Did you know three out of 10 Australians have high blood pressure? Dietitians Cindy Williams and Caitlin Reid explain how you can manage your levels in 10 easy steps.
What is high blood pressure?
High blood pressure is an alarming problem in Australia. It is actually responsible for more trips to the doctor – and medical prescriptions – than any other condition.
Latest figures indicate that almost 30% of Australians have high blood pressure, with more than half of these cases going untreated. The consequences are serious; high blood pressure accounts for 60% of all strokes and 50% of heart attacks, with 2005 statistics labelling heart disease our leading cause of death and disability.
The good news is that diet and lifestyle changes can have a big impact on blood pressure levels, enabling you to keep your heart healthy and functioning at its best.
High versus low
When doctors take your blood pressure, they are checking the force of blood against your artery walls. It is measured in millimetres of mercury (mmHg) and recorded as two numbers – systolic pressure (when the heart beats) over diastolic pressure (when the heart relaxes between beats).
Your blood pressure rises and falls throughout the day, but when it stays elevated over time, it's called high blood pressure or hypertension. This means the heart works harder, and the high force of blood flow can harm arteries and organs like the heart, brain, eyes and kidneys. Blood pressure is often called the 'silent killer,' as it usually has no symptoms and often goes unnoticed. In fact, the only way to find out whether your blood pressure is high is to get it checked by your doctor.
The other extreme is low blood pressure, or hypotension, which means the pressure of blood circulation around the body is lower than normal. Hypotension is a relative term however, as you may have lower blood pressure than the person next to you, but still be perfectly healthy.
Hypotension is only a problem if it has a negative impact on your body, such as vital organs being starved of oxygen and nutrients.
Blood pressure readings (from the Heart Foundation)
Less than 120
Less than 80
Normal – high
120 - 139
80 - 89
Mid-hypertension (grade 1)
140 - 159
90 - 99
Mid-hypertension (grade 2)
160 - 179
100 - 109
Mid-hypertension (grade 3)
180 or more
110 or more
What about iodine?
Although an adequate intake of iodine is important for health, it's a little known fact that AWASH (Australian Division of World Action on Salt and Health) does not recommend adding iodised salt to food, whether you have high blood pressure or not. It's better to get your iodine from alternate sources such as seafood, milk and seaweed, and iodine-fortified products like Milo B-Smart.
10 steps to lower your blood pressure
Step 1: Up the fruit and vegies
For healthy blood pressure, it's important to maintain the right balance of minerals. This means less sodium, more calcium and magnesium and importantly, more potassium. Potassium blunts the effect of sodium on blood pressure.
Results from the Third National Health and Nutrition Examination Survey in 2001 found that a diet containing 8.5 daily serves of fruits and vegetables (providing 4100mg of potassium), lowered blood pressure by 7.2mmHg systolic and 2.8mmHg diastolic in people diagnosed with high blood pressure, compared to a diet providing only 3.5 serves of fruits and vegetables (1700mg of potassium). It's normally recommended that we eat at least two serves of fruit and five serves of vegies a day, but you can boost your daily potassium intake by increasing this to four to five servings of fruit, and four to five servings of vegetables.
As long as kidney function is normal, potassium supplements can also help people who have moderate to severe hypertension, but it's generally recommended to increase potassium intake through diet instead.
Step 2: Include low-fat dairy
Low-fat dairy foods not only promote strong bones and teeth - they can also positively affect high blood pressure.
In a Harvard study of nearly 29,000 American women aged 45 or older, it was found that those who consumed at least two serves of dairy per day were 11% less likely to develop high blood pressure than women who ate less than one daily serve of dairy. The nutrient in dairy responsible for producing this effect against hypertension is thought to be calcium. However, as there is no strong evidence that taking calcium supplements lowers blood pressure significantly, it's better to include calcium-rich, whole foods in your diet.
Health experts recommend we eat three or more serves of low-fat dairy products every day. For breakfast, have some low-fat yoghurt in your muesli or have a skim milk and banana smoothie. For extra calcium, add fish containing bones, such as salmon or sardines, to your diet.
Step 3: Eat more plant- based foods
A 2005 review of the effect of vegetarian diets on blood pressure levels showed that, on average, vegetarians tend to be slimmer than meat eaters, which may help explain their lower incidence of hypertension.
Plant-based foods containing soluble fibre, like oats, legumes and seeds, may also reduce blood pressure. A 2008 study found that a fibre increase of 17g per day caused blood pressure to decrease slightly.
It's also a good idea to increase your intake of magnesium-rich foods, as they appear to slightly lower blood pressure too. Dried beans, lentils, split peas, nuts and wholegrains are all good options, so have porridge or muesli for breakfast, snack on nuts, and add red lentils to your soups and stews.
Step 4: Drop the salt
Although the suggested dietary target for sodium is 1600mg per day, or 4g, the average Australian consumes much more than that – around eight or nine times more! Even if you don't add salt to your food, processed foods like bread, sauces, breakfast cereals, cheese, soups and processed meat contain plenty – enough to make up about 75% of our intake.
Populations with a high average salt intake suffer higher levels of hypertension, but it's been found that patients who follow a low-sodium diet can reduce blood pressure by 5-7mmHg.
If you do have to cut back on sodium, your food may taste bland initially, but don't despair - taste buds do adjust. Look for products that are salt-reduced, low-salt (less than 120mg of sodium per 100g), or contain no added salt.
Step 5: Manage your stress
Unsurprisingly, stress raises blood pressure levels – but the good news is, relaxation may lower them. Although more research is needed, preliminary studies suggest relaxation activities like meditation and yoga may help. People are more likely to comply with other blood pressure-reducing lifestyle measures when relaxed, too – so make sure you take time to de-stress each day.
Step 6: Reduce caffeine
The National Heart Foundation recommends limiting intake of caffeinated drinks to no more than one or two cups of coffee, tea or cola per day. But coffee drinkers should note that Australian research has found caffeine content to vary considerably between places - some café cups contain two to three times more caffeine than what's found in a cup of instant coffee. To limit intake, try switching to tea instead – it contains about half the caffeine of instant coffee.
Step 7: Achieve and maintain a healthy weight
Excess weight has been found to be the main cause of high blood pressure in some overweight people, but a 2007 Italian study found that half of all overweight, hypertensive people can achieve normal blood pressure by achieving a healthy weight following a six-month, kilojoule-restricted diet. Losing just five kilos has an effect on most people with mild to moderate hypertension, so aim to be in the healthy weight range.
Step 8: Boost your omega-3 intake
Omega-3 fats help to relax blood vessel walls so they can expand as blood rushes through. One study of 46,500 people aged over 40, with a range of blood pressure readings, found those who ate more omega-3-rich foods had lower blood pressure.
Find your short-chain omega-3 fats in canola oils, walnuts and flaxseeds and your long-chain omega-3 fats in oily fish like tuna, salmon and mackerel.
The Heart Foundation suggests consuming 500mg of long-chain omega-3 fats (two to three serves of fish each week) and 2g of short-chain omega-3 fats (a range of plant-based omega-3 foods) each day. The best way to get your omega-3s is through food, but a supplement is also fine (for more on omega-3s, see article Omega-3s: The good fats.
Step 9: Get active
Being physically active can reduce high blood pressure as much as some anti-hypertensive drugs. Just 30 minutes a day of moderate intensity exercise – like walking, cycling, swimming, dancing or gardening – helps lower your blood pressure and your weight. You don't have to do all 30 minutes at once – research shows you can break it up into 10-minute bursts and it's just as effective as one continuous workout.
It's commonly thought that people with hypertension should not participate in resistance training, but this is not the case. Apart from the many other health benefits, moderate strength training lowers blood pressure. The trick is to skip heavier weights, as they require more strain, which can elevate blood pressure levels. Instead, lift lighter weights and do more repetitions of each exercise.
Step 10: Watch the alcohol
Several studies have found that drinking excessive amounts of alcohol can raise blood pressure to unhealthy levels. In fact, research shows that heavy drinkers who cut back to moderate drinking can lower their systolic blood pressure by up to 4mmHg and their diastolic blood pressure by up to 2mmHg.
Males with high blood pressure should limit alcohol consumption to no more than two standard drinks per day, while females with high blood pressure should limit their intake to one standard drink per day. Everyone should have two alcohol-free days per week. A standard drink is 100ml wine, 285ml beer or 30ml of spirits.
Remember that alcohol can also have an effect on prescription drugs, including blood pressure medications, interfering with their effectiveness and increasing their side effects.