Protein is so important for everyone’s health, and in particular in those suffering with neurological issues and diseases. Over recent years there have been myths circulating about protein, about its acidity in the body, and about its growth promoting properties which has been conflated with being cancer-promoting, particularly from animal foods.
Let’s start by laying out the facts about protein.
What it is,
where it comes from,
how we digest and absorb it,
and what we need it for.
The what
Protein is a macronutrient and can be broken down into its building blocks called amino acids. Think of a house made of bricks. The bricks are the amino acids joined together to form a protein structure, using this analogy, the house is the protein.
There are 9 essential amino acids which must be consumed from our diet, hence why they are called ‘essential’ because the human body cannot synthesise them.
1) Phenylalanine
2) Valine
3) Threonine
4) Tryptophan
5) Methionine
6) Histidine
7) Isoleucine
8) Lycine
9) Leucine
When we consume protein our body breaks it down to amino acids to be utilised throughout the body. They are used to create different protein structures, much like Lego bricks that can be pulled apart and reattached in thousands of different shapes and forms.
The why
Protein forms the basis of our very structure: muscles, blood, skin, and bones. It is required for muscle contraction and extension in myosin and actin filaments. Collagen is a protein material used for building dermis, artery walls, ligaments, tendons, etc. Proteins are also needed for the replacement of fast-replicating cells, such as the stomach inner lining, gut wall tract, and skin. It is also required to bond to fat-based molecules throughout the body, helping to ferry vitamins, minerals, and other molecules to their target receptors. Albumin is key constituent of blood which has many roles to play but is well known for its role in blood osmolarity - helping to keep fluid within the blood vessels.
Protein forms the basis of our very structure
Enzymes, another protein structure, is the very reason you can read this article, and the very reason I could write this article. Think of them as chemical catalysts and are the reason anything happens at all in the body. The body is a perfect and delicate balance of parameters keeping us in a Goldilocks state of homeostasis. However, this state does not provide an environment of escalation, de-escalation, or adaptation to change – meaning chemical reactions, or any volatility, cannot occur. Enter: enzymes.
Another name for protein is peptide, and the two are often used interchangeably. We have peptide hormones which require sufficient intake of amino acids to build them. These are:
Thyroid hormones: thyroid-releasing hormone (TRH) from the hypothalamus, thyroid-stimulating hormone (TSH) from the pituitary gland, thyroxine (T4 – the inactive hormone) from the thyroid gland, and triiodothyronine (T3 – the active hormone) converted from T4. This delicate system is heavily reliant on protein, namely tyrosine, formed from our essential amino acids.
Dopamine, norepinephrine, epinephrine -> formed from tyrosine protein
Serotonin, melatonin
Insulin, glucagon
Para-thyroid hormone, calcitonin
Hormones and neurotransmitters need to connect to something on their target cells, tissues and organs, and they do this using receptors, which are also proteins.
Some amino acids have side chains in their chemical structure which can help pick up or drop off hydrogen molecules in the blood and elsewhere. This makes these amino acids good buffers, helping maintain the acid-base balance within the body.
The amino acid histidine is one such example of this
Protein has an enormous role to play in the structure of antibodies of our immune system, and haemoglobin structures in our red blood cells that help us oxygenate the body. Protein is vital for bone health and muscle growth, repair and maintenance. Protein is essential for fat burning, supporting your metabolism, and supporting the thyroid and adrenals.
Protein has multiple roles throughout the entire body
Protein not only builds muscle but also builds the supporting structures of muscles and joints, such as ligaments, tendons, cartilage and other body tissues.
An adequate intake of good quality protein from animals and plants helps promote weight loss in large part due to its satiating factor. It helps retain lean muscle mass whilst improving resting energy metabolism. Essentially, this means your metabolism increases whilst keeping all those muscle gains in your workouts.
Protein supports our mood. The macronutrient is important in the synthesis of neurotransmitters and hormones. In people lacking certain amino acids, people can experience anxiety, low mood, irritability, and depression.
Protein stabilises our blood sugars. In contrast to a high-sugar, high-carbohydrate diet where blood sugars fluctuate dramatically, the increased intake of protein helps slow down the absorption of carbohydrates, resulting in a slow release of energy throughout the day.
We need protein for bone remodelling, repair and maintenance, especially as we age.
It has been shown that a high protein intake helps reduce the risk of cardiovascular disease and can help reduce high blood pressure.
Amino acids are critical for synthesising enzymes, hormones and neurotransmitters for brain health. A steady supply of these amino acids helps us maintain focus, concentration and memory formation and retention.
The amount
There is much debate on the amount of protein from foods that is required for our body to be healthy; none of the advances in biology have provided a definitive solution so far.
There are no unequivocal biochemical or physiological deficiency symptoms other than those of severe deficiency (growth failure, tissue wasting) → we can only identify levels below requirement
All methods of determining protein requirements are imprecise
The body is a wonderfully complex biological system rather than a mathematical model, and there are simply too many variables, (not to mention the unique individual requirements), to emphatically state specific numbers required for optimal protein intake.
However, the general rule is 0.75g per kilo of body weight per day in a person who leads a sedentary lifestyle, 1g per kilo of body weight in the minimally active, 1.3g per kilo of body weight in the moderately active, and 1.6g per kilo of body weight in the intensely active.
For pregnancy an additional 6g/day is recommended
For lactation an extra 11 g/day 0-6 months and 8 g/day 6+ months
Long-term consumption of protein at 2 g/kg/day is safe for healthy adults
The tolerable upper limit is 3.5g/kg/day for well-adapted subjects
Protein intake is very dependent on a person’s health and fitness goals. It is thought that most people in the UK are getting enough protein in the diet, but people looking to lose fat and lose weight, (women in particular), may actually be protein insufficient. For one reason or another, people are veering toward plant-based proteins, which are not always adequate to support all the various roles protein offers for human health.
Excess of any macronutrient without an appropriate expenditure of energy will result in it being converted and stored as fat. If you are looking to increase protein you should be looking to reduce the carbohydrate intake. By consuming 0.75g or more of protein per kilo of body weight you will essentially be replacing those extra carbohydrates in your diet with protein. With protein’s ability to satiate the digestive hormones effectively you may find yourself eating less anyway, but it is something to be aware of.
Despite living in a food-abundant environment, certain demographics or eating habits can put an individual at risk of protein deficiency. These are:
Children whose diets are rich in refined sugars, sweets, soft drinks, and low amounts of wholefoods.
The elderly whose digestive health, appetite, dentition and immobility may negatively affect their ability to consume enough.
Teenagers who diet, restrict foods/calories, or eat high-refined sugars, processed foods, soft drinks, etc.
Anorexia nervosa sufferers
Recovering patients from surgery, illnesses, infections
According to the Joint FAO/WHO/UNU Expert Consultation on Protein and Amino Acid Requirements in Human Nutrition 2002, an intake of twice the recommended intake <of protein> is likely to be safe as long as plenty of fruit and veg is consumed alongside
The where
There “where” we get our protein from matters because if you veer toward a more vegetarian diet, your sources of protein may need to come from a greater variety of foods. Grains, cereals, legumes and soybeans contain some, but not all, of the 9 essential amino acids. The exception is quinoa, buckwheat, tempeh and natto, which are considered complete proteins, meaning they contain all the essential amino acids. Furthermore, you often need to eat a bigger portion of the protein-rich plant foods to get a sufficient amount of your essential amino acids. In the case of quinoa, you would need to consume a huge amount daily to meet the bodily requirements for amino acids, whilst doing this at the expense of omitting other sources of micronutrients, minerals, and vitamins. Vegetarians and vegans need to be mindful of these aspects of the meat-free diet to provide their body with a large variety of plants and cereals to meet the appropriate amount of protein for optimal health.
Another disadvantage of plant-based proteins are the inhibitory factors in plant foods that can negatively impact the digestion and absorption of amino acids. Such inhibitory factors found in edible crops are saponins, tannins, phytic acid, gossypol, lectins, protease inhibitors, amylase inhibitor, and goitrogens. These components of plant foods negatively alter the bioavailability of macro- and micro- nutrient absorption. Legumes and cereals contain trypsin inhibitors and phytates, reducing the digestibility of protein and its absorption. This can lead to micronutrient deficiencies and malnutrition. The good news is there are workarounds to improving the digestibility and absorption from plant-based protein foods, and that is through prepping the foods using fermentation, germination, debranning, autoclaving and soaking. These processes help to reduce the anti-nutrient factors in plant foods.
To make proteins, a cell must have all the required amino acids available simultaneously; if one essential amino acid is missing, a cell must dismantle its own protein to obtain it.
Low quality proteins: some essential amino acids are present in lower amounts - most plant foods belong to this group
High quality proteins: contain all the essential amino acids in relatively the same amounts as humans require; all foods of animal origin belong to this group
With that said, here are the top 10 sources of protein for maximum digestion and absorption:
Meat
Fish
Poultry
Eggs
Dairy
Quinoa
Buckwheat
Fermented soy (tempeh or natto)
Why is protein important for mental health?
The foods we eat play an important role in the structure and function of the brain, and therefore our mood and emotional regulation.
Neurotransmitters
The neurotransmitters, hormones and receptors required for mental function are all protein-based, meaning we require a good intake of all the essential amino acids listed above to help our body produce bigger protein structures, in this case, neurotransmitters like dopamine and serotonin which are important in supporting depression and anxiety. Consider also the enzymes involved in all chemical reactions in the body, including the breaking down and building of molecules and compounds, are protein based.
Low dopamine levels are associated with:
Depression
Addiction
ADHD
Dementia
Schizophrenia
Low serotonin levels are associated with:
Anxiety
Depression
Aggression
Impulsiveness
Cognitive decline
Insomnia
Dementia
Research into serotonin suggests this neurotransmitter may also be involved in pain modulation, energy metabolism, immune system response, heart and liver function, digestion and sleep. Serotonin deficiency is implicated in diabetes, obesity, fatigue, osteoporosis, cardiovascular disease, and gastrointestinal issues such as irritable bowel syndrome.
Immune system
Your immune system is reliant on the intake of the essential amino acids. Antibodies are protein structures and are required to fight infections but are also part of our first line of defence such as secretory IgA (sIgA) which can be found within the mucosal membranes of the oral and nasal cavity, trachea, oesophagus, or any area of the body that are exposed to particles from the outside.
If your body is chronically lacking in the materials to build and support a healthy immune response, the body will become chronically infected, weak and susceptible to disease. Our immune system is not only effective at launching pro-inflammatory responses but it is also synthesises moderating chemicals to halt the inflammation progression. The pro-inflammation response is known as a positive feedback loop; a cut on the skin will bleed, become red, warm and will be painful. Clotting factors react quickly to stem the bleeding and close the wound. Initially the immune response is rapid and escalates further before slowly tapering off. It is the tapering and slowing that is called a negative feedback loop; the clotting ceases, the redness lessens, the pain subsides, the warmth of the wound dissipates.
The same applies to internal stressors and injuries whereby the immune system launches a response, followed by moderating or inhibitory immune cells to halt the inflammation process. The latter process is so important. This wonderfully complex ‘war and peace’ process is heavily reliant on amino acids and proteins.
BDNF
Brain-derived neurotrophic factor (BDNF) is a protein structure. It plays an important role in the growth, differentiation and maintenance of nerve cells in the brain. BDNF may be the link in those with depression and anxiety as this protein structure is low in these patients. Sugar suppresses the activity of BDNF as well so reducing the carbohydrate load and increasing the protein in the diet is a win for BDNF activity.
There is a huge body of research implicating the absence or dysregulation of BDNF in many neurological disorders and diseases. Patients with psychiatric and neurodegenerative disorders consistently present with low concentrations of BDNF in the brain and blood. The current theory is that neuroinflammation is responsible for the protein’s lack of healthy levels. Neuro-inflammation has been shown to negatively affect BDNF-related signalling pathways. Low levels of BDNF have been shown in: Alzheimer’s, accelerated aging, poor neural development, neurotransmitter dysfunction, obesity, depression, and even schizophrenia.
Iron & B Vitamins
Iron is important for energy metabolism. Low mood, lethargy, depression, fatigue, can all be linked to iron-anaemia.
Red meat, or animal protein sources, are rich in haem iron. Haem iron is readily absorbed in the body and does not compete with most other factors in the diet, making it one of the most effective sources of food for iron.
In contrast, non-haem iron from cereals, beans, and dark leafy green vegetables are poorly absorbed. Non-haem iron needs to be solubilised then hydrolysed before absorption is possible. This requires a healthy gastric acid secretion and correct pH levels. The factors known to inhibit non-haem absorption is vegetable proteins, phytic acid, oxalic acid, zinc, calcium, eggs, tea and coffee.
The body will absorb what it needs from haem-rich foods so there is little danger of consuming too much iron.
It is critical to get enough B12 into the diet as an insufficiency of this vitamin can result in low moods, poor energy levels, poor memory, fatigue, depression, chronic stress and burnout. B12 deficiency may cause:
Memory loss
Neurodegenerative diseases
Depression/anxiety
B12 is also needed to support healthy nerve cells, helping to facilitate neurotransmission. B12 with B9 (folate) is vital for the production of SAMe (S-adenosyl-methionine). SAMe is a vital compound required for normal neurological function, dealing with stress and emotion regulation.
B12 exists in many forms, and the two that are active in human metabolism are methylcobalamin and 5-deoxyadenosylcobalamin. The best sources of B12 are dairy foods, eggs, red meats, fish, poultry and organ meats. It is thought that B12 sourced from nutritional yeast, fortified grain foods, and sea vegetables are not nearly as absorbable as natural animal sources. A vegan or vegetarian diet will be lacking in B12 so supplements will be necessary.
B9 (folate) is also crucial for nervous system function. Folate is required for cell differentiation, such as in the production of red blood cells. As discussed earlier with iron, poor red blood cell production will cause symptoms of low mood, lethargy, depression and fatigue. Low levels of folate and B12 have been associated with cognitive decline and dementia.
B2, B3, B5, B6 can all be found in animal foods and in some vegetables, seeds and nuts. B1 and folate can be found in vegetables, fruits, and nuts and seeds. The whole spectrum of B vitamins is required for good mental health, helping to mitigate the symptoms of depression and anxiety. B vitamins can help with mood regulation, mental acuity, memory, and energy metabolism.
Conclusion
The importance of protein intake for good mental health is key. The fear-mongering around moderate to high animal food intake being associated with increased risks of cancer, cardiovascular disease and other lifestyle diseases is often based on studies either with unhealthy cohorts (smoking, sedentary, high intake of high-refined sugars and carbohydrates, alcohol), or studies with unknown variables in lifestyles of the trial participants. Increasing protein in the diet helps to satiate the digestive hormones, meaning you eat less. Blood sugar levels stabilise throughout the day, helping to maintain your energy levels instead of the crash-and-burn patterns seen in high-sugar, highly processed foods. Protein also helps build and maintain lean muscle mass. The more muscle mass you have, the higher your resting metabolism, the more weight you will lose or the easier it will be to keep the weight off.
Protein also helps your mood by providing the building blocks for hormone and neurotransmitter synthesis, such as serotonin. Serotonin is a precursor to melatonin (our sleep hormone and potent antioxidant), so a good intake of protein is vital for good sleep. Melatonin is a powerful antioxidant that is useful in combatting a high inflammation state, which is often the case in people with depression and anxiety.
We can also produce the protein-based hormone and neurotransmitter dopamine, which is involved in the reward pathways in the brain. It is a potent “feel-good” hormone. Alongside the hormones endorphins (a natural pain reliever), and oxytocin (reduces anxiety), protein really is the foundation for good mental health.
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