The Science of Yogurt: Fermentation and Live Cultures
At its core, all yogurt begins with live cultures. The transformation of milk into yogurt is a process of bacterial fermentation, primarily using two starter cultures: Streptococcus thermophilus and Lactobacillus bulgaricus. These bacteria consume the milk's natural sugars (lactose), producing lactic acid, which causes the milk proteins to thicken and gives yogurt its characteristic tangy flavor and texture.
What "Live and Active Cultures" Really Means
For a yogurt to contain beneficial live cultures, these bacteria must remain viable and active. While the initial starter cultures are a given, their survival to your spoon is not guaranteed. Some manufacturers heat-treat their yogurt after fermentation to extend its shelf life. This secondary pasteurization process kills the beneficial bacteria, eliminating the probiotic benefits. Therefore, merely being labeled "natural" does not guarantee a high count of live cultures.
The Importance of the Live & Active Cultures (LAC) Seal
To help consumers, the International Dairy Foods Association (IDFA), formerly the National Yogurt Association (NYA), established a voluntary Live & Active Cultures (LAC) seal. This seal indicates that the product contained a significant number of live and active cultures at the time of manufacture (100 million cultures per gram for refrigerated yogurt). While many brands have live cultures without this seal, it is the most straightforward way to confirm their presence and quantity.
Decoding the Labels for Health Benefits
Live Cultures vs. Probiotics
It's important to differentiate between general live cultures and probiotics. As the Australian division of Activia notes, all probiotics are live cultures, but not all live cultures are probiotics. The term "probiotic" is reserved for specific live microorganisms that, when administered in adequate amounts, confer a health benefit on the host, as defined by the FAO/WHO. Many companies add extra, scientifically-backed probiotic strains, such as Lactobacillus acidophilus or Bifidobacterium, to their products to offer targeted health benefits.
Ingredients and Added Sugars
For maximum health benefits, choosing plain, unsweetened yogurt is often recommended. Added sugars in flavored varieties can counteract the positive effects of the bacteria and feed less desirable gut flora. The healthiest option is often plain natural yogurt, where you can add your own fresh fruit or a drizzle of honey to control sugar intake.
Natural Yogurt vs. Greek Yogurt: Which Has More Live Cultures?
Both natural (unstrained) and Greek (strained) yogurt start with the same live cultures. However, the straining process to make Greek yogurt removes some of the whey and lactose, which can concentrate the remaining milk solids, leading to a higher protein content. Greek yogurt can also have a higher concentration of probiotic bacteria due to this process. The key takeaway is that both can be excellent sources of live cultures, but the label is the ultimate source of truth.
Comparison of Yogurt Types
| Feature | Natural (Strained) Yogurt | Greek (Strained) Yogurt |
|---|---|---|
| Texture | Thinner and more liquid | Thicker and creamier |
| Protein Content | Lower per serving | Up to double the protein of regular yogurt |
| Calcium Content | Higher, as calcium is lost in the straining process | Lower per serving |
| Lactose Content | Higher | Lower, due to straining |
| Live Cultures | Contains live cultures unless heat-treated | Contains live cultures unless heat-treated |
| Potentially Higher CFU | Varies by brand | Often has a higher concentration of bacteria |
Storing Yogurt to Protect Live Cultures
For the live cultures to remain active and potent, proper storage is essential. Yogurt should always be kept refrigerated at or below 40°F (4.4°C). Avoid leaving it out at room temperature for extended periods. When consuming, enjoy it cold, as cooking or heating yogurt can destroy the beneficial bacteria. While frozen yogurt can contain live cultures, it typically has fewer than refrigerated versions, and some are heat-treated, killing the cultures.
The Verdict on Natural Yogurt and Live Cultures
Yes, natural yogurt contains live cultures as part of its manufacturing process. However, the crucial step for ensuring you receive the probiotic benefits is to check the product's label for the "Live & Active Cultures" seal or a specific list of bacterial strains. Brands that use a heat-treatment step after fermentation will not contain viable cultures. Ultimately, a savvy consumer who reads the label can easily select a natural yogurt brimming with beneficial microbes for digestive health.
