What foods have C15 in them?

October 17, 2025 •

3 min read

For decades, C15:0 (pentadecanoic acid) was overlooked, but recent research suggests it may be a beneficial odd-chain saturated fatty acid with a role in metabolic and cardiovascular health. This guide explains what foods have C15 in them, helping you incorporate potential sources into a balanced diet.

Quick Summary

C15, or pentadecanoic acid, is primarily found in full-fat dairy products, ruminant meats, and some types of fatty fish. Its concentration is influenced by farming practices and modern dietary shifts. Trace amounts can also be found in certain plant-based foods.

Key Points

Rich Source in Full-Fat Dairy: Whole-fat dairy products like butter, cream, and cheese are the most concentrated dietary sources of C15:0.
Content Varies with Farming: The C15:0 content in dairy and meat is often higher in grass-fed animals compared to those raised on grain.
Present in Ruminant Meat: Beef, lamb, and bison contain C15:0 in their fat, contributing to dietary intake.
Found in Certain Fish: Fatty fish such as mackerel, catfish, and sardines contain smaller amounts of C15:0.
Traces in Plant Foods: Some plant-based sources like brown algae and specific oils have trace amounts, but are not significant sources for C15:0.
Lower Levels in Modern Diets: The rise of low-fat dairy consumption has likely contributed to lower C15:0 levels in the population.
Supplementation Available: For those seeking to increase C15:0 levels without consuming more saturated fats, supplements are an option.

Understanding C15: A Unique Fatty Acid

C15:0, or pentadecanoic acid, is an odd-chain saturated fatty acid, which means it has an odd number of carbon atoms (15). This distinguishes it from the more common even-chain saturated fats found in the diet. C15:0 has been identified as a marker for dairy fat intake, but more recently, it has garnered interest for its potential health benefits, including supporting metabolic and cellular health.

Endogenous Production vs. Dietary Intake

It's important to understand that while C15:0 can be produced endogenously in the body (from the metabolism of propionic acid by gut bacteria), dietary intake is the main factor influencing circulating levels. This means that the foods you consume play a significant role in your C15:0 levels. Studies have shown that vegans and omnivores can have similar levels, but that does not discount dietary sources. High-fiber diets can increase endogenous production, but the most significant concentrations still come from diet.

Primary Food Sources of C15

The richest and most reliable dietary sources of C15:0 are animal products, particularly from ruminants, and certain types of fish.

Full-Fat Dairy

Full-fat dairy is the most prominent source of C15:0 in the human diet. However, modern agricultural practices and the move toward low-fat dairy have caused a decline in C15:0 levels in many products. Grass-fed animal products tend to have higher concentrations than those from grain-fed animals.

Butter: One of the most concentrated sources, especially from grass-fed cows.
Whole Milk & Cream: Whole, full-fat milk, cream, and fermented dairy products are good sources.
Cheese: Many full-fat cheeses, like cheddar, gouda, and parmesan, contain substantial amounts of C15:0.
Yogurt: Full-fat yogurt, particularly made from cow or goat milk, is a notable source.

Ruminant Meats

Meat from ruminant animals, such as cows, sheep, and bison, also contains C15:0 in its fat. Grass-fed and finished meat products are generally richer in C15:0.

Beef: Grass-fed beef can have significant levels of C15:0.
Lamb: A rich source of odd-chain fatty acids.
Bison: Another source of C15:0 from ruminant animals.

Fatty Fish

Certain fish species contain small, but measurable, amounts of C15:0, particularly in the fatty parts of the fish like the skin.

Mackerel
Catfish
Cod
Sardines

Trace Plant-Based Sources

While not primary sources, some plant-based foods and oils contain trace amounts of C15:0.

Brown Algae: A unique and lesser-known plant source.
Tamarind Kernel Oil

C15:0 Content in Common Foods

To better understand the relative concentrations, here is a comparison of C15:0 content in selected foods. Note that values can vary based on sourcing and preparation.


Food (per 100g)	C15:0 Content (approx. mg)	Primary Source	Notes
Butter (unsalted)	820-880	Dairy	Highest concentration found in dairy fat.
Sour Cream (30%)	~350	Dairy	Contains significant C15:0 due to high fat content.
Cheddar Cheese	320-390	Dairy	A staple source of C15:0.
Beef (raw ground)	~78	Meat	Lower concentration per 100g compared to butterfat.
Pacific Saury (fish)	~160	Fish	Representative of C15:0 content in certain fish.
Palm Oil	~82	Plant	Contains some C15:0, but in lower amounts than dairy.
Coconut Oil	~15	Plant	Only contains trace amounts of C15:0 despite being high in saturated fat.

Conclusion: Making Informed Dietary Choices

C15, or pentadecanoic acid, is an intriguing fatty acid with research pointing toward potential cellular and metabolic health benefits, though definitive proof of essentiality is still debated. The most concentrated sources are full-fat dairy products from ruminants, particularly butter and cheese, as well as ruminant meats and some fatty fish. However, due to concerns about the overall saturated fat intake, increasing C15:0 through food alone can be challenging. Individuals concerned about their C15:0 levels may consider diet modifications towards grass-fed dairy and meat, or explore supplementation after consulting with a healthcare professional. As with any nutritional consideration, a balanced diet incorporating a variety of nutrient-rich foods is the best approach to overall health. For further research on C15:0 and its role in health, a good starting point is the National Institutes of Health website at https://pubmed.ncbi.nlm.nih.gov/.

Frequently Asked Questions

C15:0, or pentadecanoic acid, is an odd-chain saturated fatty acid with 15 carbon atoms. It is considered unique because, unlike common even-chain saturated fats, it has been associated with potential health benefits and acts differently at a cellular level.

Yes, your body can produce small amounts of C15:0 endogenously, primarily from the metabolism of propionic acid produced by gut bacteria. However, dietary intake, especially from full-fat dairy, is the primary determinant of circulating C15:0 levels.

Studies suggest that C15:0 levels tend to be higher in dairy and meat from grass-fed animals compared to those that are corn-fed. This is due to differences in the ruminal bacteria that produce C15:0 precursors.

The classification of C15:0 as an essential fatty acid is a topic of ongoing research and debate. Some researchers propose it as potentially essential, but most major nutrition authorities do not currently recognize it as such.

Lower C15:0 levels in modern populations are likely due to decreased consumption of full-fat dairy products, a shift towards plant-based alternatives, and changes in agricultural practices that reduce C15:0 content in animal products.

While trace amounts of C15:0 can be found in some plants and algae, plant-based foods are not a significant source. Relying solely on plant sources would not be an effective way to increase C15:0 levels significantly.

C15:0 is available as a dietary supplement. Supplementation may be an option for those looking to increase their intake without a high calorie load from fatty foods. As with any supplement, consulting a healthcare professional is advisable.