Salt linked with stubborn blood pressure problems

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Last Wednesday I wrote about ‘mindful eating’, and mentioned I was in the process of reducing my own weight. Actually, I don’t really care about my weight, it’s fat I’m attempting to lose. My aim is to improve my body composition, and to this end weight is relatively irrelevant. However, I confess that I have been weighing myself daily, along with taking other measurements, to get as complete a picture of my changing body as possible.

I’ve plotted my weight loss on a graph, and after a rapid drop, my loss appears to have been quite consistent with, obviously, a bit of wavering from day-to-day. Except for one day, when my weight jumped up a pound and a half, but came down to ‘normal’ the following day.

When I look at the graph, this day sticks out like a sore thumb. What happened? Well, the evening before I was at a Portuguese barbeque (the Portuguese may be relevant, as you’ll see). I ate nothing different and no more than normal. I had barbequed chicken and pork, and green leafy salad. There was a lot of my favourite beer around, and I didn’t want to be tempted due to thirst, so I drank a lot of water. So, how come the following day my weight was up a pound and a half?

I think the answer is most likely to be ‘salt’. The Portuguese put a lot of salt in and on their food. One potential risk of excessive salt consumption is raised blood pressure, which itself is a risk factor for cardiovascular disease, particularly stroke. When I’m in Portugal, I am amazed at the number of not-so-elderly people who have been affected by ‘thrombosis’ (the common expression for stroke in Portugal). My brother-in-law, an expert in stroke, informs me that Portugal is regarded as the stroke capital of Europe. Salt, I suspect, has a lot to do with it.

So, one thing I remember about the food at the barbeque is that it tasted really salty. When salt levels in the body are high, the body tends to retain fluid (in an effort to dilute the salt). My suspicion is that my little blip in weight was down to this and nothing more.

The relationship between salt, fluid levels in the body and blood pressure was highlighted recently in a study published on-line in the journal Hypertension [1]. In this study, individuals were put at different times on low and high sodium diets, each for a period of a week. These individuals were all suffering from what is termed ‘resistant’ hypertension. Which means that despite multiple medications, the blood pressure remains high. The average number of medications taken by participants in this trial was 3-4. Average blood pressure was 146/84 mmHg.

The high sodium diet contained 5.75 grams of sodium (about 14.5 grams of salt) a day. The low sodium diet contained 1.15 grams of sodium (about 2.9 grams of salt) a day.

Compared to the high salt diet, the low-salt diet reduced blood pressure significantly: the systolic (higher) and diastolic (lower) blood pressure dropped by about 23 and 9 mmHg respectively. Chemical analysis of the blood revealed that this was most likely due to a reduction in blood (plasma) volume.

Those with raised or borderline raised blood pressure may like to consider cutting back on salt. 80-90 per cent of the salt consumed in the Western diet comes from processed foods, some of which are extremely salty but don’t necessarily taste it. For example cornflakes, gram for gram, contain as much salt as seawater. Processed food is the place to look to effectively cut down on salt intake. After that, we might consider limiting what we add during cooking and at the table too.

Another nutritional approach to combating high blood pressure is to increase intake of potassium (found, for example, in fruits and vegetables). For more on this, see here.


1. Pimenta E, et al. Effects of Dietary Sodium Reduction on Blood Pressure in Subjects With Resistant Hypertension. Results From a Randomized Trial. Hypertension 2009 Jul 20. [Epub ahead of print]

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