Scientists are not clear where the beneficial effect comes from, but they say low-fat dairy might be a crucial component of a healthy diet.
"If you like to eat dairy products, you may be better off watching the fat content," says Dr. Luc Djousse at Brigham and Women's Hospital. "Low-fat dairy products may be better than full dairy products, where the saturated fat especially is high.”
For the new study, the investigators looked at a possible link between dairy consumption and blood pressure among 4,797 participants of the Family Heart Study, sponsored by the National Heart, Lung, and Blood Institute (NHLBI).
High Dairy Intake Works, Low-Fat a Must
The researchers divided participants into four groups based on the amount of dairy consumed.
Those consuming the most dairy products said they ate more than three servings per day, while those consuming the least averaged less than half a serving per day. Dairy included cheese, yogurt, and milk.
Systolic blood pressure was 2.6 millimeters of mercury (mm Hg) lower, on average, for people eating the highest amount of dairy, compared with those eating the least amount of dairy.
Systolic blood pressure is the first (higher) number in a blood-pressure reading, and it indicates the pressure in the arteries when the heart beats.
But when saturated fat content was taken into account, the beneficial effect on blood pressure was only seen among those who ate lower amounts of saturated fat.
In this group, participants who ate the most dairy had a systolic blood pressure that was 3.5 mm Hg lower than those who ate the least dairy.
Among participants who ate lower amounts of saturated fat, those who also ate the most dairy had 54 percent lower odds of high blood pressure than those eating the least amount of dairy.
The study was not able to identify those people who ate low-fat dairy, but it had data on total fat, polyunsaturated fat, and saturated fat.
Samantha Heller, nutritionist at New York University Medical Center says: "The association [in the study] was mainly among people with less saturated fat. We know this is a bad fat, and [you should] eat as little as possible."
Fruits and Veggies Add Extra Help
About one in three Americans suffers from high blood pressure, which is a major risk factor for stroke and heart attack as well as kidney and heart failure.
Medications can treat the condition, as can lifestyle changes such as diet.
The Dietary Approaches to Stop Hypertension (DASH) diet, which is low in salt and rich in fruits, vegetables, and low-fat dairy products, has been shown to significantly lower blood pressure.
But the secrets to the success of the DASH diet have remained elusive.
"There was such a combination of factors that we don't know whether the effect of DASH came from low sodium, low cholesterol, or fruit and vegetables," explains Dr. Djousse. "It has been hard to tell which part of that, or a combination of all, that were producing the effects.”
It is not clear where the benefit is coming from or even if it is cause-and-effect. It is unlikely to be calcium, Dr. Djousse says, although potassium and magnesium, which are also plentiful in the DASH diet, might be responsible.
"Our study showed that dietary potassium and magnesium were associated with lower odds of high blood pressure," says Dr. Djousse.
The bottom line? "It would help to eat dairy products as long as you keep the saturated fats in check," explains Dr. Djousse.
Always consult your physician for more information.
As noted by Dr. Jamy Ard, assistant professor of Nutrition Sciences and Internal Medicine, since the original DASH study which combined a number of healthy food
groups like fruit and vegetables, whole grains, and low-fat dairy, many people have been searching for the one component of the dietary pattern that is responsible for the blood pressure lowering effect. I think it will be unlikely that anyone identifies a single component, such as dairy or calcium, because there are so many nutrient interactions occurring that make it difficult to sort out. It is likely that the combination of nutrients, including potassium, magnesium, fiber, heart-healthy fats, and calcium, all work synergistically to have beneficial health effects. I think the best message to take from this study is that people should preferably choose low-fat dairy products. Low-fat dairy products are recommended as a part of the DASH dietary pattern, and this study shows lower saturated fat intake may be critical to obtaining the full benefit of ingesting dairy.
Read more about the DASH Diet in UAB Insight.