DASH stands for Dietary Approaches to Stop Hypertension. The DASH diet is based on DASH study results published in 1997. The study showed that a diet rich in fruits, vegetables, and low-fat dairy foods, with reduced saturated and total fat, could substantially lower blood pressure. It is the diet recommended by the National Heart, Lung and Blood Institute (part of the National Institutes of Health) for lowering blood pressure.
High blood pressure affects about one in three adults in the United States and is defined as blood pressure consistently above 140/90 mmHg. The top number, 140, is the systolic pressure exerted by the blood against the arteries while the heart is contracting. The bottom number, 90, is the diastolic pressure in the arteries while the heart is relaxing or between beats. The concern is the higher the blood pressure, the greater the risk for developing heart disease, kidney disease, and stroke. High blood pressure is known as the silent killer as it has no symptoms or warning signs.
The DASH study by the National Heart, Lung, and Blood Institute (NHLBI), published in the New England Journal of Medicine in 1977, was the first study to look at the effect a diet rich in potassium, magnesium, and calcium, not supplements, had on blood pressure.
The study involved 459 adults with and without high blood pressure. Systolic blood pressures had to be less than 160 mmHg and diastolic pressures 80 to 95 mmHg. Approximately half the participants were women and 60% were African American. Three eating plans were compared. The first was similar to a typical American diet—high in fat (37% of calories) and low in fruit and vegetables. The second was the American diet but with more fruits and vegetables. The third was a plan rich in fruits, vegetables, low-fat dairy foods, and low in overall fat (less than 30% of calories). It also provided 4,700 milligrams (mg) potassium, 500 mg magnesium, and 1,240 mg calcium per 2,000 calories. This has become known as the DASH diet. All three plans contained equal amounts of sodium, about 3,000 mg of sodium daily, equivalent to 7 grams (g) of salt. This was approximately 20% below the average intake for adults in the United States and close to the current salt recommendations of 4–5 g daily. Calorie intake was adjusted to maintain each person's weight. These two factors were included to eliminate salt reduction and weight loss as potential reasons for any changes in blood pressure. All meals were prepared for the participants in a central kitchen to increase compliance with the diets.
Results showed that the increased fruit and vegetable and DASH plans lowered blood pressure, but the DASH plan was the most effective. For participants without high blood pressure, it reduced systolic pressure by 6 mmHg and diastolic by 3 mmHg. The results were better for participants with high blood pressure—the drop in systolic and diastolic was almost double, at 11 mmHg and 6 mmHg, respectively. These results showed that the DASH diet appeared to lower blood pressure as well as a 3 g salt-restricted diet, but, more importantly, had a similar reduction to that seen with the use of a single blood pressure medication. The effect was seen within two weeks of starting the DASH plan, which is also comparable to treatment by medication, and continued throughout the trial. This trial provided the first experimental evidence that potassium, calcium, and magnesium were important dietary factors in affecting blood pressure, rather than just sodium alone.
The diet is based on 2,000 calories a day, with the following nutritional profile:
These percentages translate into more practical guidelines using food group servings.
An example breakfast menu is: cornflakes (one cup) with 1 tsp. sugar, skim milk (one cup), orange juice (1/2 cup), a banana, and a slice of whole wheat bread with one tablespoon jam. Suggested snacks during the day include dried apricots (1/4 cup), low-fat yogurt (one cup), and mixed nuts (1.5 oz. or 40 g).
These guidelines are available in the National Institutes of Health (NIH) updated booklet, “Your Guide to Lowering Your Blood Pressure with DASH,” which also provides background information, weekly menus, and recipes.
DASH eating plan
1 slice bread
1 oz. dry cereal†
½ cup cooked rice, pasta, or cereal
1 cup raw leafy vegetable
½ cup cut-up raw or cooked vegetable
½ cup vegetable inice
1 medium fruit
¼ cup dried fruit
½ cup fresh, frozen, or canned fruit
½ cup fruit iuice
Fat-free or low-fat milk and milk products
1 cup milk or yogurt
1½ oz. cheese
Lean meats, poultry, and fish
6 or less
1 oz. cooked meats, poultry, or fish
Nuts, seeds, and legumes
4-5 per week
⅓ cup or 1½ oz. nuts
2 Tbsp. peanut butter
2 Tbsp. or ½ oz. seeds
½ cup cooked legumes (dry beans and peas)
Fats and oils
1 tsp. soft margarine
1 tsp. vegetable oil
2Tbsp. salad dressing
Sweets and added sugars
5 or less per week
1 Tbsp. sugar
1 Tbsp. jelly or jam
½ cup sorbet, gelatin 1 cup lemonade
*Whole grains are recommended for most grain servings as a good source of fiber and nutrients.
†Serving sizes vary between ½ cup and ¼ cups, depending on cereal type. Check the product's Nutrition Facts label.
‡Since eggs are high in cholesterol, limit egg yolk intake to no more than four per week.
SOURCE: National Heart, Lung and Blood Institute. Your Guide to Lowering Your Blood Pressure with DASH Rev. Ed. NIH publication no. 06-5834. Washington, DC: National Institutes of Health. Department of Health and Human Services. https://www.nhlbi.nih.gov/files/docs/public/heart/dash_brief.pdf . (accessed April 3 2018).
The DASH diet was not designed for weight loss, but it can be adapted for lower calorie intakes. The NIH booklet provides guidelines for a 1,600-calorie diet. Vegetarians can also use the diet, as it is high in fruits, vegetables, beans, seeds, and low-fat dairy, which are the main sources of protein in a vegetarian diet.
The DASH meal plan is a healthy diet recommended for those with and without high blood pressure.
The DASH diet may lower blood pressure as much as taking medication, but without the risk of unwanted side effects. The dietary changes can also have immediate effects, comparable with drug therapy. A blood pressure reduction of the degree seen in the DASH study is estimated to reduce the incidence of coronary artery disease by 15% and stroke by 27%.
The DASH plan may also lower blood pressure just as well as restrictive low-salt diets of 3–4 g of salt per day. Many people find low-salt foods be bland, and with 70%–80% of salt intake coming from processed foods, including baked foods such as breads, people may have trouble adhering to low-salt diets. The DASH diet is an adaptation to healthy eating, so it has no restrictions but instead follows standard dietary guidelines for the general public.
Adding high-fiber foods to the diet should be done gradually to avoid side effects such as gas, bloating, and diarrhea. It is important to increase fluid at the same time, as fiber draws water into the bowel. High fiber intake with inadequate fluid can cause hard stools and constipation.
Increasing fruits and vegetables increases the potassium content of the diet. For healthy people with normal kidney function, a higher potassium intake from foods does not pose a risk as excess potassium is excreted in the urine. However, individuals whose urinary potassium excretion is impaired, such as those with end-stage renal disease, severe heart failure, or adrenal insufficiency, may be at risk of hyperkalemia (high levels of potassium in the blood). Hyperkalemia may cause cardiac arrhythmias (irregular heartbeat), which could be serious. Some common drugs can also decrease potassium excretion. Individuals at risk should consult a doctor before staring the DASH diet, as higher potassium intakes in the form of fruit and vegetables may not be suitable. Care should also be taken with potassium-containing salt substitutes.
Currently, there are no known risks associated with the DASH diet. However, the long-term effects of the diet on morbidity and mortality are still unknown.
Studies over the years have suggested that high intakes of salt play a role in the development of high blood pressure. Dietary advice for the prevention and lowering of high blood pressure has focused primarily on reducing sodium or salt intake. A 1989 study looked at the response an intake of 3–12 g of salt per day had on blood pressure. The study found that modest reductions in salt, 5–6 g salt per day, caused blood pressures to fall in people with hypertension. The best effect was seen with only 3 g of salt per day, with blood pressure decreasing by an average of 11 mmHg systolic and 6 mmHg diastolic. More recently, the use of low-salt diets for the prevention or treatment of high blood pressure has come into question. The Trials of Hypertension Prevention Phase II in 1997 indicated that energy intake and weight loss were more important than the restriction of dietary salt in the prevention of hypertension. A 2006 Cochrane review, which looked at the effect of longer-term modest salt reduction on blood pressure, found that modest reductions in salt intake could have a significant effect on blood pressure in those with high blood pressure, but a lesser effect on those without. It was agreed that the 2007 public health recommendations of reducing salt intake from levels of 9–12 g/day to a moderate 5–6 g/day would have a beneficial effect on blood pressure and cardiovascular disease.
The effectiveness of the DASH diet for lowering blood pressure is well recognized. The 2015 Dietary Guidelines for Americans recommend the DASH Eating Plan as an example of a balanced eating plan, consistent with the existing guidelines, and it forms the basis for the USDA MyPlate. DASH is also recommended in other guidelines, such as those advocated by the British Nutrition Foundation, American Heart Association, and American Society for Hypertension.
Although reducing sodium and increasing potassium, calcium, and magnesium intake play a key role in lowering blood pressure, the reasons the DASH eating plan have a beneficial effect remain uncertain. The researchers suggest it may be because whole foods improve the absorption of the potassium, calcium, and magnesium, or it may be related to the cumulative effect of eating these nutrients together rather than the individual nutrients themselves. It is also speculated that it may be something else in the fruits, vegetables, and low-fat dairy products that accounts for the association between the diet and blood pressure.
The Salt Institute supports the DASH diet but without the salt restriction. They claim that the DASH diet alone, without reduced sodium intake from manufactured foods, would achieve the desired blood pressure reduction. Their recommendation is based on the fact that there are no evidence-based studies supporting the need for dietary salt restriction for the entire population. The Cochrane review in 2006 showed that modest reductions in salt intake lower blood pressure significantly in people with hypertension but have less of an effect on individuals with normal blood pressure. Restriction of salt for those without hypertension is not recommended.
There is a continued call for the food industry to lower the use of salt in processed foods from governments and health associations. The New York City Health Department spearheaded the National Salt Reduction Initiative in the United States, and a number of other health-related organizations joined this effort. Their goal was to reduce the consumption of salt by 20% in the United States by 2014. The coalition worked closely with food manufacturers and restaurants that voluntarily agreed to reduce sodium levels in their products. In addition, the U.S. Department of Health and Human Services, along with several other federal and private sector organizations, led the Million Hearts initiative. Their goal was to prevent the occurrence of one million heart attacks and strokes in the United States between 2012 and 2017. Reduction of sodium levels in the diet to aid in lowering blood pressure was a major component of this initiative as well.
There is some debate on whether patients can follow the diet long-term. The 2003 PREMIER Clinical Trial (a multi-center trial) studied the effects of diet on blood pressure and found that the DASH diet results were less than the original study. This difference was thought to be because participants in the DASH study were supplied with prepared meals, while participants in the PREMIER study prepared their own foods. As a result, only half the fruit and vegetable intake was achieved in the PREMIER study, which affected the overall intakes of potassium and magnesium. The researchers concluded that compliance with the DASH diet in the long term was questionable, but agreed that patients should still be encouraged to adopt healthy interventions such as the DASH diet, as it does offer health benefits.
In terms of heart health, the DASH diet lowered total cholesterol and LDL cholesterol, but it was also associated with a decrease in high-density lipoprotein (HDL), the “good” cholesterol. Low HDL levels are considered to be a risk factor for coronary heart disease, while high levels are thought to reduce the likelihood of heart disease. The decrease was greatest in individuals who started with a higher level of the protective HDL. Researchers agreed that the reasons for the decrease in HDL levels needed further review, but concluded that the overall effects of the DASH diet were beneficial in terms of preventing heart disease.
While the long-term health effects of the DASH diet are yet to be established, the diet closely resembles the Mediterranean diet, which has been shown to have other health benefits, including a reduced risk for heart disease and cancer rates. It is thought that the DASH diet is likely to offer similar health benefits.
See also American Heart Association No-Fad Diet ; Calcium ; Coronary heart disease ; Low-fat diet ; Magnesium ; Mediterranean diet ; Sodium .
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American Heart Association, 7272 Greenville Ave., Dallas, TX, 7523, (800) 242-8721, http://www.heart.org .
American Society for Hypertension, 45 Main St., Ste. 712, Brooklyn, NY, 11201, (212) 696-9099, http://www.ash-us.org .
British Heart Foundation (BHF), Greater London House, 180 Hampstead Rd., London, UK, NW1 7AW, http://www.bhf.org.uk .
British Nutrition Foundation, High Holborn House, 52-54 High Holborn, London, UK, WC1V 6RQ, +44 020 7404 6504, http://www.nutrition.org.uk .
The Cochrane Collaboration, Summertown Pavilion, 18-24 Middle Way, Oxford, UK, OX2 7LG, +44 1865 516300, Fax: +44 18 6551 6311, http://www.cochrane.co.uk .
Food Standards Agency UK (FSA), Aviation House, 125 Kingsway, London, UK, WC2B 6NH, http://www.food.gov.uk .
National Lung, Blood and Heart Institute (NHLBI), PO Box 30105, Bethesda, MD, 20824-0105, (301) 592-8573, http://www.nhlbi.nih.gov .
Salt Institute, 700 N. Fairfax St., Ste. 600, Alexandria, VA, 22314-2040, http://www.saltinstitute.org .
Tracy J. Parker, RD
Revised by Stacey J. Chamberlin