Twenty years ago, when I started my research, our major focus was on reducing total blood cholesterol levels to below 150 mg/dL and cutting LDL levels to 80 mg/dL or less. But today, it is clear to me that in achieving those goals through plant-based nutrition, we also achieved a corollary result: we restored the body’s own powerful capacity to resist and reverse vascular disease. Plant-based nutrition, it turns out, has a mighty beneficial effect on endothelial cells, those metabolic and biochemical dynamos that produce nitric oxide (see Figure 5).
And nitric oxide, as I have noted, is absolutely essential to vascular health—a finding that won the Nobel Prize for Medicine in 1998.8
1. It relaxes blood vessels, selectively boosting blood flow to the organs that need it.
2. It prevents white blood cells and platelets from becoming sticky, and thus starting the buildup of
vascular plaque.
3. It keeps the smooth muscle cells of arteries from growing into plaques.
4. It may even help to diminish vascular plaques once they are in place.
To understand how plant-based nutrition facilitates nitric oxide production, you need to have a sense of the biochemistry at play. The essential building block for nitric oxide production is a substance called L-arginine, an amino acid that is in rich supply in a variety of plant foods, especially legumes, beans, soy, and nuts. Figure 6 shows, schematically, how L-arginine fits neatly into the enzymatic action of nitric oxide synthase, which then produces nitric oxide from the arginine and oxygen.
However, as you can also see in Figure 6, there is a competitor for nitric oxide synthase:
asymmetric dimethyl arginine, or ADMA, which is manufactured by our bodies in the course of normal protein metabolism. When we have too much ADMA, then L-arginine is edged out for a position in nitric oxide synthase, and the production of nitric oxide fails. There is another delicate enzyme with a formidable name—
dimethyl arginine dimethyl amino hydrolase, or DDAH—that destroys ADMA, in order to favor production of nitric oxide. But the usual cardiovascular risk factors (high cholesterol, high triglycerides, high homocysteine, insulin resistance, hypertension, and tobacco use) all impair the ability of that delicate enzyme to destroy ADMA.