It's time for dietary guidelines to make this clear: People's blood pressure would be lower if they worried less about the salt they're eating and more about the sugar. That's the message from a recently published review of studies on high blood pressure and heart disease.
Dietary approaches to controlling blood pressure have generally focused on lowering salt. It's a reasonable suggestion, supported by solid science: salt raises blood pressure because it causes blood vessels to take up extra water, which puts more pressure on the vessels.
The problem is that decreasing dietary salt doesn't seem to lower people's blood pressure very much. There have been enough studies showing this that the role of salt in diet has become controversial.
Higher sugar intake increased systolic blood pressure by about seven points and diastolic blood pressure by about six points.
Sugar, on the other hand, has a big effect on blood pressure. A literature survey of clinical trials lasting eight weeks or longer found that higher sugar intake increased systolic blood pressure by about seven points and diastolic blood pressure by about six points.
The sugar fructose may be even more potent, with one study finding that just two weeks of a high-fructose diet increased systolic blood pressure by seven points and diastolic pressure by five.
Just as most of the salt we eat doesn't come from the salt shaker, most of the sugar we eat doesn't come from the sugar bowl — it's sugar that's been added to processed foods. And its health effects go way beyond raising blood pressure.
A study published earlier this year found that a diet with 25% or more of its calories coming from added sugar may triple the risk of death from cardiovascular disease — diseases of the heart and blood vessels.
Sugar means calories and too many calories mean weight gain. Extra pounds burden every part of the body, especially the heart, cutting life expectancy and lowering quality of life.
Just as most of the salt we eat doesn't come from the salt shaker, most of the sugar we eat doesn't come from the sugar bowl.
High sugar consumption has also been linked to increases in other metabolic woes, such as diabetes.
The American Heart Association recommends no more than six teaspoons of sugar a day for women and nine teaspoons for men. A 12-ounce can of Coke contains about 10 teaspoons of sugar, pushing people's consumption over the limit by itself.
For people who don't want to count dietary calories, there's a simple strategy: eat less processed food and more real food, especially fruits and vegetables. The same processed foods that are high in salt generally also contain a lot of added sugar.
And while fruit does contain some sugar, it doesn't seem to be causing any of the health problems that added sugar does. Quite the opposite, according to the study.
“Added sugars probably matter more than dietary sodium for hypertension, and fructose in particular may uniquely increase cardiovascular risk by inciting metabolic dysfunction and increasing blood pressure variability, myocardial oxygen demand, heart rate, and inflammation…” the authors write.
“The evidence is clear that even moderate doses of added sugar for short durations may cause substantial harm.”
The full review appears in the open access journal, Open Heart.