1. Yogurt (with live cultures)
The first EFSA-approved live microbe claim — Metchnikoff's Bulgarian shepherds, lactose, and modern Bifido RCTs.
Yogurt in 1 minute
What does it provide? Live yogurt cultures (Streptococcus thermophilus + Lactobacillus bulgaricus — ≥ 10⁸ CFU/g per Codex), whose β-galactosidase enzyme supports digestion of milk sugar (lactose) — this is the world's first, and to this day the only, health claim accepted by EFSA for live microbes. High-biological-value protein (≈ 4 g/100 g plain, ≈ 10 g/100 g Greek), calcium (≈ 120 mg/100 g), and vitamin B12. "Probiotic" versions (BB-12, DN-173 010) shorten colonic transit time in RCTs.
How much? 150–250 g (1 cup) of plain, unsweetened, live-culture product daily. On the label: "live yogurt cultures" or "live active cultures" — NOT pasteurized/heat-treated.
When to avoid? Cow's milk protein allergy (strictly avoid — choose live-culture soy/plant yogurt); galactosemia (absolute contraindication); severe immunosuppression (chemo-induced neutropenia, post-organ-transplant period — Lactobacillus bacteremia is rare but reported); severe lactose intolerance (choose lactose-free or Greek/strained variants); histamine intolerance with aged versions; ≥ 2 hours separation from levothyroxine, tetracycline, ciprofloxacin, iron supplements (calcium chelation).
Yogurt and its relatives were born in the shepherd cultures of Central Asia and the Near East more than six thousand years ago: the Turkish word "yoğurt" ("to thicken") first appears in the 11th-century Dīwān Lughāt al-Turk dictionary by Māhmūd al-Kāshgharī and is based on the summer-milk preservation of Turkish and Balkan shepherds. Modern scientific "appearance on the scene" was defined by Nobel laureate Ilya Metchnikoff: in 1904, in his theory of aging, he pointed to the connection between the long lives of Bulgarian peasants and their consumption of sour-milk yogurt, and with that he made lactic acid bacteria one of the early symbols of "functional food" in the 20th century.[1722]
In 1905, the young Bulgarian doctor Stamen Grigorov isolated one of the key bacteria of yogurt in Geneva, later named Lactobacillus delbrueckii subsp. bulgaricus in honor of his homeland — this became the foundation of industrial production and research. In the 20th century, the standardization of starter cultures, the cold chain, and pasteurization made yogurt globally available, and today's definitions are set out by Codex Alimentarius and regional regulators. EFSA's official health claim states that live yogurt cultures improve lactose digestion — this is the world's first EFSA-accepted nutritional claim based on "live microbes."
Scientific Background
The definition of yogurt (Codex Alimentarius): symbiotic lactic-acid fermentation of milk by two strains — Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.[1716] The two strains have a mutualistic relationship: Streptococcus produces amino acids that Lactobacillus uses; Lactobacillus provides peptides that Streptococcus uses. The endpoint is pH 4.2–4.6, where the milk proteins coagulate.[1721]
The EFSA claim (world first): Live yogurt cultures produce β-galactosidase enzyme, which improves lactose digestion in lactose-malabsorbing individuals. Condition: ≥ 10⁸ CFU/g live starter at the time of consumption. This is the world's first and to date only EFSA-accepted health claim for live microbes.[1715]
Heat-treated yogurt: Pasteurized (post-heat-treated) yogurt contains almost no live LAB — per Codex it is a separate category. Only a postbiotic effect is expected.
Probiotic supplementation: Many industrial yogurts contain additional strains, most often Bifidobacterium animalis subsp. lactis (BB-12, DN-173 010 = "Activia"). These bring a separate body of clinical evidence:
- Colonic transit time shortening (DN-173 010 — Marteau RCT, Roy RCT).[1718]
- Bowel parameter improvement.
- Reduction of functional GI symptoms.
Microbiota RCTs: Thanks to the fermented-food portfolio (including yogurt) of the Wastyk 2021 Stanford study, microbiome diversity rose and 19 inflammatory signaling proteins decreased.[106] Synbiotic yogurt (inulin + probiotic) produces Bifidobacterium elevation and a favorable SCFA profile.[1720]
Natural lactose reduction: During fermentation, most of the lactose (≈ 30–50%) is converted to lactic acid, which is why plain yogurt is tolerated by many lactose-intolerant individuals. Lactose-free yogurt can be part of a low-FODMAP pattern.
- + Inulin/FOS/GOS: synbiotic synergy — Bifidobacterium elevation.
- + Berries (raspberry, blueberry, strawberry): polyphenol + LAB = favorable microbiota substrate.
- + Oat β-glucan, whole-grain müesli: fiber + LAB combination.
- + Flaxseed, chia: fiber + omega-3 + LAB synergy.
- + With honey (small amount): classic, natural prebiotic oligosaccharides.
- + Turmeric, cinnamon (golden yogurt): polyphenol–gut-barrier synergy.
- Added-sugar / flavored yogurts: they worsen the metabolic profile — choose plain and flavor it yourself.
- Antibiotic course (right alongside): separate by ≥ 2 hours.
- Levothyroxine (T4): calcium interferes — separate by ≥ 4 hours.
- High-dose iron supplements: separate by ≥ 2 hours.
- Heating to high temperatures (≥ 80 °C): live LAB is destroyed.
- Tetracycline, ciprofloxacin: calcium chelation — separate by ≥ 2 hours.
- Cow's milk protein allergy: strictly avoid (choose a plant alternative, e.g., soy yogurt with live cultures).
- Severe lactose intolerance: choose lactose-free or Greek/strained yogurt (lower lactose).
- Severe immunosuppression (chemo neutropenia, post-transplant): Lactobacillus bacteremia is rare but reported — to be avoided.
- Galactosemia: strictly avoid.
- Histamine intolerance: some aged versions are problematic.
- Acute (viral) diarrhea: moderate — certain probiotic strains (LGG) may help.
- Infant < 6 months: to be avoided (infant feeding guidelines).
- Hashimoto's + iodine sensitivity: dietary amounts OK.
Daily serving
150–250 g (1 cup or 1 larger müesli bowl) daily.
Preparation pattern — homemade yogurt
- 1 liter whole milk scalded to 85 °C (denser texture).
- Cool to 42–45 °C.
- Add 2 tbsp live yogurt or starter culture.
- In a thermos or yogurt maker at 42 °C for 6–12 hours.
- Refrigerate.
Classic patterns
Müesli bowl: yogurt + rolled oats + berries + flaxseed + walnut.
Tzatziki: strained yogurt + cucumber + garlic + dill + olive oil.
Lassi: yogurt + water + cardamom + honey (sweet) or salt (savory).
Meat/fish marinade: yogurt + spices — enzymatic tenderizing.
Dressing: yogurt + Dijon + lemon + olive.
Storage
Refrigerated airtight for 7–14 days. Surface whey is normal.
What not to do
Don't boil (loss of live LAB). Don't leave at room temperature. Don't choose sweetened, flavored yogurt if microbiota is the goal.
References
[106] Wastyk HC, Fragiadakis GK, Perelman D et al. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021. Link
17-week randomized prospective trial (n=18/arm) in healthy adults comparing high-fibre versus high-fermented-food diets with multi-omics microbiome and host immune profiling. The high-fibre diet increased microbiome-encoded glycan-degrading CAZymes despite stable diversity. The high-fermented-food diet increased microbiome diversity and decreased multiple inflammatory markers. Findings demonstrate diet-specific microbiome–immune effects and support fermented foods as a strong, diversity-promoting modulator of the gut–immune axis.
[1715] EFSA NDA Panel. Scientific opinion on the substantiation of health claims related to live yoghurt cultures and improved lactose digestion2010;8(10):1763. EFSA Journal. Link
EFSA NDA Panel opinion under Article 13(1) (claims ID 1143, 2976): based on the submitted human studies the Panel established a cause-and-effect relationship between consumption of live yoghurt cultures (L. delbrueckii subsp. bulgaricus and S. thermophilus) and improved digestion of lactose in yoghurt among lactose maldigesters. To obtain the effect the yoghurt should contain at least 10^8 CFU live starter bacteria per gram.
[1716] Codex Alimentarius. Standard for Fermented Milks (CXS 243-2003, Rev. 2025). . 2003. Link
Codex Alimentarius Standard for Fermented Milks (CXS 243-2003, Rev. 2025).
[1718] Marteau P et al. Bifidobacterium animalis strain DN-173 010 shortens colonic transit time2002. Aliment Pharmacol Ther. Link
BACKGROUND: A previous study has suggested that Bifidobacterium animalis DN-173 010 shortens the colonic transit time in women. AIM: To confirm this effect and to determine whether modifications of the faecal bacterial mass and/or faecal secondary bile salts may be the explanation. METHODS: A double-blind, cross-over study was performed. Thirty-six healthy women were studied in four consecutive 10-day periods. During periods 2 and 4, they ingested three 125 g cups per day of a fermented milk which was either a product containing B. animalis DN-173 010 or a control without bifidobacteria. Periods 1 and 3 were run-in and washout periods, respectively.
[1719] Hill C et al. ISAPP consensus on the term "probiotic"2014;11(8):506–514. Nat Rev Gastroenterol Hepatol. 2014. Link
An expert panel was convened in October 2013 by the International Scientific Association for Probiotics and Prebiotics (ISAPP) to discuss the field of probiotics. It is now 13 years since the definition of probiotics and 12 years after guidelines were published for regulators, scientists and industry by the Food and Agriculture Organization of the United Nations and the WHO (FAO/WHO). The FAO/WHO definition of a probiotic--"live microorganisms which when administered in adequate amounts confer a health benefit on the host"--was reinforced as relevant and sufficiently accommodating for current and anticipated applications. However, inconsistencies between the FAO/WHO Expert Consultation Report and the FAO/WHO Guidelines were clarified to take into account advances in science and applications. A more precise use of the term 'probiotic' will be useful to guide clinicians and consumers in differentiating the diverse products on the market. This document represents the conclusions of the ISAPP consensus meeting on the appropriate use and scope of the term probiotic.
[1720] Sanders ME et al. Probiotics and prebiotics in intestinal health and disease2019;16(10):605–616. Nat Rev Gastroenterol Hepatol. Link
Probiotics and prebiotics are microbiota-management tools for improving host health. They target gastrointestinal effects via the gut, although direct application to other sites such as the oral cavity, vaginal tract and skin is being explored. Here, we describe gut-derived effects in humans. In the past decade, research on the gut microbiome has rapidly accumulated and has been accompanied by increased interest in probiotics and prebiotics as a means to modulate the gut microbiota. Given the importance of these approaches for public health, it is timely to reiterate factual and supporting information on their clinical application and use. In this Review, we discuss scientific evidence on probiotics and prebiotics, including mechanistic insights into health effects.
[1721] Mantzouridou FT, Paraskevopoulou A. Yogurt manufacture — chemistry & technology 2020. Crit Rev Food Sci Nutr. 2020.
Article in Crit Rev Food Sci Nutr (2020) on yogurt manufacture chemistry and technology.
[1722] . Metchnikoff E1908. The Prolongation of Life: Optimistic Studies. Link
Metchnikoff's 1908 work, The Prolongation of Life: Optimistic Studies.