The Swiss have a 26% prevalence of hypertension in their general population with 50% hypertension in those more than 60 years old. The medical community in this country is seeking a strategy to reduce salt to prevent hypertension. The article (1) to be discussed in this post presents the reasoning behind their strategy.
Countries To Successfully Reduce Salt Intake
There are 6 countries that have reported positive results from reducing the sodium in their population's diet. These countries have not let the disputes that we have discussed in the past few posts hold them back. Finland was the first of these countries and started its program in the 1970s. It has been able to reduce its prevalence of cardiovascular disease and stroke by 60%, as we've discussed in this post.
Since then other countries to reduce salt intake include Great Britain, France, Ireland, Japan, and the most recent is Portugal. These countries also have reported improvements in health. Great Britain between 2003 and 2011 reduced the average intake in their population by 1.4 grams of salt per day. This reduced the average blood pressure and the number of cardiovascular events in their population. However, as with most other countries that reduce salt intake, Great Britain also reduced the amount of smoking and cholesterol, and increased the potassium intake in the population. This makes it difficult to figure out how much each of these factors contributed to the improvement.
Switzerland has already assessed their population's salt intake and prevalence of hypertension. The Swiss found a mean salt intake of 10.6 g/day in men and 7.8 g/day in women. The prevalence of hypertension is 32.3% in men and 19.1% in women.
They started a program with many of the same approaches used by other national programs. The Swiss authorities began to encourage voluntary salt reduction by the food producers. They began improvement in labeling of food products. And they started several research projects to test the feasibility of lowering the salt content in some basic food products.
The goals that Switzerland is considering come from publications that we have discussed in many of our posts, such as Intersalt and TOHP. Because of the disputes in the literature, such as the U-curve sodium-mortality association and the determination of salt sensitivity, they also have concerns about some of the details of their strategy.
Concerns About Sodium Reduction
One of the major concerns was the effect that a reduction of salt will have on children. They were seeking the correct reduction that will not be harmful. They were aware that the salt level in a child's food tends to define the level consumed as an adult. The Swiss also questioned the amount of reduction that should occur in, and the effect on, pregnant women, fetuses, and the newborn children. There may be a need for a higher level of consumption in these groups.
They also questioned whether the strategy should be used on the general population or just the high risk population. They had concern about the risks of the low salt diet, and the effect of salt sensitivity. They pointed out that there is no definitive evidence that high risk patients are improved by a low salt diet.
We feel that this is an area they should be concerned about. These high risk patients are the least likely to be improved by a low salt intake. If the patients already have end-organ damage, a low salt diet may not improve their condition. The end-organ damage results in reduced function because the functional cells are replaced by non-functional scar tissue.
A low-salt diet will not regenerate normally functioning cells, and it will not replace these areas of scar tissue with normally functioning cells. It could lead to increased mortality in some subgroups of ill patients. For example, it could lead to too little blood volume to adequately fill the heart in hypertensive heart failure patients.
However these patients should be under the care of a physician. The effect of the sodium in the patient's diet should be monitored and adjusted according to its effect.
The Swiss are also concerned that there may be a difference in salt sensitivity in people. A different approach may be needed based on salt sensitivity. The salt sensitive people may be the ones that would benefit the most from less salt.
Salt sensitivity is still an area of discussion in the medical community. It is not certain whether there are groups who have a separate salt sensitivity that differs qualitatively. Some studies indicate that genetic differences may indicate a Gaussian distribution of salt sensitivity rather than a bimodal distribution. But if salt sensitivity has a Gaussian distribution, those at the high end of the spectrum could still be considered salt sensitive, and would still have greater gains from a salt restricted diet.
The Swiss Plan At Present
Overall the Swiss are taking a cautious approach. Their plan is to reduce salt consumption below 8 g/day within 4 years and below 5 g/day in the long-term. They are also going to try to monitor salt consumption in their country, and increase the information available to physicians and patients on the risks of the high salt diet. They intend to improve the labeling of their food products and also convince the food industry to progressively reduce salt content in their products.
1. Salt, blood pressure and cardiovascular risk: what is the most adequate preventive strategy? A Swiss perspective. Burnier M, Wuerzner G, Bochud M. Front Physiol. 2015 Aug 13;6:227. doi: 10.3389/fphys.2015.00227. eCollection 2015.