Can salty food make you bloated? Your questions answered

After a restaurant meal or a salty snack, plenty of people say they feel puffier the next day. For years, that was mostly anecdote. Then researchers went back to a large, carefully controlled US feeding trial and looked at what salt did to bloating.

Here's what they found, what it doesn't tell us, and how to use it at your own table.

What did the study actually test?

The DASH-Sodium trial ran in 1998 and 1999 and supplied participants' food during each feeding period. Healthy adults were randomized to either the DASH diet, which is high in fiber (32 grams a day), or a lower-fiber typical Western diet (11 grams a day). On their assigned diet, each person then ate three different sodium levels for 30 days each, in random order, with short breaks in between (Peng et al., 2019).

The sodium levels were 50, 100 and 150 mmol a day at a 2,100-calorie intake, which works out to roughly 1,150, 2,300 and 3,450 mg of sodium. The 412 participants had an average age of 48, and 57% were women. At the start of the study, 36.7% reported bloating (Peng et al., 2019).

So does salt cause bloating?

In this trial, it raised the risk. Regardless of which diet people were eating, high sodium intake increased the risk of bloating by about 27% (risk ratio 1.27) (Peng et al., 2019).

Bloating was recorded as a simple yes or no, so the study can't tell us how severe it was or when in the day it happened. But because the food was controlled and each person went through all three sodium levels, this is stronger evidence than a survey asking people what they usually eat.

Is salt bloating gas or water?

Nobody knows yet. The researchers wrote that future work is needed to understand how sodium and diet influence bloating (Peng et al., 2019). It's tempting to assume salt simply makes you hold on to water, but the trial didn't measure that.

It's also worth knowing that salt isn't behind every kind of puffiness. In a small study at the National Institutes of Health, researchers followed 13 healthy women over three menstrual cycles, including two months on a lower-sodium diet. Bloating and breast tenderness around the period didn't come from sodium retention. The women actually lost more sodium in the second half of their cycle, and cutting salt didn't change how severe their symptoms were (Olson et al., 1996).

Wait, did the high-fiber diet increase bloating too?

Yes. Across all three sodium levels, the high-fiber DASH diet raised the risk of bloating by about 41% compared with the lower-fiber diet (risk ratio 1.41). That effect was stronger in men than in women (Peng et al., 2019).

That doesn't make fiber the villain. The authors suggested that bloating from healthful high-fiber diets may be partly offset by eating less sodium. In practice, it's a reminder to increase fiber gradually and to think about the type. Some fibers ferment much faster than others.

Where does most of the salt come from?

Mostly not the salt shaker. In a study of 450 adults in Birmingham, Alabama, Palo Alto, California, and the Minneapolis-St. Paul area, sodium added to food outside the home, in processed and restaurant foods, made up 70.9% of total sodium intake. Salt added while cooking at home accounted for 5.6%, and salt added at the table for 4.9% (Harnack et al., 2017).

So putting the shaker away rarely makes a big difference on its own. The bigger levers are packaged foods, takeout and restaurant meals.

What's a sensible way to test it?

1. Week 1: eat as usual. Each afternoon, rate your bloating from 0 to 10 and note any restaurant or takeout meals.
2. Week 2: cook more meals at home, and compare Nutrition Facts labels on bread, soup, sauces, deli meats, cheese and snacks, choosing lower-sodium versions.
3. Keep fiber steady. Don't overhaul your fiber intake at the same time, or you won't know which change mattered.
4. Compare. Look at your weekly average, and especially at the days after salty meals.

A few easy ways to lower sodium without making food bland:

• Compare milligrams of sodium per serving between brands, and check that the serving sizes match.
• Season with lemon, vinegar, garlic, black pepper, fresh herbs or spice blends without added salt.
• At restaurants, ask for sauces and dressings on the side, and take half home.
• Build a few go-to meals you can make at home in 20 minutes for busy nights.

If your bloating drops in week 2, you've learned something useful. If nothing changes, salt probably isn't a major factor for you, and you can focus elsewhere.

If you have a heart, kidney or blood pressure condition, or you've been told to eat more salt, check with your doctor before changing your intake.

When is puffiness a reason to see a doctor?

Swelling in your legs or ankles, rapid weight gain, or puffiness together with shortness of breath isn't a digestive issue and should be checked promptly.

On the digestive side, see a doctor for new bloating on most days, especially with early fullness, pelvic pain or urinary urgency, and for blood in your stool, unexplained weight loss or symptoms that wake you at night.

Sources

1. Peng AW, Juraschek SP, Appel LJ, Miller ER 3rd, Mueller NT. Effects of the DASH diet and sodium intake on bloating: results from the DASH-Sodium trial. Am J Gastroenterol. 2019;114(7):1109-1115. PMID 31206400
2. Olson BR, Forman MR, Lanza E, et al. Relation between sodium balance and menstrual cycle symptoms in normal women. Ann Intern Med. 1996;125(7):564-7. PMID 8815755
3. Harnack LJ, Cogswell ME, Shikany JM, et al. Sources of sodium in US adults from 3 geographic regions. Circulation. 2017;135(19):1775-1783. PMID 28483828

This article is for general information and isn't medical advice. If you have a heart, kidney or blood pressure condition, or you have been given specific sodium advice, follow your healthcare provider's guidance before changing your salt intake.