What are the DASH studies?
The DASH Diet is based on two studies, DASH and DASH-Sodium, that looked at ways of reducing blood pressure through changes in diet. In the DASH study, people were given one of three eating plans: a plan similar in nutrients to what most North Americans eat; the same plan but with extra vegetables and fruit; or the DASH diet, which is rich in vegetables, fruit and low-fat dairy foods and lower in saturated fat, total fat and cholesterol.
The results were compelling. The diet higher in vegetables and fruit and the DASH diet both reduced blood pressure. The DASH diet had the greatest effect on blood pressure, lowering levels within two weeks of starting the plan. Not only was blood pressure reduced, but total cholesterol and low-density lipoprotein (LDL) or "bad cholesterol" were lower, too.
In the DASH-Sodium study, participants were given one of three sodium plans: the DASH diet with 3,300 mg of sodium per day (a normal amount for many North Americans); 2,300 mg of sodium (a moderately restricted amount); or 1,500 mg of sodium (a more restricted amount, about 2/3 of a teaspoon of salt). Blood pressure was lower for everyone on the DASH diet. However, the less salt people consumed, the greater the decrease in blood pressure. People who already had high blood pressure had the largest decrease in blood pressure.
Why is a healthy blood pressure important?
High blood pressure causes the heart to work harder to pump nutrient- and oxygen-rich blood to the body. The arteries that deliver the blood become scarred and less elastic. Although these changes happen to everyone as they age, they happen more quickly in people with high blood pressure. As the arteries stiffen, the heart has to work even harder, causing the heart muscle to become thicker, weaker and less able to pump blood. When high blood pressure damages arteries, they are not able to deliver enough blood to organs for their proper functioning. As a result, organs may become damaged, too. For example, this type of damage can affect the heart, causing a heart attack, the brain, causing a stroke, and the kidneys, leading to kidney failure.
How is DASH different from Canadian recommendations?
The DASH diet isn’t unique – it is very similar to Canada’s Food Guide. Canada’s Food Guide has a greater range in the number of servings than the DASH diet, which also recommends a higher level of vegetable and fruit intake.
The DASH eating plan
DASH Food Groups:
- Vegetables
- Fruit
- Grains (mainly whole grains)
- Low Fat or No-Fat Dairy Foods
- Lean meats, poultry and fish
- Nuts, seeds and dry beans
- Fats and Oils
Vegetables: 4-5 servings
- 250 mL (1 cup) raw leafy vegetables
- 125 mL (½ cup) cooked vegetables
- 170 ml (6 oz) juice
- 1 medium piece of fruit
- 63 mL (¼ cup) dried fruit
- 125 mL (½ cup) fresh, frozen or canned fruit
- 1 slice bread
- 250 mL (1 cup) ready to eat cereal
- 125 mL (½ cup) cooked rice, pasta or cereal
- 250 mL (1 cup) milk
- 250 ml (1 cup) yogurt
- 50 g (1½ oz) cheese
- 3 ounces cooked lean meats, skinless poultry, or fish
- Nuts, seeds and dry beans: 4-5 servings per week
- 1/3 cup (1.5 oz.) nuts
- 30 mL (2 tbsp) peanut butter
- 2 tbsp (1/2 oz.) seeds
- 1/2 cup cooked dry beans or peas
- 5 ml (1 tsp) soft margarine
- 15mL (1 tbsp) low-fat mayonnaise
- 30 mL (2 tbsp) light salad dressing
- 5 ml (1 tsp) vegetable oil
Many people require medication to control their blood pressure. Lifestyle modification, which includes healthy eating and regular physical activity, may be the only treatment needed in those with mild high blood pressure. In those that require medication to control their blood pressure, following a healthy lifestyle may reduce the need for, or the amount of, medication required.
What next?
A full healthy lifestyle, including healthy eating, is part of the Canadian recommendations for the management of high blood pressure. Heart and Stroke is involved in developing blood pressure guidelines, which are updated every year. To control your blood pressure and reduce the risk of heart disease, the guidelines recommend that you:
- Be active 30 to 60 minutes most days of the week.
- Choose the following more often: vegetables, fruit, low-fat dairy or dairy alternatives, whole grains and protein from a variety of foods, such as beans, lentils, nuts and seeds, lean meats, poultry and fish. Limit fast foods, processed foods because they usually have more sodium.
- If you are overweight, losing about 10 lb (5 kg) will lower your blood pressure. Reducing your weight to within a healthy range for your age and gender will lower your blood pressure even more.
- Eat less salt by:
- limiting your use of salt in cooking and at the table
- avoiding salty foods
- choosing fresh or plain frozen food
- avoiding canned or prepared foods that are high in salt
- reading the Nutrition Facts table on food packages for sodium content
- using other seasonings such as herbs, spices, lemon juice and garlic during food preparation
- If you drink alcohol, limit yourself to no more than 2 drinks a day, to a weekly maximum of 10 for women and 3 drinks a day to a weekly maximum of 15 for men. (Do not drink when you are driving a vehicle, taking medications or other drugs that interact with alcohol, pregnant or are planning to be pregnant, making important decisions, doing any kind of dangerous physical activity, living with alcohol dependence or mental or physical health problems, or responsible for the safety of others. If you are concerned about how drinking may affect your health, talk to your doctor).
- Be smoke-free. It is important to stop smoking if you have high blood pressure. Smoking increases the risk of developing heart problems and other diseases. Your home and workplace should also be smoke-free.
- Take your medication as prescribed.
- Monitor your blood pressure regularly.
- Avoid drinking sugar sweetened beverages. Choose safe drinking water, low fat milk or tea instead.
- Changing your diet means a life-long commitment to healthier lifestyle choices. People who make small changes in their diet over a longer period of time, rather than a dramatic change all at once, are more likely to stay committed to a healthier diet.
How much salt?
We recommend Canadians consume no more than 2,300 mg of sodium (about 1 teaspoon/5 mL of table salt) a day. The amount of salt you eat isn’t just what you shake onto your food – it is already added in large quantities to prepared foods, canned products, snack foods and restaurant meals.
2 ways to get started on the DASH diet
Change gradually
- If you now eat one or two vegetables a day, add another serving at lunch and dinner.
- If you don’t eat fruit now or have only juice at breakfast, add a serving of fruit to your meals or switch out your juice for the whole fruit.
- Treat meat as one part of the whole meal, instead of the main focus.
- Limit meat and alternatives to about 6 oz (170 g) a day, over two meals (two servings). Each serving is about the size of a deck of cards or the palm of your hand. Choose fruit or low-fat foods as desserts and snacks.
- Fruit and low-fat foods offer great taste and variety. Fresh fruit require little or no preparation. Dried fruit is easy to carry with you.