Beef is slowly earning its way back into dietary plans via real science, thereby getting a viable chance to increase market share.
One of the most recent of these studies showed increased beef in the diet can decrease systolic blood pressure, even in people who have normal blood pressure. Systolic blood pressure is the top number in blood pressure analysis and it measures the pressure in the arteries when the heart beats.
One reason this number is considered important, says the American Heart Association, is systolic blood pressure typically rises steadily with age because of increasing stiffness of large arteries, long-term build-up of plaque, and/or increased incidence of cardiac and vascular disease.
The Pennsylvania-based study basically compared the substitution of lean beef for vegetable proteins in a diet which has been shown to decrease systolic blood pressure. That comparative diet is called Dietary Approaches to Stop Hypertension, or DASH.
DASH leans heavily on a content of fruits and vegetables and low-fat dairy products, with increased dietary protein provided primarily from plant protein sources and carbohydrate consumption limited to whole grains. It has been shown to decrease blood pressure in at-risk individuals. Yet no studies had to that point evaluated the effects of a DASH-like diet with increased dietary protein from lean beef upon blood pressure and vascular health.
The study included 36 people with normal blood pressure and compared two BOLD-modified DASH diets. The BOLD acronym stands for Beef in an Optimal Lean Diet.
The original DASH diet has 28 grams of beef. The modified diets substituted beef for vegetable protein up to 113 grams per day (BOLD) and 153 grams per day (BOLD+). The study also included a DASH diet and a Healthy American Diet, which has lower fiber and higher saturated fat.
The researchers measured blood pressure, endothelial function and vascular reactivity and found the aforementioned reduction in systolic blood pressure, as well as a reduction in peripheral vascular constriction.
The BOLD study is the first controlled clinical trial to show that a moderate-protein diet based on the DASH eating plan, but using lean beef as the main protein source, could reduce systolic blood pressure in people with normal blood pressure. The winner in this trial was the BOLD+ diet, which had 10% more calories from protein. The increase in beef consumption also reduced the amount of carbohydrates and saturated fat in the diet.
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Previous research has shown people report better adherence to dietary advice when the regimen includes some lean beef, so this is an additional advantage. Also, the inclusion of lean beef (4.0 to 5.4 ounces per day) in a DASH-like diet decreased total cholesterol and low-density lipoprotein cholesterol similarly to the DASH diet.
Researchers also mentioned the similarities of this trial to the OmniHeart trial, which showed larger increases in cardiovascular measurements among pre-hypertensive people fed a diet similar to the BOLD+ diet.
They suggested the positive effects of the BOLD+ diet and the OmniHeart diet together could reflect a total protein effect on cardiovascular health, or it might result from the reductions in carbohydrate consumption.
In addition, the researchers noted that potassium, magnesium, sodium and calcium are minerals of importance with respect to their role in modulating blood pressure and said potassium and magnesium levels were lower in the HAD diet compared with the BOLD+ diet. Sodium and calcium intakes were similar for the HAD and BOLD+ diets. The researchers said magnesium supplementation alone has not proven it can lower blood pressure, but also said it could have additive benefits in changed diets such as these.
Researchers also said it is unlikely that dietary fiber is responsible for the reduction in systolic blood pressure. A meta-analysis of 25 randomized controlled trials found no effect of dietary fiber intake on systolic blood pressure in people with normal blood pressure.
There was yet another interesting finding in this study which seems worth mentioning. Researchers said a secondary analysis of the data revealed the significant reduction in arterial stiffness occurred only in younger participants, specifically men under 45 and women under 55.
This measurement, called the augmentation index, is an indirect measure of arterial stiffness. Medical researchers say the AI usually increases with age in men and women. So even though the data showed an overall decrease in systolic blood pressure, the diet did not seem able to change arterial stiffness over the short run.
The fact the BOLD+ diet did not change this measure in older people suggests earlier dietary changes may be important to older-aged health. Put another way, they said dietary interventions designed to improve vascular reactivity may need to be initiated earlier in life to have a significant effect. On the other hand, this trial only ran for five weeks, so the jury seems out on the measurement of arterial stiffness.
You can read the study in the June 19, 2014, online issue of the Journal of Human Hypertension.