How Much Salt Is Too Much & What Are The Side Effects?
Article by Georgia Beaty BSC AFN Student and Imogen Stockman BSC AFN Student
So, What Actually Is Salt and Is It All Bad?
Salt (Sodium Chloride), a well debated nutrient, is essential in many functions in the body including fluid and electrolyte balance, muscle function and neuronal activity. Sodium plays a central role in the membrane potential for the majority of cells and in the action potential for the contraction of muscles (1).
Sodium can occur naturally in foods such as beets, mushrooms and milk, however, it is also added to foods for preservation and taste. Unfortunately, a diet with excess salt intake is a cause of high blood pressure which subsequently increases the risk of cardiovascular disease (CVD). Therefore, it is recommended in the UK that adults should have less than 6g/day of salt which is the equivalent of a level teaspoon (2). It is also a public health aim to reduce the intake of salt to 3g/day by 2025 as a prevention method for CVD; the leading cause of death in the world (3). The average intake of salt in the UK is around 8g/day, exceeding the recommendation. Foods high in salt can include ready meals, soups, cheese and savoury snacks. Despite the food industry in the UK showing success with a 20-30% reduction of salt in their products, 80% of our salt consumption is from these processed foods (4).
Salt, Blood Pressure, CVD and Brain Health
There have been a number of clinical trials that have confirmed the link between salt intake and a raise in blood pressure (hypertension). Essentially, salt consumption increases the presence of sodium in the blood which draws water into the arteries creating extra fluid that the kidneys struggle to remove, leading to increased blood pressure. It is very similar to when we eat salty snacks and quickly need a big gulp of water (ever wondered why they give you salty peanuts in a pub - so you buy more drinks!).
A long-term diet high in salt can lead to stiffer and thicker arteries to cope with the extra fluid. This may sound like a good thing, however, thicker arteries narrow the space that carries blood and oxygen, further increasing blood pressure. Damaged arteries can lead to reduced oxygen and blood reaching the heart and brain, severely compromising these vital organs. According to the World Health Organisation (WHO), high blood pressure is responsible for 62% of strokes and 49% of coronary heart disease (5). It is actually thought that high salt intake can have a direct and independent effect on risk of stroke, irrespective of blood pressure. To further confirm this link, many controlled trials have shown a reduction in salt in the diet can reduce CVD (6).
With regards to brain health, a study in rats showed a high salt diet caused cognitive impairment induced by hypertension. This also included memory decline and dementia-like symptoms in rats therefore salt could contribute to neurological disease in humans (7).
Is Pink Himalayan Salt Good for You?
Pink Himalayan salt has become a popular ingredient due to its fantastic pink colour. This tinted pink colour is actually from trace minerals such as potassium, magnesium and calcium which makes up around 2% of the salt content (98% is sodium chloride). Despite people claiming this is the healthier salt option, due to the very small content of these trace minerals, those who opt for pink salt are unlikely to reap any significant benefits due to the small amounts consumed.
Should Salt be Iodised In The UK?
In some countries, table salt is iodised in order to meet requirements for iodine. Iodine is a mineral important for the production of thyroid hormones, needed for a variety of functions within the body such as brain development, growth and a healthy metabolism. However, the UK has not made iodised salt mandatory (8). An alternative to table salt would be preferred to prevent contradicting advice on the consumption of salt and keeping the main health priority focused on reducing salt intake for prevention of hypertension and CVD.
Can Potassium Protect The Effects of Sodium?
Interestingly, a high intake of fruit and vegetables can have a protective effect on hypertension and help to lower risk of CVD. It is the potassium content in fruit and vegetables that has the opposite impact of sodium (5).
Salt or Sodium?
Some food labels only show the sodium content and not the salt content which can be confusing! To convert sodium to salt, multiply the sodium amount by 2.5, e.g. 1g of sodium per 100g is 2.5g of salt per 100g. The recommended 6g of salt per day is equivalent to 2.4g of sodium per day.
How Can We Reduce Our Salt Intake?
• Try to avoid adding table salt when cooking or at the table, but if you do choose to add salt, just add a small pinch.
• Prepare your own meals using fresh foods such as fruit and vegetables to manage how much salt is added.
• Rinse canned foods which are soaked in salt water such as tuna, beans and vegetables.
• Be aware of foods high in salt such as meat (including processed meat), cheese, ready-made soups, ketchup, soy sauce, stock cubes, gravy powder, tinned food containing salt, salted snacks such as crisps, nuts, biscuits, popcorn, ready-meals, takeaway meals, bread.
• Try to choose foods with less than 0.3g/100g of salt which will be shown on food labels.
• Use alternatives such as herbs and spices to add extra flavour to food and also have additional health benefits including anti-inflammatory and cholesterol-lowering effects.
The British Dietetic Association (BDA) have perfectly summarised what we have discussed; “Most of us are still eating too much salt. High salt intake lead to high blood pressure that can pose significant health risks. Reducing your intake of salty foods can dramatically improve your health outcomes” (9).
This blog post was written by Georgia Beaty (BSc Biomedical Science, MSc Clinical Nutrition, AfN) and Imogen Stockman (BSc Human Nutrition, AfN) who are currently studying a postgraduate degree (PGDip and MSc) at King’s College London to qualify as Registered Dietitians (RD). Imogen and Georgia work together to share interesting content on popular topics in the nutrition and dietetic world, you can find them on Instagram @dietitians_UK.
References:
1.Kaushik S, Kumar R, Kain P. Salt an Essential Nutrient: Advances in Understanding Salt Taste Detection Using Drosophila as a Model System. Journal of experimental neuroscience. 2018 Nov;12:1179069518806894.
2.Salt SA. Health report. London The Stationery Office. 2003.
3.Cappuccio FP. Expert testimony on salt and cardiovascular disease. NICE CVD guidance expert testimony paper. 2009 Feb 9;3.
4.Ji C, Kandala NB, Cappuccio FP. Spatial variation of salt intake in Britain and association with socioeconomic status. BMJ open. 2013 Jan 1;3(1):e002246.
5.World Health Organization. The world health report 2002: reducing risks, promoting healthy life. World Health Organization; 2002.
6.He FJ, MacGregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. Journal of human hypertension. 2009 Jun;23(6):363-84.
7.Guo CP, Wei Z, Huang F, Qin M, Li X, Wang YM, Wang Q, Wang JZ, Liu R, Zhang B, Li HL. High salt induced hypertension leads to cognitive defect. Oncotarget. 2017 Nov 10;8(56):95780.
8.Bath S, Rayman M. BDA food fact sheet–iodine. 2013.
9.Daniels, L. BDA food fact sheet: salt. 2016.