Yoghurt, kefir and candida: what the evidence really says about sugar, strains and survival

Interest over fermented foods and beverages, including yoghurt, kefir, sauerkraut, tempeh and kimchi has been on the rise due to emerging evidence of the benefits of consuming these foods. These include a possible reduction of the risk of cardiovascular disease and type 2 diabetes, and possible influence on the gut-brain axis, impacting mood and brain activity (source; source). 

Claim 1: “There’s only two or three strains of microbes in yoghurt” and “most of yoghurt (bacteria) never gets through the stomach”

Fact-check: This claim is misleading.

In order to call yoghurt a yoghurt, and align with international standards, it requires the milk to be fermented with two types of bacteria, Streptococcus thermophilus and Lactobacillus delbrueckii subsp bulgaricus, at a minimum count of 10 million CFU (Colony-Forming Unit) per gram, which is more than ‘a few million bacteria’, as stated in this post by Eric Berg. In that sense, the claim that yoghurt may have only ‘two or three’ strains accurately describes the regulatory minimum for standard yogurt. However, several commercial products intentionally include additional probiotic bacteria for added benefits, including Bifidobacterium and Lactobacillus (source; source). 

As for whether these bacteria survive the journey to the gut, the evidence is more nuanced than the original claim suggests. The evidence does not currently support the blanket statement that most yoghurt bacteria never get through the stomach. Stomach acid is indeed highly acidic (fasting pH can be around 1–2), but this does not mean all ingested bacteria die. The key question is what proportion of yoghurt bacteria survive in the real conditions of digestion (with food buffering the acid) and reach the intestine alive.

In human studies, viable yoghurt-associated bacteria have been recovered from feces, showing that at least some cells survive gastrointestinal transit; however, survival is strain-specific, and depends on the product matrix and dose, as well as individual factors (source; source). For instance, yoghurt helps buffer the acidity of the stomach, which in turn may enhance probiotic survival (source). 

Another factor is that, even though all yoghurts start out with live and active cultures, some yoghurts are heat-processed after fermentation is complete (to extend shelf life), which can kill a significant portion, or all of the bacteria (source) . 

Claim 2: ‘Yoghurt makes candida worse’ and ‘most yogurt that you buy also has added sugar which actually ends up feeding yeast or candida or the bad bacteria’

Fact-check: This claim is misleading. 

This post by Eric Berg starts with a woman (in voiceover) asking ‘wait, yoghurt makes candida worse?’ However, once Berg starts his explanation, he speaks about the number of strains in yoghurt and their survival as they are digested, and it is only later in the post that he makes a remark that yoghurt “makes candida worse” because the yoghurt bought by most of us has added sugar, and sugar “ends up feeding yeast or candida.” Though these statements contain grains of truth, the claims are overstated.

What is Candida? Candida is a type of yeast that is part of the normal human microbiome, living on the skin and mucosal surfaces. However, certain conditions that change the body’s environment, such as a weakened immune system, hormonal changes, microbiome changes or medication use, may cause candida to overgrow and cause an infection, called Candidiasis (source).  

There is currently limited direct evidence to link dietary sugar consumption with ‘worsened’ candidiasis in non-diabetic individuals, nor is there consensus on a no/low sugar diet to prevent or treat candida. However, a high sugar consumption, on a regular basis, can negatively affect the body in different ways, and may encourage candida overgrowth. For instance, high sugar intake is a known risk factor for type 2 diabetes, and people with uncontrolled diabetes may be at significantly higher risk of candidiasis due to elevated blood glucose levels, which can promote yeast growth (source; source). 

Take away: there is currently no evidence that links yoghurt consumption with candidiasis, and some evidence (from small clinical trials) suggests  a possible benefit of eating plain yoghurt with live cultures to help reduce/inhibit candida colonisation, though more recent and larger studies are required (source; source). Yoghurt is also a great source of protein, calcium, vitamin B12, and choosing plain or low added sugar yoghurts (from plant or animal sources) remains a reasonable approach to keeping daily sugar intake within recommended limits, currently set at less than 25g of added sugar per day by major health bodies.