In 2020 the BMJ and Swiss Re Institute collaborated to produce a second series of articles on nutritional science. Included in these was a discussion around whether current guidelines around salt should be taken with the proverbial pinch. You can read the article and watch the presentations here.
In this blog we consider current intake and recommendations and where exactly where all this salt is coming from.
Goldilocks amount of salt
Salt is sodium chloride, you can multiply sodium by 2.5 to get the salt content of a food. Sodium is a trace mineral required in very small amounts in the diet. It is absolutely essential for health. In combination with other minerals and electrolytes, it supports normal cellular, muscular and nerve functions. However, too much salt can contribute to excess water retention and raise blood pressure in some adults.
Current recommendations call for less than 6g of salt/ 2.4 g sodium per day. The average daily salt intake in Ireland is high – approximately 10g in adults. Measurement of sodium intake is far from an exact science however. Unless done in controlled feeding studies, self-reported intake and the use of food diaries is fraught with error and under reporting. The estimated global intake is similar to Ireland at 9g of salt/ 3.6 g sodium to 10g of salt/ 4 g sodium per day 1, 2. USA, Canada and UK also call for intake to be lowered to approx. 6g of salt/ 2.4 g sodium per day but other health bodies such as the American Heart Association would prefer an ideal limit of 3.75g of salt /1.5g sodium per day for an adult, in particular for hypertensive adults. Other sources do not support lower limits 3.
The Dietary Approaches to Stop Hypertension or DASH study is perhaps the most well-known study in relation to a causal relationship between sodium levels and hypertension. DASH was a feeding study with randomisation to DASH or control diets with high, medium, and low salt intake, approx. 8.25g, 6g and 3.75g respectively for 30 days. The DASH diet was rich in fruit, vegetables, low-fat dairy products and a reduced total and saturated fat intake. Eligible participants were aged 22 years or older, had blood pressure of 120-159/80-95 mm Hg, and were not taking anti-hypertensive medication. It found a graded reduction in blood pressure with lower sodium intake, with a stronger effect among those with hypertension at baseline 4.
This is important as cardiovascular disease (including heart disease and stroke) is the single highest cause of death in Ireland, accounting for approximately 40% of all deaths. Hypertension is one of the major modifiable causal factors in the development of cardiovascular disease.
Where is our salt coming from?
It is estimated that about 15-20% of total dietary sodium intake is from salt added at the table or in cooking. This is referred to as discretionary intake. 15% comes from naturally occurring sodium in unprocessed foods and about 65-70% from processed foods. Two food types in particular – processed meats and bread account for over 50% of salt intake from foods, with the remainder contributed by various other processed foods, including well loved and often consumed breakfast cereals and confectionary. Given these sources, it is apparent how an overall reduction of processed foods may result in a natural reduction in salt and (if replaced with whole foods) an increase in vitamin, mineral and phytonutrient intake. All protective of good health and a reduction in chronic disease risk.
Whilst 6g of salt may be considered an achievable goal for the population it is still perhaps not optimal. Other sources would maintain that 4g salt per adult per day is sufficient to meet the physiological needs of 97.5% of the population. That said, as long as your diet is one based on whole foods lower in sodium then adding some sea salt to cooking shouldn’t pose a risk for most people. Interestingly, evidence also suggests that salt taste thresholds fall with decreasing intake. Food with a high salt content becomes less palatable after a period of a lower salt intake 5.
Of course, our food still needs to have flavour but we probably don’t need the amount of salt we add at the table and we certainly don’t need salt coming from processed foods. Instead of salt, try flavouring your food with other options such as nutritional yeast, garlic, herbs and spice mixes or lemon, lime or balsamic vinegar. We love this easy tomato vinaigrette.
- 1 large ripe tomato, seeds removed and roughly chopped
- 1/3 cup olive oil.
- Few leaves of fresh basil (optional)
- Salt and pepper to taste
Directions: Using a hand blender combine the ingredients and use to dress a mixed salad or as a dip for vegetable sticks
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- McCarron, D. A., Kazaks, A. G., Geerling, J. C., Stern, J. S., & Graudal, N. A. (2013). Normal range of human dietary sodium intake: a perspective based on 24-hour urinary sodium excretion worldwide. American Journal of Hypertension, 26(10), 1218-1223.
- Powles, J., Fahimi, S., Micha, R., Khatibzadeh, S., Shi, P., Ezzati, M., … & Global Burden of Diseases Nutrition and Chronic Diseases Expert Group (NutriCoDE. (2013). Global, regional and national sodium intakes in 1990 and 2010: a systematic analysis of 24 h urinary sodium excretion and dietary surveys worldwide. BMJ open, 3(12), e003733.
- Graudal, N. (2016). A radical sodium reduction policy is not supported by randomized controlled trials or observational studies: grading the evidence. American journal of hypertension, 29(5), 543-548.
- Sacks, F. M., Svetkey, L. P., Vollmer, W. M., Appel, L. J., Bray, G. A., Harsha, D., … & Cutler, J. A. (2001). Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. New England journal of medicine, 344(1), 3-10.
- Suckling, R. J., & Swift, P. A. (2015). The health impacts of dietary sodium and a low-salt diet. Clinical medicine (London, England), 15(6), 585–588. https://doi.org/10.7861/clinmedicine.15-6-585