What is Food pH and What Determines It?
To understand whether cheese and bread are acidic, it's crucial to grasp the concept of pH. The pH scale is a measure of acidity or alkalinity, running from 0 to 14. A pH of 7 is neutral (like pure water), a pH below 7 is acidic, and a pH above 7 is alkaline. A lower number indicates a higher level of acidity. For food, acidity can stem from various sources, including natural acids, fermentation, and additives. For example, citrus fruits are inherently acidic, while vegetables like spinach are more alkaline.
The Acidity of Cheese
Yes, cheese is an acidic food. This is a fundamental aspect of cheesemaking, driven by lactic acid. The process begins with milk, which has a nearly neutral pH of about 6.7. A starter culture of bacteria is added to the milk, which consumes lactose (milk sugar) and produces lactic acid. This lowers the milk's pH, causing the milk proteins (casein) to coagulate and form curds.
- How Lactic Acid Affects Cheese: The amount of lactic acid determines a cheese's final pH, which significantly impacts its texture, flavor, and shelf life.
- Variety in Acidity: Different types of cheese have different pH ranges, depending on the specific cultures, aging process, and moisture content. For example, fresh cheeses like cottage cheese are often more acidic than some aged varieties. Some cheeses, like blue cheese, start acidic and then have their pH increase due to the metabolic activity of mold.
The Acidity of Bread
Like cheese, most bread is also considered acidic, especially sourdough, but even standard white bread falls on the acidic side of the pH scale. This is a result of the leavening process. During fermentation, yeast and bacteria produce acids, including lactic and acetic acid.
- Standard Yeast Bread: Even in standard white bread, the fermentation process results in a pH slightly below 7, typically ranging from 5.3 to 5.8.
- Sourdough Bread: Sourdough bread is notably more acidic because it relies on a starter culture containing wild yeast and lactobacilli. This creates a higher concentration of lactic and acetic acid, giving it its characteristic tangy flavor and lower pH, often as low as 4.
- Sodas and Chemically Leavened Breads: Breads leavened with baking soda, such as soda bread, may be more alkaline, especially if not fully neutralized by an acid (like buttermilk) in the recipe.
The Alkaline Diet and Metabolic Acidity
For some, the question of whether cheese and bread are acidic is linked to the popular 'acid-ash hypothesis,' which suggests that eating certain foods can affect the body's overall pH. This theory is largely unsupported by science, as the body has robust systems to regulate blood pH within a very narrow, slightly alkaline range (7.35–7.45). Consuming acidic foods simply causes the body to excrete more acid in the urine; it does not make your blood acidic. The benefits often associated with the alkaline diet are typically due to its emphasis on eating more fruits and vegetables and fewer processed foods, not a change in blood pH.
Comparison Table: Acidity of Common Cheeses and Breads
To illustrate the range of acidity, here is a comparison table with approximate pH values for several common items.
| Food Item | Approximate pH Range | Acidity Level | Notes |
|---|---|---|---|
| Milk | 6.7 | Slightly acidic | Starting point for cheese |
| Cottage Cheese | 4.6–4.9 | Acidic | Fresh, unaged cheese |
| Cheddar | 5.1–5.4 | Moderately acidic | Final pH impacted by aging |
| Mozzarella | 5.2–5.4 | Moderately acidic | Affects melting properties |
| Parmesan | 5.2–5.4 | Moderately acidic | High calcium content |
| Brie | 6.0–6.5 | Slightly acidic | Molds can raise pH during ripening |
| White Bread | 5.3–5.8 | Slightly acidic | Result of yeast fermentation |
| Sourdough Bread | ~4.0 | Acidic | Higher acid content from lactobacilli |
| Rye Bread | 5.2–5.9 | Slightly acidic | Varies based on recipe |
Practical Implications for Digestion
While eating cheese and bread won't alter your blood's pH, the acidity can impact digestion, particularly for individuals with specific sensitivities or conditions like gastroesophageal reflux disease (GERD). For those with GERD, acidic foods can trigger or worsen symptoms like heartburn. This is not a universal experience, and individual reactions vary greatly. Choosing less acidic foods, like more alkaline options, can help manage symptoms in some people.
The Bottom Line for a Balanced Diet
Since cheese and bread are acidic, it's helpful to consider this in the context of your overall diet. The goal isn't to eliminate acidic foods, but to achieve a balanced nutritional intake. Both cheese and bread can be part of a healthy diet. Cheeses provide protein and calcium, while whole-grain bread offers fiber and nutrients. A diverse diet rich in fruits, vegetables, lean proteins, and whole grains ensures you get a wide range of essential nutrients, helping to counteract any potential issues associated with a diet overly reliant on one type of food.
For more information on the acid-alkaline balance in food and diet, the National Cancer Institute provides a definition of the alkaline diet and discusses the metabolic effects of different foods: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/alkaline-diet.
Conclusion
Ultimately, the acidity of cheese and bread is a matter of food science, not a fundamental health risk for most people. The presence of lactic acid makes cheese acidic, while fermentation makes most bread acidic. For individuals with acid reflux, these foods might exacerbate symptoms, but for the general population, the body's natural regulatory systems keep blood pH stable. Instead of focusing on acidity alone, aim for a balanced diet rich in a variety of foods to promote overall health and well-being.
