Lactose intolerance is the inability to fully digest lactose, the sugar found in milk, because the small intestine does not produce sufficient amounts of the lactase enzyme. When undigested lactose moves into the colon, it ferments and causes uncomfortable symptoms like bloating, gas, and abdominal pain. For many people with this condition, yogurt is generally well-tolerated, unlike milk. This increased tolerance is due to the activity of the bacteria used in the fermentation process.
How Yogurt Helps Digest Lactose
The mechanism for improved tolerance rests on the presence of “live and active cultures” within the yogurt. These cultures, primarily Lactobacillus bulgaricus and Streptococcus thermophilus, contain their own lactase enzyme. The bacteria begin the work of breaking down lactose into simpler, more digestible sugars during the fermentation process itself.
Crucially, these bacterial cells survive their passage through the harsh acidic environment of the stomach, protected by the yogurt’s buffering capacity. Once the yogurt reaches the small intestine, the bacteria’s lactase enzyme remains active, continuing to break down the remaining lactose. This essentially gives the body a temporary, external source of the enzyme it is lacking.
The physical nature of yogurt also contributes to better digestion. Its semi-solid consistency slows its transit time through the gut compared to liquid milk. This slower movement gives the bacterial lactase more time to act on the lactose, further aiding digestion and reducing the likelihood of symptoms.
Comparing Lactose Content in Dairy
The fermentation process significantly reduces the total lactose content in yogurt compared to milk. While an eight-ounce serving of regular cow’s milk contains around 12 grams of lactose, a similar serving of plain yogurt typically contains a notably lower amount, often ranging from 4 to 8 grams. This quantitative reduction alone often brings the lactose load below the personal tolerance threshold for many individuals.
The lactose content varies across different dairy products based on how they are processed. For instance, hard, aged cheeses like cheddar or Swiss are naturally very low in lactose, often containing less than one gram per serving, because the lactose is removed with the whey during curdling and then broken down by bacteria during the aging process. Fresh, soft cheeses like cottage cheese or ricotta have a higher, but still manageable, lactose content because they retain more whey.
Yogurt sits in the middle of this spectrum, containing more lactose than hard cheese but significantly less than milk. The initial fermentation is what sets yogurt apart from milk, but additional processing can create further variation in the final lactose amount.
Selecting the Best Yogurt for Tolerance
When selecting yogurt for better tolerance, certain varieties are preferable due to their lower lactose content. Greek yogurt is often the most highly recommended option because it undergoes a straining process that physically removes a large portion of the whey. Since whey is the liquid portion of the milk that contains most of the remaining lactose, this straining results in a significantly lower final lactose count, often around 4 grams per serving.
It is important to look for the “Live and Active Cultures” seal on the container. This seal confirms that the beneficial bacteria are present in sufficient numbers to aid in lactose digestion after consumption. Plain, unsweetened yogurts are a better choice because added sugars can sometimes mask or exacerbate digestive discomfort.
Consumers should be wary of ingredients that can increase lactose content, such as added milk solids, whey protein concentrates, or powdered milk, which are sometimes used to thicken the yogurt. These additions contain concentrated lactose and can negate the tolerance benefits of fermentation. A good strategy is to begin with a small serving, such as a half-cup, to assess personal tolerance before incorporating larger portions into the diet.