Yogurt typically has no significant impact on blood glucose levels, but here are a few things everyone should consider about the popular dairy product. The glycemic index (GI) reflects how much a specific food raises blood glucose levels from ingestion to two hours after consumption, relative to the equivalent amount of pure glucose (which has a GI of 100). For anyone watching their blood sugar, the GI of a specific food is close to the top priority when considering what to eat because the lower a food’s GI, the less overall risk they take of having elevated blood sugar as a result of eating it. GI isn’t the full story for any food, however, and some low-GI foods can provoke a stronger insulin response than other foods with the same GI. This concept is known as the insulinemic index (II), and unfortunately in yogurt this index is substantially higher than the glycemic index. Despite this, overall high yogurt consumption is still associated with a lower risk of type 2 diabetes mellitus.
Although this is encouraging information for people looking to keep their blood glucose levels within a healthy range, it is an open question why exactly yogurt is associated with a lower risk of T2DM. Yogurt, in its simplest form, is just the product of milk left to ferment in the presence of bacteria such as Lactobacillus species. Fermentation in turn is simply the extraction of energy from carbohydrates, in this case lactose since the basic ingredient is milk, without the presence of oxygen. A product of this fermentation is lactic acid, which in some studies has been shown to reduce the rate of gastric emptying, which would in turn presumably lower the glycemic index as it will take longer for all the energy absorbed to make its way into the gut, although when lactic acid is added to bread it has no impact on its GI. Funny enough, when we exert ourselves for an extended period, such as when sprinting, our own muscle cells will run low on oxygen and resort to anaerobic respiration, which produces lactic acid as a byproduct of the metabolism of glucose metabolites without oxygen, rather than the lactose present in milk.
Probiotics and Glucose Control
Probiotic yogurt is not a clearly defined concept, but most yogurt is first produced then treated with heat to kill the bacteria used to ferment the lactose. We could most likely correctly call this non-probiotic yogurt, as it doesn’t contain these lactose-fermenting bacteria upon ingestion. The rest we could then call probiotic yogurt, although there are different lines of bacteria used to create various proprietary brands of probiotic yogurt you can buy at the supermarket. Since lactose-fermenting bacteria are taken into the gut, there may be a benefit for people with lactose intolerance as these bacteria can digest the lactose. The European Food Safety Administration has also approved lactose intolerance alleviation as a valid health claim a producer can make about their probiotic yogurt.
In a population of overweight and obese patients with T2DM, consumption of probiotic yogurt caused a significant decrease in HbA1C levels, an indirect measure of long-term blood glucose levels done by assessing the amount of glucose bound to hemoglobin, as well as one marker of inflammation among the three tested. Although there were no changes in weight, lowering the blood glucose level over the long term in a diabetic population is a worthy goal, as this may prevent some of the complications of T2DM. For the general population, the possible reduction in inflammation is probably more relevant, but it is worth noting that for both blood sugar and the inflammatory marker, the effects were modest; likewise, the population was quite small.
There is a strong relationship between an individual’s microbiome composition and their metabolic health. Those with a higher diversity of healthy bugs in their gut had better controlled glucose levels and lower rates of diabetes. There are many different mechanisms connecting this relationship between glucose and the microbiome, but we do know that dysbiosis (or an abnormal microbiome) is a predictor of metabolic conditions like diabetes. Therefore, nourishing our microbiome with foods like live probiotics can help to optimize our metabolic health.
Things to Keep in Mind when Choosing Yogurt
What appears to be most relevant to explain yogurt’s low GI is the balance between the fats and carbohydrates present in yogurt, although this balance changes depending on the type of yogurt and any sugars added to it in production. The most important thing to keep in mind when choosing a yogurt is to make sure that there are no added sugars. The best way to know this for sure is to check the ingredient list on the nutrition label. Look for ingredients like “sucrose, high fructose corn syrup, and sugar”. The ingredient list should mostly just contain milk and bacteria strains, usually listed after the phrase “live and active cultures”. Additionally, the higher the fat content and, to a lesser extent, the higher the protein content, the more likely a yogurt will be to have a low GI and a less severe impact on blood glucose. Choosing an unsweetened yogurt with some fat in it will help to even out a glucose response, increase satiety, and increase nutrient absorption. Some of the most important nutrients in yogurt, like Vitamin D, are fat soluble and require some fat in the meal to be optimally absorbed.
Which Type of Yogurt is Best?
- The first distinction to make is between skim and whole milk yogurt, and as discussed above the whole milk yogurt has a more favorable GI.The fat content of the yogurt will further aid the glycemic index profile of the food, which is good for keeping your blood glucose levels within a manageable range.
- The second distinction to make is between yogurt left with its lactose=fermenting bacteria or yogurt in which these bacteria are killed by heat, and there is likely a mild benefit for consuming probiotic yogurt in diabetic populations.
- Among the regional varieties of yogurt, there are some that are likely gentler on blood glucose levels. Greek yogurt is produced normally then strained to remove lactose and liquid milk proteins, which has the overall effect of raising the fat-to-carbohydrate ratio.
- Similarly, Icelandic yogurt is made from heated skim milk mixed with lactose-fermenting bacteria and rennet, the contents of a mammalian stomach that contains a variety of enzymes. The end result is a dairy product high in protein and low in both fat and carbohydrates, ideal for maximizing the benefits of yogurt.
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Kara Collier is the co-founder and VP of Health at Nutrisense, one of America’s fastest-growing wellness-tech startups, where she leads the health team. She is a Forbes 30 under 30 recipient, frequent podcast guest & conference speaker.