Channel 4’s Dispatches series recently broadcast a programme where they had been investigating the amount of salt in processed food. They sort of assumed we already knew what the problem with eating too much salt is. They mentioned that it led to a high blood pressure.
This sounds bad because it obviously should be normal and not high. But what actual symptoms does high blood pressure cause? The answer is not many and they only occur rarely. But those symptoms are related to poor heart function and include fatal heart attacks. So although it’s a low risk, it’s a low risk of something that is pretty serious.
It makes sense of course. Your heart pumps your blood so this is going to be harder work if your blood is at a higher pressure. But the programme also mentioned another consequence of salt consumption that I hadn’t heard before.
The presenter doubled the amount of salt she ate for a week. This probably sounded like a much better idea when they thought of it than it turned out to be in the programme itself. On screen it looked very much like someone eating a perfectly ordinary food. And given that they hadn’t established the risk of a high salt diet very strongly it didn’t really have that much dramatic tension.
But there were some interesting bits.
I learnt something that I had never thought to question before. If it says on a label that a product contains 1 gram of salt, how accurate does that value have to be? It turns out that the manufacturers can have up to 20% either side. So it could be 0.8g or 1.2g. Food is pretty variable stuff so it is fair enough to give the food makers some leeway. But the Dispatches team went to the trouble of actually taking products off the shelf and testing them for their salt content.
Most were within the permitted tolerance. But interestingly the majority had salt levels that were greater than the label claim. This suggests to me that many food manufacturers do have a higher degree of control over their salt content than the regulations assume and are choosing to game the system to make their products look as good as they can. In a competitive market it is hard to imagine them doing any differently, but it is worth bearing in mind if you are trying to limit your salt intake. And maybe this is something the legislators might want to consider. If the manufacturers can add 20% extra salt that soon mounts up. The recommended daily intake is 6g, If you add 20% that means if you read the packs and think you are hitting the target you might be nearer to 7.2g, which is enough to make a difference.
A lot of people count the calories they eat. I don’t think anywhere near as many track their salt intake as closely. But if you are you should probably assume the figures on the packs are underestimating by around 5 or 10%.
The presenter’s experiment with a high salt diet was not particularly good television because it turned out not to greatly affect her life in any obvious way. But there was one thing that was quite intriguing. She instantly put on about 3 kilograms in weight. This was due to water retention. There is nothing particularly mysterious about this. All other things being equal anything with a higher salt content is going to hold onto more water. This is one of the motives for including so much of it in processed food. It stops it from drying out so quickly.
But I was surprised by how big the effect was. The presenter had a telegenic willow like figure that I estimated must weigh about 65 kilograms – so that was an increase of about 5%. That seemed a lot. I did my own experiment. I didn’t dare double my salt intake. As a middle aged male with a distinctly non-television friendly level of body weight I am at way higher risk of a heart attack. Instead I cut salt out altogether and lost a kilogram in 48 hours. This is, sadly, only a bit over 1% of my body weight. But nonetheless it confirmed that salt could have a rapid and significant effect on body mass. The speed it worked at surprised me, but I suppose it really shouldn’t have. Salt dissolves quickly and can get through the whole body quickly so it makes sense that its effects can be felt more or less straight away. It is a good job I am not cynical, because it would be a great way to get a noticeable weight reduction over a weekend at a spa for example. Just eat mainly salad and you are there.
I imagine its effects on blood pressure would be equally rapid as well. I dare say this has been studied but there is so much published on this subject that I couldn’t find any actual data with a quick online search.
So to get back to my question, should we be avoiding salt? High blood pressure is not desirable but it doesn’t seem to be that bad on a day to day basis if you aren’t in a high risk group for heart disease. But it could be quite bad if combined with strenuous exercise. I am not qualified to give out medical advice, but here is what I take away from it. I think if I were planning to run a marathon, go to a disco or move house I’d certainly think it a good idea to avoid salty foods for a day or two in advance. On a more general level, we do eat a lot more salt that we have evolved to. There doesn’t seem to be any indication that this gives us any long term problems – life spans are still increasing after all. And salt does make things taste better. Or does it?
Another thing they did on the programme was that they replicated a study that indicated that although people like bread with a lot of salt in it, they could hardly tell the difference between the standard level and bread with half the level. This is quite interesting because most of the salt we eat comes not from the salt cellar but from processed food. One of the arguments the food industry puts forward is that we like the taste of salt so they have to use a lot in their products or we won’t eat them. I am not a food scientist but I would hazard a guess that the salt has rather more benefits to the manufacturer than simply making things taste nice. Looking at the levels of salts quoted for the products in my larder I find that there is loads of the stuff in everything.
This has led campaigners to push for lower salt levels in processed food. The government has picked up on this and has put pressure on the food industry and brought in regulations to bring down the levels slightly. This has had some effect, though there is still a lot of salt in the kinds of things most of us eat most of the time. I think it would be hard to describe this as a public health triumph, even if it has probably done some good.
I think in any case I would rather eat processed food that has been made following the logic of what makes a good processed food. Reducing the salt level might make it slightly healthier, but it still isn’t real food. It will still have high levels of sugar and low levels of vitamins. I think it is better to leave processed food as it is and treat it as something only to be eaten when you are short of time. There are times when a tin of baked beans or a burger are just the ticket. But they are not the ideal thing to be eating regularly, even if the salt content was lower. Processed food should be regarded as a food substitute or a rare treat, not a staple.
(This link shows that our high salt diet is clearly not natural, though that doesn’t in itself necessarily mean it is harmful.