Natural yogurt, Greek yogurt, skyr, kefir and buttermilk all belong to the broad family of cultured or fermented dairy foods.
But they are not nutritionally or microbiologically identical.
They also do not have the same amount of long-term research behind them.
For healthy aging, it is useful to separate what we know about long-term health outcomes from what we know about the nutritional and microbial characteristics of each product.
Yogurt has direct long-term evidence
Yogurt is one of the fermented dairy foods with substantial long-term observational research.
In a 2026 meta-analysis of prospective studies, higher yogurt consumption was associated with approximately 7% lower all-cause mortality.
However, associations with cardiovascular and overall cancer mortality were not statistically significant.
Importantly, this evidence relates to yogurt as a broader category.
It does not establish that natural yogurt, Greek yogurt or any other specific type of yogurt is responsible for the association. It also does not show that one type of yogurt is superior for longevity.
Greek yogurt and skyr provide a different advantage
Greek yogurt is typically strained or concentrated, which generally increases its protein content compared with standard natural yogurt.
Skyr is a cultured dairy product traditionally closer to a fresh cheese. It is also typically high in protein.
This can be particularly relevant with age.
Adequate protein intake helps support the maintenance of muscle mass and function, especially when combined with resistance exercise.
The potential advantage of Greek yogurt and skyr is therefore clear from a nutritional perspective: they can provide a relatively concentrated source of high-quality protein.
But this should not be confused with direct longevity evidence.
Current research does not establish that Greek yogurt or skyr reduces mortality more than standard natural yogurt.
Kefir is microbiologically distinctive
Kefir offers something different again.
Traditional kefir fermentation involves a diverse community of microorganisms, including both bacteria and yeasts. Conventional yogurt is produced using a more defined group of bacterial cultures.
This makes kefir particularly interesting in research examining fermented foods and the gut microbiome.
However, being microbiologically more diverse does not automatically mean that kefir provides greater long-term health benefits.
Current product-specific mortality evidence for kefir is considerably more limited than the evidence available for yogurt as a broader category.
And what about buttermilk?
Cultured buttermilk — maślanka — is produced through bacterial fermentation.
It can provide protein, calcium and other nutrients naturally present in milk. However, specific long-term evidence for buttermilk and healthy aging remains limited.
It should therefore not automatically be assigned the same health effects observed for yogurt or the broader fermented milk category.
Different products offer different characteristics
There is currently no scientific basis for naming one fermented dairy product as universally best for healthy aging.
Yogurt has more direct long-term mortality evidence.
Greek yogurt and skyr can be particularly useful when a higher protein intake is important.
Kefir is distinctive for its more diverse microbial fermentation.
Buttermilk is another fermented dairy option, but its product-specific long-term evidence is less developed.
The choice also depends on the individual product. Protein, fat, added sugar and ingredients can differ considerably between brands and varieties.
