What Is Lost When Acid Whey is Removed from Yogurt to Make Greek Yogurt?

Don't rely on Claude, AI, or health websites to reliably answer this question

The skeptical cardiologist allowed Claude to write part of his last post on strained yogurt. I’ve finally gotten around to fact-checking the AI chatbot from Anthropic¹ and have discovered that he/it did not correctly answer my question “What are the downsides of removing acid whey from yogurt in terms of nutritional content?”

I hinted (in my post revisiting the health benefits of yogurt) that acid whey is the dark side of strained yogurts like Siggi’s Skyr and “Greek” yogurt, referencing the problems BIG YOGURT is having getting rid of the millions of gallons of that mysterious substance that are generated when factories process regular yogurt.

Since then I’ve spent hours wheying the pros and cons of strained yogurt. According to my totally unscientific poll, many of you are eating Greek yogurt or skyr due to its higher protein content or thicker texture.

We may or may not ultimately sort out whether strained yogurt is better or worse for you than unstrained but first, we must fact-check Claude.

Claude Apologizes for Making Stuff Up

Claude said that “when acid whey is removed during the straining process to make Greek yogurt or skyr, several nutritional components are lost.”

This is correct, but Claude went on to list seven such components that were diminished, and upon further scrutiny of the scientific literature, analysis of the USDA nutritional database, and re-interrogation of the AI chatbot, it appears Claude made up most of these differences.

To be fair this is a complicated area and yogurt nutritional components vary markedly depending on the dairy source and the fermentation process. And, I suspect, Claude was drawing on all of the online websites that give nutritional information by asking a random “expert” without checking original sources.

Taking the factors one by one

1. Reduced calcium content:

   Claude: “A significant amount of calcium is lost in the whey portion. Regular yogurt typically contains about 30% more calcium than Greek yogurt or skyr, which is important to consider since dairy is a primary calcium source for many people.”

   TSC: True. Per 3/4 cup I found 170 mg listed for Siggi’s skyr versus 291 mg in my Straus European-style yogurt. The differences are less in the products tested and reported on the USDA nutritional database.

2. Loss of water-soluble vitamins:

   Claude: "The whey contains water-soluble B vitamins, particularly riboflavin (B2), which supports energy metabolism, and B12, which is essential for nervous system function and red blood cell formation.”

   However, when I asked Claude this time to “compare the B vitamin levels in Greek yogurt and regular yogurt it implied the opposite-that Greek yogurt was higher in B12 and riboflavin:

   

   When I asked Claude for a reference he/it profusely apologized and offered “a more transparent approach:”

   

   When I checked the USDA National Nutrient Database I found no significant differences between Greek yogurt or regular yogurt in levels of thiamine, riboflavin or B6. The USDA database doesn’t report B12 levels.

   Various sources suggest 2% milk as containing about 1 mcg of B12 per cup and I could find nothing to suggest there is any significant difference between strained and non-strained yogurt.

   I did find one article from Turkish investigators published in 2000 suggesting substantial losses of nutrients using traditional methods (straining with a special cloth bag) to produce Torba yoghurt (from cow, goat or sheep milk.)

   

   The abstract concludes:

   “In this study, the losses of nutrients during the straining of yoghurt ² were as follows: 51.8% thiamin, 60.5% riboflavin, 7.28% protein, 0.77% fat, 71.1% lactose, 70.2% sodium, 68.2% potassium, 65.6% calcium and 50.2% phosphorus. Among the amino acids the least loss occurred in the amount of tyrosine (2.24%) and the loss of histidine was highest (11.4%)

3. Reduced potassium:

   Claude: “The straining process removes potassium, an essential electrolyte that helps regulate fluid balance, muscle contractions, and nerve signals.”

   TSC: Potassium is removed but the levels drop only slightly from 164 mg to 147 mg.

4. Lower magnesium levels:

   Claude:”Some magnesium is lost in the whey, which is important for muscle and nerve function, blood glucose control, and bone health.”

   TSC: No significant change per USDA database.

5. Depletion of natural milk sugars

   Claude: “While the reduction in lactose is often considered beneficial, these natural milk sugars can provide quick energy and help fuel beneficial gut bacteria.

   TSC: The USDA database lists 3.35 grams of lactose in plain, whole-milk yogurt versus 2.57 grams in plain whole-milk Greek yogurt which seems very minimal. I found a much larger range for lactose in regular yogurt at many seemingly authoritative websites with no references given.

6. Fewer bioactive peptides:

   Claude: Whey contains various bioactive peptides that may have immune-enhancing properties and other health benefits that are reduced in strained yogurts.

   TSC: It’s complicated. This invited review for the Journal of Dairy Science describes in a very lengthy and well-referenced article, the potential health benefits of the major protein constituents of acid whey, bioactive phospholipids,

   It concludes: “Acid whey has promising applications related to potential health benefits, ranging from antibacterial effects to cognitive development for babies to human gut health.”

   

   There are dozens of studies in humans and animals suggesting that whey may have beneficial properties, possibly related to betaines, l-carnitine, and acylcarnitines.

   From the above-mentioned review:

   Numerous studies have shown the pharmacological ability of whey to ameliorate energetic homeostasis and muscle mass rate in cancer patients . In vitro and in vivo studies proved its anticancer activities. Whey induced cell cycle arrest and apoptosis via caspase-3 activation by limiting glucose uptake and interfering with mitochondrial energy metabolism via sirtuin(s) modulation in different colorectal cell lines while it sustained necroptotic death and metabolic stress in xenograft mice.

7. Reduced volume of probiotics:

   Claude: “Although the concentration of probiotics may be higher in Greek yogurt, the overall volume of the product is reduced, potentially resulting in fewer total probiotic organisms compared to the

   TSC: I could find no evidence for this claim

   As defined by the 2003 Codex Standard for Fermented Milks, yogurt must contain viable, live, and abundant cultures of the lactic acid bacteria (LAB) Lactobacillus bulgaricus and Streptococcus thermophiles species at a minimum concentration of 10⁷ CFU/g at the time of manufacture.

Protein Changes

Straining yogurt definitely yields a product that is thicker and has approximately double the amount of protein per volume consumed, but does that alone make it healthier?

Cow milk protein is typically 80% casein and 20% whey (human milks 60% whey, 40% casein). Thus, once relieved of its whey, strained yogurt will be predominantly casein. Whey protein is mostly beta-lactoglobulin and alpha-lactalbumin.

The whey protein you see bodybuilders adding to smoothies comes from sweet whey from production cheese made by rennet coagulation³ not from acid whey.

The shift to Greek yogurt consumption has occurred primarily because consumers have been convinced that they should be consuming more protein.

To me this trend is eerily reminiscent of the earlier shift to nonfat from full-fat dairy products which was driven by non-science-based recommendations to reduce all types of saturated fat in the diet. Food and dairy companies were happy to take out that dairy fat and sell it to you in another form.

Now food and dairy companies are happy to industrially manipulate yogurt in ways that traditional strained yogurt producers wouldn’t recognize. Since there is no standard of identity for Greek yogurt in the US, various companies have created high-protein yogurts that were formulated with added milk protein concentrates/isolates and whey protein concentrates and labeled as Greek yogurt.

Much of the perceived value of strained yogurt relative to unstrained yogurt rests on this enhanced protein content but it remains to be seen whether that higher protein content outweighs the loss of calcium, bioactive peptides, and unmeasured micronutrients in the acid whey.

Lactobacillacusly Yours,

ACP (aka the reluctant cardiologist)

1. According to Claude.ai

“Claude is a next-generation AI assistant built by Anthropic and trained to be safe, accurate, and secure to help you do your best work. You can get an introductory account for free.”

2. I love spelling yoghurt with an h and certainly the Turks can stake a claim for primacy here. However, there are lots of names to choose from. Concentrated yoghurt produced traditionally in Turkey alone could be Kurut, Torba yoghurt, Tulum or pesküten . .”Historically, yogurt was strained to decrease its water content and to help delay spoilage, and this condensed form of yogurt is a traditional component of Mediterranean, Middle Eastern, and South Asian cuisines. Similar products are manufactured by traditional methods are known as Labneh or Lebneh in the Middle East, Leben Zeer in Egypt, Skyr in Iceland, Chakka and Shirkland in India, Than or Tan in Armenia and Ymer in Denmark.”

3. “Whey protein is collected following the coagulation or precipitation of casein during cheese manufacture. Most whey protein recovery and whey protein products are made from sweet whey from the production of cheeses made by rennet coagulation. After removal from cheese vats, liquid whey is centrifuged to reduce fat content and pasteurized to prevent further lactic acid production by starter organisms. Whey protein can be concentrated using ultrafiltration and dried to produce whey protein concentrate (WPC; protein content 30–90%) or whey protein isolate (protein content >90% “(https://www.sciencedirect.com/science/article/pii/S0022030219306381)