Salt and cardio-vascular disease: Policy and Science clash

The recent video we posted of Dr SalimYusuf’s PURE study had a section on sodium intake, where he showed that the lowest risk of cardiovascular events, cardiovascular deaths and all-cause mortality was associated with an intake between 3000 and 6000 mg of sodium per day (equivalent to 7 to 15g salt per day). The current US average sodium intake is 3800 mg placing the general population nicely within this sweet spot, although towards the lower end.

Current US and UK dietary recommendations recommend an upper limit at 2300mg of sodium (6g of salt) whilst cardiovascular recommendations by bodies such as the American Heart Association aim to reduce sodium intake to 1500 mg per day (approx 3.75 g salt). If the PURE study is right (and it is not alone in questioning the current guidelines), then these aspirations would do more harm than good.

How did such discrepancy arise? The problem may be the use of surrogate markers. The thinking goes like this: Salt raises blood pressure. Raised blood pressure increases CVD risk, so salt increases CVD risk. This kind of thinking was evident in 2011 when the American Heart Association (AHA) called for salt targets to be reduced to 1500mg per day.At the time MedPage Today explained:

The evidence linking salt intake with blood pressure — and the major adverse outcomes of heart disease, stroke, and kidney disease — is “impressive,”…

That evidence includes more than 50 trials assessing the blood pressure effects of salt, as well as a meta-analysis showing that cutting salt intake by about 1,800 mg per day lowered blood pressure by 5 mm Hg systolic and 2.7 mm Hg diastolic.

This is a “critically important public health issue,” according to Appel and colleagues, and this AHA advisory must be considered “a call to action.”

On the basis of this ‘A leads to B leads to C, therefore A leads to C’ thinking initiatives were instigated all round the world to reduce public consumption of salt. A task force of concerned scientists even formed a lobby group to put pressure on food manufacturers, which successfully led to reductions in added salt in manufactured foods.

However, within a short time of the AHA call to action reports started coming in contradicting this advice.

Over this period it is clear that scientists were becoming more and more irritated with the dogmatic approach of the AHA and government bodies, and by the last article were publicly calling the AHA anti-scientific!

Despite all of the research questioning the validity of further salt reduction US and UK policy remains stubbornly wedded to the ‘less is best trajectory’. In their 2016 survey the UK government reported proudly that average sodium consumption fell from 3500mg in 2005 to 3200 mg in 2014.

Their report claimed “Too much salt in the diet can raise blood pressure which increases the risk of heart disease and stroke. A reduction in average salt intake from 8g to 6g per day is estimated to prevent over 8000 premature deaths each year and save the NHS over £570million annually.”

Yet contrary evidence from studies including PURE would suggest that this is not simply futile but probably harmful. You would think that with the swathe of research challenging the low salt dogma that public policy would be questioning the wisdom of further reductions. Not a bit of it. Dr Alison Tedstone, chief nutritionist at Public Health England, makes no bones about it:

Our analysis makes clear that there is a steady downward trend in salt consumption. While people are having less salt than 10 years ago, we are still eating a third more than we should.

Many manufacturers and retailers have significantly reduced the salt levels in everyday foods. However, more needs to be done, especially by restaurants, cafes and takeaways.

The intransigence of health policy makers leads researchers to exasperation and despair. As one writer put it:

…the ‘salt hypothesis’ is rather like a monster from a 1950s B movie. Every time you attack it with evidence it simply shrugs it off and grows even stronger. – Malcolm Kendrick

In an interview with MedPage today researchers who found that patients with heart failure who ate more salt did better than those who ate less made the following statement which we have published before, but is such a gem it deserves another outing:

“We have had no basis for any of our recommendations regarding sodium restriction during the past 50 years, although these recommendations have changed a great deal (for no good reason). After this report, we still have no basis for any of our recommendations regarding sodium restriction. We were ignorant before; we are not any smarter now. Did we really need this report to tell us that we lack evidence for our recommendations regarding dietary sodium in patients with heart failure?”
Milton Packer, Professor in the Division of Cardiology, UT Southwestern

Further reading:

Salt vs sodium measurements

We made a boo-boo in out recent post (Cardiologist attacks diet dogma at 2017 symposium) where we summarised the findings from the PURE study regarding salt intake. We originally stated that 3 to 6 grams of salt per day appeared optimal but this should have read 3 to 6 grams of sodium per day.

What’s the difference?

Salt is a simple compound sodium chloride, NaCl, composed of sodium and chlorine atoms in a 1:1 ratio. Sodium has an atomic mass of 23 and chlorine a mass of 35, so the the fraction by weight of sodium in salt is 23/58 = 40%; or said the other way round, 1 gram of sodium is found in 2.5g of salt. To make things even more confusing, sodium is often quoted in milligrams (mg) whilst salt is given in grams, so the conversion becomes: 1000mg sodium = 2.5g salt

Let’s put this to the test with a confusing pair of health policies: UK guidelines recommend you eat no more than 6g of salt per day, whereas US guidelines place the limit at 2,300 mg of sodium per day. How do these compare?

First, converting the US 2,300 mg of sodium to grams gives 2.3 g of sodium. Next, convert this to the equivalent amount of salt by multiplying by two and a half: 2.3g x 2.5 =  5.75g. This figure rounds to 6g. i.e. they are essentially recommending the same thing, but expressing them in different ways. (That’s the special relationship for you!)

Here is a handy table for converting between sodium, salt and teaspoons:

Salt in
grams
Sodium in mg Approx. equivalent to                Guidelines – daily limit
0.5 200 Average pinch of salt
2.5 1000 Half a teaspoon salt
3.75 1500 ¾ a teaspoon salt Recommended (AHA)
5 2000 One teaspoon salt
6 2400 1¼ teaspoons salt Upper limit (UK / US)
10 4000 2 teaspoons salt Current average consumption
15 6000 3 teaspoons salt Upper limit (PURE study*)

*The PURE study found that the lowest risk of cardiovascular and all-cause mortality was associated with a sodium intake of 3000 to 6000 mg per day. A concern I will look at in the next post is that public health policy does not take into account the lower limit, and assumes that less salt is always better. PURE and other studies suggest otherwise!

This sodium/salt mistake crops up a little too often and leads to confusion. For example MedPage Today, a respected medical news site, reported in 2011 that the American Heart Association had called for salt intake to be limited to 1,500 Mg. (I will write more about the conflict between this figure and the findings of the PURE study in my next post)

First off, I’m sure they meant milligrams (mg), not mega grams (Mg). Autocapitalising their title, put them out by a ‘trifling’ factor of one billion, but that’s forgivable. Where they really sowed confusion was by muddling up sodium and salt like I did. The AHA were calling for sodium intake to be reduced from 2300mg per day to 1500 mg per day (for adults), but MedPage reported these figures as salt not sodium.

One bemused commenter wrote “This article suggests 1 1/2 gms of salt a day, in the UK we are told 6gms per day”

So to clarify, the UK and US recommended upper limit is 2300 mg sodium per day (= 6 g salt), and the AHA recommendation is 1500 mg sodium (=just under 4g of salt). In contrast the PURE study found the ideal range was 3000 to 6000 mg sodium (=between 7.5 and 15g of salt per day).

Why then do researchers and nutrition labels quote sodium, not salt quantities? Because in principle at least, you could get sodium from sources other than sodium chloride. In practice non-salt sources of sodium are insignificant.

Anyway, hope that clears up the confusion about measuring sodium levels.

Next up I’ll tackle how the national guidelines are pushing us in the opposite direction to that suggested by the PURE study.

Goodwood Wins Cheese Award

Goodwood’s Charlton Farmhouse cheese is made from the milk from their pasture raised dairy shorthorn cows and it is easily my all-time favorite cheese. This is the one I increasingly reach for at breakfast, lunch, or after dinner – delicious on its own, with a tomato, pickled onion or apple slice. In fact in the last few months I have stopped buying any other cheese as my appreciation of Charlton has grown.

I was, therefore, extremely pleased to see that this excellent product has just won the Best Organic Cheese 2015 award at the British Cheese Awards, gaining a Gold medal in the Mature Cheddar category, which is particularly notable as it is the largest and most competitive category in the whole event. We at Rosemary Cottage Clinic wish to congratulate Goodwood on this achievement, and heartily recommend this cheese to all our readers! (Please note, this is made from cow’s milk, so is not suitable for those who need to avoid cow’s milk products and stick to goat’s instead, unfortunately.)

(See all the 2015 British Cheese Award winners here)

Goodwood_Cheese_Award_2

I find most commercial cheddars, although perfectly good for grating and cooking, to be less than optimal for straight eating. They are often too cloying on the palate, rather rubbery in texture and can have an off-putting acidic tang. Because of these disappointments I had shifted to Wensleydale for the cheese board, reserving cheddars for cooking and grating over hot vegetable dishes.

Charlton, however, is excellent both for cooking and nibbling. It has a slightly crumbly texture, does not stick to the roof of the mouth, and has a really good flavor without undue acidity. I am not surprised in the least that it received a gold medal accolade!

What’s more, if you are a Goodwood raw-milk customer you can purchase Charlton at the wholesale price of just £10 per kilo when you visit the farm to collect your milk, making this not only the tastiest cheese you will find but the best value for money too.

And please don’t worry about the amount of this that you are drawn to consume, as  Charlton is high in heart-healthy dairy fats. Yes, heart healthy. Scientists are increasingly recognising that consumption of full-fat dairy, especially fermented products like hard cheeses, are inversely associated with cardiovascular disease, i.e. eating more cheese is associated with a lower risk of cardiovascular events. In addition to that heart warming fact you will be pleased to know that good cheeses, especially those from grass fed herds, are good sources of that essential and frequently overlooked nutrient, vitamin K2 (in the form of menaquinone 7) which is now known to enable calcium in foods to be deposited in the correct tissues, i.e. the bones, rather than the soft tissues such as arteries where it causes huge problems. So be of good cheer, Charlton Farmhouse cheese is here (well, it’s at Goodwood) and now everyone knows just how wonderful it is.

Healthy, delicious, award-winning and great value for money – what’s not to like? (No, we have not been paid to write this post, it is our true opinion).

Dr Malcolm Kendrick – Autumn Seminar – Tickets now available

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Cholesterol: why it does not and cannot cause heart disease

For our 2014 Autumn Seminar we are very pleased to present Dr Malcolm Kendrick, author, speaker and blogger, who will expose the myths and misunderstanding around cholesterol and heart disease.

This talk is not to be missed whether you simply wish to understand your own health better, are wanting to become more informed about the current national health debate, or are concerned about politics and corruption in the medical establishment.

Dr Kendrick will also be signing copies of his book The Great Cholesterol Con
during the break.

Date: Saturday September 27th 2014 7:30pm-10:00pm (doors open 7:00 pm)
Venue: The Assembly Room, North St, Chichester, PO19 1LQ
Parking
Northgate (Festival Theatre) Car Park – download directions (pdf)

Tickets

  • Online booking: . . . . .  from £ 8.50 . . . click here for secure online booking
  • Telephone booking: . . . . . . £10.00 . . . 0333 666 3366 (national landline rate)
  • On the door: . . . . . . . . . . . . £10.00 . . . subject to availability on the night

For further information or assistance contact Afifah on 01243 868108
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