Hypertension (high blood pressure) is a condition that affects millions of people every year.
The main risk factors for high blood pressure include an unhealthy diet (high in salt, saturated and trans fat and low in fibre and plant foods), being sedentary, consuming alcohol and tobacco and being overweight.
A family history of hypertension, being over 65 and having co-existing diseases such as diabetes or kidney disease can also increase your risk of developing hypertension.
Nonetheless, modifying your diet can be one of the most reliable ways to reverse hypertension.
This is where the DASH diet comes in.
DASH stands for Dietary Approaches to Stop Hypertension.
It focuses on including an abundance of fruit, vegetables, low-fat dairy and whole grains, limiting protein to lean options, and reducing intake of salt.
This dietary approach reduces the sodium in your diet and encourages an increased intake of nutrients that help lower blood pressure, such as potassium, calcium and magnesium.
What Does The DASH Diet Look Like?
The DASH diet follows very similar principles to the Australian Dietary Guidelines. Even in the way it prescribes what foods to eat and what to limit.
The DASH diet doesn’t list specific foods but rather focuses on food groups.
The number of servings you can eat of each food group depends on how many calories you consume but in general, your diet should include the following on a daily basis:
Wholegrains (6-8 serves)
Whole grains include foods such as brown rice, quinoa, oats, wholemeal pasta, wholegrain cereal, and wholemeal and rye bread. Most Australians have an overemphasis on refined grains in their diet. So most people should likely focus on including more wholegrain options but they are a particular focus on the DASH diet.
1 serve = 1 slice of bread, 1/2 of a bread roll or 1/2 cup cooked grains such as pasta or rice
Fruit (4-5 serves) & Vegetables (4-5 serves)
The positive impact of fruit and vegetables on health and longevity has been extensively confirmed in academic literature and research.
An adequate fruit and vegetable intake has been linked to improved weight management, better gut health and a reduction in the risk of developing some cancers, type 2 diabetes and of course, hypertension.
1 serve of fruit = 1 medium piece of fruit (banana), 2 small pieces of fruit (plums) OR a small handful of dried fruit
1 serve of vegetables = 1 cup of salad vegetables OR 1/2 cup cooked vegetables
Low-Fat Dairy (2-3 serves)
Dairy is a great source of calcium, vitamin D, protein, and a range of other useful nutrients. The DASH diet recommends a focus on low-fat dairy to reduce the consumption of saturated fat.
Saturated fat which is predominately found in animal products, is considered ‘bad fat’ which increases cholesterol. Particularly, LDL cholesterol, which prompts blockages to form in the arteries of the heart. These blockages increase blood pressure and can lead to heart attacks and stroke.
1 serve = 1 cup low-fat milk, 1 cup low fat-yogurt OR 30g low-fat cheese
Lean Meat, Poultry & Fish (<3 serves)
Whilst animal proteins can be a rich source of iron, zinc, protein, and B-vitamins, they can also be a significant source of saturated fat. The DASH diet recommends focusing on lean proteins such as chicken breast, turkey, eggs, and seafood.
It is also recommended that you trim away skin and fat from meats as well as aim to include some heart health fish. Seafood such as salmon is high in omega-3 which has been shown to have a significant positive effect on heart health.
The DASH diet recommends having less than 6 serves of this food group per day. However, the suggested serving sizes are only 1-ounce or 28g each. So for the sake of making the servings sizes closer to those suggested in the Australia Dietary Guidelines, we suggest <3 serves of the following serving size.
1 serve = 2 eggs OR 60g lean meat/poultry/fish
Nuts, Seeds & Legumes (4-5 serves)
Nuts, seeds and legumes are often under-consumed by the general public. But they are packed full of fibre, phytochemicals, iron, zinc, protein and healthy fats making them some real powerhouses of nutrition.
Legumes can be a great replacement for animal proteins in main meals or a great addition to reduce the amount of animal products in a meal.
1 serve of legumes = 1/2 cup cooked legumes
On the other hand, nuts and seeds can make great snacks and bulk up meals with a source of healthy fats. Nuts and seeds have a small serving size as they are quite calorically dense so that is something to be aware of also. Especially if you are trying to reduce your weight.
1 serve of nuts & seeds = 30g or a small handful of nuts, 2tbsp of seeds OR 1 tbsp nut/seed butter
Technically, soy foods can also be grouped into this category as soybeans are a legume. Edamame, tofu, tempeh and bean curd can be a great addition to your diet for protein whilst limiting saturated fat intake and increasing fibre intake.
Fat & Oils (2-3 serves)
The DASH diet strives to limit fat to less than 30% of daily calories, with a focus on healthier monounsaturated and polyunsaturated fats.
Ideally, fat would mostly come from plant-based sources such as nuts, seeds, avocados and high-quality plant oils.
Aim to limit fat from animal sources (except for seafood), coconut and palm.
Examples of one serving include 1 teaspoon soft margarine, 1 tablespoon mayonnaise or 2 tablespoons salad dressing.
Processed & Discretionary Foods (Less Than 5 Serves Per Week)
You don’t need to completely eliminate processed foods from your diet but it is definitely recommended to limit them.
Food like baked goods, chips, crackers, and confectionary can be a significant source of sodium, saturated fat, and calories. They also are mostly lacking in helpful nutrients.
The DASH diet recommends limiting these foods to less than 5 serves per week.
1 serve = 1tbsp of sugar, 1/2 cup ice cream OR a single handful of chips
Dietary Fat Intake
When following the DASH Diet, fat will make up ~27% of your total energy intake (TEI). The general recommendation for fat intake is 20-30% of your daily calories.
What is most important about the DASH fat recommendation is that only 6% of TEI comes from saturated and trans fat.
Take the example of a 50-year-old overweight woman who leads a sedentary lifestyle in an office job. Her daily energy requirements come in at around 8,700kJ/day. 27% of this is ~522kJ/day. There are around 37kJ/g in fat, so, the woman may consume no more than ~14g saturated and trans fat/day.
Apply these calculations to yourself to determine your own recommended fat intake.
It is important that people with hypertension limit saturated and trans fat because such fats are linked with increased LDL cholesterol.
This augments the build-up of plaque within the blood vessels, narrowing the lumen (opening for blood to pass through).
Think about it like a straw; pushing a quantity of water through a thin straw requires a lot more pressure than through a thick straw. The same principle applies to your blood!
By widening the lumen, through reductions in atherosclerotic plaque, blood pressure is reduced. To achieve the DASH recommendations for fat, fatty cuts of meat, fried and processed food will need to be strictly limited.
Salt is delicious! The salty goodness does, unfortunately, come with consequences for some.
The DASH recommendation for salt is 2300mg/day which is considerably lower than the average Westerner’s dietary intake.
Salt’s a tricky one because sometimes it’s hidden where you do not expect it, particularly in restaurant foods and as a preservative in even sweet processed foods.
Salt exists as NaCl on the table, but, it is the Na (sodium) we really have to worry about in the body.
It is stored mainly in extracellular fluid, which includes blood. Here, it exerts an osmotic pressure that draws water to itself. Hence, increasing the water content and overall volume of blood.
Back to the straw analogy; pushing a large volume of water through a straw takes a lot more pressure than if that volume was reduced, right? Well, the same thing with your blood.
Increasing blood volume increases the pressure it exerts on the vessels, hence, causing hypertension.
It is speculated, there is an internal homeostatic point set for sodium, and excess is excreted. If this were the case, you could eat it by the spoonful.
Unfortunately, the excretion system is still somewhat misunderstood and unlikely to be able to deal with the copious amounts of sodium in the Western diet. Although, it is speculated that some people are able to tolerate higher sodium intake than others. This is commonly referred to as salt sensitivity.
It is the current belief that only 20-25% of people are salt-sensitive-hypertensive, which means the excretion mechanism is vastly underdeveloped in these people.
This is likely why reducing salt intake can make a significant impact on blood pressure for some people but not others.
Nonetheless, a better reduction in blood pressure had been observed with an intake of less than 1500mg per day as opposed to 2300-3000mg per day.
So sodium intake definitely plays a role in hypertension and should be focused on in combination with the other dietary changes the DASH diet advocates for.
The DASH diet’s focus on having adequate low-fat dairy in the diet can contribute to an increase in calcium consumption.
In fact, the DASH diet has a recommendation of at least 1250mg calcium per day. Which is 250mg above recommendations for most of the general adult population.
Calcium is an excellent mineral for vasodilation.
Vasodilation means relaxation muscles that surround the vessels, increasing the lumen. Hence, reducing the pressure of blood within the vessel.
The DASH recommends high potassium at 4700mg/day.
Potassium is found in dark green leafy vegetables, bananas and other fruit and vegetables. Hence the large focus on increasing these foods in the diet.
Unlike sodium, potassium promotes the retention of calcium, allowing blood vessels to reap its vasodilation effects. It also promotes the excretion of sodium, and you already know the benefits of this!
Similar to calcium, magnesium has blood pressure lowering effects. As such, it is recommended in high doses by DASH (500mg). Foods high in magnesium include nuts, whole grains and (yet again) green leafy vegetables.
Fibre has a plethora of health benefits, including some pertaining to cardiovascular health.
For this reason, DASH recommends a high fibre intake of 30g/day. Fibre binds cholesterol and promotes its excretion.
Due to consequential body cholesterol decline, cholesterol is removed from the blood to the liver for healthful purposes (for example, hormone and bile production).
The lowered blood cholesterol resulting, reduces atherosclerotic plaque, increasing lumen and finally, decreasing blood pressure.
Should You Try The DASH Diet?
The DASH Diet requires dramatically increased consumption of fruits, vegetables, legumes, nuts, seeds, low-fat dairy, and whole grains for most people while limiting highly processed foods and animal products high in saturated fat.
Studies on this style of diet have been promising. By following the DASH diet, you may be able to reduce your blood pressure by a few points in just two weeks.
Even better results can be seen over time and can make a significant difference to your health risks including the risk of heart attack and stroke.
To follow the DASH Diet style of eating you should:
- Eat more vegetables and fruits
- Swap refined grains for whole grains
- Choose low-fat dairy products.
- Choose lean protein sources such as seafood, poultry, legumes, and soy foods
- Have nuts and seeds regularly
- Cook with vegetable oils instead of animal fats
- Limit your intake of highly processed foods and drinks
- Limit your intake of foods high in saturated fats like fatty meats, full-fat dairy, butter, coconut and palm oil.