High blood pressure: doctor’s ignorance the real disease?


By Marika Sboros

Can you turn something into a disease just by giving it a fancy Latin title? Scottish GP Dr Malcolm Kendrick says you can.

Dr Malcolm Kendrick

High blood pressure is just one example. Most medical doctors don’t know what causes high blood pressure in their patients, says Kendrick. At medical school, they learned that in most cases – around 90% – they’ll never know the cause, he says.

That percentage is probably higher. But whatever the number, he says it’s rare to find a clear, specific cause. The real problem of the medical profession’s ignorance about causes of high blood pressure, as he sees it is ignorance. Many doctors are not very good at admitting when they haven’t a clue about something. And haven’t ever been.

Their solution, in this case, has been to name the condition “essential hypertension”. And leave it at that. Of course, essential hypertension sounds impressive but does it help doctors to understand the condition? No, says Kendrick, and he should know.

Kendrick has a special interest in and extensive clinical experience of cardiovascular disease (CVD) treatment. He does research into CVD. He also set up the online educational system for the European Society of Cardiology, working with the European Commission.

Malcolm KendrickKendrick is author of The Great Cholesterol Con, The Truth About What Really Causes Heart Disease And How To Avoid It. He is also author of Doctoring Data, How To Sort Out Medical Advice From Medical Nonsense. And he is an original member of the Centre for Evidence-Based Medicine in Oxford and of The International Network of Cholesterol Sceptics (THINCS). (It’s well worth a read.)

In the article below, Kendrick looks at whether doctors can reliably claim that high blood pressure causes CVD. Or whether they put the medical cart before the horse out of ignorance.

He also gives his prescription for lowering blood pressure. Spoiler alert: he doesn’t bother with drugs – until pressure is far higher than current medical guidelines recommend.

By Malcolm Kendrick

A raised blood pressure, as a clinical sign, has always rather perturbed me. At medical school we were always taught – and this has not changed as far as I know – that an underlying cause for high blood pressure will not be found in 90% of patients.

In truth, I think it is more than this. I have come across a patient with an absolute, clearly defined cause for their high blood pressure about five times, in total. And I must have seen 10,000 people with high blood pressure.

I must admit I am guessing at both figures and might be exaggerating for dramatic effect. Whatever the exact figures, it is very rare to find a clear, specific cause.

The medical profession solved this problem by calling high blood pressure with no identified cause, “essential hypertension”. The exact definition of essential hypertension is “raised blood pressure of no known cause”.

Facing ignorance

I must admit that essential hypertension certainly sounds more professional than announcing: “Oh my God, your blood pressure is high and we do not have the faintest idea why.”

But it means the same thing.

Click to read: Saturated fat causes heart disease? Bollocks – Kendrick!

Doctors have never been good at admitting they haven’t a clue about something. Which is why we have a few other impressive-sounding conditions that also mean: We haven’t a clue:

  • Idiopathic pulmonary fibrosis – progressive damage of the lungs – and we don’t know why;
  • Cryptogenic stroke – a stroke caused by something – but we don’t know what;
  • Essential hypertension – high blood pressure – we haven’t a clue why it’s high.

Can you turn something into a disease, simply by giving it a fancy Latin title? It appears that you can. Does it help you to understand what you are looking at? No, it most certainly does not.

High blood pressure and salt

So, why does the blood pressure rise in some people and not in others? It is an interesting question. You would think that, by now, someone would have an answer but they don’t. Or at least no answer that explains anything much.

Click to read: Take this with more than a pinch of salt! 

Some have blamed excess salt consumption. However, even if you take the more dramatic figures, we are talking no more than 5mmHg.

Indeed, the effect of reducing salt intake on people without high blood pressure is about 1mmHg, at most.

“Almost all individual studies of participants with normal blood pressure (BP) show no significant effect of sodium reduction on BP.”

Which would mean that the effect of raising salt intake would be almost zero. So, if it is not salt, what is it? A magic hypertension fairy that visits you at night? Could be, seems as likely as anything else.

When you have a problem that is difficult to solve, I always like to turn it inside out and see what it looks like from the opposite direction.

Link to heart disease

Presently, we are told that essential hypertension increases the risk of cardiovascular disease.

Looking at this from the other direction, could it be that CVD causes high blood pressure? Well, this would still explain why the two things are clearly associated, although the causal pathway may not be a → b. It could well be b → a.

I must admit that I like this idea better because it makes some sense. If we think of CVD as the development of atherosclerotic plaques, leading to thickening and narrowing of the arteries, then we can see CVD is going to reduce blood flow to vital organs. Among these organs: the brain, the kidneys, the liver, the heart itself.

These organs would then protest, leading to the heart pumping harder to increase the blood flow and keep the oxygen supply up. The only way to increase blood flow through a narrower pipe is to increase the pressure.

Which is what then happens.

Effects of high blood pressure

Over time, as the heart is forced to pump harder and harder, the muscle in the left ventricle will get bigger and bigger, causing hypertrophy. Hypertrophy means “enlargement”. Therefore, in people with long-term, raised blood pressure, we would expect to see left ventricular hypertrophy (LVH).

Which is exactly what we do see.

Doctors often consider LVH a cause of essential hypertension. I would argue that LVH is a result of CVD. This is not exactly a new argument but it does make sense.

Two models strongly support the idea that CVD causes high blood pressure. The first is a rare condition called renal artery stenosis. This is where an artery to one of the kidneys narrows or starts life narrowed. This causes the kidney to protest at a lack of blood supply and increase the production of renin.

Narrowing arteries

Renin converts angiotensinogen, a protein made in the liver that floats about in the blood, into angiotensin I. Then angiotensin converting enzyme (ACE) turns angiotensin I into angiotensin II. And angiotensin II is a very powerful vasoconstrictor (narrows blood vessels). Thus, this raises the blood pressure.

Angiotensin II also stimulates the release of aldosterone, a hormone produced in the kidneys. Aldosterone increases the reabsorption of sodium and water into the blood from the kidneys, simultaneously driving the excretion of potassium (to maintain electrolyte balance). This increases the volume of fluid in the body, which also increases blood pressure.

This whole system is called the Renin angiotensin aldosterone system (RAAS), sometimes shortened to RAS. Activate at your peril.

Angiotensin II is, amongst other things, a potent nitric oxide (NO)antagonist. Which, as you might expect, can do very nasty things to endothelial cells and the glycocalyx (glycoprotein layer that protects artery walls).

If you discover that the patient with very high blood pressure has renal artery stenosis, the artery can be opened, and the blood pressure will – in most cases – rapidly return to normal. Which proves that narrow arteries can, indeed, lead to high blood pressure.

Blood clots in lungs

The other model is the situation whereby a number of blood clots build up in the lungs. That’s a condition known as chronic thromboembolic pulmonary hypertension. It is not nice. The arteries are effectively narrowed by blood clots – in order to keep the blood flow up, the heart must pump harder. In this case, the right side of the heart because it is this side that pushes the blood through the lungs.

So, you usually end up with Right Ventricular Hypertrophy (RVH). Eventually, the heart cannot pump any harder and starts to fail, leading to Right Ventricular Heart Failure (RVF). Shortly after this, you die.

There is an operation that surgeons can do to remove all the blood clots from the lungs. It has a very high mortality rate. Basically, you open up the lungs and pull out a great big complicated blood clot that looks a bit like a miniature tree. If the operation is not fatal (pulmonary endarterectomy), the blood pressure drops, the LVF improves rapidly and the outcomes are excellent.

This is another example that demonstrates that a rise in blood pressure is caused by narrowed blood vessels. Again, if you open the blood vessels, the pressure drops, the stress on the heart falls, and rapid improvement can take place.

Do patients need drugs?

So, if CVD causes high blood pressure, is there any point in trying to lower the blood pressure with drugs. After all, you are doing nothing for the underlying disease.

Well, you would be taking pressure off the heart. Therefore, you might be improving left ventricular hypertrophy, and/or left ventricular failure. But of course, you are also lowering the blood flow to important organs, which is not so good.

Indeed, it is well recognised that, in the elderly, you can increase the risk of falls by lowering the blood pressure – which can lead to fractured hips, and such like.

Also, if you lower the blood pressure too much, the kidneys start to struggle, another major problem in the elderly. In fact, I often tell nurses working with me in Intermediate Care that dealing with the elderly can turn into a battle between the heart and the kidneys. Get one under control and the other one goes off.

Sodium, potassium problems

Then, if you lower the blood pressure you are in danger of triggering the RAAS system into action as the body tries to bring the pressure back up again. And the RAAS system can be quite damaging to the blood vessel themselves.

You will definitely disrupt the control of blood electrolytes such as sodium and potassium as aldosterone kicks into action.

I am forever battling to keep sodium levels up and potassium levels down, or vice versa, depending on which anti-hypertensives are being used. All of these are reasons why I do not bother to treat high blood pressure with drugs, until it is far higher than the current medical guidelines would recommend.

What I do recommend to patients is:

  • Increase potassium consumption;
  • Go on a high-fat, low-carb diet;
  • Use relaxation techniques: mindfulness, yoga, whatever floats your boat;
  • Take exercise;
  • Get out in the sun – this stimulates NO synthesis;
  • Try L-arginine and L-citrulline – as above;
  • Increase magnesium consumption

This will often, if not always, do the trick.

And, best of all…

If you must take medication, I was a very strong supporter of ACE-inhibitors, in that they blocked angiotensin II, and increased NO synthesis. Both good things.

However, some research has come out recently, suggesting (these drugs) may increase the risk of lung cancer. Not by a great deal but there you go.

Best to take nothing at all, if you possibly can.



  1. Obviously, that hypertension isn’t a disease it’s a symptom/result of some underlying condition.
    Obviously, that underlying condition has vascular nature.
    But what causes that vascular issue?
    How to find it’s the root cause?

  2. The salt thing is not right in some people. I am one such person. Because you can’t lower BP in normal people by reducing salt, it doesn’t mean that you can’t raise it in others by increasing salt. I began to eat more salt some time ago because of my diet etc., and monitoring my BP I noticed that it was higher some days. Anyway one day I really did the dog on salt, as we say here, and I achieved a systolic BP of over 200mm. This was alarming. I got BP monitoring and it showed I was hypertensive. During the night of my monitoring I’d also been awakened by a power-failure, a storm and my house alarm which had been struck by lightning and couldn’t be turned off and the police calling to the door, so I’d a rotten sleep. I asked for the monitoring to be repeated in a week, during which I’d cut out coffee, alcohol and cut my salt back a lot. After a week it was normal.
    I’ve since experimented to find out which factor was causing it and it clearly is salt. If I have a high-salt day (which I’ve tried) my systolic will rise by 30mm or more. One low-salt day brings it down to normal (My normal is 117/58 in the morning).
    An interesting difference between the two 24 monitorings is that I had nocturnal hypertension on the first and low BP on the second at night, which is normal. In people who’re salt-sensitive (15% population and it’s genetic) this pattern is seen and fixed by reduction of salt. One of my sisters had the same very salt-sensitive BP.

    As for essential hypertension. Weight loss reduces it. It’s probable that essential hypertension is LARGELY caused by Insulin Resistance and lowcarb diet very often fixes it. The one caveat here is don’t eat too much salt if it’s not working as you may be salt sensitive. The other point is that there’s a 15% chance you’re salt sensitive so don’t assume you aren’t. Check by monitoring your BP.

    How much salt can I eat with normal low BP? Not more than 6g, I think, unless I’m doing a lot of cycling. That’s 2.4g Sodium.
    I’d got into the habit of eating a packet of Parma Ham, on occasions, and that’s 6g salt alone if 100g ham. I no longer eat Parma Ham and check food for salt content.
    I find the easiest way to cut your salt is to have a fairly low salt meal once a day.

    There are two other things which raise my BP. Going to the doctor (he no longer takes it as it’s always 30mm raised, though I get it normal before and afterwards) and a really bad night’s sleep. Same effect, 30mm rise).

    My mother-in-law had a way of saying “he told me all about his diseases.” It was “he put his guts out on the table!”

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