What is stomach acid?

Ever wondered what makes your stomach capable of breaking down food so effectively? It’s all thanks to stomach acid, also called gastric acid—a powerful digestive fluid produced by the stomach lining. This acid plays a vital role in breaking down food and absorbing nutrients, keeping your digestive system running smoothly.¹

The acidity of stomach acid serves as a defence mechanism for your body, killing harmful bacteria and pathogens that may enter with food. Without this protective barrier, your digestive system would be more vulnerable to infections. When stomach acid production is balanced, it supports healthy digestion and nutrient absorption. However, when stomach acid levels become unbalanced, it can lead to digestive discomfort such as acid reflux, heartburn or bloating. Let’s dive into the importance of stomach acid, how it works, and practical tips to help you maintain healthy stomach acid levels.

How stomach acid works

Stomach acid does more than just sit in your stomach—it’s a powerhouse of digestion. Made up mainly of hydrochloric acid, it’s produced by specialised cells in your stomach lining. Together with digestive enzymes, this acid breaks down proteins and other nutrients into forms your body can absorb easily.² Here’s a step-by-step breakdown of the process:

Food enters the digestive system

The process begins when we eat, with chewing breaking food into smaller pieces and saliva starting carbohydrate digestion. The food is swallowed and travels down the oesophagus into the stomach.

Stomach acid is produced

When food reaches the stomach, special cells in the stomach lining release stomach acid, making the environment highly acidic. This acidity is essential for breaking down food and starting the digestion process.

Acid and enzymes break down food.

Stomach acid creates an acidic environment that helps enzymes break down proteins into smaller pieces. It also softens food, breaks apart tough tissues, and releases nutrients so your body can absorb them. At the same time, it helps protect you by killing harmful bacteria and other germs in your food. By aiding digestion, fighting off pathogens, and preparing nutrients for use, stomach acid plays a key role in keeping your digestive system healthy.²

The PH of stomach acid

Acidity is measured using the pH scale, which ranges from 0 to 14. A lower pH number means something is highly acidic, while a higher pH indicates less acidity. Stomach acid falls on the very low end of the scale, with a pH of around 1.5 to 3.5, making it one of the most acidic substances in the body.

This high acidity is essential for breaking down food, especially tough proteins and complex ingredients, into simpler forms that your body can easily absorb and use for energy, growth, and repair. It also acts as a natural defence system, destroying harmful bacteria, viruses, and other potential threats that might come with the food you eat, keeping your digestive system and overall health in balance.¹

High stomach acid symptoms and causes

Sometimes, your stomach produces too much acid, also known as hyperacidity. This can result in a range of uncomfortable symptoms and digestive issues. It’s important to recognise the symptoms and understand the potential causes so that you’re able to manage this discomfort. Some of the common signs include:

• Heartburn: A burning sensation in your chest or throat that often occurs after eating or when lying down, caused by acid irritating the lining of your oesophagus.
• Acid reflux: The unpleasant flow of stomach acid into your throat, leaving a sour or bitter taste in your mouth and causing discomfort.
• Indigestion: Pain or discomfort in the upper abdomen after eating. This can feel like bloating, nausea or a sense of fullness.  
• Nausea: A queasy feeling that can make you lose your appetite or feel like you might vomit, often triggered by excessive stomach acid irritating your stomach lining.
• Bloating: An uncomfortable feeling of fullness or tightness in your abdomen, sometimes accompanied by excessive gas or burping.¹

Causes of high stomach acid

Having too much stomach acid can happen for a variety of reasons. Some common causes include:

• Stress: High levels of stress can overstimulate acid production in some people.
• Diet Choices: food triggers like spicy foods, caffeine, alcohol, and overeating can all trigger extra acid production.
• H. pylori Infection: This bacterium can sometimes increase stomach acid levels.
• Certain Medications: Some medications may irritate the stomach and increase acid.

Understanding these triggers can help you make small changes to ease symptoms and keep your stomach feeling balanced.⁵

Low stomach acid symptoms and causes

On the flip side, low stomach acid can be just as problematic and lead to symptoms like:  

• Bloating: A feeling of fullness or tightness in the stomach, often caused by undigested food fermenting in the digestive tract.
• Indigestion: Discomfort or pain in the upper abdomen, often accompanied by feelings of heaviness or sluggish digestion after meals.
• Gas or burping after meals: Excess gas production can lead to frequent burping or passing gas, as your stomach struggles to break down food effectively.
• Diarrhea: Loose or watery stools may occur when undigested food passes too quickly through your digestive system due to insufficient acid levels.

Causes of low stomach acid

Low stomach acid can happen for a variety of reasons, and understanding these can help you keep your digestion on track. Some common causes include:

• Aging: It’s normal for stomach acid production to slow down as we get older.
• Chronic Stress: Ongoing stress can interfere with how much acid your stomach produces.
• Poor Diet: Eating too many processed foods or not getting enough nutrients can throw off your acid levels.
• Nutrient Deficiencies: Not getting enough zinc or B vitamins—both important for stomach acid production—can make a big difference.

By recognising these factors, you can take steps to support healthy acid levels and keep your digestion running smoothly.⁵

Stomach acid and reflux

Stomach acid isn’t just about digestion – it’s also directly tied to reflux. You know that uncomfortable feeling when acid sneaks up from your stomach into your chest? That’s acid reflux, and it happens when stomach acid flows into the oesophagus, causing irritation and discomfort. This is often associated with the overproduction or dysregulation of stomach acid, but it can also occur when stomach acid isn’t produced in the right amounts.

How stomach acid leads to acid reflux

Normally, the lower oesophageal sphincter (LOS), a muscle at the bottom of your oesophagus, acts as a valve to prevent stomach acid from flowing into the oesophagus. However, if the LOS becomes weak or relaxed, acid can escape and enter the oesophagus, causing acid reflux. This flow of stomach acid into the oesophagus can lead to symptoms such as⁶:

• Heartburn: A burning sensation in the chest, typically after meals.
• Regurgitation: The feeling of acid or food rising back into the throat or mouth.
• Difficulty Swallowing: A sensation that food is stuck in the chest or throat.

Managing stomach acid and reflux

If you’re experiencing acid reflux symptoms, managing stomach acid is important. Here are some strategies that can help:

1. Adjust your diet: Avoid common triggers like spicy foods, caffeine, citrus, and fatty meals.
2. Eat smaller meals: Eating smaller, more frequent meals can help prevent the stomach from becoming too full and increasing the risk of acid reflux symptoms.
3. Avoid lying down after meals: Wait at least 2-3 hours after eating before lying down to reduce the risk of acid flowing back into the oesophagus.
4. Consider antacids: Antacids can help to relieve symptoms such as heartburn and indigestion on the go.
5. Maintain a healthy weight: Excess weight can increase pressure on the stomach, contributing to acid reflux symptoms.
6. Quit smoking: Smoking can weaken the LES and exacerbate symptoms of acid reflux.

Maintaining healthy stomach acid levels