Yogurt and kefir, both fermented milk products, have long histories and unique characteristics that set them apart. Yogurt has a tangy flavor and a creamy texture requiring a spoon for consumption. Yogurt dates back to the ancient Middle East. Herdsmen discovered milk carried in intestinal gut bags would curdle and sour, effectively preserving the milk.¹ In contrast, kefir is a viscous beverage with a more pronounced tanginess. Its history goes back to the Balkans, Eastern Europe, and the Caucasus region.²

Both yogurt and kefir offer a wealth of nutrients and beneficial bacterial strains, making them compelling choices for health-conscious consumers. Delve into their production methods, differences, and health benefits to discover which is right for you.

How Are Yogurt and Kefir Made?

Yogurt and kefir are made of milk that’s been fermented and acidified.²¹ While the main purpose of food fermentation is to ensure food safety and prolong shelf life, fermented foods are increasingly recognized for their potential health benefits.³

The process of making yogurt starts by using milk. The milk is first pasteurized to destroy harmful microorganisms. After that, a “starter culture”, specifically the bacterial strains Lactobacillus bulgaricus and Streptococcus thermophiles, are added to begin fermentation. The milk is kept at a specific warm temperature to allow bacteria to convert lactose, the naturally occurring sugar in the milk, into lactic acid. This fermentation process makes the milk acidic, which gives yogurt its tangy taste and thick, smooth consistency.⁴

Yogurt often has other bacterial strains added to it, namely Lactobacillus acidophilus and Bifidobacteria spp.⁴

Similar to yogurt, kefir is a fermented milk product that starts with pasteurized milk. To make kefir, kefir grains, which look like small slimy cauliflower florets, are mixed with milk. Just like with yogurt, the fermentation process is done at a specific temperature. Kefir grains contain naturally occurring bacteria and yeast that ferment the lactose in the milk, resulting in the tangy and bubbly beverage that we know as kefir.²

Yogurt and kefir come in dairy and non-dairy as well as plain and flavored options.²⁵ There is also Greek yogurt—yogurt that’s been strained to make a thicker, creamier, and higher-protein yogurt.⁵

Nutrition

The nutrition information below compares yogurt to kefir.678

Both yogurt and kefir are packed with nutrients, making them valuable additions to the diet. When comparing a one-cup plain low-fat serving of each, they share similarities in calorie content and essential nutrients like calcium, phosphorus, and vitamin B5 (pantothenic acid).

However, there are some differences to note. Yogurt edges ahead in zinc and riboflavin (vitamin B2) compared to kefir and boasts higher levels of vitamin B12. On the other hand, kefir offers a bit more protein and shines with higher amounts of selenium, vitamin A, and vitamin D.

Which Has More Probiotics?

Probiotics are living microorganisms that offer health benefits when taken in adequate amounts. Probiotics, also known as “good bacteria” are naturally present in your gut and can support gut health in various ways. They can make it easier for things to move through the intestines, stop harmful microorganisms from growing, and strengthen the gut’s protective lining.⁹ Over 100 trillion microorganisms are inside the gut.¹⁰

Probiotics are also found in fermented foods like yogurt and kefir. Studies on yogurts containing S. thermophilus and L. delbrueckii subsp. bulgaricus found varying levels, from less than 10,000 to over one billion colony-forming units per gram or millimeter (CFU/g or ml). Colony-forming units (CFUs) are a way of counting live microorganisms.¹¹ According to research, yogurt contains an average of 100 million colony-forming units per gram.¹²

Microorganisms in Kefir

The starter culture in kefir is kefir grains, made up of bacteria and yeast. The predominant bacterial species in kefir grains are:¹³

• Lactobacillus kefiranofaciens
• Lacticaseibacillus paracasei
• Lactiplantibacillus plantarum
• Lactobacillus acidophilus
• Lactobacillus delbrueckii subsp. bulgaricus

The most common yeast species in kefir grains are:¹³

• Saccharomyces cerevisiae
• S. unisporus
• Candida kefyr
• Kluyveromyces marxianus ssp. marxianus

The number of live microorganisms in kefir grains is as follows: 100 million CFUs of lactic acid bacteria, 1-10 million CFUs of yeast, and 100,000 CFUs of acetic acid bacteria per gram.¹³

While kefir may seem to be fermented with a wider array of microorganisms and in greater quantities, cultured dairy products generally maintain higher levels of microorganisms compared to other fermented foods. Still, the microbial count in a fermented product may fluctuate depending on its age and origin. Unfortunately, there’s little information available on the number of live microorganisms in most fermented products sold in stores. This information is usually not included on product labels.¹¹

One easy way to determine if a cultured dairy product has significant amounts of live microorganisms is to search for the “live and active cultures” seal on the product. This seal indicates that the product has at least 100 million cultures per gram of product at the time of manufacturing, which is ten times higher than the minimum levels required by the U.S. Food and Drug Administration (FDA).¹⁴

Which Has More Lactose?

Below are the lactose contents—in grams per 100 grams (g) or 3.5-ounce (oz) serving—of various yogurt and kefir products, sourced from the USDA Food and Nutrient Database.^15771617 For reference, a 100-gram portion of whole milk contains 4.81 g of lactose. It’s important to note that lactose content for other yogurt and kefir types, like low-fat yogurt, flavored yogurt, and whole milk kefir, is not available in the USDA database.

• Plain whole milk yogurt: 3.35 g
• Plain whole milk Greek yogurt: 2.61 g
• Plain non-fat Greek yogurt: 2.57 g
• Plain low-fat kefir: 3.7 g
• Strawberry low-fat kefir: 3.23 g

Based on the lactose content data provided, on a gram-for-gram basis, it appears that Greek yogurt, both whole milk and non-fat varieties, generally has lower lactose content compared to the other yogurt and kefir options listed.

However, research shows that consuming yogurt or kefir containing live, active cultures can improve the digestion of lactose and decrease symptoms of lactose intolerance in individuals who have difficulty digesting lactose.¹⁸ The live and active cultures in yogurt and kefir may provide lactase, the enzyme required to break down lactose.¹⁹

It’s important to distinguish lactose intolerance from dairy (whey or casein) allergy, which is a condition where the immune system reacts to the proteins in milk and milk products. Individuals with lactose allergy should avoid lactose-containing products. If you suspect you have either condition, seeking guidance from a healthcare professional is recommended for proper diagnosis and management.²⁰

How To Use Yogurt and Kefir

Creamy and slightly tangy, yogurt is a versatile dairy product enjoyed on its own or as an ingredient in both sweet and savory dishes. Its smooth texture makes it perfect for breakfast with granola or fruit, or as a creamy base for salad dressings and dips.

Yogurt is available in various flavors like plain, fruit-added, or Greek-style. Options include non-fat, low-fat, and whole-milk varieties, as well as plant-based alternatives made from sources such as soy and almond.

With a thinner consistency and a more pronounced tanginess compared to yogurt, kefir is a fermented dairy beverage. Its effervescent nature makes it a refreshing drink on its own or blended into smoothies.

Kefir’s tangy flavor profile adds a unique twist to dishes when used as a substitute for buttermilk in recipes or drizzled over salads as a dressing. You can use kefir in place of milk for French toast and find recipes for kefir ice cream online. Similar to yogurt, there are various options available for kefir including whole-milk-based, low-fat, non-fat, plain, flavored, and plant-based.

Which Is Better for Health?

Whether yogurt or kefir is better for health ultimately depends on individual preferences. Given that dairy is a food group rich in essential nutrients such as protein, calcium, and potassium, and recognizing that 90% of Americans don’t consume enough dairy, opting for any form of dairy, whether it’s yogurt, kefir, or another dairy or fortified non-dairy product, is preferable to abstaining entirely.²¹

Plus, research suggests that regularly consuming fermented milk products, like yogurt and kefir, is linked to a lower risk of breast cancer and colorectal cancer, as well as type 2 diabetes. It can also help with maintaining a healthy weight and promote better heart, bone, and gut health.¹⁸

A Quick Review

Yogurt and kefir are fermented milk products that provide a rich source of essential nutrients like protein, vitamins, and minerals and also boast the presence of beneficial live and active cultures. These cultures contribute to digestive health and may offer additional health benefits.

Both yogurt and kefir are incredibly versatile, seamlessly integrating into a variety of meals and snacks. Their versatility allows for easy incorporation into a balanced diet, promoting overall health and well-being.

Sources:

1. Aryana KJ, Olson DW. A 100-Year Review: Yogurt and other cultured dairy products. J Dairy Sci. 2017;100(12):9987-10013. doi:10.3168/jds.2017-12981
2. Azizi NF, Kumar MR, Yeap SK, et al. Kefir and Its Biological Activities. Foods. 2021;10(6):1210. doi:10.3390/foods10061210
3. Leeuwendaal NK, Stanton C, O’Toole PW, Beresford TP. Fermented Foods, Health and the Gut Microbiome. Nutrients. 2022;14(7):1527. doi:10.3390/nu14071527
4. U.S. Dairy. How Dairy Is Made: A Step-By-Step Guide.
5. Academy of Nutrition and Dietetics. What to Look for in Yogurt.
6. U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels.
7. U.S. Department of Agriculture FoodData Central. Kefir, low-fat, plain, LIFEWAY.
8. U.S. Department of Agriculture FoodData Central. Yogurt, plain, low-fat.
9. National Institutes of Health Office of Dietary Supplements. Probiotics.
10. Thursby E, Juge N. Introduction to the human gut microbiota. Biochem J. 2017;474(11):1823-1836. doi:10.1042/BCJ20160510
11. Rezac S, Kok CR, Heermann M, Hutkins R. Fermented Foods as a Dietary Source of Live Organisms. Front Microbiol. 2018;9:1785. doi:10.3389/fmicb.2018.01785
12. Le Roy CI, Kurilshikov A, Leeming ER, Visconti A, Bowyer RCE, Menni C, et al. Yoghurt consumption is associated with changes in the composition of the human gut microbiome and metabolome. BMC Microbiol. 2022;22(1):39. doi:10.1186/s12866-021-02364-2
13. Prado MR, Blandón LM, Vandenberghe LP, Rodrigues C, Castro GR, Thomaz-Soccol V, Soccol CR. Milk kefir: composition, microbial cultures, biological activities, and related products. Front Microbiol. 2015;6:1177. doi:10.3389/fmicb.2015.01177
14. International Dairy Foods Association. Live & Active Cultures Seal.
15. U.S. Department of Agriculture FoodData Central. Kefir, lowfat, strawberry, LIFEWAY.
16. U.S. Department of Agriculture FoodData Central. Yogurt, plain, whole milk.
17. U.S. Department of Agriculture FoodData Central. Yogurt, Greek, plain, nonfat.
18. Savaiano DA, Hutkins RW. Yogurt, cultured fermented milk, and health: a systematic review. Nutr Rev. 2021;79(5):599-614. doi:10.1093/nutrit/nuaa013
19. National Dairy Council. Science Summary: Lactose Intolerance.
20. U.S. Dairy. The Difference Between Lactose Intolerance and Dairy Allergy.
21. U.S. Department of Agriculture. MyPlate Dairy.

Important Notice: This article was originally published at www.health.com by Johna Burdeos, RD where all credits are due. Medically reviewed by Kayla Girgen, RD

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