Salt Isn't Your Enemy: Why Your Body Needs It

Salt has a public relations problem. The headlines say less is better. The biology says the dose makes the poison. Sodium is essential for nerve transmission, muscle contraction, blood volume, and hydration. Without enough, the body falters. With too much, persistent over years, blood pressure climbs and cardiovascular risk rises. The truth sits in the middle and most UK adults are above the sensible range, not below it.

Public Health England advises UK adults stay under 6 g of salt a day (about 2.4 g sodium). The latest National Diet and Nutrition Survey data show the average UK adult eats around 8.4 g a day, mostly from processed food. The over-consumption sits in bread, processed meat, ready meals and sauces, not the salt shaker on the table.

Sources: Public Health England. UK NDNS. O'Donnell M et al. NEJM. 2014 (PURE cohort).

Why your body needs sodium

Sodium is one of the most important electrolytes in the body. Every contraction, every nerve signal, every shift of fluid across a cell membrane depends on it.

• Plasma volume and blood pressure. Sodium pulls water with it. Plasma volume controls blood pressure within a safe range. Too little sodium drops volume and triggers symptoms (lightheadedness, fatigue, cramps).
• Nerve and muscle function. The action potential that fires a nerve signal or a muscle contraction depends on sodium crossing the cell membrane. Low sodium impairs both.
• Glucose and water absorption. The sodium-glucose cotransporter (SGLT1) in the gut pulls water and glucose across the intestinal wall together. This is the basis of WHO Oral Rehydration Solution, credited with saving tens of millions of lives.
• Adrenal and thyroid signalling. Sodium works alongside potassium, magnesium, and calcium in the broader electrolyte system that supports hormonal balance.

When more sodium becomes a problem

Persistent intakes above the body's needs raise blood pressure in salt-sensitive individuals. The 2014 NEJM PURE cohort analysis (O'Donnell et al.) tracked over 100,000 adults across 17 countries. Risk of cardiovascular events and mortality rose at both extremes: very low (under 3 g sodium per day) and very high (over 6 g sodium per day). The sweet spot sat between 3 and 6 g of sodium per day, equivalent to 7.5 to 15 g of salt.

The PURE findings caused controversy because they conflicted with the long-standing public health line that lower is always better. NICE clinical guidance for hypertension still supports lowering salt in adults with raised blood pressure (NG136), and BHF guidance follows. For adults with normal BP and no kidney disease, the data suggest the harm sits more at the upper end of typical UK intake than at the recommended limit.

Where most UK sodium comes from

Most adults dramatically overestimate the salt they add at the table and dramatically underestimate the salt baked into processed food. The five categories below account for the majority of UK salt intake.

Reading labels in 5 seconds. UK traffic lights flag salt red above 1.5 g per 100 g, amber between 0.3 and 1.5 g, green under 0.3 g. Choose green on the staples you eat daily; the occasional red item across a week is fine.

When you may need more sodium, not less

Endurance athletes, adults who sweat heavily, and those on low-carb or ketogenic diets often need more sodium, not less. A long ride, a hot training session, or a couple of months on keto can drop body sodium meaningfully. Symptoms include headache, lightheadedness on standing, cramps, brain fog, and salt cravings.

A pinch of salt (around 1 g of salt = 400 mg sodium) in water on a hot training day, or alongside a sweaty long run, is sensible. Adults following keto often add 2 to 4 g of salt above their food intake during the first weeks of adaptation. None of this applies to adults with hypertension, kidney disease, or heart failure, where the GP's specific advice overrides general guidance.

A balanced UK approach

• Cook from scratch more often. Home-cooked salt is usually a fraction of restaurant or processed-food salt.
• Read the back, not the front. Use UK traffic-light labels. Green and amber on staples.
• Swap salt for flavour. Lemon, garlic, herbs, spices, vinegar carry flavour without the sodium load.
• Watch the hidden five. Bread, processed meat, ready meals, sauces, cheese.
• Add salt during heavy training or hot weather. A pinch of salt in water counts as smart electrolyte management, not a public health crime.
• Follow specific guidance if you have a condition. Hypertension, kidney disease, heart failure: do what your GP advises.

Frequently asked questions

Bottom line

UK adults eat more salt than is sensible, but the answer is not to fear the salt shaker. The answer is to cook more, shop the traffic lights, and target the hidden five (bread, processed meat, ready meals, sauces, cheese). Athletes and adults on low-carb diets often need more sodium, not less. People with hypertension or kidney disease follow specific clinical advice. Everyone benefits from understanding that the dose makes the poison.

Sources

1. O'Donnell M, Mente A, Rangarajan S, et al. Urinary sodium and potassium excretion, mortality, and cardiovascular events. N Engl J Med. 2014, vol 371, issue 7, pages 612 to 623.
2. Public Health England. Salt: NDNS data and UK reduction programme. gov.uk
3. National Institute for Health and Care Excellence. NICE NG136: Hypertension in adults: diagnosis and management. nice.org.uk/guidance/ng136
4. NHS. Salt: the facts. nhs.uk