How Lowered Dairy Fat Intake Has Impacted Millennials and Zoomers Since Birth

Healthy Aging

Generational Gaps In Healthy C15:0

The updated Dietary Guidelines for Americans (2026-2030) turned the food pyramid upside down. At the top? Whole fat dairy products, including cheese and whole fat milk, at the top. The reasoning? Whole fat dairy products can offer a suite of beneficial nutrients, including C15:0, that support our long-term health. Alas, these products also have high levels of some fats that are known to be proinflammatory.

A new peer-reviewed study was just published which evaluated fatty acid levels not only in whole fat cow’s milk, but milks from other ruminants. They also measured C15:0 in human milk and infant formulas. This week, let’s dive into how different milk sources stack up as they relate to C15:0… and how those levels have been changing over time.

So, which milks have the highest C15:0 levels?

Najjar et al. showed that, among ruminants, cow’s milk ruled the herd. Here’s a breakdown of the amount of C15:0 (based on the % among all fatty acids) measured in different whole fat milks:

• Cow milk = 1.8%
• Camel milk = 1.1%
• Buffalo milk = 1.0%
• Sheep milk = 0.8%
• Goat milk = 0.8%

If you’re wondering about plant-based milks, so did Moore et al. This is what they found regarding C15:0 levels:

• Rice milk = 0.05%
• Soy milk = 0%
• Coconut milk = 0%
• Oat milk = 0%
• Almond milk = 0%

So… whole fat cow’s milk is the best source of dietary C15:0, while plant-based milks basically don’t have C15:0. And if you happen to be drinking camel or buffalo milk, they come in a distant second place.

This is important because, as we have extensively shared, 100+ peer-reviewed studies support the long-term health benefits of C15:0 (check out all the studies at DiscoverC15.com/resources). And understanding where we can (and can’t) get our dietary C15:0 matters.

Our first dietary source of C15:0: Mom.

As a foundational nutrient, C15:0 should be in the first food we all get: mom-milk. Interestingly Najjar et al. showed, in their study, that there was no detectable C15:0 in human milk. The “interestingly” turns to “disturbingly” when we look at what prior studies have shown that measured C15:0 in mom’s milk.

• Mom’s milk C15:0 levels depend on how much C15:0 mom eats. Yuan et al. showed that the more C15:0 a woman had in her diet, the higher the C15:0 in her milk. Specifically, the more cheese she ate, the more of that good C15:0 she provided to her baby. This benefit was not present if mom ate reduced-fat dairy products.
• Modern-day moms have an average of 0.21% C15:0 in their milk. In a 2025 review paper, Yang et al. looked at C15:0 levels in mom’s milk, as reported in the recent, modern-day literature (2018-2023). Of 1,462 human milk samples, the average C15:0 level was 0.21% among all fatty acids.
• Human milk C15:0 levels differ greatly by country. Back in 2006, Yuhas et al. measured C15:0 in human milk across nine countries. They found significant differences based on region, with Australian women’s milk having the highest C15:0 levels (0.39%) and China having the lowest (0.12%). American women had the third lowest C15:0 levels (0.29%).
• Over 30 years ago, women who routinely ate dairy products had double the C15:0 levels (0.42%) in breastmilk compared to the average amounts today. Go back even further to 1991, and Dagnelie et al. showed that women who ate dairy products had C15:0 levels of 0.42% in their breastmilk. They also found that women who avoided dairy products had significantly lower C15:0 breastmilk levels – nearly half (0.22%)… which matches the average mom-milk C15:0 levels today.

So, to go from 0.42% of C15:0 in mom-milk during the 1990s to an average of 0.21% between 2018-2023 – and no C15:0 detected in the most recent study, these studies support that declining intake of whole fat dairy products (due in part to movement to plant-based milks) among moms has resulted in lower C15:0 levels in mom’s milk. A summary of data from most of the studies above, is provided below.

We care because higher C15:0 from mom is linked to better development in kiddos.

As we have shared in previous Science Says! issues, multiple studies have linked higher C15:0 from mom’s milk to better health in their children. For example:

• George et al. showed that the higher the C15:0 in breastmilk fed to infants, the better the infant’s body growth and development, including head circumference.
• Yuan et al. demonstrated that the higher the mom’s C15:0 levels in her red blood cells and milk during and after pregnancy, the better her child’s overall cognitive development and language skill development at ages 3 and 6 years old.
• Duan et al. showed that C15:0 supplementation improved average daily body growth, mitochondrial function, and gut health in piglets, a common model used to understand human infant nutrition needs.

Combined, these studies support the need for 1) mom to get adequate C15:0 in her diet, to 2) help her baby get adequate C15:0 in their diet, to 3) enable both mom and baby to enjoy long and healthy lives.

Well, that seems important. What about C15:0 in infant formulas?

Good question! Here’s what a few studies have found:

• Najjar et al. tested five different commercially available infant formulas and found that only one had measurable C15:0 levels (0.18% of total fatty acids). This particular formula had goat milk powder. Four out of five infant formulas tested had no measurable C15:0 levels. This isn’t much of a surprise, since these products contained either skim or nonfat (vs. whole fat) cow’s milk.
• Purkiewicz et al. tested two infant formulas and showed that they only had C15:0 levels of 0.06% and 0.04%.
• In their more extensive review including 99 infant formula samples, Yang et al. demonstrated that the mean C15:0 level was 0.19% – but with a high standard deviation of 0.19%.

These studies show that there is high variation of C15:0 levels in infant formulas, with many apparently having little to no C15:0. This is due to the increased use of nonfat and skim fat milk in lieu of whole fat cow’s milk in infant formulas.