Salt in POTS: evidence and everyday practice

Most people with POTS are running on too little blood. Multiple imaging and tracer studies put the plasma volume deficit at roughly 10 to 20 per cent, and the body’s usual hormonal fix for that, the renin-angiotensin-aldosterone system, misfires in ways that make the shortfall self-perpetuating. That is why sodium, a nutrient the rest of the population is told to cut back on, sits at the top of almost every international guideline for POTS. This post walks through what the physiology actually says, what the major cardiology societies recommend, how to raise intake without living on crisps, and ten recipes that put the theory on a plate. As with ivabradine or low-dose naltrexone, the evidence is real but not limitless; expect nuance rather than miracles.

For a broader overview of salt alongside fluid and compression as a combined non-pharmacological strategy, see the salt, water, compression, and electrolytes evidence review. This post goes deeper on the physiology and practical sodium delivery specifically.

The mechanism, in plain language

On standing, something like 500 to 1000 ml of blood pools in the legs and splanchnic veins. Return to the heart falls, stroke volume drops, and the baroreflex fires off a wave of sympathetic activity to keep blood pressure up. If your starting plasma volume is already low, the same orthostatic challenge hits harder: a smaller preload means a bigger fall in stroke volume, which the body compensates for with a bigger jump in heart rate. This is a large part of what the NASA lean test and tilt-table are measuring.

Dietary sodium matters because it is the dominant osmotic driver of extracellular fluid. Eaten with enough water, salt draws fluid into the vascular compartment and expands plasma volume. More preload means a gentler reflex response on standing, so heart rate does not need to rise as steeply to keep you upright. In the one randomised crossover trial of dietary salt in adult POTS, six days of high-sodium intake (about 300 mmol, roughly 7 g sodium or 17 g salt) corrected the plasma volume deficit from minus 11 per cent to essentially zero, dropped standing noradrenaline from 959 to 753 pg/ml, and reduced the orthostatic heart rate rise from a median of 60 bpm to 46 bpm (Garland and colleagues, Journal of the American College of Cardiology, 2021). A subsequent systematic review of 14 studies in orthostatic intolerance syndromes put the average fall in orthostatic heart rate at about 4 bpm and symptom improvement in 62 per cent of patients, though the authors rated the evidence as low quality and noted short follow-up (Loughlin and colleagues, American Journal of Medicine, 2020).

Why the body does not fix this itself

A normally functioning kidney responds to low plasma volume by releasing renin, which generates angiotensin II and aldosterone, which then retain sodium and water. In POTS this loop is broken. Raj and colleagues described the “renin-aldosterone paradox” in Circulation in 2005: despite a measured blood volume deficit of nearly 700 ml on average, plasma renin activity failed to rise and aldosterone was about half that of controls. Stewart’s group later showed that plasma angiotensin II is, confusingly, elevated in the low-flow POTS subtype, and Mustafa and colleagues (Heart Rhythm, 2011) linked this to reduced activity of ACE2, the enzyme that normally degrades angiotensin II. This is a biologically interesting detail in the long-Covid era, because SARS-CoV-2 binds and downregulates ACE2; it offers one plausible thread connecting post-viral onset to the same hormonal pattern seen in classical POTS, and sits alongside the broader picture covered in long COVID, ME/CFS, POTS, and dysautonomia: making sense of overlapping conditions.

The clinical upshot is blunt: because the kidney is, in effect, salt-wasting, you have to replace what it will not retain. Fludrocortisone (a synthetic aldosterone analogue) does this pharmacologically. Dietary salt does it through sheer mass action. Reassuringly, Garland’s 2021 data show that the salt-wasting tendency does not prevent plasma volume expansion when intake is high enough; the kidney can be forced to play along.

It is worth saying what salt does not do. Even on 300 mmol of sodium a day, patients in the Vanderbilt trial still met heart rate criteria for POTS and still had abnormally high upright noradrenaline. Hypovolemia is a contributor, not the whole story, and not every patient has a measurable volume deficit; Stewart’s work located it mainly in the low-flow subtype. Salt is a foundation, not a cure.

What the guidelines actually say

The Heart Rhythm Society 2015 Expert Consensus (Sheldon and colleagues) recommends, for patients with known or suspected hypovolemia, at least 2 to 3 litres of water per day and roughly 10 to 12 g of salt, equivalent to about 4 to 4.7 g of sodium, using salt tablets if necessary. The Canadian Cardiovascular Society 2020 position statement (Raj and colleagues) sits just below this at at least 3 litres of fluid and 10 g of sodium chloride per day, delivered through food, sachets or tablets, and specifically suggests monitoring adherence with a 24-hour urinary sodium. The European Society of Cardiology 2018 syncope guidelines recommend generous fluid and salt intake without specifying grams. Patient organisations and autonomic centres (Dysautonomia International, PoTS UK, Vanderbilt, Standing Up to POTS) converge on 8 to 10 g of salt, or 3 to 4 g of sodium, daily, which is the figure most UK clinicians quote in clinic.

A quick translation, because UK labels are made to trip people up on this. One gram of sodium is 2.5 g of salt; conversely, one gram of salt contains about 400 mg of sodium. A level teaspoon of table salt weighs around 6 g and supplies roughly 2.4 g of sodium. UK packaging shows “salt (g)” front-of-pack, while American products, salt-tablet brands and most clinical papers show “sodium (mg)”. Getting the factor wrong in either direction is the commonest source of patients thinking they are well salted when they are not, or vice versa. The practical guide to increasing salt intake covers measurement and daily targets in more detail.

The sodium only works if the water comes with it. Salt raises plasma osmolality, which triggers antidiuretic hormone release and thirst; the retained water, not the salt itself, is what expands the vascular compartment. Most guidelines specify 2 to 3 litres a day, with a useful practical rule of thumb being roughly 250 to 500 ml of water per additional gram of sodium.

When salt is the wrong answer

None of this applies uniformly. The hyperadrenergic subtype of POTS, marked by a rise in systolic blood pressure on standing and high upright noradrenaline, can be made worse by aggressive salt loading; central sympatholytics or ivabradine often suit these patients better. The distinction between POTS subtypes and how it affects treatment choices is covered in more depth in the POTS and IST article. Salt is contraindicated, or needs careful oversight, in chronic kidney disease, heart failure, nephrotic syndrome, and uncontrolled hypertension. It interacts with fludrocortisone in ways that amplify potassium wasting, so electrolytes need checking. There is also a longer-term question, flagged by Raj, Opie and Arnold in Autonomic Neuroscience in 2022, about blood-pressure-independent effects of sustained high sodium on vasculature, bone and brain in a predominantly young, predominantly female population that may eat this way for decades. The honest summary is that short-term benefit is well demonstrated, long-term safety is inferred rather than proven, and anyone using salt as a mainstay of their treatment should have a clinician who knows what they are doing and a baseline set of observations to track. If you are preparing to discuss this with your GP, the appointment preparation guide covers how to frame the conversation.

Getting salt in without living on crisps

The trial evidence uses dietary sodium, not tablets, and for most people most of the time food is more agreeable than capsules. A single gram of sodium all at once tends to produce stomach ache and little else; spread through the day it actually stays in you. Vanderbilt’s clinic teaches a simple trick of putting a level teaspoon of salt into a small bag each morning and using it across meals, as a check on what has actually been consumed.

The morning is the hard part. Overnight recumbency promotes diuresis, so people with POTS wake hypovolemic, and symptoms are typically worst in the first hour after rising. A robust patient protocol, echoed by PoTS UK, Standing Up to POTS and the Lurie Children’s team, is to keep a bottle of water or electrolyte drink on the bedside table and drink 400 to 600 ml before getting out of bed, ideally with a pinch of salt or a salt capsule, before slowly moving from lying to sitting to standing. The same principle, front-loading fluid and sodium, applies before showers (heat dilates vessels and vasovagals love a hot shower), before prolonged standing and before exercise. If you feel close to fainting, PoTS UK’s advice of drinking two glasses of cool fluid quickly is well founded: rapid gastric distension itself produces a pressor response within minutes.

For fluids, most British sports drinks are a disappointment. Lucozade Sport has around 250 to 300 mg of sodium in a 500 ml bottle, perhaps a fifth of what a serious electrolyte drink delivers. The genuinely useful UK options are O.R.S Hydration Tablets (around 177 mg sodium each, NHS-prescribable, and sold at most chemists), Dioralyte sachets (about 300 mg sodium each, designed for gastroenteritis but widely used off-label), SOS Hydration (around 330 mg), and LMNT (1000 mg of sodium per sachet, imported via Healf and similar retailers, popular but expensive). A homemade WHO-style oral rehydration solution, which works because glucose actively co-transports sodium across the gut, is cheaper and just as effective: half a teaspoon of salt and six teaspoons of sugar dissolved in a litre of water, with a squeeze of citrus for taste, providing about 1170 mg of sodium per litre. Make it fresh each day.

Salt tablets earn their place when nausea, gastroparesis or sheer exhaustion make food unworkable, or when you need a precise, portable dose at school or work. SaltStick Vitassium capsules (250 mg sodium each, buffered with potassium citrate, marketed as a medical food for POTS and related conditions) are the most widely used in the UK and are generally better tolerated than plain sodium chloride tablets. Slow Sodium, at 391 mg of sodium per tablet, is prescribable on the NHS and is the standard if you need larger amounts under a specialist. Take any tablet with at least a glass of water and never as a substitute for fluid.

Where food will do the job, whole-food sources beat ultra-processed ones not for sodium content but for everything else that comes with it. Olives, anchovies, feta and halloumi, miso, soy sauce, smoked mackerel, capers, samphire, cured meats, sauerkraut, good stocks and decent bread deliver salt alongside protein, minerals, fibre and omega-3s. Living on instant noodles and ready meals will hit the target but drag micronutrient intake down and often irritates the gut and mast cells of patients with overlapping MCAS. A pragmatic rule is to build meals around two or three salty whole-food ingredients and use the salt cellar to fine-tune.

The type of salt barely matters. Table salt, sea salt, Himalayan pink salt and kosher salt are all 97 to 99 per cent sodium chloride; the trace-mineral differences are nutritionally negligible, you would need to eat well over a kilogram of pink salt to meet a day’s potassium requirement. The one meaningful variable is iodine. Unlike much of Europe, the UK has no mandatory iodisation policy, and only a minority of supermarket table salts are iodised (Bath and Rayman’s Public Health Nutrition work). Because POTS patients eat more salt than average and often drink less milk than average, deliberately choosing an iodised variety for at least part of your intake is a cheap way to cover iodine status. Avoid so-called “low-salt” products like LoSalt, which is two-thirds potassium chloride: the opposite of what you want, and unsafe in renal disease.

Tracking helps more than most people expect. UK labels give salt in grams per 100 g or per serving; imported products give sodium in milligrams. Cronometer has the most detailed micronutrient breakdown and is free; Nutracheck has the best UK supermarket barcode database. A once-a-month 24-hour urinary sodium, if your GP or autonomic specialist will arrange it, is the objective check that matches the Vanderbilt trial methodology and can surface both under- and over-shooting. For tracking your orthostatic heart rate response as part of the same picture, the NASA lean test and stand test logger are useful companions, and what I’m tracking and why covers how I tie these metrics together day to day.

Finally, the reasons to pause. Swollen ankles that leave sock imprints, a sudden weight gain of a kilo or two over a few days, persistent morning headaches that feel like they come from the back of the head, breathlessness at night, or a home supine reading above about 140/90 are all signals to stop pushing intake and speak to a GP. Confusion, muscle cramps or severe headache after heavy fluid intake without adequate salt can also suggest dilutional hyponatraemia, which is the mirror-image hazard. Pregnancy, childhood dosing and any new cardiac or renal diagnosis are specialist territory.

Ten recipes that carry their weight in salt

Every recipe below delivers at least 2 g of salt (roughly 800 mg of sodium) per portion while keeping the rest of the plate recognisable as real food. Sodium figures are calculated from typical UK supermarket labels and should be treated as approximate; check your own brands if you need precision. Low-effort flare-day options are marked.

1. Morning miso soup with silken tofu and spring onion (low effort, 5 minutes)

A gentle, warming way to put salt in before you are properly awake. Serves 1.

For one mug-sized bowl, rehydrate 1 teaspoon of dried wakame in a splash of just-boiled water for two minutes, then drain. Let the kettle cool for a minute (boiling water damages miso’s flavour) and measure 350 ml of hot water into a bowl. Whisk 1 heaped tablespoon (about 20 g) of white shiro miso into a ladle of the water until smooth, then stir back in. Add 80 g of silken tofu, cubed, the wakame, 1 finely sliced spring onion, a pinch of toasted sesame seeds and a few drops of toasted sesame oil.

About 2.5 g salt, 1000 mg sodium per serving. Roughly 8 g protein plus iodine from the seaweed.

2. Anchovy, lemon and rocket spaghetti

A 15-minute storecupboard pasta in which anchovies melt into garlicky oil and stop tasting fishy. Serves 2.

Cook 180 g of wholewheat spaghetti in unsalted water until al dente, reserving a mugful of cooking water. Meanwhile, warm 3 tablespoons of olive oil over low heat, soften 3 thinly sliced garlic cloves for a minute, then add 10 chopped anchovy fillets in oil (about 40 g) and half a teaspoon of chilli flakes; stir until the anchovies dissolve. Off the heat, add the zest of 1 lemon and a splash of pasta water to emulsify. Toss with the drained spaghetti, the juice of the lemon, 60 g of wild rocket and half of 25 g of grated Parmesan. Finish with the rest of the Parmesan, black pepper and a final anchovy per plate if you fancy it.

About 2.3 g salt, 920 mg sodium per portion.

3. Halloumi, watermelon, mint and black olive salad (low effort, 10 minutes)

Salty squeaky cheese against cold sweet watermelon; no oven needed. Serves 2.

Griddle 180 g of halloumi, sliced 1 cm thick, brushed with 1 teaspoon of olive oil in a dry pan over medium-high heat for 1 to 2 minutes a side. Arrange 400 g of cubed ripe watermelon, 60 g of pitted Kalamata olives, half a small red onion very thinly sliced and a small handful of fresh mint leaves on two plates. Top with the halloumi. Whisk 1 tablespoon of extra virgin olive oil with 1 tablespoon of red wine vinegar and drizzle over. Black pepper. On a worse day, skip the griddle and eat the halloumi sliced cold.

About 3.4 g salt, 1360 mg sodium per portion. Hydrating from the watermelon.

4. Smoked mackerel pâté on rye with pickled cucumber (low effort, 8 minutes)

Protein-heavy, no cooking beyond toasting, keeps in the fridge for two days. Serves 2.

Whisk 2 tablespoons of cider vinegar with half a teaspoon of caster sugar and a pinch of salt, add half a cucumber, thinly sliced, and leave for five minutes. Flake 200 g of skinless smoked mackerel fillet into a bowl and mash roughly with a fork with 80 g of full-fat crème fraîche, 1 tablespoon of creamed horseradish, the juice of half a lemon and plenty of black pepper; keep it textured. Toast 4 slices of dark rye bread (about 40 g each), pile the pâté on top, lay the drained cucumber over and scatter with dill or chives.

About 2.85 g salt, 1140 mg sodium per portion. Roughly 25 g protein and 2.5 g of omega-3 fats.

5. Chorizo, butter bean and spinach stew

One pan, 25 minutes, smoky paprika oil from the chorizo doing most of the work. Serves 3.

Fry 150 g of cooking chorizo, skinned and sliced, in 1 tablespoon of olive oil in a deep pan until the orange oil releases. Add 1 diced onion and cook until soft. Stir in 3 sliced garlic cloves, 1 teaspoon of smoked paprika and 1 sliced red pepper; cook 2 minutes. Add a 400 g tin of chopped tomatoes, two 400 g tins of drained butter beans and half a tin of water; simmer 10 minutes. Stir in 200 g of baby spinach in handfuls until wilted. Finish with black pepper and a squeeze of lemon.

About 3.6 g salt, 1450 mg sodium per portion with standard tinned beans; drops to around 2.4 g salt if you use no-added-salt beans. Roughly 20 g protein and 12 g fibre.

6. Baked feta with cherry tomatoes, olives and eggs

Everything in one roasting tin. Serves 2.

Heat the oven to 200°C fan. Place a 200 g block of feta in the middle of an oven dish. Scatter 300 g of cherry tomatoes, 60 g of pitted green olives and 2 sliced garlic cloves around it. Sprinkle with 1 teaspoon of dried oregano, half a teaspoon of chilli flakes, 2 tablespoons of olive oil and black pepper. Bake 20 minutes, then make four wells in the tomatoes and crack 4 medium eggs into them. Return for 5 to 7 minutes until the whites are just set. Serve with 2 warm wholemeal pittas and a scatter of parsley.

About 4.6 g salt, 1840 mg sodium per portion. Halve the feta if that is too much in one sitting. Roughly 25 g protein.

7. Soy-glazed salmon with ginger greens and brown rice

Japanese-style traybake that takes 20 minutes. Serves 2.

Rinse 120 g of brown basmati rice and simmer in 300 ml of unsalted water, covered, for about 25 minutes. Mix 3 tablespoons of dark soy sauce, 1 tablespoon of mirin, 1 teaspoon of grated fresh ginger and 1 teaspoon of toasted sesame oil. Sit 2 salmon fillets (around 130 g each) on a foil-lined tray, spoon half the glaze over, and grill on medium-high for 8 to 9 minutes, basting with the rest halfway. Meanwhile, stir-fry 200 g of tenderstem broccoli with 1 sliced garlic clove in 1 tablespoon of neutral oil with a splash of water to steam. Plate rice, greens and salmon; spoon pan juices over; finish with 1 sliced spring onion and 1 teaspoon of sesame seeds.

About 2.2 g salt, 880 mg sodium per portion. Roughly 30 g protein and 2 g of omega-3 fats.

8. Ploughman’s plate (low effort, 5 minutes, no cooking)

Proper British assembly job for an exhausted evening. Serves 1.

Arrange on a plate: 70 g of mature Cheddar, 30 g of Parma ham or 40 g of good cooked ham, 2 pickled onions, 1 tablespoon of Branston pickle, a stick of celery cut into batons, a sliced crisp apple, a few radishes and a thick slice of sourdough (around 50 g) with 10 g of unsalted butter.

About 4.0 g salt, 1600 mg sodium with cooked ham; about 4.7 g salt, 1880 mg sodium with Parma ham. Roughly 28 g protein.

9. Parma ham, fig, rocket and Parmesan with balsamic (low effort, 10 minutes, no cooking)

Salty, sweet, peppery and creamy in four ingredients. Serves 2.

Pile 80 g of rocket on two plates. Drape 80 g of Parma ham (about 8 thin slices) loosely over. Tuck in 4 quartered ripe figs (or a quartered ripe pear if out of season). Scatter 30 g of Parmesan shavings over. Drizzle with 2 tablespoons of extra virgin olive oil and 1 tablespoon of aged balsamic vinegar; black pepper. Serve with 2 slices of sourdough toast rubbed with a cut garlic clove.

About 3.1 g salt, 1240 mg sodium per portion.

10. Prawn, samphire and caper linguine

Seashore pasta, ready in the time it takes the water to boil. Serves 2.

Cook 180 g of linguine in unsalted water; in the last minute drop in 100 g of rinsed, trimmed samphire. Reserve a mugful of cooking water and drain. In a large pan, warm 2 tablespoons of olive oil, soften 2 sliced garlic cloves and half a teaspoon of chilli flakes for a minute, then add 200 g of raw king prawns and cook for 2 to 3 minutes until pink. Add 2 tablespoons of drained capers in brine, the zest of 1 lemon, 25 g of unsalted butter and a splash of pasta water; swirl to emulsify. Toss through the linguine and samphire with the lemon juice and chopped flat-leaf parsley. No added salt needed.

About 2.65 g salt, 1060 mg sodium per portion. Roughly 25 g protein.

The set deliberately draws salt from ten different sources: miso and wakame, anchovies, halloumi and brined olives, smoked mackerel and rye, chorizo and tinned pulses, feta, soy sauce, Cheddar and cured ham and pickles, Parma ham and Parmesan, and samphire and capers. Five of the ten (numbers 1, 3, 4, 8 and 9) can be put together in ten minutes or less with minimal standing, which is usually what matters on a flare day.

What this all adds up to

The case for salt in POTS is not that it is a treatment, but that it is the least glamorous part of a foundation that has to be in place before anything more interesting will work. The physiology is consistent (hypovolemia plus a broken renin-aldosterone loop), the short-term randomised evidence is positive if modest (a median 14 bpm fall in orthostatic tachycardia in Garland’s 2021 trial), and every major society places salt and fluid at the top of its non-pharmacological list. The caveats are real: about half of patients are true responders rather than all of them, hyperadrenergic subtypes may react badly, and the decades-long safety of eating at two to three times national guidance has not been formally tested.

Two practical takeaways are worth holding on to. First, salt is a companion to water, not an alternative to it; the combination matters more than the exact gram count, and most of the physiological work is done by the water that sodium holds in the vessels. Second, a diet built on olives, anchovies, feta, halloumi, miso, smoked fish, cured meats and decent bread will deliver the required sodium along with a great deal of what the rest of the body needs, which is something a tub of salted peanuts and a sachet of instant noodles will never do. Keep a clinician in the loop, measure when you can (home blood pressure, occasional 24-hour urinary sodium), and treat the target as a range rather than a number.