Nearly half of American adults suffer from high blood pressure, also known as hypertension. As a leading cause of heart disease, kidney disease, and stroke, the condition is tied to an estimated 7.5 million deaths each year, or about 13% of all global deaths.
That's where Professor Lawrence Appel's DASH Diet comes in.
The Dietary Approaches to Stop Hypertension (DASH) diet is a heart-healthy eating plan that prioritizes vegetables, fruits, low-fat dairy, and whole grains while limiting saturated fats, tropical oils, sodium, and sweetened foods. It was named the Best Heart-Healthy Diet and the Best Diet for High Blood Pressure by U.S. News and World Report earlier this year, as well as the second-best Overall Diet.
"Chronic disease is a problem largely related to lifestyle," says Appel, the former director of the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins. "Figuring out how to prevent and control chronic disease rests not just on drugs. I do believe in drugs and medication, but you can also get a big impact from diet."
In the late 1990s, Appel and his team received NIH funding to test the connection between dietary patterns and blood pressure. The study included 459 adults, some with confirmed high blood pressure, some without. Each participant was fed either a "typical American diet," a typical American diet plus extra fruits and vegetables, or the DASH diet. Each diet contained an equal 3,000 milligrams of sodium per day. The participants followed these diets for 11 weeks, consuming only food and beverages provided by the study.
The results were clear: Adults who followed the DASH diet had the most success in lowering their blood pressure. The diet was especially effective for those with hypertension and also for Black Americans.
"The amount of blood pressure reduction was striking and similar to what would be achieved by medication," Appel recalls.
His subsequent NIH studies fine-tuned the diet and confirmed even more benefits. In addition to lowering blood pressure, the DASH diet can decrease a patient's risk of heart disease, kidney disease, stroke, hypertensive complications of pregnancy, Alzheimer's disease, and certain forms of cancer. It can also help patients lose weight and lower their LDL cholesterol.
But despite all this good news, it's nearly impossible for researchers like Appel to find funding outside of the NIH for the types of studies that he does. Feeding hundreds of people continuously for several months is expensive and labor-intensive, especially when the results are designed to help patients, not a company's bottom line.
"No food company is going to pay for these studies," Appel explains. "Nobody has the patent on fruits and vegetables, so why would the banana trade association fund a large study that was testing a dietary pattern that also included tomatoes, vegetable oils, and healthy meats? It's just not going to be done."
According to Appel, although feeding studies and other types of clinical trials are challenging and expensive, they remain crucial to understanding the relationship between diet and health.
"There are a lot of people who say ultra-processed foods are bad, but those are based largely on observational studies, not clinical trials," Appel says. "With observational studies, you really can't be sure. Is it really something special about ultra-processed foods? Or is it the fact that most ultra-processed foods are high in salt or high in sugar? ... Instead of cutting the funding for research, they should be increasing the funding."
