Should You Avoid High-Acid Foods? And 7 Acidic Foods to Know

There are many reasons why a person may want to avoid eating acidic foods and more than one way to go about it.

For instance, an alkaline diet plan for long-term renal health is vastly different from acid-avoiding diets for gastrointestinal disorders like acid reflux.

So are there benefits to these types of diets and should you really avoid high-acid foods? Here's what you need to know.

The factor by which any substance is measured to be acidic or alkaline is called pH, according to the U.S. Geological Survey. The pH scale goes from 0 to 14.

• ​Acidic substances​ have a pH of 0 to 7. Highly acidic substances include things like battery acid and stomach acid.
• ​Alkaline or basic substances​ have a pH of 8 to 14. Highly alkaline or basic substances include liquid drain cleaner, ammonia and bleach.
• ​Neutral substances​ have a pH of 7. Pure distilled water is neutral.

Most food is slightly to moderately acidic before it is eaten, with a few exceptions. Fruits typically fall between 2.8 and 4.6 on the pH scale, vegetables 5.0 to 7.0 and meats 5.1 to 7.1. Even milk is on the mildly acidic side with a pH of 6.5 to 6.8, according to the Environmental Protection Agency.

A food's pH level is determined by the number of free hydrogen ions, which are molecules released by acids in food. The sour taste you associate with acids like vinegar or lemon juice is caused by these hydrogen ions, according to Clemson College of Agriculture, Forestry and Life Science.

However, when people talk about "acidic foods" or "alkaline foods" they are rarely talking about their pre-digestion qualities. Instead, the largely debunked acid-ash hypothesis suggests that foods influence health based on the acidity of the products remaining after they are metabolized.

The renal system does most of the work involved in balancing the body's pH. A June 2016 review on alkaline diets published in ​BMJ Open​ tells us that urine can range in pH from acidic to basic depending on what a person eats.

In the acid-ash theory, the base of an alkaline foods diet, foods are categorized by their potential renal acid load (PRAL). Foods with a negative acid load include most fruits and vegetables, including some of the most acidic fruits, like lemons and grapefruit.

Foods that have a high acid load cause calcium salts to be released from the body's stores, as positively charged ions, which balance the negatively charged ions created during digestion.

Foods that cause this reaction are considered to have a positive acid load. These foods include:

• Meat of any kind, including beef, pork, lamb, goat, chicken, turkey and game
• Fish and seafood of all types, including shellfish, wild or farmed
• Dairy, including milk, cheese and butters from any animal
• Grains, which are the seeds of any grass, including wheat, rye, oats, corn and rice

Concerns that the release of calcium ions from the body's stores might contribute to osteoporosis are unfounded. But acidity's effects on other long-term health outcomes is still being studied.

An April 2018 review in the journal ​Nutrients​ concluded that younger people and those with better renal function are able to maintain blood pH more efficiently and can better respond to changes in renal excretion. But, the study also notes that dietary acid load doesn't seem to be a detectable factor in bone mineral density and developing osteoporosis.

It's difficult to say how much the acidity or alkalinity of a diet affects health overall. That's because "it is impossible to separate one characteristic of a food from the rest of the food," University of California San Diego nutrition expert Traci Roberts, RD, said in an April 2019 interview with UC San Diego Health.

An alkaline diet plan does, however, encourage people to eat a large amount and a wide variety of fruits and vegetables.

And the benefits of a produce-rich diet are far-reaching. A fruit- and vegetable-rich diet is linked to lower blood pressure, heart health, lower rates of cancers, healthy blood sugar, good eye health and weight loss/maintenance, according to Harvard T.H. Chan School of Public Health.

If your doctor has recommended you avoid the most acidic foods, acid-producing foods or irritating foods, it is likely because of heartburn, gastroesophageal reflux disease (GERD) or another upper gastrointestinal disorder. According to Harvard Health Publishing, GERD is one of the most common causes of heartburn: a chronic condition where stomach acid backs up into the esophagus.

In this case, foods that are acidic in their natural state are the issue. This includes citrus fruit, pineapple, tomatoes, vinegar and coffee.

Following a bland diet can help too. That means avoiding foods that are spicy or fried, as well as steering clear of caffeine, alcohol and chocolate, according to the U.S. National Library of Medicine. People on a bland diet may need to avoid whole grains, beans, legumes, nuts and seeds, along with some vegetables, so they will need to be careful to eat enough fiber from approved foods. Your doctor can help you decide if a bland diet is right for you.

Other tips for improving symptoms of acid reflux associated with GERD include, per the U.S. National Library of Medicine:

• fasting for at least two hours before bed
• wearing loose-fitting clothing
• eating your food in multiple small meals throughout the day (instead of two or three large meals)

Limiting or avoiding acidic foods is one of the best ways to prevent heartburn flare-ups. If you deal with acid reflux or GERD, here's a list of acidic foods to avoid or limit.

Lemons, oranges and grapefruits their juices typically have a pH between 2 and 3. They're more acidic than most other fruits and are a common heartburn trigger.

Vinegar is highly acidic, with a pH level between 2 and 3. That includes apple cider vinegar, which is sometimes mistakenly touted as a remedy for heartburn.

Sweetened, carbonated soft drinks are about as acidic as grapefruit and orange juice, with a pH level of 3. And cutting them out of your diet won't just help with heartburn: Saying no to soda is an easy way to take in fewer added sugars, which can help you manage your weight and lower your risk for type 2 diabetes, according to the Mayo Clinic.

Carbonated water is also an acidic drink that you'll want to limit.

Raw tomatoes and tomato products like sauce, ketchup or juice have a pH between 4 and 5. Tomato juice is more acidic than raw tomatoes, so you might find it more irritating than plain fruits, according to Clemson College of Agriculture, Forestry and Life Science.

With a pH of 5, black coffee is actually more acidic than acid rain. Thankfully, you might not need to steer clear of your morning mud altogether. Because milk has a more neutral pH, adding a generous splash to your coffee could potentially make it more tolerable by bringing the acidity down. Everyone's different, so experiment to see what's right for you.

Thanks for cocoa's fairly high acid content — it can have a pH as low as 5 — chocolate is a common reflux trigger.

You may want to steer clear of that strawberry-rhubarb pie if you have GERD as rhubarb is an acidic vegetable. The red stalks have a pH of around 3, so they might be a source of irritation.