Protein is one of the three macronutrients, along with fat and carbohydrates. Most of us probably know that protein is ‘good for us’, but we may be surprised to learn in just how many ways this macronutrient works to support our health.

Proteins are made of molecules called amino acids. The body uses these for a multitude of functions, including:

• Maintenance and repair of body tissues
• Immune function
• Digestive enzymes
• Cell communication and signalling
• Energy 

You can read this article to learn more about the  Benefits of Protein.

Your body needs around 20 different amino acids in order to keep these processes going. We can naturally synthesise and recycle 11 of these but there are nine amino acids essential for good health which cannot be made or stored in the body. These must therefore be obtained from your diet. You can read more about this later in the article.

We can see from the above just how important protein intake is for physical health, but can it also help our mental health?

Can protein help our mood?

It’s well-established that our diet can have either a positive or negative effect on our wellbeing(⁽¹⁾. Certainly B vitamins like biotin and folate are well-known for their ability to help to support the nervous system and good psychological function, whereas a high sugar diet is increasingly associated with poor mental health⁽²⁾. Protein might not be the first thing you think of when you want to change your diet to support good mental health, but there’s an increasing weight of evidence that indicates protein consumption is linked to mood^(3,4).

But exactly how does protein help mental health?

We’ve seen that proteins have numerous functions in the body. All of these processes will keep us feeling healthy and lead to an overall sense of wellbeing. However, there are couple of ways in which protein may directly help to improve our mood:

• Neurotransmitter synthesis

Protein is required for the production of neurotransmitters, chemical messengers that send instructions between our nerves, muscles, or glands. Neurotransmitters such as serotonin and dopamine are active in the brain where they regulate sleep, emotion, appetite, and cognitive function. Research is still evolving but it’s suggested that low protein intake might result in low levels of these amino acids and neurotransmitter deficiencies^(5).

Dopamine and serotonin are derived from the essential amino acids phenylalanine and tryptophan. The body can’t synthesise these amino acids so we need to source them from our diet. They are found in high-protein food sources like eggs, soybeans, fish, beef, and chicken. It’s believed that having your protein foods with some healthy carbohydrates (wholegrains, fruits, vegetables) might help more of these neurotransmitters to reach the brain⁽⁶⁾, so have some of these healthy foods with your proteins.                             

Tip: Our gut bacteria help to produce neurotransmitters in the gut, so try eating some gut-friendly foods with your proteins too. Fermented foods, wholegrains, and fruit and vegetables will help to keep your gut bacteria populations healthy.

• Balances blood sugar levels

One of the first things nutrition professionals will consider when trying to put a protocol together to support mental health is blood sugar regulation. Fluctuating blood sugar levels can play havoc with our mood. When blood sugar levels are high it can make us feel tired and sluggish, and low blood sugar can make us feel anxious and irritable. These fluctuations are typically caused by eating sugars and refined carbohydrates, which are quickly digested and released into the bloodstream. This causes an initial spike in blood sugar, followed by a slump, each causing these unpleasant symptoms. If you’re unaware of the mental and physical effects this blood sugar rollercoaster might be having on your wellbeing, you may just think you’re suffering from anxiety and/or low mood or fatigue.

Protein itself has little effect on blood sugar, but because it takes longer to digest, it can slow down the digestion of carbohydrates, helping to stabilise blood sugar levels ⁽⁷⁾. In turn this can help to avoid the negative effects on mood that poor glucose metabolism may have.

Tip: Eating your protein before your carbohydrates will further slow down digestion and promote the release of hormones that can reduce the release of both glucagon and insulin, resulting in improved post-prandial glucose responses, help suppress appetite and promote satiety.⁽⁸⁾

Which sources of protein are best for mental health?

Animal-based protein sources are typically higher in protein and are ‘complete’ proteins, meaning that they contain all of the 9 essential amino acids. They also contain good levels of iron which helps to prevent fatigue and low mood.

Animal protein sources:

• Meat
• Poultry
• Fish
• Eggs
• Dairy (Milk and cheese)

However, there is some evidence that relying solely on animal protein can actually adversely affect mood^(9,10), so it’s best to eat a broad range of protein foods from both animal and plant sources. Plant proteins are also lower in fat and higher in gut-friendly fibre than animal sources.

The only consideration is that not all plant proteins contain every one of the 9 essential amino acids we need. If you are vegetarian or vegan and rely solely on plant-based proteins, combine different types of plant sources each day, e.g. nut butters with whole grains, to ensure you complete your amino acid requirements. Read this related article to find out more about how to get enough protein if you're vegetarian.

Complete plant protein sources:

• Soybeans
• Tempeh/tofu
• Quinoa
• Amaranth
• Hemp
• Chia
• Spirulina
• Plant-based meat alternatives

Other plant protein sources:

• Nuts
• Peanuts
• Wholegrains (oats, wholemeal wheat or rye bread. whole grain pasta, brown rice)
• Beans and pulses
• Lentils
• Seeds

How much protein should you eat each day?

Thankfully it’s rare to have a serious protein deficiency, but it’s important to get the optimum intake for your needs as everybody’s requirements are different. 

The standard recommended daily intake of protein is around 0.75g of protein per kg of body weight per day for average weight adults ⁽¹¹⁾. This typically translates to around 60g/day for men and 45g/day for women. However, this is just the minimum required to keep your body functioning, and individual needs will vary depending on your age, level of activity, or life stages like pregnancy or lactation in women.

Many individuals have an increased need for protein, including athletes who train regularly, who may need to consume between 1.2- 2g of protein per kg of bodyweight daily ⁽¹¹⁾, and pregnant women who should consume at least 1.1g of protein daily in their final two trimesters⁽¹²⁾. Older adults also need to consume more protein as they age, and should aim to consume 1-1.6g per kg of their weight.⁽¹³⁾ 

Read our related blog to find out more about how much protein you should be eating. In conclusion, if you’re looking to support your mental wellbeing, it’s well worth considering the part that diet plays in your overall well being, and keeping an eye on your protein intake as you may not be eating enough. Try to include a protein at every meal, and vary your protein sources.

If you enjoyed this article, you may also like to read these other articles on our site:

The Benefits of Fibre 

Sugar - Are You Consuming Too Much?

Are You Getting Enough Sleep

References:

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2. Knüppel A, Shipley MJ, Llewellyn CH, Brunner EJ. Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study. Sci Rep. 2017 Jul 27;7(1):6287. doi: 10.1038/s41598-017-05649-7. PMID: 28751637; PMCID: PMC5532289.
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4. 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. doi:10.3389/fpsyt.2020.00207
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