The fourth system of health, the LOVE, is based in the heart and the lungs. The heart is an especially fascinating organ about which current medical opinion is evolving rapidly. For many years, conventional medicine considered the heart as little more than a pump—a mechanical device rather than a dynamic organ. Of course, even as a pump, the heart is a pretty amazing instrument. Every day it moves thousands of liters of blood through every inch of your body, disseminating the life force to your lungs, muscles, bones, eyes, ears, and brain, supplying every one of your cells with life-giving blood.
Recently, however, cutting-edge research has brought us to a more advanced view, seeing the heart not just as a pump but as a complex participant in the neuroendocrine system, producing hormones that activate the body in a variety of ways. Indeed, a group of scientists at the University of Ottawa have advanced a new specialty: cardiovascular endocrinology, the study of the biochemical effects of the heart. If the heart is a core player in the endocrine system, it affects thought, perception, and emotion as well as providing our cells with blood.
Recent research has also taught us that the heart is related to our emotions. All those metaphors about “let your heart guide you,” “a heartfelt emotion,” and “being heartbroken” have an actual physical component. When you are stressed or distressed, your heart beats faster, your blood pressure rises, and stress hormones inflame your system, putting you at risk of heart disease, stroke, and other cardiovascular ailments, which we now know are sparked and fueled by inflammation. When you are calm and full of joy, your heart beats at a healthy rhythm and your blood courses through your arteries at a healthy pressure.
I associate the color green with the elements of the heart, healing and expansion. Just as the leaves on a tree open naturally, green represents an unfolding of love, service, and gratitude from within. You might have thought that red would be associated with the heart; however, green is the color of the fourth system of health.
Researchers have discovered some fascinating links associating this color with the heart. For example, an Austrian experiment found that exposing people to green fluorescent light seemed to have a soothing effect on their hearts, affecting heart rate variability (HRV). People who endure continual worry and anxiety seem to have decreased HRV, which is also associated with a number of disorders, including congestive heart failure and depression. If exposure to green light increases HRV, we can imagine that has heart- protective effects and might help to heal grief—precisely the associations suggested by the fourth system of health.
You can use the power of green and nature to bring more LOVE into your life. Take a walk in the woods or on some green grass. Breathe in the loving breath of nature and revel in the expansiveness of greenery.
Similarly, considering trying the Japanese technique of “forest bathing”. Known as shinrin- yoku, or “taking in the forest atmosphere” or “forest bathing,” recent research has ratified the cardiovascular benefits of this green practice. Forest environments were found to promote lower concentrations of cortisol, lower pulse rate, lower blood pressure, greater parasympathetic nerve activity, and lower sympathetic nerve activity than do city environments. 
If the weather is against you or if the nearest green space is too far away, bring the green to you in the form of plants at home or at work. Even a small representative of something green—living, growing, sprouting—can bring the expansiveness of love and compassion into an everyday world that may feel like it’s collapsing down on you. Consider an herb garden in your kitchen window or a potted fern on your desk—anything to which you can direct love and feel love coming back in return.
Plants and nature not your thing? Go the other way with some green money. Spend something on self- care in the form of a massage, a funny movie, a bottle of scented lotion—something that makes you open up and remember just how wonderful you are.
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 Ochiai, H., H. Ikei, C. Song, M. Kobayashi, A. Takamatsu, T. Miura, T. Kagawa, et al. “Physiological and Psychological Effects of Forest Therapy on Middle- Aged Males with High- Normal Blood Pressure.” International Journal of Environmental Research and Public Health 12, no. 3 (2015): 2532–42. doi:10.3390/ijerph120302532.
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 Lee, J., B. J. Park, Y. Tsunetsugu, T. Ohira, T. Kagawa, and Y. Miyazaki. “Effect of Forest Bathing on Physiological and Psychological Responses in Young Japanese Male Subjects.” Public Health 125, no. 2 (2011): 93–100. doi:10.1016/j.puhe.2010.09.005.