Monthly Archives: May 2013

Salt intake – What of Nuns?

11 Replies

Excess salt intake is one of the great issues in preventative medicine. Last year I watched a bus go by, with an advert for reducing salt plastered all over the side. Some restaurants have taken salt cellars off their tables, to protect customers. Many foodstuffs now have their salt content clearly labelled, with high salt content given a red sticker.

Given all of this you would think, would you not, that the case for excess salt consumption causing cardiovascular disease had been made beyond even the slightest possibility of doubt. One of the arguments in support of the dangers of salt consumption (the one that I am looking at in this article), comes from the native peoples living in the Amazon

The Amazon is an extremely low salt environment, and the average salt consumption of those living there is at very low. Several studies have found that the tribes people living in the Amazon have very low blood pressure which does not increase with age. They also have very little in the way heart disease and strokes.

‘Primitive societies who ingest little or no salt have no hypertension1’

Proof, the anti-salt lobby cry, that it is excess salt intake that causes our blood pressure to rise dangerously.

Or is it? When presented with ‘proof’ like this I tend to look for contradiction, rather than confirmation. Are there, I wondered, other populations that fail to demonstrate a rise in blood pressure with age, that do not have a low salt consumption. My attention was drawn to nuns, living in Italy.

‘The powerful effect of psychosocial and acculturating influences on population blood pressure trends seems to be confirmed, through longitudinal observations, in the nuns in a secluded order. After initial observations had been made on culture, body form, blood pressure, diet, and other variables in 144 nuns and 138 lay women, included as a control group, a 30-year follow-up study was undertaken. Most striking were opposite trends noted between the two groups in blood pressure trend. During the follow-up period, blood pressure remained remarkably stable among the nuns. None showed an increase in diastolic blood pressure over 90 mm Hg.’

So, nuns do not develop high blood pressure as they age. What happened to the control women in this study?

‘By contrast, the control women showed the expected increase in blood pressure with age. This resulted in a gradually greater difference (delta>30/15 mm Hg) in systolic and diastolic blood pressure between the two groups, which was statistically significant.’

No difference in diet or salt consumption, yet one population developed the ‘normal’ Western rate of hypertension whilst the other did not. What did the authors of this thirty yearlong study think was the reason for this finding?

‘In conclusion, it seems reasonable to attribute much of the difference in blood pressure and cardiovascular events, to the different burden in psychosocial factor and to the preserved peaceful lifestyle of the nuns2.’

Now I do not know for sure if those living in the Brazilian rain forests have managed to preserve a traditional peaceful lifestyle – but it seems a reasonable assumption to make.

However, the main point I am trying to make here is that you do not need a low salt diet in order to prevent hypertension. You can find populations with a normal salt diet who do not develop hypertension either.

What factor, or factors, appears to link these two populations? The factor appears to be living a preserved peaceful lifestyle. This would suggest that stress is the cause of hypertension and cardiovascular disease, and not salt. Whilst association cannot prove causation, a lack of association disproves it.

1: Freis ED. The role of salt in hypertension. Blood Pressure 1992; 1: 196-200.

2: Timio M, et al: ‘Blood pressure in nuns in a secluded order: A 30-year follow-up.’ Miner Electrolyte Metab. 1999 Jan-Apr;25(1-2):73-9

What does cause heart disease?

28 Replies

(Part one of an occasional series)

So what does cause heart disease then, if it is not cholesterol?  This is question I am often asked – with varying degrees of accusation – by other doctors. Usually after I’ve given a talk dismissing raised cholesterol as a risk factor.

The simplest answer is that the most important causal factor of cardiovascular disease aka the development of plaques (thickenings) in the arteries, is stress (sorry about that rather clumsy form of words). However, as with many simple answers, explaining how stress causes ‘heart disease’ is a bit more complicated.

Which means, gentle reader, that we must go back to the beginning of the whole story, and weave a number of interconnected strands together.

The first strand here is to explain what ‘stress’ may be. I must admit that this is not easy, because few people have an agreed definition of stress. Many concepts are bandied about, and everyone has their own ideas on the subject, but most of them are rather too vague to be of any real use.

I define stress as a measurable dysfunction in the Hypothalamic-Pituitary-Adrenal axis (HPA-axis). But that may be jumping ahead rather too fast, and it requires many steps to get to this point. The first step is to attempt to break stress down into its component parts.

To do this, we have to start by accepting that stress has two basic components. There is the Stressor – the thing causing stress, and the Stressee – the individual affected by the stressor. Without making this important distinction, we will constantly mix up two concepts that need to be kept separate.

For example, many people talk about having a stressful day. I would immediately ask. Does this mean you were impacted on by lots of different stressors e.g. a traffic jam, a tight work deadline, your children getting ill. Or that you found yourself unable to cope with stressors that you would normally be able to cope with. Or both. [To be truthful I would rarely ask this, as I don’t want people shuffling away from me at the dinner table. But I might think it].

By looking at stress as having a cause, or causes, (the stressor), and then looking at their impact upon an individual (the stressee) we can start to disentangle the things that cause stress, from their actual impact.

In addition to this important distinction, there is also a need to accept that different stressors can create positive or negative effects, depending on how the person reacts to them.  Without getting too tangled in this issue, I will attempt put these first ideas into their simplest possible form

Stress has four distinct components:

  • Stressor – positive
  • Stressor – negative
  • Stressee reaction – positive
  • Stressee reaction –negative

Positive stressors could be:

  • Exercise
  • Winning the lottery
  • Giving a well-accepted speech
  • Watching your children perform on stage

Negative stressors could be:

  • Using cocaine
  • A close relative dying
  • Severe criticism at work/being bullied
  • Getting hit by a bus
  • Watching your army comrades being blown to bits by an IED

Some negative stressors are very short acting and, as such, the human psyche and physiology can cope and restore homeostasis (unless the trauma is gigantic). The problems start to arise when negative stressors act hour after hour, day after day, week after week. For example, being repeatedly physically or sexually abused as a child. Or being bullied day after day at work.

Problems created by a constant battering of negative stressors are also made significantly worse if your coping mechanisms are poor. Being bullied at work is not so bad if you have a good social life, a supportive partner, and a loving family. It also helps significantly if you are physically, fit and free from significant chronic disease.

If, however, you have no friends, no supportive family, and you have a chronic illness that weakens you, it does not take too much else to tip your system over the edge.

Unfortunately, early life trauma, and abuse, can leave people with very poor coping mechanisms. In addition, people who have suffered repeated negative stressors through their childhood often find themselves in a cycle of repeating negative behaviour. They are also likely to have poor coping skills, and difficulty with interpersonal relationships.

Effectively, therefore, the same ‘stressor’ can have very different effects on people, depending on their resilience. This resilience can be both psychologically and physically determined, and is hugely important. A ‘strong’ person can cope with stressors that might seriously damage a ‘weak’ person.

Some people say that stress can be simplified into the flight or fight response being constantly activated and eventually ‘burning’ out. Whilst it is true that a constantly stimulated flight or fight response is key to understanding the physiological damage that ‘stress’ causes, it is not the only factor in play.

A lack of social support is not the same thing as the flight or fight response. However, it can create significant problems with production of stress hormones. Depression is not the flight of fight response going wrong. Not having human contact, or touch, can damage your hormonal and autonomic/unconscious nervous systems just as much as being bullied.

In short, stress is not just determined by external factors, such as perceived – or real – threat. A vastly important aspect of stress lies within the individual, their responses to life events, and their resilience. As social animals, loneliness is just as damaging, if not more so, than someone threatening to fire you.

In my world, therefore, being depressed is a form of ‘stress’, and it causes exactly the same type of physiological damage as, say, post-traumatic  stress disorder. This is why you cannot look at an event in someone’s life e.g.  losing their job, or getting divorced, or suffering a car crash and loss of a limb, and score this from one to ten on how stressful this is.

  • Loss of job =2
  • Moving house = 3
  • Getting divorced = 4

For some people losing a job may be a blessed relief. For other a terrible humiliating shame. Others may just shrug their shoulders and move on.

For some of us, an apparently trivial event can be devastating e.g. a passing comment on our appearance.  Others will just laugh it off. Some years ago I was told by a doctor that stress couldn’t be a cause of heart disease because he had seen a well-off lady living in rose covered cottage in the country who had just had a heart attack.

I just replied ‘How do you know she wasn’t stressed?’ The externally idyllic existence may, in reality, be a battleground. Perhaps her smiling, smart, well-off, magistrate husband got home and beat the living daylights out of her every weekend. If so, it wouldn’t be the first time – and most certainly would not be the last.

In short, there is no point in guessing if someone is stressed. Often, there is no point asking them either. Most of us play complex internal games with regard to stress. Where it is considered a badge of honour to be ‘stressed’ and working incredibly hard – people will tell you how stressed they are. – even if they are not. Equally, if you have had a terrible upbringing, you may be so desensitised to stress that you cannot even recognise that you are suffering.

At this point I should probably attempt to bring together what makes up the concept of ‘stress’

Stress consists of stressors, and the stressee. Stressors can be positive, or negative. They can be psychological, or physical.

The same stressor can have a completely different impact on the stressee depending on their resilience.

Resilience can be damaged by such factors as:

  • Abuse in childhood
  • Long-term illness
  • A lock of supportive relationships, friends, family, church

Resilience will be improved by

  • A loving upbringing
  • Good health
  • Supportive relationships
  • Good interpersonal skills

There is no point in guessing is someone is suffering the physiological consequences of stress. Equally, there is no point in asking someone if they are stressed – they may well not know. The only way to know if someone is actually suffering from the consequences of repeated negative stressors is to measure their biochemistry and physiology.

Part two: How to measure if a person is ‘stressed’.

A simple Question – that opens a can of worms

29 Replies

A day or so ago I received this e-mail from a doctor in London.

Dear Dr Kendrick,

I work as a GP in Wandsworth London and I read that you don’t
believe that much in cholesterol and CHD.

I do agree up to 50% of MI patients have normal cholesterol
but some say what’s normal for UK is actually high. Is this argument valid?

Best wishes

Define ‘normal.’ Does normal mean average? If we took the average height of everyone in the UK we would find (very nearly) that 50% of those dying of CHD (coronary heart disease) were above average height and 50% below. So average is clearly normal, but then again so is being tall, or short.

However, if we decided that average height of everyone living in the UK was above ‘normal’, and we then lowered the definition of ‘normal height’ by three inches, we would find that the vast majority of people dying of CHD were now above average height. At which point we could decree that being taller than normal was a risk factor for CHD.

This would obviously be a completely bonkers thing to do. Yet, you can do it with cholesterol levels and everyone nods in general agreement.

Aha, but the argument goes that our lives are completely different than the lives of our ancestors, which has caused our cholesterol levels to be unnaturally high.

An article in the Journal of the American College of Cardiology best summed up this line of thinking. Under the heading ‘Why average is not normal’, O’Keefe, the lead author, made the claim that: ‘Atherosclerosis is endemic in our population, in part because the average LDL (“bad” cholesterol) level is approximately twice the normal physiologic level.’ In short, according to O’Keefe, our cholesterol level should be about 2.5mmol/l, not 5.2mmol/l.

He based his argument, in part on looking at the cholesterol levels of various animals e.g. elephants, and boars, and suchlike. He also used the argument that very young babies (neonates) have cholesterol level of about 2.5mmol/l. Now, in my opinion, anyone proposing this argument should have their medication increased. We should base our cholesterol levels on those found in other animals species….yes, of course we should. You mean those animal species with an average life expectancy of ten years, for example.

However, this argument is now pretty widely accepted by the medical community. We are all, everyone, living in the West, living in such an ‘unhealthy’ way that our cholesterol levels are unnaturally high. The true normal cholesterol levels is 2.5mmol/l.

Fine, if we re-set normal at 2.5mmol/l we will find that 99% of people dying of heart disease do have a ‘high ‘cholesterol level. Problem sorted, average is no longer normal, and the hypothesis that a high cholesterol level is a risk factor for heart disease is now true.

Hold on, I’ve got an idea…