by increasing the amount of fluid the heart needs to pump through the body. Potassium can help remove excess sodium from the body.

In the current study, researchers examined data on sodium and potassium levels in urine, as well as blood pressure, height, weight and eating habits from adults aged 40 to 59 in Japan, China, the UK and the U.S.

Higher sodium levels were associated with elevated blood pressure for both men and women at all ages in the study, regardless of race and ethnicity or socioeconomic status.

The connection between sodium and blood pressure was similarly strong for both normal weight and obese people in the study, although the connection was weaker for overweight individuals who weren’t obese.

Potassium appeared to weaken the connection between dietary salt and elevated blood pressure only for people who had low sodium levels in their urine, the researchers also found.

The study wasn’t a controlled experiment designed to prove whether or how dietary salt or other things people eat might directly alter blood pressure. Another limitation is that surveys used to assess eating habits can be unreliable snapshots of what people actually consume.

Even so, the results add to evidence that managing blood pressure requires paying attention to salt, said Cheryl Anderson, a researcher at the University of California San Diego School of Medicine who wasn’t involved in the study.

“Even though potassium can help lessen the blood pressure-raising effects of sodium, eating more potassium isn’t a license to eat more sodium,” Anderson said by email.

The American Heart Association recommends the Dietary Approaches to Stop Hypertension (DASH) diet or a Mediterranean-style diet to help prevent cardiovascular disease. Both diets emphasize cooking with vegetable oils with unsaturated fats, eating nuts, fruits, vegetables, low-fat dairy products, whole grains, fish and poultry, and limiting red meat and added sugars and salt.

“There is data showing that when the DASH dietary pattern is combined with sodium reduction there are substantial effects on blood pressure,” Anderson said by email. “This can be as powerful as taking a drug prescription for high blood pressure.”

SOURCE: Hypertension, online March 5, 2018.