There are many reasons why a person may want to avoid acidic foods and more than one way to go about it. An alkaline diet plan for long-term renal health is vastly different from acid-avoiding diets for gastrointestinal disorders like acid reflux. Which acidic foods should you avoid?
Acidic Foods vs. Alkaline Foods
The factor by which any substance is measured to be acidic or alkaline is called pH. The pH of a food is determined by the number of free hydrogen ions, molecules released by acids in food. The sour taste you associate with acids like vinegar or lemon juice, according to the Clemson College of Agriculture, Forestry and Life Science, is caused by these hydrogen ions.
A pH of zero is where you find the most acidic substances, like battery acid, with 10,000,000 times the concentration of hydrogen ions found in water. This is compared to a pH of seven, considered neutral, the pH level of pure distilled water. The most alkaline or basic substances have a pH of 14, like liquid drain cleaner, with a 1 in 10,000,000 concentration of the hydrogen ions found in water.
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.
In the diet and fitness world, 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 impact health based on the acidity of the products remaining after they are metabolized.
The Alkaline Diet Debate
The renal system does most of the work involved in balancing the body's pH. An extensive literature review on the subject of an alkaline diet plan published in the 2012 issue of the Journal of Environmental and Public Health, describes how urine can range in pH from acidic to basic, depending on the ions in contains: sulfate, chloride, phosphate and organic acids, sodium, calcium, potassium and magnesium.
In the acid-ash theory at the base of an alkaline foods diet, foods are categorized by their potential renal acid load (PRAL). Foods with a negative acid load include pretty much all 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 have been shown in numerous studies to be unfounded, but the issue of the effect acidity has on other long-term health outcomes is still An April 2018 review of the existing literature, published in Nutrients, says 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.
The Nutrients review states, "Diets high in acid precursors add to the body's acid burden. For the majority of people eating typical western diets ... whose renal function and acid excretory ability is normal, dietary acid loads would not be a readily detectable factor in altering bone mineral density leading to the development of osteoporosis."
Should You Eat Acidic Foods?
As Melanie Peters points out in an April 2019 article published by the UC San Diego Health Newsroom, it is difficult to say how much the acidity or alkalinity of a diet impacts health overall "because it is impossible to separate one characteristic of a food from the rest of the food."
An alkaline diet plan does, however, encourage people to eat a large amount and a wide variety of fresh fruits and vegetables. Increasing your intake of produce, as the 2012 Journal of Environmental and Public Health review says, "may benefit bone health, reduce muscle wasting, as well as mitigate other chronic diseases such as hypertension and strokes."
Overall, the "eat more fruits and vegetables diet" is pretty simple to follow, without all the other rules. The Centers for Disease Control and Prevention reports that only one in 10 Americans gets the recommended daily intake of fruits and vegetables — 1.5 to 2 cups per day of fruit and 2 to 3 cups per day of vegetables.
For more guidance, look to the 2015-2020 Dietary Guidelines for Americans. These U.S. Department of Health and Human Services guidelines suggest increasing fruits and vegetables, whole grains, plant proteins and healthy fats, while limiting added sugar, fruit juice, alcohol, red meat and sodium. Ask your doctor if this diet is appropriate for your long-term health goals.
GERD, Heartburn and Acid Reflux
If your doctor has recommended that you avoid 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, 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.
These limitations are part of what the U.S. National Library of Medicine calls a "bland diet" which entails avoiding all spicy, minty, fried or raw foods, caffeine, chocolate and alcohol. People on a bland diet may need to avoid whole grains, beans, legumes, nuts and seeds, along with a number of vegetables, so they will need to be careful to eat sufficient fiber from approved foods.
Other tips for improving symptoms of acid reflux associated with GERD, according to the U.S. National Library of Medicine, include fasting for at least two hours before bed, wearing loose-fitting clothing and eating your food in multiple small meals throughout the day, instead of two or three large meals.
If symptoms of heartburn persist, consult a doctor. If your heartburn symptoms are accompanied by any of the other potential signs of a heart attack — pain in the back, neck, jaw or throat, nausea or vomiting, extreme fatigue or shortness of breath — seek emergency medical care immediately.
Nontraditional symptoms like indigestion or heartburn, according to the Office of Women's Health at the U.S. Department of Health and Human Services, are more likely to signal a heart attack in women.
- Clemson College of Agriculture, Forestry and Life Science: "What Is pH?""
- Journal of Environmental and Public Health: "The Alkaline Diet: Is There Evidence That an Alkaline pH Diet Benefits Health?"
- Nutrients: "Acid Balance, Dietary Acid Load, and Bone Effects—A Controversial Subject"
- UC San Diego Health Newsroom: "pHear pHactor: Debunking the Alkaline Diet"
- Centers for Disease Control and Prevention: "Only 1 in 10 Adults Get Enough Fruits or Vegetables"
- Annals of Internal Medicine: "The Association Between Dietary Patterns at Midlife and Health in Aging: An Observational Study"
- Harvard Health Publishing: "What to Eat When You Have Chronic Heartburn?"
- U.S. National Library of Medicine: "Bland Diet"
- U.S. National Library of Medicine: "GERD"
- U.S. Department of Health and Human Services: Office of Women's Health: "Heart Attack Symptoms"
- U.S. Department of Health and Human Services: "2015-2020 Dietary Guidelines for Americans"