If the yogurt section of your local dairy case seems to have expanded in the last few years, it could be because yogurt is big business in the United States -- Americans spend almost 7 billion dollars a year on the cultured dairy product, according to the National Yogurt Association. Although it’s famous for its bone-building calcium, yogurt is also a good source of protein, B vitamins and vitamin D. Many products also contain live probiotics for gut health. As a fermented food product, yogurt is naturally acidic.
pH Value of Yogurt
Pure water or any other substance that is neutral -- neither acidic nor alkaline -- has a pH value of 7. A substance with a pH value above 7 is considered alkaline, while an acidic substance has a pH value of less than 7. Milk, which is generally considered alkaline, can actually be slightly acidic. According to Oregon State University Extension, the pH value of milk can range from 6.3 to 8.5, depending on how it’s produced. Yogurt, which is made by curdling cow’s milk with purified cultures of beneficial bacteria, is inherently more acidic than milk. This is because the bacteria convert milk sugar, or lactose, into lactic acid, which ultimately increases the acidity of the final product. Lactobacillus acidophilus, the bacteria often used in yogurt production, has a pH value of 4. The average pH value for yogurt is about 4.4.
Acidic Foods and Health
Yogurt’s primary health benefits come from its high nutritional value and, when present, active cultures. Although its acidity isn’t directly associated with any health benefits, it isn't a cause for concern, either. In general, the average healthy person can eat a wide variety of foods without experiencing any kind of adverse reaction stemming from the pH values of those foods.
Acidic foods can be bothersome, however, to those affected by frequent heartburn or gastroesophageal reflux disease, also known as GERD. Although GERD and heartburn have many causes unrelated to diet, for some people, certain foods can trigger or exacerbate the condition. This includes highly acidic foods, such as citrus fruits. Fresh tomatoes, which are about as acidic as yogurt, are also known to trigger heartburn in some people. Though yogurt's acidic nature may trigger heartburn for certain individuals, eating yogurt made from whole milk can trigger symptoms for an entirely different reason -- fatty foods can also cause heartburn, which is why low-fat dairy products are often recommended for people following a GERD diet.
Acid-Alkaline Diet Theory
When it comes to food, the terms “acid” and “alkaline” can mean something other than pH value. These words are also used to describe where a food fits within the acid-alkaline diet theory, which suggests that foods either produce acidic or alkaline substances as you metabolize them, and that eating a diet high in acid-producing foods can lead to an acid imbalance in your body. According to the theory, the standard American diet, which is rich in refined grain products and sugar and low in vegetables, is highly acid-forming. Proponents suggest that it’s best to consume mostly alkaline-forming foods for optimal health.
In this theory, most vegetables and many fruits are alkaline-forming, while all meats and most dairy products are acid-forming. A food’s pH value has nothing to do with whether or not it’s metabolized as an acid or an alkaline -- lemons, which are highly acidic, are considered a highly alkalizing food. Plain yogurt is generally considered a low acid-forming food, while sugar-sweetened yogurt may be considered moderately or highly acid-forming.
Is Yogurt Acidifying?
The acid-alkaline diet theorizes that eating too many acid-forming foods can lead to mild, chronic metabolic acidosis, or a buildup of acids in bodily fluids. Although the National Institutes of Health notes that this condition can occur with uncontrolled type 1 diabetes, poorly functioning kidneys or liver failure, eating a diet rich in so-called acid-forming foods isn’t regarded as a potential cause of metabolic acidosis.
Although yogurt is acidic and considered by some to be acid-forming, eating yogurt won’t disrupt your body’s acid-alkaline balance. That’s because a healthy body is able to tightly regulate the pH value of its fluids as it absorbs and metabolizes nutrients. A 2011 study published in the Journal of the American College of Nutrition backs up this notion, concluding that dairy products are not acid-producing, and that consuming milk and milk products such as yogurt does not alter body pH.
- National Yogurt Association: Know Your Yogurt
- The Dairy Council: Production of Yogurt
- Thermo Fisher Scientific: pH of Yogurt
- Oregon State University Extension Service: pH Values of Various Foods
- University of Maryland Medical Center: Gastroesophageal Reflux Disease and Heartburn
- Medline Plus: Metabolic Acidosis
- Journal of the American College of Nutrition: Milk and Acid-Base Balance -- Proposed Hypothesis Versus Scientific Evidence
- The Acid Alkaline Food Guide: A Quick Reference to Foods and Their Effect on pH Levels; Dr. Susan E. Brown and Larry Trivieri, Jr.
- Better Bones: Acid-Forming Foods
- Better Bones: Alkaline-Forming Foods