Is kimchi an alkaline food? Unpacking the Science of Fermentation and Your Diet

October 30, 2025 •

5 min read

According to the Codex Alimentarius, kimchi is defined as a fermented food with lactic acid production, which gives it a distinctly tangy flavor and a low pH. This fact leads to the common question: Is kimchi an alkaline food? The answer is more nuanced than a simple yes or no, as it requires differentiating between a food's pH and its metabolic effects on the body.

Quick Summary

While kimchi is acidic in pH due to its fermentation process, its overall metabolic effect on the body can be alkaline-forming. This is largely because the mineral-rich vegetables used to make it outweigh the acid produced by beneficial bacteria, a key distinction for understanding its place in an alkaline-focused diet.

Key Points

pH vs. PRAL: Kimchi is acidic in pH due to lactic acid from fermentation but is considered alkaline-forming metabolically due to its vegetable base.
Lactic Acid Bacteria: The fermentation process introduces beneficial probiotics, like Lactobacillus, which are excellent for digestive and immune health.
Nutrient-Dense Superfood: Kimchi is rich in vitamins (A, C, K, B vitamins), minerals, antioxidants, and fiber, contributing to overall wellness.
Aids Digestion: The probiotics and fiber in kimchi support a healthy gut microbiome, improving digestion and potentially managing weight.
Sodium Content: Kimchi is high in sodium, so it should be consumed in moderation, especially for those with concerns about blood pressure.
Versatile Ingredient: It can be easily incorporated into many meals, acting as a probiotic boost and a flavorful condiment.

The Acidity of Fermentation: The pH of Kimchi

To understand whether kimchi is alkaline, we must first look at its production. Kimchi is a fermented food, typically made from napa cabbage, radishes, and various seasonings. The fermentation process relies on naturally occurring lactic acid bacteria (LAB) that flourish in the salt-brined vegetables.

These good bacteria, primarily from the Leuconostoc and Lactobacillus species, consume the sugars in the cabbage and produce lactic acid as a byproduct. This is what gives kimchi its characteristic sour, tangy taste and is the mechanism that preserves the food. As the fermentation progresses, the pH of the kimchi decreases, often falling to an optimal range of around 4.2–4.5. A pH below 7 is acidic, which means that in its finished state, kimchi is scientifically an acidic food.

The Alkaline Diet and Potential Renal Acid Load (PRAL)

Advocates of the alkaline diet are not concerned with a food's intrinsic pH but rather with its effect on the body's pH balance after it has been metabolized. This is measured by the Potential Renal Acid Load, or PRAL. The PRAL value indicates whether a food produces an acid-forming or an alkaline-forming 'ash' once digested. A positive PRAL value means the food has an acid-forming effect, while a negative value signifies an alkaline-forming effect.

Unlike many fermented foods, such as certain varieties of Japanese natto that use Bacillus species, kimchi's fermentation is driven by lactic acid bacteria. However, this doesn't automatically categorize it as acid-forming in the metabolic sense. Many foods, like sauerkraut, which is also a lactic acid-fermented cabbage, taste acidic but have an overall alkalizing effect on the body. This is because the metabolic process treats the organic acids differently than it would, for example, the sulfuric acid produced from metabolizing high-protein animal products.

Is Kimchi Alkaline-Forming? Decoding the PRAL Score

Determining kimchi's exact PRAL score can be tricky due to the variability in its ingredients and fermentation length. However, we can analyze the components to form a general understanding.

Raw Cabbage: The primary ingredient, napa cabbage, is an alkaline-forming vegetable.
Garlic and Ginger: These common additions are also considered alkaline-forming.
Fish Sauce (if used): While a small amount is used, this ingredient could have a more neutral or slightly acidifying effect due to its animal protein content.
Lactic Acid: The acid produced during fermentation is an organic acid. The body metabolizes these organic acids efficiently, often resulting in an alkalizing effect, similar to how lemons and limes, which are acidic in nature, are considered alkaline-forming in the body.

Given the high proportion of alkaline-forming vegetables, it is widely believed that kimchi has a net alkaline-forming effect on the body, even though its pH is acidic.

Nutritional Profile and Health Benefits

Whether it’s alkaline-forming or not, kimchi is lauded as a superfood for numerous reasons beyond its potential impact on pH. Its nutritional and probiotic qualities offer a host of health benefits:

Probiotic Powerhouse: The fermentation process creates an abundance of beneficial lactic acid bacteria, which are probiotics that promote a healthy gut microbiome.
Immune System Support: A healthy gut is strongly linked to a robust immune system. The probiotics in kimchi can help bolster your body's defenses against illness.
Rich in Nutrients: Kimchi is packed with essential vitamins (A, C, K, and B vitamins like folate and B6) and minerals (calcium, potassium, iron).
High in Fiber: The cabbage and other vegetables provide dietary fiber, which is crucial for healthy digestion.
Weight Management: As a low-calorie, high-fiber food, kimchi can help you feel full, potentially aiding in weight loss or management.
Antioxidant and Anti-Inflammatory Effects: The ingredients, especially red pepper, garlic, and ginger, contain antioxidants and anti-inflammatory compounds.

Comparing Kimchi's pH vs. Metabolic Effect


Feature	Intrinsic Acidity (pH)	Metabolic Effect (PRAL)
Measurement Focus	A substance's immediate hydrogen ion concentration, measured on a scale of 0-14.	A food's acid-forming or alkaline-forming effect on the body after digestion.
Kimchi's Status	Acidic (Low pH of 4.2-4.5).	Alkaline-Forming (Likely negative PRAL value).
Primary Cause	Lactic acid produced by beneficial bacteria during fermentation.	The high concentration of mineral-rich, alkalizing vegetables.

How to Incorporate Kimchi into an Alkaline-Focused Diet

Kimchi is an excellent addition to a diet emphasizing fruits and vegetables, which are naturally alkaline-forming. You can enjoy it as a side dish to balance out meals containing acid-forming ingredients, such as meat or grains. Just a small serving, about a quarter to a half-cup, can provide a significant probiotic boost. It pairs well with grain bowls, salads, and is a staple condiment in many Korean dishes. However, be mindful of its sodium content. Different kimchi varieties and brands can vary significantly, so those monitoring their sodium intake should be aware of this.

A Note of Caution on Sodium

While a superfood in many ways, kimchi is prepared with salt, which means its sodium content can be high. This is necessary for the fermentation and preservation process. For individuals with high blood pressure or those who need to limit sodium for other health reasons, it's essential to consume kimchi in moderation. Some modern varieties may be lower in sodium, but it's always best to check the label.

Conclusion: The Final Verdict

So, is kimchi an alkaline food? The definitive answer is that it is not alkaline in terms of its pH, which is acidic. However, when viewed through the lens of an alkaline diet, the metabolic effect of consuming this probiotic-rich, vegetable-based food is widely considered to be alkaline-forming. The key is to understand the difference between the food's initial acidity and its ultimate metabolic impact. Packed with vitamins, fiber, and beneficial bacteria, kimchi remains an exceptionally healthy food, regardless of its classification in the pH spectrum. Its benefits for gut health and overall wellness are well-established, making it a delicious and smart addition to a balanced diet. Learn more about the alkaline diet concept and PRAL values here.

Sources:

Codex Alimentarius (2001). Kimchi Standard.
Medical News Today (2021). Kimchi: Benefits, nutrition, and risks.
WebMD (2024). Health Benefits of Kimchi.
Korea University (2024). Exploring the Health Benefits of Kimchi on Kimchi Day.
Mother-in-Law's Kimchi (n.d.). Kimchi 101.
ScienceDirect (2024). Effects of kimchi consumption on body fat and intestinal....
The Good Bug (2024). Optimal Daily Dose of Kimchi for Gut Health Benefits.
Helsana (2025). Alkaline foods: an overview.
Basica (2022). Food: Sour doesn't always mean acidic.

Frequently Asked Questions

No, as kimchi ferments, the lactic acid bacteria produce more lactic acid, which causes the pH to decrease and become more acidic. However, its overall metabolic effect on the body remains alkaline-forming.

Fermented kimchi is acidic in terms of its pH level due to the lactic acid produced by bacteria during fermentation. For those following an alkaline diet, the food is considered alkaline-forming because of its vegetable components.

Some individuals with acid reflux might find that the acidity or spiciness of kimchi can be a trigger for their symptoms. However, for others, the probiotics in fermented foods can help balance stomach acid and support gut health. It is best to start with a small amount and monitor your body's reaction.

This is a key concept in the alkaline diet. The metabolic effect, measured by PRAL, is what matters. While the lactic acid makes kimchi physically acidic, the body metabolizes this acid differently than it would inorganic acids. The high mineral content from the vegetables contributes to a net alkalizing effect after digestion.

Experts suggest starting with a small portion, such as a quarter to a half-cup (around 80g), and gradually increasing to one cup (about 150g) daily as your body adjusts. This provides a good dose of probiotics without overwhelming your digestive system.

No, not all fermented foods are considered alkaline-forming. The metabolic effect depends on the raw ingredients and the specific fermentation process. For example, some fermented foods use different microbes that produce different metabolic byproducts.

In small quantities, the fish sauce typically used in kimchi recipes is unlikely to significantly alter the overall alkaline-forming nature of the final product, as the volume of alkalizing vegetables is much higher. However, for a strictly plant-based alkaline diet, a kimchi without animal products should be used.