Baking soda, or sodium bicarbonate, is a strongly alkaline compound that neutralizes acid on contact. When it enters your body, whether swallowed, applied to skin, or used on teeth, it shifts the local pH toward a more basic (less acidic) environment. That single property drives nearly every effect it has, from settling an upset stomach to boosting athletic performance to causing problems when you use too much.
How It Works in Your Stomach
When you swallow baking soda dissolved in water, it reacts immediately with hydrochloric acid in your stomach, producing water, salt, and carbon dioxide gas. This reaction raises the pH of your stomach contents, which is why it relieves heartburn, sour stomach, and acid indigestion quickly. The carbon dioxide is also why you’ll likely burp soon after drinking it.
Relief tends to be fast but short-lived compared to commercial antacids designed for slower, sustained release. Because baking soda neutralizes acid so rapidly, your stomach may respond by producing more acid afterward, a phenomenon called acid rebound. That makes it a reasonable option for occasional, short-term relief but a poor choice for chronic acid reflux.
The Sodium Load Is Significant
Half a teaspoon of baking soda contains about 716 milligrams of sodium. A full teaspoon pushes past 1,400 mg, which is already close to the entire daily sodium limit recommended by most health organizations. If you’re using baking soda regularly for heartburn, that sodium adds up fast and can raise blood pressure, increase fluid retention, and strain your cardiovascular system. People on sodium-restricted diets or blood pressure medications should be especially cautious.
What Happens if You Take Too Much
Overdoing baking soda pushes your blood pH too far toward alkaline, a condition called metabolic alkalosis. Your body keeps blood pH in an extremely tight range, and forcing it outside that range disrupts how your muscles, nerves, and heart function.
Symptoms of baking soda overdose include muscle spasms, muscle weakness, irritability, convulsions, nausea, vomiting, and diarrhea. If the vomiting and diarrhea become severe, the resulting dehydration and electrolyte imbalances can trigger dangerous heart rhythm disturbances. This isn’t a theoretical risk: emergency departments see cases of baking soda toxicity, often in people who took large amounts hoping to treat indigestion or other conditions at home.
Effects on Athletic Performance
During intense exercise, your muscles produce acid (mostly in the form of hydrogen ions) faster than your body can clear it. That acid buildup contributes to the burning sensation and fatigue that force you to slow down. Baking soda increases the buffering capacity of your blood, meaning your bloodstream can absorb and neutralize more of that acid before it impairs performance.
This effect is well documented. Meta-analyses show roughly a 2 to 3% improvement in power, speed, and work capacity during high-intensity efforts lasting 1 to 10 minutes. The strongest evidence comes from sports like swimming, rowing, and middle-distance running, though benefits have also been reported in team sports, racquet sports, and combat sports that involve repeated bursts of effort.
The Australian Institute of Sport recommends athletes take 200 to 400 mg per kilogram of body weight about 2 to 3 hours before competition, paired with a small carbohydrate-rich meal. For a 70 kg (154 lb) person, that works out to roughly 14 to 28 grams. The buffering effect peaks within that window and lasts 3 to 4 hours. Gastrointestinal distress (bloating, nausea, diarrhea) is the main side effect, which is why athletes are advised to test their tolerance well before any competition.
Effects on Your Teeth
Baking soda is one of the gentlest abrasives you can put on your teeth. Abrasiveness in toothpaste is measured on a scale called Relative Dentin Abrasivity, or RDA. Plain baking soda scores a 7, which is extremely low. Most commercial toothpastes fall between 60 and 120, and the upper safety limit is 250. So while baking soda can help scrub surface stains, it’s unlikely to damage enamel through abrasion alone.
Several toothpaste brands include baking soda as an active ingredient for this reason. On its own, though, it doesn’t contain fluoride, so using plain baking soda as your only toothpaste means missing out on the cavity-prevention benefit fluoride provides.
Why It’s Harsh on Skin
Your skin’s outer layer maintains a slightly acidic pH, typically between 4.5 and 5.5. This acid mantle serves as a barrier against bacteria, fungi, and moisture loss. Baking soda has a pH of about 9, which is strongly alkaline relative to your skin. Applying it topically strips away protective oils, disrupts the acid mantle, and can lead to dryness, irritation, and increased vulnerability to infection and breakouts. People who use baking soda as a DIY deodorant or face scrub often develop redness and irritation over time, even if it feels fine initially.
Kidney Health and Metabolic Acidosis
When kidneys lose function, they become less efficient at removing acid from the blood. This creates a condition called metabolic acidosis, where blood pH drifts lower than normal. Left uncorrected, that chronic acidity accelerates further kidney damage in a destructive feedback loop.
Oral sodium bicarbonate is sometimes prescribed to people with chronic kidney disease specifically to correct this acidosis. Several clinical studies have suggested that raising blood bicarbonate levels slows the rate of kidney function decline in these patients. This is a medically supervised treatment, not a home remedy. The doses, timing, and monitoring involved require a physician, especially because the sodium content can worsen the fluid retention and high blood pressure that often accompany kidney disease.
Baking Soda and Cancer: What the Science Actually Shows
You may have seen claims that baking soda can fight cancer. The reality is more nuanced. Tumors tend to create an acidic microenvironment around themselves, and that acidity suppresses the immune cells that would otherwise attack the cancer. In lab experiments, acidic conditions completely shut down the production of key immune signaling molecules in T cells, the immune cells responsible for killing tumor cells.
In mouse studies, adding sodium bicarbonate to drinking water neutralized some of that tumor acidity and allowed immune cells to infiltrate tumors more effectively. When researchers combined bicarbonate with immunotherapy drugs, the results improved further. In one melanoma model, combining bicarbonate with immune cell therapy produced long-term survival in 40% of mice, compared to 10% with the immune therapy alone.
These findings are genuinely interesting, but they come from animal models and laboratory experiments, not human clinical trials. The doses used in mice would translate to roughly 800 mg per kilogram of body weight per day in humans, which is an enormous amount of sodium bicarbonate. Early-phase human trials have been conducted, but there is no evidence yet that drinking baking soda treats or prevents cancer in people. Anyone undergoing cancer treatment should not self-medicate with baking soda based on preclinical research.
How It Interacts With Medications
Because baking soda changes the pH of your stomach and urine, it can alter how your body absorbs and eliminates certain drugs. Some medications are designed to dissolve in acidic environments, so neutralizing your stomach acid can reduce how much of the drug actually enters your bloodstream. Others are cleared through the kidneys at rates that depend on urine pH, meaning baking soda can cause them to be flushed out faster or retained longer than intended. If you take any prescription medications regularly, even occasional use of baking soda as an antacid is worth mentioning to your pharmacist.