Hypertension in the 21st Century: High Blood Pressure and What We Know Now, and What We Need to Know
Presented by: Glenn Chertow, MD, MPH
Stanford University Medical Center
May 12, 2011
Though salt is essential to health, most people eat way too much of it.
When there is too much salt in your diet, the kidneys cannot process it all and it can end up in your blood, which raises blood pressure, causing hypertension.
About one out of every three adults in the United States has high blood pressure, and you can have it for years without knowing it. But even though it usually has no symptoms, hypertension can damage the heart, blood vessels, kidneys, and other organs, and can lead to coronary heart disease, heart failure, stroke, kidney failure, and other health problems.
The recommended amount of salt for people with high blood pressure is about 1,500 milligrams a day. You need about 500 milligrams of salt every day for your body to function, but most people take in about 10 times that amount daily.
Cutting back on salt is one of the most important ways to address the risk factors for hypertension, but it’s not easy to do.
“Anyone who has had any kind of processed food in the past few years is getting way too much salt,” said Glenn Chertow, MD, a professor of nephrology, at a presentation sponsored by the Stanford Health Library. “These foods are loaded with salt, and they just make you crave more.”
Part of the problem with salt in American diets is that it is not regulated. Despite systematic reviews, the FDA still classifies salt as Generally Regarded As Safe (GRAS) and does not consider it harmful to the general public. Because it is not considered a food additive, salt merely needs to be labeled rather than regulated, said Dr. Chertow, and it retains its GRAS status despite growing concern of its deleterious effects.
And salt is everywhere. The highest levels of salt are in bread and breakfast cereals, and the “secret ingredient” in fast food is generally different variations of sodium. About 77 percent of most people’s salt intake comes from processed foods, said Dr. Chertow. “It’s not a matter of reading the labels. You should be eating nothing that comes in a box or a bag if you’re interested in reducing your salt intake.”
Doctors recommend following the DASH diet to lower high blood pressure. The DASH diet is an eating plan rich in fruits and vegetables, whole grains, nuts, fish, lean meats, and low-fat dairy. A study that compared different levels of dietary salt intake found that the DASH diet was as effective as most blood pressure medications, particularly for African-Americans and older participants.
Another study found that lowering salt intake showed a 20 percent reduction in stroke, coronary heart disease, and heart attack in at-risk patients. Reducing salt intake by 1 gram could reduce mortality from these diseases better than weight loss or taking statins, Dr. Chertow said.
“Smoking, weight, and salt are the most preventable risks to longevity,” said Dr, Chertow, who advocates taking salt off the FDA’s GRAS list. “Salt should be regulated as a food additive. The effects of interventions are huge, and the whole country benefits when you think of it as a public health issue. Lowering dietary salt would save tens of thousands of lives.”
Blood pressure is considered normal with a systolic measure (the top number) lower than 120 and a diastolic measure lower than 80 (the readout would look like 120/80). For people with hypertension, the goal is to maintain a systolic blood pressure of 140. However there is little scientific evidence to prove that this is the optimal blood pressure target. Scientists and clinicians believe further knowledge of blood pressure and more exact management could significantly influence the rate of cardiovascular disease and diabetes.
Stanford is taking part in a national study launched by the National Institutes of Health to determine whether maintaining blood pressure levels lower than current recommendations reduces the risk of cardiovascular and kidney diseases, or age-related cognitive decline.
“We don’t really have any idea of what the ideal blood pressure should be,” said Dr. Chertow. “For people with hypertension, we need to know if lowering blood pressure to 120 is better than a moderate reduction to 140 in terms of reducing cardiac risk.”
The Systolic Blood Pressure Intervention Trial (SPRINT) will try to determine whether lower really is better. The long-term study will track participants who will be treated with commonly available blood pressure medications to achieve one of two different levels of blood pressure control—either less than 140 or less than 120. SPRINT participants will be regularly tested to determine the health of their heart, kidneys, and brain. The study will also look at the relationship between blood pressure, memory and dementia.
“High blood pressure is not a natural part of aging, but it does tend to increase,” said Dr. Chertow. “And we will see if it affects cognitive function in older people.”
Dr. Chertow is looking for volunteers to participate in the study, who will be clinically tracked for about five years.
“SPRINT will help to dispel the myth that we know all the answers. It’s likely that the risks can be reduced even if the reduction in blood pressure is small,” he added. “The SPRINT trail will provide evidence of these benefits, as well as the potential risks of blood pressure control medications. Anything we do to improve our health can make a major difference.”
About the Speaker
Glenn Chertow, MD, MPH, is a professor of medicine and chief of the Division of Nephrology, who specializes in kidney disease, renal failure, and hypertension. He received his medical education at Harvard Medical School and completed his residency and fellowship at Brigham and Women’s Hospital. After nine years at the University of California, San Francisco, he joined Stanford in 2007, where he maintains a clinical practice for adults and children. He is Board Certified in nephrology by the American Board of Internal Medicine.
For More Information:
About Dr. Chertow
To register for the SPRINT Study
Division of Nephrology
Center for Science in the Public Interest