Salt sense

Posted by Andrew Wadge on November 9th 2007 in Science, safety and health

Last week I bemoaned the confusing messages that consumers sometimes receive on what's safe and healthy to eat, particularly when we provide plenty of good advice. So I was disappointed to read a headline in The Mail on Sunday that 'Now scientists say (guess what) salt isn't bad for you'. 

Disappointing for two reasons: first because the compelling evidence for an association between salt and blood pressure – which is a risk factor for cardiovascular disease (CVD) – has been described in detail in the report on Salt and Health from the independent experts on the  Scientific Advisory Committee on Nutrition (SACN).  And second, because it implies that 'scientists' are somehow changing their minds week in week out on what's good and bad.

This displays a fundamental lack of understanding about how scientific understanding progresses – which is usually incrementally.  So whilst individual studies can lead to conflicting opinions, we always base our advice to the public on an assessment of all of the available evidence – guided by independent experts – rather than the views of one individual scientist.

The study referred to in the Mail on Sunday is in fact a review of existing evidence and actually confirms that reducing salt intake lowers blood pressure but questions whether there is a direct link between salt and CVD.  This is mainly because of the difficulties of carrying out large studies of the effect of salt on CVD as CVD usually takes a long time to manifest and because CVD has a number of causes.  However, since high blood pressure is a major risk factor for CVD then reducing blood pressure will also lower the risk of CVD.

So please don't give up the attempts to reduce your salt intake – it is sensible advice backed by good science.

add new comment

Thanks, but...

Posted by Andrew Wadge on 02/01/2008 - 15:24

Dear Anonymous,
Thanks for your comment. I'm not sure what you mean about my earlier intolerant reply though. Nothing's been withdrawn or amended.

Objectivity

Posted by Anonymous (not verified) on 19/12/2007 - 22:35

Hi Bruce

In answer to your comment, I would not expect scientific objectivity from any newspaper, least of all the Daily Mail, but the danger is if scientists do not follow the rigours of science and take all shades of opinion into account then we see confused scientific advice that undermines public confidence. There is always the possibility that scientist will have different interpretations of the facts but when it appears that not all of the fact or opinions are being considered then this danger can only increase.

By the way Andrew it would have been more genuine if you had left your initial, quite intolerant, reply on the website and issued a further clarification rather than withdraw it and substitute another, a facility that none of the rest of us have.

Approach to Science; Salt sense

Posted by Bruce Osborne (not verified) on 14/12/2007 - 05:58

Andrew,
Interesting comment from "Anonymous" becrying your one-sided approach.

I wonder how many people read The Mail On Sunday's heading "...salt isn't bad for you" - and no further. There's nothing more one-sided (and misleading) than headlines like that.

Bruce

Approach to science and other comments

Posted by Andrew Wadge on 30/11/2007 - 17:22

Thanks for all your responses. I think we all need to be vigilant about taking an objective approach to what the science says and keeping an open mind, and this is what we strive to do.

As I said in my previous blog about the Daily Mail article, whilst individual studies can lead to conflicting opinions, we always base our advice to the public on an assessment of all of the available evidence, guided by independent experts, rather than the views of one individual scientist.

The Agency’s recommendation to consume no more than 6g/day of salt is based on advice from the Scientific Advisory Committee on Nutrition (SACN). There is a considerable body of evidence for the relationship between sodium and blood pressure, which is detailed in SACN’s report Salt and Health which was published in 2003. SACN considered a wide range of evidence from over 200 studies and concluded that there was clear evidence for a link between dietary salt and blood pressure.

Furthermore, hypertension is a serious public health problem in the UK. The 2003 Health Survey for England showed that about one-third of adults have hypertension which becomes an even more serious problem as we get older with 64% of men and 75% of women aged over 75 years having hypertension. The survey also found that 43% of people with hypertension were undiagnosed and 58% of those diagnosed were not receiving any anti-hypertensive treatment.

Since the risk of hypertension is so widespread, the population as a whole is at a relatively high risk of premature mortality. Additionally, the risk from CVD associated with hypertension is not just restricted to hypertensives but includes people with normal blood pressure. A large Service Unit (Prospective Studies Collaboration, 2002) which combined the results of 61 studies of blood pressure and mortality, with data for one million adults with no history of CVD, found a continuous relationship between increasing blood pressure, from as low as 115/75 mm Hg (normotensive), and risk of death from CVD.

Overweight and obesity is usually assessed by body mass index (BMI). In the UK, advice from the Department of Health, which is endorsed by the National Institute of Clinical Excellence, is that overweight (BMI of 25-29.9) and obesity (BMI of 30 and above) pose a major risk to health by increasing the likelihood of chronic diseases including CVD, hypertension, and type 2 diabetes.

Evidence has consistently shown that adults with BMI above 30 are clearly at increased risk. However the evidence is more mixed for BMI of 25-30; so while the study you refer to suggests that the ideal BMI for morbidity outcomes may be 25-30, the scientific consensus is that a BMI above 25 increases the risk of several chronic conditions and as I stated earlier, our recommendations are not based on a single study.

Finally, the question about which type of salt is healthiest has been commented on. It is a common assumption that unrefined sea salt and rock salt are healthier than ordinary table salt which has been refined; however, sea salt, rock salt and table salt all comprise sodium (40%) and chloride (60%). Rock salt can contain traces of other essential minerals (mainly calcium and magnesium). However these are also found in a wide variety of foods including milk, fruits, and vegetables, which are far healthier sources of these minerals.

Although sodium is an essential nutrient, which plays a key role in maintaining the water balance of the body, evidence has shown that consuming too much sodium can raise blood pressure which increases the risk of having a heart attack or a stroke. The sodium contained in sea salt and rock salt is handled by the body in the same way as the sodium from table salt, so too much of these types of salt can also raise your blood pressure.

So the key message is try to keep salt intakes below 6g per day.

Approach to Science

Posted by Anonymous (not verified) on 22/11/2007 - 20:50

Andrew

I am becoming very worried about the one sided approach you appear to be taking on a number of issues where you appear very ready to discuss any science which matches the views you espouse but are silent or very disparaging about any reports that do not.

As I understand the Mail item they appeared to be making the very valid point that there is significant evidence that salt is an exacerbating factor in the hypertensive individual and can increase the pre-disposition in these individuals to develop CVD but that the rises in blood pressure seen from studies were not sufficiently pronounced to demonstrate that there is a causative mechanism between salt and the development of hypertension in the normotensive population.

Also the recent study from the USA indicating that the ideal Body Mass Index for morbidity outcomes may be 25-30 which would be classed as slightly overweight and today's report that the Foresight Report had significantly over-estimated the potential costs of obesity have been met with a deafening silence from yourself.

I would have thought that as the Chief Scientist you would be ingraining into all your staff the importance of maintaining an open mind and hence the value of reporting and discussing constructively all shades of opinion.

In response to your other correspondent, sea salt seems to be one of those trendy things that the wholefood lobby somehow seem to think is preferable. There is absolutely no difference in the sodium content of sea salt as opposed to any other salt and any other minerals are only present in such trace amounts that any nutritional benefit must be questionable.
It is therefore no better or worse than any other salt

salt & health

Posted by Bob Stevens, Public Analyst (not verified) on 22/11/2007 - 11:54

Francoise – I wish you well with your whole food cooking classes, and support you in encouraging the consumption of more home prepared food. However, the problem with salt is the sodium content and sea salt contains as near as makes no difference the same amount of sodium as table salt. The trace minerals it contains are just that, and the amounts potentially contributed are small.

Salt

Posted by Francoise Auvray (not verified) on 19/11/2007 - 13:29

What I think is confusing is that no distinction is made regarding the quality of salt. My understanding is that good quality sea salt is important in cooking to help the cooking of grains, vegetables, protein etc - it makes them more assimilable by the body. Sea salt also contains other minerals which are important for health. Also, it is important to use during the cooking time, not after (added on the table). However, what we don't need is the processed table salt found in most shops and processed foods etc. So may be the advice should be more on reducing already prepared food, restaurant meals in one's diet. I help run a centre in London where we give wholefood cooking classes and it is interesting to see that some people are very worried about using salt in cooking because of the message of 'salt is bad for you'. It might be worth being more clear about what is bad and what is good about salt. Sea salt is an essential food. Thank you