The Difference Between Starter Cultures and Probiotics
During the manufacturing of all yogurts, milk is fermented using two specific starter cultures: Lactobacillus bulgaricus and Streptococcus thermophilus. These bacteria are responsible for turning milk into yogurt, giving it its characteristic texture and tangy flavor. However, these starter cultures are not always considered true probiotics. For a bacterial strain to be considered a probiotic, it must survive digestion in sufficient quantities to provide a specific health benefit to the host. The starter cultures used in traditional yogurt-making are often destroyed by stomach acid and may not colonize the intestines effectively.
The Impact of Processing: Heat Treatment
A major reason why some yogurts don’t contain viable probiotics is post-fermentation heat treatment. This process, also known as pasteurization, kills off bacteria to extend the product’s shelf life. While heat-treated yogurt still retains many nutritional benefits, such as protein and calcium, it loses the probiotic advantage of live cultures.
- Yogurts with live cultures: These products do not undergo a final heat-treatment step, preserving the beneficial bacteria. The product label will often indicate this with phrases like “contains live and active cultures”.
- Heat-treated yogurts: These have been heated after the fermentation process, rendering the bacteria inactive or dead. These products do not offer the probiotic benefits of live cultures.
How to Identify Probiotic-Rich Yogurts
Becoming a savvy shopper in the yogurt aisle is key to ensuring you get genuine probiotic benefits. Here’s what to look for:
- The “Live and Active Cultures” (LAC) Seal: In the United States, the National Yogurt Association (NYA) offers a voluntary seal for products that contain at least 100 million live and active cultures per gram at the time of manufacturing. This is a reliable indicator that the yogurt contains viable bacteria, though some probiotic brands may not carry this specific seal.
- Check the Ingredient List: Look for specific strain names in the ingredients. Brands that contain true probiotic strains, in addition to the standard starter cultures, will often list them explicitly. Common additions include Bifidobacterium lactis, Lactobacillus acidophilus, and Lactobacillus casei.
- Mind the Sugar: Many flavored yogurts are high in added sugar, which can impact the survival and efficacy of probiotics. Choosing plain, unsweetened yogurt is often the healthiest option, as it contains no added sugars or artificial additives that can negatively affect bacterial viability.
- Refrigerate Properly: Probiotics are sensitive to temperature. Proper refrigeration is crucial for maintaining the viability of live cultures. Never leave probiotic yogurt at room temperature for extended periods.
Comparison Table: Live vs. Heat-Treated Yogurt
| Feature | Live and Active Yogurt | Heat-Treated Yogurt |
|---|---|---|
| Bacterial Status | Contains viable, living bacteria, including starter and sometimes added probiotic strains. | Cultures are killed by heat, meaning no live bacteria are present at consumption. |
| Shelf Life | Generally shorter shelf life due to active bacteria. | Longer shelf life due to pasteurization. |
| Probiotic Benefit | Provides live microorganisms that support gut health. | Offers no probiotic benefits, only the nutritional value of the dairy. |
| Labeling | Often displays a “Live and Active Cultures” seal and lists specific strains. | Typically, no mention of live cultures, though may be labeled as “yogurt”. |
| Texture | Can vary, but may have a tangier, fresher flavor. | Often contains added stabilizers and thickeners to achieve desired texture. |
Which Types of Yogurt Are Most Likely to Be Probiotic?
While you must always check the label, certain types of yogurt are more likely to contain and effectively deliver probiotics:
- Plain Greek Yogurt: Many Greek yogurts are excellent sources of probiotics. The straining process concentrates the cultures, and choosing a plain variety minimizes added sugar.
- Icelandic Skyr: Similar to Greek yogurt but even thicker and higher in protein, skyr is a potent source of probiotics, especially in plain varieties.
- Kefir: A fermented milk drink, kefir often contains a higher number and wider variety of probiotic strains than traditional yogurt.
- Yogurt with Added Strains: Some brands fortify their products with additional strains like Lactobacillus acidophilus or specific Bifidobacterium strains. Look for these listed on the ingredients panel.
Conclusion
Not all yogurt is created equal when it comes to gut health. While all varieties are made using starter cultures, the presence of viable, health-benefiting probiotics is not guaranteed and is largely dependent on the manufacturing process. Heat-treated yogurts lose their live cultures, while those with a “Live and Active Cultures” seal, or with explicitly listed probiotic strains, retain their beneficial bacteria. For maximum gut health support, always read the product label carefully, opt for unsweetened varieties, and choose reputable brands with proven strains. A plain Greek yogurt or kefir often provides the best probiotic bang for your buck. For more comprehensive information on probiotics and health, a useful resource is the NIH Health Professional Fact Sheet on Probiotics.
