The All-Important Endothelium

Great Food, Great Sex
by Robert Fried, Ph.D., Lynn Edlen-Nezin, Ph.D.

(Page 2 of 2)

Arterial blood vessels carry oxygenated blood from the lungs to body tissues. They range in size from large arteries down to smaller arterioles and finally to capillaries. Capillaries connected to the venules carry deoxygenated blood back to the lungs. Venules are the smallest of the veins in the body.

Arteries are made up of muscle rings and three major wall layers. Most important to us is the endothelium, the inner cell lining of the vessels. It is this cell lining that determines the way that the vessels control blood flow by their ability to expand or to constrict.

The endothelium responds to a number of the so-called action hormones (noradrenaline and others) that may constrict them to increase blood pressure. But most important, the endothelium produces the gas nitric oxide to relax the blood vessels and increase blood flow to organs ranging from the heart to the sex organs.

The endothelium can be considered to be the business end of the blood vessels, and its control by NO is the discovery that resulted in the awarding of the 1998 Nobel Prize to three American scientists. No one knew before that event that the endothelium was anything but a sheet lining the inside of blood vessels. No one even knew that it served any biological purpose — much less that it actually controls the blood vessel. The endothelium is so critical to blood flow that capillaries are nothing but a tubular structure made up entirely of endothelial cells.

As you'll read in detail through this book, the Great Food, Great Sex eating plan is built around three Food Factors that each supply the body with the ability to synthesize NO. Yet as powerful as these Food Factors are, they cannot compensate for inadequate hormone levels. Conversely, hormone levels may be adequate and sexual dysfunction may still occur if there is inadequate NO for this reason:

Sexual function requires an adequate arterial blood supply to the endothelium. If the neurochemical message does not reach the target, or the endothelium is too damaged to respond, the sequence is in vain. Damaged endothelial tissue results in impaired blood flow to the genitals during sexual arousal.

Our typical American diet is particularly damaging to the endothelium, and this impaired blood flow is the principal culprit in sexual dysfunction in men, and also in women up to menopause (Bernardo, 2001; Park, Goldstein, et al., 1997).

Medical science has made enormous strides in finally unraveling the mechanism of sexual arousal and response and also what causes damage to it. One of the principal culprits is elevated serum low-density lipo- protein (LDL) (bad) cholesterol and its frequent result, atherosclerosis (hardening of the arteries).

Scientists from the University of South Carolina have found that impotence is a very compelling reason to avoid cholesterol: Men with lower blood levels of the bad LDL cholesterol or higher levels of the good high-density lipoprotein (HDL) cholesterol are less likely to develop erectile dysfunction (ED) (Nikoobakht, Nasseh, and Pourkasmaee, 2005). In a similar study, men with total cholesterol levels over 240 mg/dl had nearly double the risk of ED, compared with men with readings around 180 or less. The researchers concluded that atherosclerosis impedes blood flow to the penis and thus constitutes a primary cause of impotence.

It is evident now that antioxidant-rich foods protect the body from the oxidation of LDL cholesterol. There is also overwhelming evidence that arginine can both lower serum levels of LDL cholesterol and even reverse the process of plaque deposition. The Great Food, Great Sex program supplies generous amounts of NO, antioxidants, and arginine — the three Food Factors the body needs for maximum sexual vitality.

The Owner's Guide To Male Sexual Anatomy And Function

We are living in an era of impressive lifestyle-altering pharmaceutical breakthroughs in the treatment of impotence. To understand how and why these products work (the same principles upon which the Great Food, Great Sex program is based), it helps to know how an erection actually comes about.

The anatomy of the penis is somewhat complex. Think of the structure as three cylinders of sponge-like tissue. Two are corpus cavernosa; a third cylinder is the spongeosum. In order to have and maintain an erection, the cylinders need to fill with blood. Blood is pumped into the penis under body pressure. The expanding chambers compress the veins in the penis, slowing blood outflow.

The urethra is the inner tube that carries the urine and the ejaculate (a combination of semen and various other glandular fluids). The knobby head of the penis is called the glans. Blood flows to the penis by two very small arteries that come from the systemic aorta, the main artery that courses downward from the heart. These arteries are the same size as the arteries to your finger. If these blood vessels become blocked, blood cannot get to the penis. High-fat, low-vegetable, and low-fruit diets contribute directly to blocked vessels.

All three chambers of the penis are lined with endothelial tissue, as are arterial blood vessels. You might even think of these chambers as enlargeable blood vessels.

When you feel sexually turned on, the brain releases the neurotransmitter substance acetylcholine (ACh) into the bloodstream in the sex organs. Then:

• ACh then causes the endothelium in the blood vessels and in the spongy penis chambers to produce an enzyme called nitric oxide synthase (eNOS) that helps to produce the gas nitric oxide. This is derived most commonly from the amino acid arginine or, alternatively, from nitrogen compounds in foods.

• NO then triggers the release of yet another enzyme-induced neurotransmitter, cGMP.

• At the command of cGMP, the blood vessels relax, permitting increased blood inflow to the penis.

• As the chambers of the penis engorge, the sudden surge of blood into those chambers exerts pressure on the veins.

• Now inflow is greater than outflow, and the penis remains erect so long as there is a continuous production of cGMP mediated by NO.

• At the end of sexual activity, cGMP is disabled by the enzyme PDE5, and NO production decreases, causing the penis to return to its flaccid state.

Copyright © 2006 by Robert Fried. Excerpted by permission of Ballantine Books, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.

About the Author

ROBERT FRIED, PH.D., is the director of the Stress and Biofeedback Clinic at the Albert Ellis Institute, New York City. He is also a senior professor of biopsychology at Hunter College, CUNY.

Lynn Edlen-Nezin, Ph.D., is director of behavioral science and vice president of strategic planning and research for Grey Healthcare Group. She is a graduate of the doctoral program in clinical health psychology at the Albert Einstein College of Medicine, and completed her internship at the Obesity Research Center at St. Luke's — Roosevelt Hospital Center. She is an American College of Sports Medicine certified personal trainer. Dr. Edlen-Nezin has contributed to several books, and her articles have appeared in magazines including Self and Seventeen, as well as in the New York Daily News. She lives in Jackson Heights, Queens.