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Glutamic Acid (Vegetables) May Lower Blood Pressure
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MedPage Today
July 08, 2009
LITTLE FALLS, N.J., July 8 -- Dietary glutamic acid -- the amino acid abundant in vegetables -- may have blood pressure-lowering effects, researchers have found.
The amino acid had a consistent inverse relationship with blood pressure across several models, Jeremiah Stamler, MD, of Northwestern University, and colleagues reported in Circulation, Journal of the American Heart Association.
When glutamic acid intake comprised almost 5% of total dietary protein, systolic blood pressure averaged 1.5 to 3.0 mm Hg lower than then readings in people who consumed less glutamic acid. For diastolic, the reductions ranged from 1.0 to 1.6 mmHg.
Action Points
* Explain that glutamic acid had a consistent inverse relationship with blood pressure, which may help explain the relationship between vegetable protein and blood pressure.
"This may be a key component accounting for the previously reported inverse relation of vegetable protein intake to blood pressure," the researchers said.
Glutamic acid is one of the most abundant amino acids in the human diet. So to assess whether it has any effect on blood pressure, the researchers conducted a cross-sectional study of 4,680 patients ages 40 to 59 from 17 random population samples in China, Japan, the U.K., and the U.S.
Blood pressure was measured eight times over four visits, and dietary data were obtained from four dietary recalls and two urine collections.
They also looked at the association between blood pressure and four other amino acids -- proline, phenylalanine, serine, and cystine.
In all participants, glutamic acid was the predominant dietary amino acid, averaging 15.7 g/d, 3% kJ, and 20.1% of total protein.
The researchers said the relationship between glutamic acid and blood pressure was strongest after excluding patients with marked individual variability in nutrient intake or blood pressure.
Results were similar for each of the other amino acids in the model, the researchers said.
One of the potential mechanisms underlying the relationship may be the fact that glutamic acid may serve as an energy yielding or glutathione substitute. Glutathione in its redox state can counteract oxidative injury from free radicals and can enhance the hypotensive effects of nitric oxide, the researchers said.
It may also be a substrate for arginine, a precursor of nitric oxide and a potent vasodilator. Or, it may have an effect on enhanced kidney size and function, they said.
The study was limited by its cross-sectional design and by a possible underestimation of the effect size due to limited reliability in nutrient measurements. It's also limited in generalizability since it focused on adults ages 40 to 59.
The researchers concluded that their novel finding "needs replication in other populations."
The study was supported by a grant from the National Heart, Lung, and Blood Institute and the National Institutes of Health Office on Dietary Supplements.
The researchers reported no conflicts of interest.
Primary source: Circulation Journal of the American Heart Association
Source reference:
Stamler J, et al "Glutamic acid, the main dietary amino acid, and blood pressure" Circulation 2009; DOI: 0.1161/CIRCULATIONAHA.108.839241.
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