Salt. That tasty, little white crystal that gives French fries a certain something, that made salted caramel a “thing” and is found in almost every food imaginable. What’s the latest on salt? Whether it’s from the Himalyas, pink, white, or otherwise, salt is a chemical compound made up of sodium and chloride. In fact, about 40% of salt is sodium (60% chloride).
Sodium, while an important mineral to the body, is responsible for a multitude of functions including nerve transmission, balancing fluid levels, which affects blood volume and blood pressure.
A lot of people think of sodium and salt as being synonymous, which isn’t quite right, since sodium is only a part of salt. However, sodium is the mineral oft found in our day-to-day eating that seems to be the problem. Why?
How sodium is a problem?
Because sodium impacts fluid balance in the body, excess amounts can shift this delicate balance. When this happens we see an increase in blood volume, and with this increase in volume, there is an increased workload on the heart. This increased workload causes a rise in pressure within the heart, which we can measure with blood pressure (using a fancy instrument with an equally fancy name, sphygmomanometer). A normal reading is 120/80 mmHg (millimeters of mercury) and a high reading is 140/90 mmHg (130/80, if you have diabetes) (great resource here).
Sodium in the food supply
Sodium is naturally occurring in many foods such as milk, meat, even celery and beets contain some sodium in their raw form (though not a lot). The bigger issue in our food supply is added salt in the diet. This is when food manufacturers add salt or other sodium-containing ingredients (e.g. MSG) to foods for preservation, flavour enhancement, to retain moisture, texture or other reasons. This is where the problem lies.
Traditionally high sodium containing foods tend to include convenience foods, which typically include processed options and fast food meals. More often we see canned goods, like soup and canned vegetables, in this category, but also frozen dinners, deli meat, cheese, pasta sauce, chips and so on.
What does the evidence say?
There is a significant body of evidence from years of scientific studies that indicate reduced sodium consumption lowers blood pressure, in both groups with normal blood pressure and high blood pressure (aka hypertension). As we age, regardless of our blood pressure in our younger years, this pressure naturally rises. Given that many of the foods we eat supply a large amount of this sodium, it makes sense that we reduce our intake of high sodium containing foods.
In Canada, the average sodium intake is roughly 3500mg a day. The current guidelines recommend between 1500- 2300 mg per day (ages 14-50 years). The lower end of this range is the recommended daily intake (RDI), which decreases as we get older (age 51-70 = 1300 mg; age 71+ = 1200mg) (more details here). The top end of the range is termed the tolerable upper limit (UL), that is, the maximum amount recommended before it becomes unhealthy. Obviously, this is a population-based guideline and certain individuals may have different recommendations based on their health, i.e. low blood pressure, kidney disease and so on. If you’re unsure, talk to your family doctor or registered dietitian about what’s best for you.
A recent meta-analysis study (2014) turned the current guidelines on their ear by highlighting issues with too much of a sodium restriction. The study authors stated that strict sodium recommendations aren’t associated with a decrease in all-cause mortality. That is, if you eat less sodium in your diet, your chances of dying from any causes may not necessarily be lower. They also found an association of risk being higher in both low sodium and high sodium groups, but not in moderate sodium users. However, they did find that risk levels were lower if high intake users decreased their intake. You can just see the confusing headlines…
Beyond this, was an even more recent study from Canada’s McMaster University, which showed increased risks for heart disease, hypertension and mortality with high intakes of sodium. The risks, however, were most significant in people who were already hypertensive, not in people who had normal blood pressure.
What we can extrapolate from all this is that the risk seems highest in populations who are pre-hypertensive and hypertensive, and they are the ones who are likely to benefit most from sodium reductions in their diet. The rest of us, can’t just live it up and scarf down salt by the bucketful, but awareness and healthy choices, will likely suffice. Our sodium guidelines have not changed and we still recommend a balanced diet that is moderately low in sodium, with no more than 2300mg sodium as our upper limit.
What can we do about it?
One of the best ways to lower sodium is look at the proportion of convenience foods (pre-made, from a box/can/container, take away meals, etc.) in your diet vs. fresh, whole food choices. Evidence points us to the DASH diet, which is an acronym for Dietary Approaches to Stop Hypertension, a study that was published in the New England Journal of Medicine.
The DASH diet is high in fruit, vegetables and low fat dairy products with an emphasis on whole grains, less saturated fat, red meats, and refined sugar, and including nuts, seeds and legumes several times a week. I’m usually the one to say, “stay away from diets, diets don’t work!” But, to me, this is simply healthy eating, not a restrictive diet per se. Let’s focus on eating more fruit and vegetables, whole grains and high fibre starchy foods, moderate dairy, and lean protein with an emphasis on plant-based protein foods (dried beans, lentils, soy, nuts & seeds) as well as some poultry and fish, and a wee bit of red meat if you have to. If you can eat healthy food options like these more often, your heart and body will thank you. Advice like this is worth its salt.
Blood Pressure Canada (2015). Sodium policy. http://www.hypertension.ca/images/uploads/bpc-sodium-policy-with-endorsementskidney-foundation.pdf
Graudal et al. (2014). American Journal of Hypertension 27(9) http://ajh.oxfordjournals.org/content/27/9/1129.full.pdf+html
Mente, A. (2016). Lancet. http://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(16)30467-6.pdf
Sacks et al. (2001). A clinical trial of the effects of dietary patterns on blood pressure (DASH). NEJM. 344:3-10.
Sodium calculator (2015): https://www.projectbiglife.ca/sodium/
Sodium in the diet: https://www.nlm.nih.gov/medlineplus/ency/article/002415.htm
World Health Organization. (2015). Sodium guidelines. http://www.who.int/elena/titles/sodium_cvd_adults/en/