Does salt cause water retention?

It’s a Friday night. Your family meets up for dinner at your favorite Italian spot. Afterward, your uncle exclaims, “I can’t get my ring off — my fingers are swollen from all that sodium!”

Sound familiar? Per conventional wisdom, folks worry that a salty meal or stick pack of LMNT will swell them up like a balloon. Which isn’t the look most of us are going for on date night, chill night, or any night for that matter.

But is salt really the culprit? The research suggests that more often than not, diet, metabolic health, and kidney function are more likely to cause swelling after a salty meal. Here are a couple examples that can explain: 

1. High-salt meals are also often high-carb, and consuming excess carbs can cause the body to retain excess salt and fluids.
2. Some folks have a sensitivity to salt that may be rooted in kidney issues, low potassium intakes, or poor metabolic health.

There are many other causes of swelling, too, including hormonal changes, heart failure, obesity, allergies, and others. If swelling is a recurrent or persistent issue, you may want to consult a trusted healthcare practitioner to find the root cause in your unique scenario.

If you know you’re salt-sensitive and want to jump to the science on that, click hereOpens in a new tab. If you’re here for the full story, though, let’s further explore what causes water retention, and salt’s role in it.

What Causes Water Retention?

Water retention (also called swelling, fluid retention, or edema) has many possible causes. Situations or medical conditions that can cause water retention include:

• Pregnancy or hormonal changes
• Heart failure
• Kidney disease
• Lymphatic dysfunction (lymphedema)
• Malnutrition
• Obesity
• Infections
• Allergies
• Potassium deficiencyOpens in a new tab 
• Certain medicationsOpens in a new tab or supplementsOpens in a new tab
• High-carbohydrate intakes

The last bullet point is worth a closer look, as it can trigger that post-meal water retention many of us are familiar with. As you may have noticed, salty meals are also often high in carbs (pasta, pizza, french fries, etc). The carbs, not the salt, may be to blame for any post-meal swelling. A high-carb meal can cause fluid retention in a couple of ways.

First, your body uses lots of fluid to store the extra carbs you’re eating. Carbs are stored in chains of sugar molecules called glycogen, and each gram of glycogen is hitchedOpens in a new tab to at least 3 grams of water.

Second, high-carb meals increase the hormone insulin, and higher insulin levels signalOpens in a new tab your kidneys to retain more salt and fluids.

So higher carbs = more water stored. Let’s talk more about salt now. 

Do High Salt Intakes Cause Water Retention?

StudiesOpens in a new tab suggest that most people won’t retain more fluids after high sodium intakes.

This goes against conventional wisdom, I know. The common belief is that any excess sodium we consume binds to water in the body, increasing water retention. There’s some truth to this logic, since sodium does help pull in water and balance fluidsOpens in a new tab in your body. 

But a big hit of sodium doesn’t necessarily lead to water retention and swelling. There’s a few explanations for this.

First, a healthy human body is equipped to maintain sodium levels. In times of salt scarcity, the body releases the hormones renin, angiotensin, and aldosterone, which help it retain salt. When we eat a bunch of salt, the opposite happens — the body suppressesOpens in a new tab these hormones. This prompts the kidneys to excrete more salt through urine, helping to restore sodium balance.

High salt intakes also increase thirst (“These chips are making me thirsty!”). Listening to this thirst signal and drinking water helps balance blood sodium levels, and the kidneys excrete excess fluid through urine.

One last point is that the body can storeOpens in a new tab sodium in the skin, blood vessel walls, and potentially other reservoirs that don’t increase water retention. In other words, the body can “bank” sodium when too much comes in.

Not everyone, however, can regulate sodium effectively. 

Salt Sensitivity and Water Retention 

Salt-sensitive folks may experience increased water retention after a high-salt meal, though salt itself may not be the root cause of this swelling. 

First, what’s salt sensitivity? Most researchers define salt sensitivity by average blood pressure increases (3–5 mm Hg for normotensives and 8–10 mm Hg for hypertensives) in response to a high-salt diet. Around 10-20% of the population is generally considered salt sensitive, with some studiesOpens in a new tab suggesting figures as high as 25% of normotensives (people with normal blood pressure) and 50% of hypertensives (people with high blood pressure). In other words, researchers don’t know yet exactly how many folks are salt sensitive, but older age, genetics, and health conditions like hypertension or kidney disease do seem to play a role.

Salt-sensitive folks may retain more fluidsOpens in a new tab at higher salt intakes. This is a bit tricky to test and requires folks to notice how their bodies respond to salty meals and drinks.

The prevalence of salt sensitivity likely reflects modern society’s poor state of metabolic health more than anything else. While salt sensitivity is most common in folks with hypertension, many factors can impair one’s sodium maintenance system and may lead to salt sensitivity. Let’s look at three of them.

Salt sensitivity and the kidneys

One factor is kidney issues. Salt-sensitive folks often have genetic mutationsOpens in a new tab that hamper their kidneys’ ability to excrete sodium properly. Remember renin, angiotensin, and aldosterone — your sodium-retention hormones? Folks with these genetic mutations make too muchOpens in a new tab of these hormones, causing the kidneys to hold on to sodium for dear life. The excess sodium can lead to increased blood pressure and fluid retention. 

Salt sensitivity and potassium intake

Another factor is inadequate potassium intake, which may worsen salt sensitivityOpens in a new tab. Here’s why. Sodium increases blood volume (which helps pump blood around the body), and potassium balances this effect by increasing sodium excretionOpens in a new tab and relaxing blood vessel walls. Unfortunately, the modern diet is notoriously low in potassium-rich foodsOpens in a new tab like fish, fruit, and vegetables. The data suggestOpens in a new tab that if folks got more potassium, we might see fewer blood pressure and water retention issues. About 3.5–5 daily grams is a science-backed rangeOpens in a new tab linked to healthier blood pressure, and this range may support sodium balance as well. 

Salt sensitivity and insulin resistance

Insulin resistance, one of the most prevalent metabolic disorders and the hallmark of type 2 diabetes, may also contribute to salt sensitivity.

Insulin resistance is the inability of the hormone insulin to regulate blood sugar levels properly. Risk factors includeOpens in a new tab overeating (particularly excess carbs) and a sedentary lifestyle, because eating too many refined carbs sans exercise can chronically elevate blood sugar. High blood sugar then stimulates the pancreas to pump out high levels of insulin to store that sugar in muscle and liver cells. Eventually, the muscle and sugar cells get accustomed to this insulin surge, and so even more insulin is required to do the same job — that’s insulin resistance. The high blood sugar x high insulin duo is linkedOpens in a new tab to many modern diseases.

How does salt sensitivity tie in? Well, insulin doesn’t just regulate blood sugar; it also helps the body retain salt. And all that insulin makes the body cling to sodium like a hungry dog to food dropped in the kitchen. That extra sodium retention may lead to water retention. 

Check out this articleOpens in a new tab for more about insulin resistance, which may help folks with salt sensitivity. Let’s talk about LMNT now. 

Will LMNT Make You Bloated or Retain Water?

For most healthy folks, LMNT shouldn’t make the body retain more water. The kidneys and thirst mechanism help manage the extra salt and keep fluids balanced in the body.

For folks who are sensitive to salt, it’ll depend on the individual. If you feel like you’re reacting to a salty meal or beverage, you may be salt-sensitive. You can work with a medical professional to test your kidneys,Opens in a new tab evaluate your metabolic health, and consider your overall electrolyte intake.

In either case, we all need some amount of sodium for our bodies to function on a day-to-day basis. And if you’re sodium deficientOpens in a new tab, you may see benefits like better energy, clearer cognition, and fewer muscle cramps by getting enough sodium. AthletesOpens in a new tab or whole foodsOpens in a new tab/ketoOpens in a new tab dieters in particular may need more salt. Test out different amounts of dietary salt and listen to your body to find the sweet spot. You can also check out our sodium calculatorOpens in a new tab for an estimate to start with. 

FAQ

What is water retention?

Water retention (also called edema) happens when your body holds onto excess fluid. It can cause puffiness, swelling, or a feeling of bloating — often in extremities like the hands or feet. While sodium intake is a common scapegoat for water retention, it’s usually not the root cause. There are many other factorsOpens in a new tab that can cause swelling, including eating a large amount of carbs, kidney issues, poor metabolic health, hormonal changes, and even allergies, to name a few.

How long does it take for sodium water retention to go away?

It can take anywhere from one to several days for sodium water retention to subside. Healthy folks often adjust after ~24 hoursOpens in a new tab as the kidneys flush out the excess sodium and fluids. But underlying conditions can stretch that to three days or moreOpens in a new tab, even when kidney function is normal. Other factors, such as exercise and reducing carbohydrate intake, may also help.

How much sodium will cause water retention?

The amount of sodium that causes water retention can vary based on a variety of factors, including someone’s baseline daily sodium intake, exercise, sweat loss, hormones, and underlying conditions. For most healthy people, moderate fluctuations in their sodium intake (say, +20-30%) likely won’t cause retention issues — you’ll excrete the excess through urine. If you’re salt-sensitive or have a lower tolerance to increased sodium intake, you may notice water retention sooner.

What are signs of too much sodium?

If you have healthy functioning kidneys, “too much sodium” is rare. If you consume more sodium than you need, your body may excrete the excess out through urine, or trigger thirst — likely causing you to drink fluids to bring your salt-to-water ratio back into balance. That said, besides thirst, signs of too much sodium can also include a mild headache (related to a fluid-electrolyte imbalanceOpens in a new tab) or increases in blood pressure (which may point to salt sensitivityOpens in a new tab).

What are tips to cut back on sodium?

Most sodium in the Standard American Diet comes from ultra-processed foods — think packaged foods like chips and cookies, or restaurants/fast food. Consuming whole foodsOpens in a new tab instead (meat, fruits, nuts) can often significantly reduce your sodium intake. Contrary to popular belief, though, this isn’t always a good thing — many of us can benefit from more sodium than popular media advertises, and people who eat healthy may not be consuming enough on a day-to-day basis to feel and perform their best. See these articles on whether sodium is good or bad for youOpens in a new tab and health risks of a low-sodium dietOpens in a new tab for more.