8 BLOOD PRESSURE L-theanine An amino acid abundant in the leaves of green tea, L-theanine has been shown in clinical studies to alleviate stress, enhance relaxation, lower blood pressure, and even boost the anti-tumor properties of chemotherapy. The impact of chronic stress on blood pressure has been widely documented. A 2007 clinical trial in Nagoya, Japan, challenged 12 participants with a mental arithmetic task in order to induce stress. Those taking L-theanine showed a reduction in physical signs of stress, such as increased heart rate and the release of cortisol. Researchers aren’t certain how L-theanine works. One theory is that this amino acid increases levels of the brain chemical gamma-aminobutryic acid, which has calming properties. It could also raise the levels of serotonin, a natural mood regulator, in the brain. Animal studies have shown that L-theanine reduces norepinephrine (a neurotransmitter) levels, which may lead to reduced blood pressure. Hawthorn Hawthorn (Crataegus oxyacantha) is well-known for its cardiovascular benefits. Like Aged Garlic Extract, vitamin E, and cayenne, hawthorn is a potent natural source of antioxidants. A randomized, controlled trial at the University of Reading in England examined the effect of hawthorn on hypertensive patients with type 2 diabetes. Individuals were given either a hawthorn extract or a placebo. The hawthorn group showed greater reductions in diastolic blood pressure than the placebo group. Furthermore, no herb-drug interaction was reported. In another study at the University of Reading, researchers looked at the effect of hawthorn on 36 individuals with mild hypertension. Volunteers were randomly assigned to take either 600 mg of supplemental magnesium, 500 mg of hawthorn extract, a combination of magnesium and hawthorn, or a placebo. The hawthorn group showed a “promising reduction” in diastolic blood pressure, as well as decreased anxiety.