High-protein diets have increased in popularity over recent years. This trend is perhaps due to protein’s prominent role in improving metabolism, regulating appetite, maintaining muscle and promoting fat loss. While there is no doubt that protein has many physiological and physical benefits (extending far beyond those having to do with weight and body composition might I add), emerging research highlights the role of protein in mental health and mood. This post will explore some of these findings, specifically in the context of high protein diets for depression, and shed light on how much protein to eat for optimal mental health. But first, it is important to understand the underlying link that connects protein to our mental well-being.
How does protein protect against depression?
1) Neurotransmitter Production
Protein is made up of small building blocks called amino acids. Some of these amino acids act as precursors for neurotransmitter synthesis. Neurotransmitters are chemical messengers that regulate mood. When these neurotransmitter levels are out of balance, it can manifest as mental health disorders like depression. In other words, the proteins you eat are used to build brain chemicals that dictate mood. The neurotransmitter dopamine is made from the amino acid tyrosine and the neurotransmitter serotonin is made from the amino acid tryptophan. Therefore, if there is a lack of any of these two amino acids, due to insufficient protein in the diet for example, you will not be able to make enough of the respective neurotransmitters and in turn, experience poor mood and symptoms of depression.
2) Blood sugar balance
Protein is also essential for balancing blood sugar levels. When you eat protein, it slows the digestion and absorption of carbohydrates, preventing rapid spikes and crashes in blood glucose. Stable blood sugar helps maintain steady energy and mood, reducing the risk of irritability, fatigue, and mood swings that can follow sudden drops in glucose.
3) Brain-Derived Neurotrophic Factor (BDNF) Support: Certain amino acids in protein also contribute to the production of Brain Derived Neurotrophic Factor (BDNF). BDNF is a protein that supports the growth, maintenance, and survival of neurons (brain cells), making it a crucial factor in learning, memory, and mood regulation. BDNF also promotes neuroplasticity—the brain’s ability to adapt, change, and form new connections. This adaptability is essential for mental health, as it allows the brain to recover from negative experiences, learn healthier emotional patterns, and strengthen neural pathways that support positive thinking and resilience. Consequently, low levels of BDNF increases the brain’s susceptibility to stress, disrupts emotional regulation and increases risk of depression.
What the research shows about eating protein for depression
One study revealed that individuals who consumed high amounts of protein were approximately 66% less likely to experience symptoms of depression compared to those who consumed very little protein (1). Furthermore, people who met the recommended daily protein intake had a 43% lower risk of depression than those who consumed less (1). Another large scale national study that examined the link between macronutrient intake and depression found that increasing protein intake by 10% led to a lower prevalence of depression (2).
How much protein do you need to eat to promote mental health?
The relationship between protein and depression appears to be L-shaped, meaning that as protein intake increases up to a certain point (approximately 1 g/kg body weight), the risk of depression decreases. Additional protein beyond this threshold does not seem to further reduce depression risk (1). This relationship may be theoretically due to the fact that amino acids compete with each other for entrance into the brain.
When you have a high concentration of amino acids in your blood from eating a lot of protein, it can prevent specific mood regulating amino acids like tryptophan from entering the brain. This is why eating protein with carbohydrates is important. When carbohydrates are added to the meal, they trigger the release of a hormone called insulin. Insulin helps muscle tissues absorb most amino acids except tryptophan. With fewer amino acids in the blood, tryptophan can cross into the brain more easily. Once in the brain, tryptophan can be converted into serotonin, which plays a key role in mood, sleep, and feelings of well-being. Thus, pairing protein with carbs can help boost serotonin levels by optimizing tryptophan availability (3).
Gender Differences in Protein Intake and Mood: Special considerations for women
Another important finding is that protein intake can affect mood differently for men and women. One 10 year study revealed that increased protein consumption appeared to protect men against severe depressive moods, while for women, it seemed to have the opposite effect, potentially exacerbating symptoms of depression (3). These differences could be attributed to
Serotonin levels
Women naturally have lower levels of the neurotransmitter serotonin than men. Since high-protein diets can potentially lower serotonin levels due to amino acid competition (if not paired with carbs), it may negatively impact a women’s mood more so than men.
Homocysteine metabolism:
Homocyesine is a byproduct of protein metabolism. Elevated levels of homocysteine in the blood have been associated with an increased risk of mood disorders, including depression. Specific B-vitamins like Folate (B9), Pyridoxine (B6) and Cobalamin (B12) are necessary for breaking down homocysteine to prevent it from accumulating in the body. Women tend to have lower folate levels than men, making it more challenging to process homocysteine efficiently, resulting in elevated homocysteine levels and in turn, adverse affects on mental health.
Ladies, I want to make this clear: protein is still incredibly important for your mental health and physically well-being. But, taking these findings into consideration, make sure you pair protein with carbohydrates like whole grains, starchy vegetables and fruit, while prioritizing folate rich foods like spinach, brussel sprouts, asparagus and beans into your diet.
Does the type of protein matter?
Plant-based protein
Unlike animal-based proteins, plant proteins tend to produce lower levels of homocysteine as a byproduct. Plant proteins are also very high in folate, which help break down homocysteine more effectively. Moreover, plant proteins are lower in saturated fat compared to to animal proteins. Saturated fat is known to increase cardiovascular disease risk, increase inflammation and negatively affect gut health, all of which can worsen mental health. The lower levels of saturated fat and homocysteine byproduct may explain why a study conducted by Sheiki et al., found that consuming more animal protein is associated with an increased risk of psychiatric disorders (4). However, certain legumes such as soy are high in phytoestrogens and can potentially worsen depression symptoms in women specifically (3). While more research is required to investigate this association, focusing on a variety of other legumes and plant proteins can provide the necessary nutrients while minimizing potential mood-related side effects.
Animal-based protein
While animal protein can have some potential adverse effects, this doesn’t mean it should be eliminated from your diet entirely. One study that investigated the association between a meatless diet and the presence of depressive episodes among adults found that individuals who avoid meat have a significantly higher prevalence of depressive episodes compared to those who consume meat (5). Specifically, non-meat eaters experience roughly double the rate of depressive episodes, even after accounting for socioeconomic and lifestyle factors (5). This can be because meat-avoiders tend to have lower levels of nutrients critical for mental health, such as omega-3 fatty acids, and vitamins B12, B6, and D, as well as iron and zinc. Not to mention animal proteins contain all essential amino acids in the proportions our body needs. Therefore, incorporating moderate amounts of meat in a balanced diet may help support mental health by providing essential nutrients that are harder to obtain from plant-based sources alone.
Conclusion
In exploring high protein diets for depression, it’s clear that protein plays a more complex role in mental health than simply supporting muscle or metabolism. Its impact on neurotransmitter production, homocysteine metabolism, and potential interactions with other nutrients emphasizes the importance of a balanced approach. While protein intake can help regulate mood, the type, quantity, and combination with other foods—like carbohydrates—play crucial roles. By focusing on diverse, nutrient-rich protein sources, whether plant or animal, individuals can support both their mental and physical well-being.
Key take aways:
Pack a protein punch Eating enough protein is essential for mental health. Aim for a minimum of 1g of protein /kg of body weight per day to potentially lower the risk of depression and support mental well-being. (Speak to a Registered Dietitian for your specific protein needs in accordance to physical activity, lifestyle goals etc)
Pair Protein with Carbohydrates: To enhance the transport of mood-boosting amino acids like tryptophan to the brain, combine protein sources with carbohydrates in your meals. This is especially important for women.
Eat your Meat: Animal proteins are important for mental health. Opt for lean sources of animal protein, such as chicken, turkey, and fish, to minimize saturated fat intake while still benefiting from essential amino acids that support neurotransmitter production.
Incorporate Plant Based Proteins: Include a variety of plant-based proteins in your diet, such as legumes, beans, and whole grains. These foods are rich in B vitamins like folate and do not significantly raise homocysteine levels, which can help improve mood and mental health.
Variety is Key: following a balanced meal model that includes protein, carbs, healthy fats and veggies at every meal will ensure you are getting adequate nutrients to support your brain and mind. Not sure how to start? Work with a Registered Dietitian like myself!
download your complete protein guide:
References:
Li, Y., Zhang, C., Li, S., & Zhang, D. (2020). Association between dietary protein intake and the risk of depressive symptoms in adults. British Journal of Nutrition, 123(11), 1290-1301.
Oh, J., Yun, K., Chae, J. H., & Kim, T. S. (2020). Association between macronutrients intake and depression in the United States and South Korea. Frontiers in psychiatry, 11, 207.
Wolfe, A. R., Arroyo, C., Tedders, S. H., Li, Y., Dai, Q., & Zhang, J. (2011). Dietary protein and protein-rich food in relation to severely depressed mood: a 10 year follow-up of a national cohort. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 35(1), 232-238.
Sheikhi, A., Siassi, F., Djazayery, A., Guilani, B., & Azadbakht, L. (2023). Plant and animal protein intake and its association with depression, anxiety, and stress among Iranian women. BMC Public Health, 23(1), 161.
Kohl, I. S., Luft, V. C., Patrão, A. L., Maria del Carmen, B. M., Nunes, M. A. A., & Schmidt, M. I. (2023). Association between meatless diet and depressive episodes: A cross-sectional analysis of baseline data from the longitudinal study of adult health (ELSA-Brasil). Journal of Affective Disorders, 320, 48-56.
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