People who eat a mainly plant-based diet, or who follow the Mediterranean way of eating, tend to have a lower blood pressure than those who eat a typical, Western, meat-based diet. Researchers therefore developed the DASH (Dietary Approach to Stopping Hypertension) diet which is a cross between the two and is high in fruit, vegetables, nuts and low-fat dairy products, supplies protein in the form of fish and chicken rather than red meat, and is low in saturated fat, cholesterol, sugar and refined carbohydrates.
Following the DASH diet significantly lowers blood pressure in those who already have high readings, and in those without hypertension – suggesting it may even help to prevent the age-related rise in blood pressure that commonly occurs. The DASH diet works by increasing your intake of potassium, calcium, magnesium and antioxidant vitamins, as well as other plant substances that have beneficial effects on the heart and circulation. Its high fibre content is also filling, and slows the absorption of fats and sugars to they are more easily handled in the body.
The DASH diet is now advised as the first-line approach to treating hypertension, before medication is started. It’s so powerful that, together with other lifestyle changes, it can help you avoid the need for drug treatment. If you are already taking antihypertensive drugs, following the DASH diet can improve your blood pressure control so that your doctor may be able to reduce the dose and number of tablets you are taking. These benefits are seen within just two weeks of following this nutritional approach.
What foods can you eat more of on the DASH diet?
The DASH diet focuses on eating fruits, vegetables, low-fat dairy foods, whole grains, poultry, fish and nuts, and includes many delicious foods.
Grains: eg bagels, bread, breadsticks, cereals, crackers, granola (unsweetened), muesli (unsweetened), oatmeal, pasta, pizza bases, rice, unsalted pretzels or unsalted popcorn.
Good alternatives to wheat include rye, buckwheat (which despite its name is a gluten-free member of the rhubarb family), hempseed, brown rice, red rice (Camargue or Bhutan), wild rice (a grass seed), corn meal, amaranth, teff, quinoa, gram/chickpea flour, millet and tapioca.
Ideally select wholegrain or brown, seeded products rather than processed white/beige versions as these contain significantly more magnesium and fibre. You can also experiment with making your own breads and pizza bases, using artisan flours.
When cooking rice and pasta, avoid adding salt.
Unless you want to lose weight, aim to eat 7 servings of wholegrains per day. If you want to lose weight, then eat fewer servings.
Vegetables: eg artichokes, asparagus, aubergine/eggplant, avocado (really a fruit) beetroot, broccoli, carrots, chard, courgette/zucchini, cucumber, kale, mushrooms, okra, peppers, tomatoes, mangetout/green peas, green/string/runner beans, spinach, squash/pumpkin, sweet potatoes, potatoes – the list of possibilities is endless.
Buy vegetables fresh, plain frozen or canned/tinned with no added salt/brine. Similarly, minimise your intake of pickles, sauerkraut or other vegetable products which tend to be high in added salt.
Aim to eat 4 to 5 portions of vegetables per day as they are a super-healthy source of antioxidants, phytonutrients, potassium, magnesium, fibre and other blood-pressure lowering ingredients.
Fruits: eg apples, apricots, bananas, blackberries, blueberries, cherries, dates, figs, grapes, guava, grapefruit (check for medication interactions), mango, melons, nectarines, olives, oranges, papaya/pawpaw, peaches, pineapple, pomegranate, prunes, raisins, raspberries, satsumas, strawberries, tangerines, watermelon and so on – whatever is in season and reasonably cheap.
Aim to eat 4 to 5 servings of fruit per day as they are full of fibre, potassium, magnesium, antioxidants and other beneficial micronutrients.
Nuts (unsalted): eg almonds, Brazils, cashews, chestnuts, coconuts, filberts, hazelnuts, macadamias, mixed nuts, peanuts (a legume), pecans, pine kernels, pistachios, tigernuts (actually a vegetable) walnuts;
Seeds: eg chia, flax, pumpkin, sesame, sunflower,
Nuts and seeds are sources of magnesium, potassium, protein, fibre and beneficial fatty acids. Aim to eat a handful (60g) of unsalted nuts and seeds a day.
Pulses: eg black beans, black-eyed peas, broad/fava beans, butter/lima beans, chickpeas/garbanzo beans, flageolet/haricot beans, mung beans, navy beans, pinto beans, red kidney/cannellini beans, all colours of lentil, soy beans, white beans.
Beans/pulses are an excellent plant-based source of protein for when you are cutting back on red meat and are an excellent source of magnesium and other beneficial minerals.
Aim to eat a portion of beans per day.
Dairy: Low-fat or fat-free milk, low-fat buttermilk, unsweetened bio yogurt, cheese, crème fraiche or fromage frais.
Eggs are a good choice, too, and you can normally eat one or two a day even if you have a raised cholesterol (unless your doctor has specifically advised you not to).
The original DASH diet recommended selecting fat-free or low fat milk. However, even full fat milk is only 5% fat – in any other food this would be deemed low fat.
Dairy foods are a good source of protein, calcium, magnesium, potassium and vitamins. Aim to eat 2 or 3 servings per day.
Meat and Fish: If you eat red meat, select lean cuts that are trimmed of visible fat. Remove skin from chicken, duck, goose and other poultry.
The DASH diet typically provided between 1 and 2 servings of meat, fish or poultry a day.
Aim to eat smaller amounts of red meat and select beans/pulses, poultry or fish instead. The World Cancer Research Fund recommends an intake of less than 500g (18 oz) red meat (beef, pork, lamb, goat etc) per week, for example, very little (if any) of which should be processed. Their ultimate goal is to get average intakes down to no more than 300g (11 oz) per person per week. In any case, cut back on cured meats such as bacon and ham as these are processed with salt.
Oily fish such as salmon, herring, mackerel, sardines, pilchards and tuna are fine because of the health-benefits of the omega-3s they provide. If eating tinned tuna, select products that don’t need draining, or which are canned in olive oil or spring water – not brine.
Cook meat and fish by grilling/broiling, roasting or boiling rather than frying.
Fats and Oils: low-fat mayonnaise, light salad dressing, olive oil.
Use minimally – 1 to 2 tablespoons olive oil per day has beneficial effects on blood pressure.
Fluids: Drink water, club soda, vegetable juice (including tomato juice although strictly speaking it’s a fruit), fruit juice (ideally diluted with water to reduce sugar intake), herbal, black and green teas.
Check labels of bought foods as those that are labelled as low fat or fat free sometimes have a higher calorie count than the regular versions due to added sugar. Where possible, select reduced sodium or no-added-salt products.
What foods should you eat less of on the DASH diet?
The DASH diet is relatively low in total fat, saturated fat, cholesterol, red meats, salted or sugar snacks such as crisps/chips, sugar, sweet foods (desserts, confectionery) and sugared drinks.
More than 75% of all dietary salt comes from processed foods, so if you do nothing else, aim to cut back on these and ideally to eliminate them altogether.
Replace candy/milk chocolate with dark chocolate which has beneficial effects on blood pressure.
Sweeten foods, when necessary, with fruit, Stevia extracts or a little maple syrup, honey or agave nectar.
Select whole foods where possible, as processed, instant, frozen and other convenience foods tend to have a high salt content (check labels and select those that are as low salt/sodium as possible.
Don’t add salt at the table, and flavour foods with herbs, spices, lemon or lime juice, vinegar or salt-free seasonings. Limit even low sodium versions of soy/teriyaki/tamari sauce, monosodium glutamate (MSG), barbecue and other sauces.
For other tips on following a low salt diet, see Why You Should Eat Less Salt.
Can you lose weight on the DASH Diet?
The original DASH diet was individually tailored to provide all the energy each individual needed (typically around 2100 calories per day) so that the effectiveness of the diet itself was not modified by any changes in weight. However, you can easily lose weight when following this stye of eating, by having more of the fruit, vegetables, pulses and nuts, and less of the grains and potatoes. Aim to eat smaller portions, too.
Losing excess weight will help to bring down your blood pressure in itself. Data from 25 trials show that you you can lose around 5kg (10.10lb) of excess fat, this can lower your blood pressure by an average of 4.4/3.6 mmHg. Overall, reductions in blood pressure readings were greatest in those who lost the most weight, so if you need to lose more, keep on going until you are within the healthy weight range for your height to achieve a Body Mass Index (BMI) between 18.5 and 24.99 Kg/M2.
What is the evidence that following the DASH diet can lower your blood pressure?
The original Dietary Approach to Stopping Hypertension (DASH) study was set up to compare the blood pressure effects of a diet providing extra fruit and vegetables against a Mediterranean-style diet that, as well as focusing on fruit and vegetables, also emphasised eating nuts, low-fat dairy products, fish, chicken and was low in red meat, saturated fat, cholesterol, sugar and refined carbohydrates.
The study involved 459 adults whose systolic blood pressure (upper reading) was less than 160 mmHg, and diastolic blood pressure (lower reading) was between 80 mmHg and 95 mmHg. The average blood pressure reading was 132/85 mmHg and just over a quarter (29%) had hypertension but none were on antihypertensive medication.
The volunteers were divided into three groups, one that followed a typical Western diet, one that followed a Western diet with extra amounts of fruit and vegetables, and one that followed the full-blown DASH Diet. All three diets were tailored to provide around 3g of sodium a day (equivalent to7.5 grams of salt – more than is ideal). All food was provided for the eight weeks duration of the trial, and the participants were asked not to eat any non-study food. Energy intakes were adjusted so that body weight did not change significantly.
- In the group eating extra fruit and vegetables, average blood pressure readings fell by around 5/3 mmHg within 2 weeks, from 132/85 mmHg down to an average of 127/82 mmHg.
- In the group following the DASH Diet, however, systolic blood pressure reduced by an impressive 8/5 mmHg within 2 weeks, down to an average of 124/80 mmHg which is an ideal reading.
Compared with those following the control diet, the DASH Diet significantly reduced blood pressure significantly. Those with hypertension saw the greatest benefits, with blood pressure reductions of 11.6/5.3 mmHg, while those with high normal blood pressure say a reduction of 3.5/2.2 mmHg. The DASH diet lowered blood pressure similarly at all times of day and night.
Just over half the benefits of the DASH diet were attributable to eating extra fruit, vegetables and nuts. These increased total potassium intakes from an initial low daily amount of 1,700 mg to a high level of 4,100 mg, for example, to help flush excess sodium and fluid from the body via the kidneys.
The DASH diet is even more effective if you also reduce salt
The researchers then looked at what happened if these two successful ways of eating – the more fruit and veg approach and the DASH Diet – were combined with lower salt intakes. This second study, known as DASH-Sodium trial, involved 412 people with blood pressures of between 120-159/80-95 mmHg of whom two out of five (41%) had hypertension but had not started medication.
Volunteers were randomly assigned to follow either the Western diet with extra fruit and veg, or the DASH diet. Then, while following their assigned diet, their sodium intakes were adjusted so that for three separate periods of 30 days each (assigned in random order), they had either:
- a low salt intake (1.5g sodium per day, equivalent to 3.75 grams of salt)
- an intermediate salt intake (2.4g sodium equivalent to 6g salt) OR
- a high salt intake (3.3mg sodium equivalent to 8.25 grams of salt).
The results were clear. Those following the DASH Diet achieved significantly greater reductions in blood pressure compared to those following the control diet, in all cases. And on both diets, blood pressure reduce most in those with the lowest salt intake.
On the higher sodium intake, blood pressures fell by 5.9/2.9 mmHg more on the DASH Diet than on the extra fruit and veg diet, to achieve an average blood pressure of around 127/81 mmHg. For some, however, blood pressures rose significantly when following a high sodium diet (in 36 people on the control diet and 7 following the DASH diet) although this was not sustained and did not need medical treatment.
On the intermediate sodium intake, blood pressures fell by 5.0/2.5 mmHg more on the DASH Diet than on the extra fruit and veg diet, to achieve an average blood pressure of around 126/80 mmHg.
On the lower sodium intake, blood pressures fell by 2.2/1.0 mmHg more on the DASH Diet than on the extra fruit and veg diet, to achieve an average blood pressure of around 124/79 mmHg.
So both dietary approaches are helpful, but if you want to achieve optimum results, with the greatest reductions in blood pressure, aim to follow the DASH Diet and cut back on your salt intake, too.
When you compare the two extremes of both beneficial approaches in people with hypertension, those following the DASH diet with a lower sodium intake saw their blood pressure fall by an average of 11.5/5.7 mmHg compared to those following the extra fruit and veg diet with the higher salt intake.
Another benefit of this way of eating is that in these trials, people following the DASH Diet experienced fewer headaches than those using the extra fruit and veg approach.
If your blood pressure is raised, self-monitoring is key to maintaining good control.
Click here for advice on choosing a blood pressure monitor to use at home.
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