Hypertension is an important public health problem that can lead to life-threatening cardiovascular events, including heart attack and stroke. Many studies have attempted to understand the complex relationship between dietary factors and hypertension; none have provided a clear explanation of the interaction between hypertension and dietary intake of n-6 fatty acids (a building block of fat), until now.

In a new study published in Nutrients, a research team from Kanazawa University investigated the relationship between dietary intake of n-6 fatty acids and hypertension, using blood pressure measurement and a diet history questionnaire, and found that the relationship between dietary intake of n-6 fatty acids and hypertension was influenced by diabetes status.

"There have been conflicting reports of the relationship between dietary intake of n-6 fatty acids and risk of hypertension," says Hiroyuki Nakamura, corresponding author on the study. "Metabolites of n-6 fatty acids can lower blood pressure in a manner influenced by blood glucose levels. Therefore, we suspected that the relationship between dietary intake of n-6 fatty acids and risk of hypertension might be affected by glucose tolerance, which is impaired in patients with diabetes."

In the study, the researchers found that the relationship between dietary intake of n-6 fatty acids and hypertension differed according to whether subjects had diabetes; in healthy subjects, high intake of n-6 fatty acids was significantly associated with hypertension, whereas high intake of n-6 fatty acids was inversely associated with hypertension in subjects with diabetes.

"Our analyses revealed a relationship between dietary intake of n-6 fatty acids and glycated hemoglobin in the blood (our definition of diabetes), which has not been previously established," says Haruki Nakamura, lead author on the study. "A previous meta-analysis showed that higher intake of a diet rich in linoleic acid (the main fatty acid in the n-6 fatty acids class) was significantly associated with higher risks of death from all causes, cardiovascular disease, and coronary heart disease in subjects with cardiovascular disease. Therefore, our results indicate that n-6 fatty acid intake may have no cardiovascular benefit in subjects who are at risk for cardiovascular disease or diabetes."

In addition to the reduction of hypertension associated with increased dietary intake of n-6 fatty acids by healthy individuals, the researchers showed no benefit, and possible hypertension-related harm, from increased dietary intake of n-6 fatty acids by patients with diabetes.

Hypertension is an important risk factor for a variety of destructive cardiovascular injuries. This study showed that increased dietary intake of n-6 fatty acids could positively impact the risk of hypertension, but that this benefit is limited to individuals who do not have impaired glucose tolerance.