For essential amino acids - are plant-based diets good enough?

The big question is – can plant-based diets provide enough proteins in general and essential amino acids in particular?

But before looking at the sufficiency of essential amino acids available in plant-based diets, let’s consider amino acids in general – what are they and why are they so important?

Quite simply, amino acids are the building blocks which collectively make proteins. Different combinations of the 20 amino acids will come together as different proteins. Additionally, they are required for such vital compounds such as hormones and neurotransmitters.

Amino acids are found in many plant-based foods such as lentils, beans, green peas, tofu (soy) and spirulina.

So, moving on from amino acids in general – what are the essential amino acids?

How are essential amino acids different from other amino acids?

What distinguishes essential amino acids is that, unlike others that the human body is able to make, they are only available from dietary sources and cannot be made from scratch.

Of the 20 amino acids the human body needs for correct function and health, 9 are categorised as essential amino acids – these are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

What are the vital functions of the essential amino acids?

The individual vital functions of these particular amino acids are as follows:

Phenylalanine

This amino acid is utilised in the production of the following neuro-transmitters:

• Tyrosine

• Dopamine

• Epinephrine

• Norepinephrine

Phenylalanine also has other vital roles in the structure and function of enzymes and in the manufacture of alternative amino acids.

Valine

This amino acid is important in muscle growth and regeneration and additionally in the body’s vital energy production.

Threonine

Functions of this amino acid include being a component of structural proteins (such as collagen), playing a role in immune function and the metabolism of fat.

Tryptophan

This amino acid is a metabolic precursor of the neurotransmitter serotonin – its therefore important in the regulation of sleep, appetite and mood.

Methionine

Essential functions of methionine include:

• Vital role in metabolism and detoxification

• Tissue growth

• Absorption of the essential minerals, selenium and zinc

Leucine

This amino acid fulfils the following functions:

• Synthesis of proteins and repair of muscular tissue

• Regulation of blood sugar levels

• Stimulation of the healing of wounds

• Production of growth hormones

Isoleucine

This amino acid is found in high concentration in muscular tissue and fulfils an important function in muscular metabolism. It additionally:

• Plays a role in immune function

• Is important in the production of haemoglobin

Lysine

This amino acid fulfils many vital roles including:

• Protein synthesis

• Absorption of calcium

• Enzyme and hormonal production

• Structural protein production

• Immune function

Histidine

This amino acid has the following vital functions:

• Immune response – it is used in the production of histamine

• Digestion

• Sexual function

• Nervous system maintenance – it is essential for the function of the protective myelin sheath

As you can see from the above, essential amino acids are of paramount importance within many vital bodily processes. For this reason, a deficiency of essential amino acids can negatively impact the entire body – including the reproductive, nervous, digestive and immune systems.

So, now we have covered the importance of dietary essential amino acids – how can they be obtained from an exclusively plant-based diet?

There are fundamentally two avenues to be explored – “incomplete” and “complete” plant-based proteins.

Incomplete proteins

Incomplete protein sources are those that provide a number of the essential amino acids (in some cases most), but not all of them. In the case of these protein sources one can ensure an appropriate intake of all of the essential amino acids by consuming a balanced variety of incomplete plant proteins derived from a number of sources, including:

• Beans – those with the highest protein content include lentils, large white beans, borlotti beans, split peas and pinto beans

• Nuts – great sources of protein include almonds, walnuts, pistachios, cashews, pine nuts, Brazil nuts and peanuts (strictly speaking a legume, not a nut)

• Seeds – these include pumpkin seeds, sunflower seeds, flax seeds and chia seeds

• Whole grains – those with an impressive protein content include cornmeal, wild rice, couscous, buckwheat and oatmeal

• Vegetables – those (not including beans – see above) with a high protein content include asparagus, spinach, artichokes, Brussels sprouts and kale

Complete Proteins

Complete protein sources are those that provide all nine of the essential amino acids. The plant-based examples of these protein powerhouses include:

• Quinoa – in addition to being an excellent source of carbohydrate, fibre (insoluble and soluble), folate, vitamins and essential minerals, this “pseudo-cereal” grain is a complete protein source. (for further information on this wonderful plant-based food do check out my article “Nutritional benefits of quinoa – can they boost your natural health?”)

• Soy – soy beans may be consumed whole, in their natural state but soy is generally consumed in a number of forms including tofu, soy flour, soy protein, soy sauce, soy milk and soybean oil. As well as being a complete protein source, soy is a rich source of phytonutrients, essential minerals, vitamins and fibre. A 2016 scientific update provides extensive detail on the wonderful nutritional benefits of soy.

Truly a “superfood”.

(do look out for our forthcoming article on soy)

• Oyster mushrooms – although not strictly speaking plant-based, this vegan and meat-free food is a complete protein source. This is, additionally, a powerhouse of nutrition – a rich source of health-protecting antioxidants, fibre, folate, vitamins and essential minerals.

(do look out for our forthcoming article on oyster mushrooms)

• Hemp seeds – in addition to being a complete protein source, hemp seeds are rich in essential fatty acids (omega-3 and omega-6), a great source of vitamin E and many essential minerals – including magnesium, potassium, phosphorus, sodium, calcium, zinc and a number of others.

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