Does Grass-Fed Butter Have C15 in It? The Scientific Link Between Diet and a Beneficial Fatty Acid

November 1, 2025 •

4 min read

Dairy from grain-fed cows contains significantly less of the odd-chain saturated fatty acid C15:0 than that from grass-fed cows. This key distinction directly answers the question, 'Does grass-fed butter have C15 in it?', and highlights how animal husbandry practices influence the nutritional content of our food.

Quick Summary

Grass-fed butter contains pentadecanoic acid (C15:0), a beneficial odd-chain saturated fatty acid, in higher concentrations than conventional butter. The cow's diet and its impact on rumen bacteria are responsible for this variation. C15:0 is linked to various cellular health benefits.

Key Points

Yes, Grass-Fed Butter Has C15:0: Grass-fed butter is a rich source of the odd-chain saturated fatty acid C15:0 (pentadecanoic acid), often containing more than conventional butter.
Cow's Diet is Key: The higher C15:0 content in grass-fed dairy is due to the fermentation process carried out by rumen bacteria, which thrive on a high-forage diet.
Potential Health Benefits: C15:0 is linked to various cellular benefits, including strengthening cell membranes and improving mitochondrial function.
Nutritional Superiority: Beyond C15:0, grass-fed butter also typically contains higher levels of other beneficial compounds like omega-3 fatty acids and CLA.
Other Food Sources: Full-fat dairy, ruminant meats (beef, lamb), and some fish are also dietary sources of C15:0.
Moderation is Still Important: While beneficial, butter remains high in calories and fat, so it should be consumed in moderation as part of a balanced diet.

The Science Behind C15:0 in Butter

Pentadecanoic acid, or C15:0, is an odd-chain saturated fatty acid that has recently gained attention in the nutritional science community. Unlike the more common even-chain saturated fats, C15:0 is increasingly being recognized for its potential health benefits, which include strengthening cellular membranes and supporting metabolic function. While C15:0 is found in all full-fat dairy products, the concentration varies depending on the cow's diet. The higher levels found in grass-fed butter are a direct result of the cow's natural diet and its effect on the gut microbiome.

Cows are ruminant animals, and their digestive system, specifically the rumen, contains a diverse microbial community. When a cow consumes a diet rich in forage, such as grass, legumes, and pasture plants, these beneficial microbes thrive and produce odd-chain fatty acids like C15:0 during fermentation. This fatty acid is then incorporated into the cow's milk fat. Conversely, cows in conventional, grain-fed systems receive feedlot rations that are grain-heavy and can suppress these beneficial microbes. This leads to significantly lower levels of C15:0 in the milk and, consequently, the butter produced from it.

Grass-Fed vs. Conventional Butter: A Nutritional Comparison

Beyond the C15:0 content, the nutritional differences between grass-fed and conventional butter are numerous and significant. Choosing grass-fed butter offers a number of advantages derived from the cow's healthier, more natural diet.

Here are some of the key nutritional benefits of grass-fed butter:

Higher C15:0 content: As established, grass-fed butter contains higher levels of this odd-chain saturated fatty acid.
Increased Omega-3 Fatty Acids: Research has shown that grass-fed butter can contain up to 26% more heart-healthy omega-3 fatty acids compared to conventional butter.
More Conjugated Linoleic Acid (CLA): Grass-fed butter is a far richer source of CLA, a polyunsaturated fatty acid with potential health benefits related to immune function and body composition. Some studies have found up to 500% more CLA in grass-fed butter.
Higher Vitamin K2: Grass-fed butter is a great source of Vitamin K2, which is important for bone and heart health by helping to regulate the body's calcium levels.
Richer in Beta-Carotene: The golden color of grass-fed butter is a result of higher beta-carotene levels, an antioxidant that the body converts into Vitamin A.

Comparing Butter Types


Feature	Grass-Fed Butter	Conventional Butter
C15:0 Content	Higher concentration due to grass-based diet.	Lower concentration due to grain-based diet.
Omega-3s	Significantly higher levels.	Lower levels.
CLA	Up to 500% higher.	Much lower levels.
Vitamins (K2, A)	Richer in Vitamin K2 and Beta-carotene.	Lower levels of these vitamins.
Color	More vibrant, golden-yellow due to beta-carotene.	Lighter yellow or white.
Texture	Often smoother and creamier.	Typically harder and tougher to spread.

The Health Benefits of C15:0

Research into C15:0 is still emerging, but preliminary findings are promising and suggest a range of potential health advantages at a cellular level. Key areas of interest include:

Strengthening Cell Membranes: C15:0 is a durable fatty acid that helps fortify cellular membranes, protecting cells from age-related breakdown. Stronger cell membranes are crucial for overall cellular function and longevity.
Improving Metabolic Health: Some studies indicate that C15:0 may support mitochondrial function, which is essential for energy production within cells. This could play a role in improving overall metabolic health and energy levels.
Lowering Inflammation: C15:0 has been shown to exhibit anti-inflammatory properties in various studies. Managing inflammation is critical for reducing the risk of numerous chronic diseases.
Potential for Disease Risk Reduction: Several studies have found associations between higher C15:0 levels and lower risks of chronic conditions, including heart disease and type 2 diabetes. However, it is important to note that these are often correlations, and more research is needed to prove causality.

Maximizing Your C15:0 Intake from Diet

To increase your dietary C15:0, consider the following strategies:

Prioritize Grass-Fed Full-Fat Dairy: Opt for high-quality, full-fat dairy products from grass-fed sources, such as butter, cheese, and milk. Truly grass-fed options will have a higher C15:0 concentration.
Incorporate Ruminant Fats: Grass-fed beef and lamb contain significant amounts of C15:0. Choosing pasture-raised meats can help increase your intake.
Choose Ghee: Grass-fed ghee, or clarified butter, is a concentrated source of butterfat and can provide a notable boost of pentadecanoic acid.
Explore Other Sources: While less concentrated, certain fish species like mullet and catfish contain C15:0. Some brown algae also contain it.
Look for High-Quality Products: Be mindful of labels. Terms like "pasture-raised" and "grass-fed" generally indicate a higher-quality product with a better fatty acid profile.

The Bottom Line: Making an Informed Choice

Deciding to incorporate grass-fed butter into your diet can be a simple step toward a more nutrient-dense nutrition plan, especially if you prioritize full-fat dairy. The higher concentration of C15:0, along with other beneficial nutrients like omega-3s, CLA, and Vitamin K2, gives grass-fed butter a nutritional edge over its conventional counterpart. However, it is crucial to remember that moderation is key, as all butter is high in fat and calories. For those looking to increase C15:0 levels without consuming more dairy, or for those following a vegan diet, supplementation is also an option, though consulting a healthcare professional is always advised. Ultimately, the emerging science behind C15:0 offers a new perspective on how and why we should be mindful of the sources of our food.

Learn more about the latest research on C15:0 and essential fatty acids in this article: Evaluation of an emerging essential fatty acid across twelve human cell systems.

Frequently Asked Questions

Yes, all full-fat butter contains some amount of C15:0 (pentadecanoic acid). However, the concentration is significantly higher in butter produced from grass-fed cows compared to conventional, grain-fed cows.

The difference is due to the cow's diet and its effect on gut microbes. Rumen bacteria in grass-fed cows produce C15:0 during the fermentation of high-forage diets. Grain-heavy diets in conventional farming suppress these microbes, resulting in lower C15:0 levels.

Emerging research suggests C15:0 may offer several health benefits at a cellular level, including strengthening cell membranes, repairing mitochondrial function, and exhibiting anti-inflammatory effects. It has also been associated with lower risks of certain metabolic diseases.

Yes, C15:0 is found in other full-fat dairy products like cheese and cream, as well as ruminant meats such as grass-fed beef and lamb. Some fish species also contain C15:0 in trace amounts.

While trace amounts of C15:0 can be found in some plants, the levels are generally not significant enough to be a meaningful source. The primary dietary sources are full-fat dairy and ruminant fats.

While saturated fat has been demonized in the past, C15:0 is an odd-chain saturated fatty acid that functions differently in the body and is associated with beneficial health outcomes. This highlights that not all saturated fats are created equal, and the source and type matter.

Look for labels that specify "100% grass-fed" or "pasture-raised." Some brands, like Kerrygold, are well-known for their grass-fed products. A vibrant, golden-yellow color can also be a visual indicator of higher beta-carotene levels from a grass diet.

This is a subject of ongoing debate and research. While supplements offer a concentrated, calorie-controlled dose of pure C15:0, they lack the full nutritional complexity of whole foods like grass-fed butter, which also contains other beneficial compounds. It is best to consult a healthcare professional for personalized advice.