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Whey Protein's Impact on Anxiety and Stress

Learn about the impact of whey protein on depression, anxiety, stress, and overall health. Explore scientific research

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By Staff Writer
Caitlin Snethlage
Edited by Caitlin Snethlage

Published May 29, 2024.

A picture of whey, a supplement that can affect anxiety, depression, and stress.

We receive many questions about the uses of whey protein. As a result, we researched how it can potentially impact levels of the blood biomarkers that InsideTracker measures.

In this first article of a three-part series, we'll explain research on how taking it may reduce chronic stress by regulating levels of cortisol and serotonin. But before we do that, let's define chronic stress and look at the chemical structures and physiological functions of whey, cortisol, and serotonin.

What is stress?

In today's society, it seems that everyone is always "stressed out." The economy still isn't great; you still need to pick up the kids from their rescheduled sports practices, and your in-laws are coming to visit.

But what does this ubiquitous term mean in the context of our health? Researchers often regard stress as a vague and highly subjective experience for people.

They most commonly define it as the brain’s response to any new demand. [1] A variety of changes can trigger it; they can be short- or long-term, positive or negative, real or perceived. For example, vacationing to Cancun for the first time fits into this definition.

Cortisol and chronic stress

Stress is a natural response to a new demand—and one with biological significance. It keeps you motivated and alert. But, if you're experiencing it for prolonged periods, it could have detrimental effects on your long-term mental and physical health.

Cortisol, one of the blood biomarkers InsideTracker measures, works to reduce hormones associated with growth and building, like testosterone. In fact, researchers say that a prolonged low ratio of these two hormones results from an imbalance between the strain during exercise training.

The athlete's tolerance of such effort may induce overreaching or overtraining syndrome. [2] Since cortisol emphasizes the catabolic over anabolic process, high levels for prolonged periods may result in:

  • Suppressed thyroid function
  • Impaired brain cognition
  • High blood pressure
  • A weakened immune system
  • High levels of glucose, known as hyperglycemia
  • Heart disease
  • Lower bone density
  • Decreased muscle mass
  • Increased rate of aging in body tissues
  • Depression
  • Anxiety [3]

Role of serotonin in mood and cognition

Scientists discovered serotonin in the late 1940s and quickly related it to the central nervous system. By the late 1950s, they were already exploring how it impacted the cardiovascular system and the gastrointestinal tract by attaching to receptors throughout the body.

Today, we know there are 15 serotonin receptors in the body, and almost 90% of them are in the gastrointestinal tract.

We often contrast serotonin to cortisol since the body similarly synthesizes it. Elevated levels of serotonin may improve mood and brain cognition. [4] And it's not harmful unless a person suffers from one of a few rare diseases or takes anti-depressants. [5]

This "happy hormone" comes from its precursor, tryptophan. A ratio between this amino acid and other neutral ones like phenylalanine and tyrosine is known as Trp: LNAA.

When it increases, the production of serotonin also does, resulting in fewer depressive symptoms. A group of researchers in 1989 were the first to support this association. [6]

Note: Medications like selective serotonin reuptake inhibitors affect the levels of the hormone in the body. The underlying mechanism behind this effect are yet to be fully understood. [4]

Whey protein's impact on anxiety and depression

Most people know whey as a muscle-building protein used by athletes and bodybuilders. But this is only one of its many physiological purposes.

Protein, its most abundant component, has approximately 65% beta-lactoglobulin, 25% alpha-lactalbumin, and a variety of other albumins and immunoglobulins. [7]

Alpha-lactalbumin is abundant in various types of mammalian milk. It stimulates constructive processes in the body, working to reduce cortisol. Since its chemical structure is similar to that of human alpha-lactalbumin, the body can easily break it down and synthesize valuable compounds.

On the other hand, beta-lactoglobulin is abundant only in cow's and sheep's milk, and its purpose remains unclear to researchers. Together, all of these compounds make up approximately 20% of the proteins found in cow's milk. The other 80% of proteins we classify as casein.

Note: Companies using modern technology can now isolate some of the whey's highly bioactive peptides, such as lactoperoxidase, which is present in cow's milk in small quantities. They can also separate native whey, a pure form devoid of casein, fat, and lactose.

A table showing various impacts of stress on the body.

» Find out how much protein is enough

What does research say?

Generally, proteins are poor in tryptophan in comparison to the other large neutral amino acids. [8] But, whey-derived alpha-lactalbumin is abundant in it. Because of this, some studies suggest that whey may reduce cortisol while increasing serotonin.

Researchers were curious to see whether a diet rich in whey protein consumption impacted the Trp: LNAA ratio, cortisol and serotonin production, and depressive and stress-related symptoms.

C. B. Markus and his team conducted a double-blind study to assess whether whey protein suppressed cortisol levels. They compared a sample of 23 stress-vulnerable subjects with high salivary cortisol with 29 relatively invulnerable participants with low levels. [9]

The former group had more fatigue, anger, and anxiety, while the latter had minor levels of these stress-related symptoms. The researchers set up both groups with nutritionally identical diets—except they provided casein to the "low-stress" people and whey-derived protein to the "high-stress" individuals.

The researchers concluded that the results “suggest that enhancing the tryptophan availability in the brain leads to a clear effect on performance, although only in high-stress individuals.” [9]

» Learn more about surprising findings from protein-restriction studies

Just the tip of the iceberg

While research on whey protein's impact on anxiety and stress is ongoing, some initial findings show promise. Whey protein, mainly due to its high alpha-lactalbumin content, may offer benefits for individuals vulnerable to stress.

If you're interested in trying whey protein to manage stress, it's wise to consult with a healthcare professional first, especially if you have any pre-existing health conditions.

Remember, a balanced diet should be the primary source of your protein intake. Based on your biomarkers, InsideTracker Ultimate Plan can also offer personalized recommendations for diet, exercise, and lifestyle changes to help you manage stress and anxiety.

Disclaimer: InsideTracker doesn't treat or diagnose medical conditions. Consult your physician for any health concerns.


[1] NIMH. "Fact Sheet on Stress". NIMH RSS. National Institute of Mental Health, n.d. Web. 11 Nov. 2014.

[2] Urhausen, A., Gabriel, H., & Kindermann, W. (1995). Blood hormones as markers of training stress and overtraining. Sports Medicine, 20(4), 251-276.

[3] Scott, E. (2014, September 13). What You Need to Know About the Stress Hormone. Retrieved November 12, 2014.

[4] WebMD. Depression (major depressive disorder). (n.d.). Retrieved November 12, 2014.

[5] Young, S. N. (2007). How to increase serotonin in the human brain without drugs. Journal of psychiatry & neuroscience: JPN, 32(6), 394.

[6] Rosenthal NE, Genhart MJ, Caballero B, et al. Psychobiological effects of carbohydrate- and protein-rich meals in patients with seasonal affective disorder and normal controls. Biol Psychiatry 1989;25:1029–40.

[7] Haug, A., Hostmark, A. T., & Harstad, O. M. (2007). Bovine milk in human nutrition–a review. Lipids Health Dis, 6(1), 25.

[8] Lieberman, H. R., Caballero, B., & Finer, N. (1986). The composition of lunch determines afternoon plasma tryptophan ratios in humans. Journal of neural transmission, 65(3-4), 211-217.

[9] C. R. Markus et al., “The bovine protein α-lactalbumin increases the plasma ratio of tryptophan to the other large neutral amino acids, and in vulnerable subjects raises brain serotonin activity, reduces cortisol concentration, and improves mood under stress,” ˜the œAmerican Journal of Clinical Nutrition, vol. 71, no. 6, pp. 1536–1544, Jun. 2000, doi: 10.1093/ajcn/71.6.1536. Available: