High blood pressure: what can we do to prevent it?

In this blog for healthy people who want to know what they can do to prevent high blood pressure and avoid the need to take medication, Robert Walton, a GP, looks at the Cochrane evidenceCochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. and gives some hints and tips. 

Take-home points

What’s the point of worrying about your blood pressure?

About a quarter of the adult population in England has high blood pressure and it’s a major factor increasing your riskA way of expressing the chance of an event taking place, expressed as the number of events divided by the total number of observations or people. It can be stated as ‘the chance of falling were one in four’ (1/4 = 25%). This measure is good no matter the incidence of events i.e. common or infrequent. of stroke and heart attack.  But the great news is that simple steps taken now can keep blood pressure under control and may even prevent it from ever being a problem.  Here we look at Cochrane evidence on what you can do to manage your own blood pressure without the need for blood pressure-lowering medicines.

Blood pressure is recorded with two numbers. The systolic pressure (higher number) is the force at which your heart pumps blood around your body.

The diastolic pressure (lower number) is the resistance to the blood flow in the blood vessels.

They’re both measured in millimetres of mercury (mmHg).

As a general guide, the NHS page on blood pressure says that:

• high blood pressure is considered to be 140/90mmHg or higher (or 150/90mmHg or higher if you’re over the age of 80)
• ideal blood pressure is usually considered to be between 90/60mmHg and 120/80mmHg

Walking to reduce blood pressure

Rapidly becoming the cure for all ills, walking is probably the most effective way of reducing your blood pressure without resorting to drugs. The Cochrane ReviewCochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. Walking for hypertension (published February 2021) found that walking probably reduces blood pressure in adults aged 40 years and under and may also reduce it in those over 40.

The benefits that you gain may seem small – a reduction of only 4mmHg in your systolic blood pressure (the higher number) is on average all you might expect.  So is it worth it?  Well, to help to put this into context a 2mmHg reduction in systolic blood pressure translates into a 10% reduction in risk of stroke and a 7% reduction in risk of ischaemic heart disease so the benefit that you gain from reducing blood pressure from walking may be well worthwhile, particularly bearing in mind the other benefits that exercise brings. Although it is worth remembering that if you are at low risk to start with then the absolute benefit that you gain could be fairly small.  To find out more accurately what this level of blood pressure reduction might mean specifically for you try this handy calculator

OK, so how much walking do we need to do?

Well, the studies included in the Cochrane Review looked at a variety of different kinds of walking and assessed them in different ways.  But it looks like “moderate‐intensity walking, three to five times per week, of 20 to 40 minutes duration, and 150 minutes per week” is a good target to aim for – and the good news is that benefits in blood pressure reduction will show after only a few months. The World Health Organization recommends that moderate‐intensity aerobic physical activity such as brisk walking should be done for 150 to 300 minutes per week.

Can eating less salt reduce blood pressure?

Well, the Cochrane Review Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride (published December 2020) finds that cutting down on salt could bring your blood pressure down a couple of points if you are white, and you might expect nearly double the effect if you are Asian or black.

It’s worth bearing in mind though that some of the people taking part in the studies included in this review achieved pretty large reductions in salt intake (from an average 11.5g per day to 3.8g per day) and this change in diet might take a while for you and your family to get used to.  A first step could be avoiding adding salt to food at the table and avoiding processed foods which often contain a large amount of sodium. The NHS advises that adults should eat no more than 6g salt a day, which is around a teaspoonful.

There’s a lot of interest in chocolate… for lowering blood pressure

It’s easy to see how the idea that blood pressure might be controlled by eating more chocolate captured the popular imagination!

There’s some evidence to back this up from the Cochrane Review Effect of cocoa on blood pressure (published April 2017).  The rationale is that the flavanols from cocoa have a blood pressure-lowering effect and the review suggests that on average this might be 1.8mmHg (systolic and diastolic) in mainly healthy adults – which could certainly be worthwhile.

Although people in the studies ate the equivalent of up to 100g of dark chocolate a day which may be more than some would wish to consume. It’s also interesting to note that the apparent benefits of eating chocolate were smaller when studies that had been sponsored by industry (i.e. chocolate manufacturers!) were excluded.  You can read more in the blog Cocoa and blood pressure: food for thought.

Can dietary supplements help to lower blood pressure?

There may be small but worthwhile reductions in blood pressure from increasing calcium intake although how best to get the calcium is up for grabs.

A recent Cochrane Review Calcium supplementation for prevention of primary hypertension (published January 2022) suggests that increasing calcium intake by 1-1.5g a day lowers blood pressure by about 2mmHg in people (and particularly young people) with normal blood pressure.

This is a very substantial increase in intake for most people and could probably only be achieved by using calcium supplements which many find unpalatable.  Perhaps the best source of calcium in the diet is skimmed milk but this level of supplementation would require drinking one or two litres a day which could be difficult to sustain in the long term.

What would be really useful to know would be how much benefit people who are normally at the lower end of calcium intake would achieve by more modest supplementation or dietary changes.  This information wasn’t available from the studies in the Cochrane Review.  Nor was there any information about possible harms of calcium supplementation.

The bottom line: there are simple ways to reduce your blood pressure without taking medication

So, doing a fair amount of extra walking – together with cutting down on salt – seems the best way forward for preventing high blood pressure and reducing the risk of stroke and heart attack.  There’s no evidence on whether doing both together gives you twice the benefit but who knows – it might!

And if you need to replace the calories used up in all that walking, then perhaps a little dark chocolate may not be such a bad option!

References (pdf)

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Robert Walton has nothing to disclose.