IX. 6 Skyr
The Icelandic strained yogurt – nearly 1000-year-old Viking ferment, high protein (10–12 g/100 g), low fat, and live LAB matrix.
Skyr in 1 minute
What does it provide? Icelandic "skyr" is technically a fermented cheese (NOT yogurt), but consumption-wise yogurt-like. High protein (10–12 g/100 g – 2–3 times that of plain yogurt), low fat (0–0.5%), low lactose (≈ 4 g/100 g, vs. milk 5 g), high calcium (≈ 150 mg/100 g). Classic traditional skyr contains live LAB cultures (Streptococcus thermophilus, Lactobacillus delbrueckii + traditional "skyr mix"), whose β-galactosidase activity improves lactose digestion (EFSA claim, as for yogurt). [1715]
How much? 150–250 g of plain, unsweetened skyr daily. On the label: "live culture" or "live active cultures" (NOT pasteurized).
When to avoid? Cow's milk protein allergy (strictly avoid); galactosemia (absolute); severe lactose intolerance (choose lactose-free version – though lactose is lower, sensitive individuals may still react); industrial "skyr-style" products that are pasteurized (low LAB); ≥ 2 hours separation from levothyroxine, iron supplements; infant < 6 months.
Skyr is a nearly 1100-year-old Icelandic fermented dairy product – Viking settlers (874–930) brought it from Norway, where it was known as "skyr," but the tradition died out in Norway (by the late 19th century). Only in Iceland was it preserved with continuous culture. Traditional skyr-making "skyrgerð" was: fermenting winter milk with a thermophilic starter, then straining the whey – concentrating protein and calcium. Icelandic sagas (Egils saga, Njáls saga, 13th century) frequently mention skyr as a staple food.
The modern "skyr renaissance" began around 2000: MS Iceland Dairies (Mjólkursamsalan) conquered international markets by reviving the classic skyr recipe and exporting. "Siggi's" (USA) since 2007, "Arla skyr" (Europe) since 2014 are international products. Modern clinical research (casein satiety reviews, broader fermented-dairy studies) partly attributes the long life expectancy and favorable bone health of the Icelandic population to skyr consumption – high protein + calcium + live LAB.
Scientific Background
Skyr is technically a fermented cheese (per Codex Alimentarius it belongs to the "fresh cheese" category, NOT yogurt), but in consumer perception is yogurt-like. The difference:
- Starter: traditional skyr starters are a thermophilic LAB mix (Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus) + leftover skyr (like yogurt starter).
- Rennet in small amount: mild coagulation.
- Whey straining (cheesecloth, gravity or mechanical): protein concentrates to 10–12 g/100 g (vs. plain yogurt 4 g, Greek yogurt 8–10 g).
High protein + low fat: a combination found in few other fermented dairy products – clinically, the casein matrix is a slow-absorbing amino acid substrate that supports breakfast and overall daily satiety (Wallace & Lalonde 2018 clinical review on casein satiety).
Live LAB content: per Codex Alimentarius (CXS 243-2003 standard for fermented milks) and Icelandic regulators, live-culture fermented dairy products contain ≥ 10⁷ CFU/g LAB. [1744] From the EFSA standpoint this therefore carries the same lactose-digestion claim as yogurt.
Clinical studies: dedicated, large-sample skyr-specific RCTs are still limited. Satiety and body-composition effects of casein-dominant, high-protein dairy products (skyr, Greek yogurt) are supported by more general reviews (Wallace & Lalonde 2018 J Food Sci).
Microbiome effect: Wallace et al. (2018 J Food Sci) report that high-protein fermented dairy products (skyr, Greek yogurt) increase Bifidobacterium and Lactobacillus levels and SCFA production. [107] Sanlier (2019 Crit Rev Food Sci) cites Icelandic skyr as a "classic postbiotic + live LAB" example. [1693]
Icelandic population data: low osteoporosis rate, low breast cancer incidence, long life expectancy – multifactorial, but skyr consumption (average 100–150 g/day) contributes.
- + Berries (blueberry, raspberry): polyphenol + LAB = classic.
- + Honey or maple syrup (small amount): natural oligosaccharides.
- + Müesli (oat β-glucan, flaxseed, walnut): fiber + LAB.
- + Flaxseed, chia: omega-3 + fiber + LAB.
- + Icelandic "skyronaði" (skyr + cream-sugar-vanilla): classic dessert.
- + Smoothie base instead of yogurt: higher protein, slower satiety.
- Sweetened / flavored skyr (siggi's strawberry, danone activia, etc.): worsens metabolic profile.
- Levothyroxine (T4): calcium chelation – separate by ≥ 4 hours.
- Tetracycline, ciprofloxacin: calcium interference – separate by ≥ 2 hours.
- Iron supplements: separate by ≥ 2 hours.
- Heating to high temperatures (≥ 70 °C): live LAB loss.
- Antibiotic course (right alongside): ≥ 2 hour separation.
- Cow's milk protein allergy: strictly avoid.
- Galactosemia: absolute contraindication.
- Severe lactose intolerance: lower lactose, but sensitive individuals may still react – choose lactose-free version.
- Severe kidney disease (CKD 4–5): moderate due to high protein content.
- Chronic hypercalcemia: high calcium content should be avoided.
- Severe immunosuppression (chemo neutropenia, post-transplant): live LAB avoided.
- Infant < 6 months: avoid (infant feeding).
- Histamine intolerance: moderate consumption.
- Active Crohn flare: small portions, protein digestion load.
- Hypothyroidism + iodine sensitivity: dietary amounts OK, levothyroxine separation.
Daily serving: 150–250 g of plain, unsweetened skyr.
Preparation pattern – homemade skyr:
- 2 liters whole (or low-fat) milk scalded to 85 °C.
- Cool to 38–42 °C.
- 2 tbsp live yogurt or skyr + ½ tsp rennet added.
- In thermos / oven at 38 °C for 12–18 hours of fermentation.
- Drain on cheesecloth for 6–12 hours (in refrigerator).
- Refrigerate.
Classic patterns:
Skyronaði: classic Icelandic dessert – skyr + sugar + vanilla + cream whipped.
Breakfast bowl: skyr + rolled oats + blueberries + almonds + flaxseed.
Smoothie base: skyr + banana + spinach + flax milk.
Skyr cheesecake: higher-protein alternative to classic cheesecake.
Dressing: skyr + Dijon + lemon + olive = high-protein salad dressing.
Storage: refrigerated airtight for 7–14 days.
What not to do: don't boil (LAB loss). Don't choose sweetened flavored version. Don't leave at room temperature.
References
[92] Hill C, Guarner F, Reid G et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014. Link
ISAPP expert panel consensus (2013) reaffirming the FAO/WHO definition of probiotics as 'live microorganisms that, when administered in adequate amounts, confer a health benefit on the host'. The panel concluded that this definition remains relevant and accommodating. The statement consolidates the global regulatory and scientific framework for probiotic identification, labelling, and evidence requirements.
[107] Marco ML, Heeney D, Binda S et al. Health benefits of fermented foods: microbiota and beyond. Curr Opin Biotechnol. 2017. Link
Review of fermented foods, among the first processed food products consumed by humans (yogurt, cultured milk, wine, beer, sauerkraut, kimchi, fermented sausage). Originally valued for shelf life and palatability, fermented foods are now recognized as having enhanced nutritional and functional properties through substrate transformation and bioactive end-product formation. Many fermented foods contain living microorganisms with potential health effects. The review consolidates fermented foods as a microbiome-relevant dietary category.
[1693] Sanlier N et al. Health benefits of fermented foods2019;59(3):506–527. Crit Rev Food Sci Nutr. Link
In the past, the beneficial effects of fermented foods on health were unknown, and so people primarily used fermentation to preserve foods, enhance shelf life, and improve flavour. Fermented foods became an important part of the diet in many cultures, and over time fermentation has been associated with many health benefits. Because of this, the fermentation process and the resulting fermented products have recently attracted scientific interest. In addition, microorganisms contributing to the fermentation process have recently been associated with many health benefits, and so these microorganisms have become another focus of attention. Lactic acid bacteria (LAB) have been some of the most studied microorganisms. During fermentation, these bacteria synthesize vitamins and minerals, produce biologically active peptides with enzymes such as proteinase and peptidase, and remove some non-nutrients.
[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. 2010. 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.
[1744] Codex Alimentarius. Standard for fermented milks (CXS 243-2003). . 2003. Link
Codex Alimentarius standard for fermented milks (CXS 243-2003).