Welcome back to another edition of Friday Q&A, where our Head Nutritionist Ben gives an in-depth answer to a question about health and nutrition each week!

This week’s question was from Georgia who was curious “Can I get enough protein on a vegan diet?”

One of the biggest dietary myths is that you can’t get enough protein from a vegan diet. Just because plant-based sources of protein are slightly different to animal proteins, it doesn’t mean that you can’t get enough of it!

In fact, eating plant proteins can have many other benefits by providing vitamins, minerals, phytoestrogens, antioxidants, and fibre that are essential for good health!

It’s important to note that there are some key differences in getting protein from plant-based sources compared to animal sources… and it’s handy to know what plants contain what amino acids (the building blocks of protein) for you to be able to thrive on a vegan diet!

In this week’s edition of Friday Q&A you’ll learn all about what proteins and amino acids are, what they do in the body, how much protein you need, the difference between plant-based protein and animal protein, and how to get enough amino acids on a plant-based diet! 

Congratulations to Georgia who won a $20 gift voucher just for asking Ben a question! You can send your questions to ben@13seeds.com.au 

What is protein and why is it important?

Protein is made up of small molecules called amino acids. Many people assume that our bodies use protein, but it’s actually the individual amino acids that our body uses.

When we eat protein containing foods, our body breaks down the protein into individual amino acids. These amino acids are then absorbed through the intestines and transported to all your cells in the body via the bloodstream.

Once your cell receives these amino acids, it then uses them to create all the protein molecules required for various important bodily functions that include: 

- Growth, repair, maintenance: Proteins are essential for the growth, repair, and maintenance of the cells in your body including your organs, muscles, bones, skin and hair.

- Transportation: Proteins transport other molecules through our blood stream and in and out of cells.

- Hormones: Some proteins act as hormones aka messenger molecules that allow cells to communicate with each another.

- Enzymes: Enzymes are proteins that allow reactions in our body to work efficiently.

- Electrolyte balance: Proteins keep electrolytes where they need to be so things like muscle contraction and nerve signalling can happen.

- Fluid balance: Proteins help keep fluids balanced and where they need to be.

- Energy source: Protein can be converted into energy when stored carbs and fats are low (1).

As mentioned, protein is also a source of energy, however, it’s not the preferred source and is only used when you have depleted all of your stored carbs and fats in the body.

When protein is used an energy source this causes a lack of protein to be used for the important functions listed above such as the growth and repair of tissues and supporting immune function… so eating enough protein is essential to avoid these effects! (2)  

As you can see proteins are required for many different functions in the body. So, it’s crucial that you consume enough essential amino acids to be able to carry out these roles!

What are the different types of amino acids?

There are 20 amino acids that the body uses, of these 9 of them are considered essential meaning that we cannot make them in the body and are therefore required in the diet. 

The 9 essential amino acids are phenylalanine, valine, tryptophan, threonine, isoleucine, methionine, histidine, leucine, and lysine (3).

How much protein do I need? 

Current Recommended Daily Intakes (RDIs) for protein in Australia are 0.84 g/kg of bodyweight for males and 0.75 g/kg for females. Older adults (over 70) require more protein with 1.07 g/kg required for older males and 0.94 g/kg for older females. 

While there is evidence to suggest this is adequate protein for the general population, plenty of research suggests that a minimum of 1 g/kg (eg. 70 kg female = 70 g/ protein per day) to be optimal and this requirement increases depending on your activity level.

The type of exercise you do requires different amounts of protein, for example endurance training is around 1.6 g/kg, while strength training/bodybuilding may need up to 2.2g /kg a day! (4, 5) 

Do I need more protein on a plant-based diet? 

A plant-based diet can easily provide enough protein when a variety of foods are eaten. People consuming a plant-based diet should get their protein from a wide variety of sources including legumes, soy products, nuts, seeds and grains. If you’re vegetarian, eggs and dairy are also quality sources of protein.

What’s the difference between plant-based and animal sources of protein? 

Although many people believe that plant-based proteins are ‘incomplete’ (don’t contain all the amino acids), this belief is false! All plant-based sources of protein contain all 9 essential amino acids, however, contain them in different amounts.

There are two essential amino acids that are lower in some plant-based sources. For example, legumes are higher in lysine and lower in the amino acid methionine, while most other plant-based proteins are lower in lysine and higher in methionine.

Just because some foods are lower in one amino acid, doesn’t mean that plant proteins are ‘incomplete’ as all plant proteins contain both methionine and lysine to some extent.

Considering methionine is available in most plant-based proteins, it’s not really a concern if you are eating a variety of plant proteins. However, lysine is predominantly found in legumes, and you should eat these regularly to avoid becoming lysine deficient (6).

The way protein quality is measured is through a measurement called the Protein Digestibility-Corrected Amino Acid Score (PDCAAS), that evaluates amino acid requirements of humans and their ability to digest proteins.

Most animal proteins (including meat, eggs and dairy products) have a PDCAAS score close to or equal to 1.0 (the maximum score), however it might shock you to know that both soy protein (0.91) and pea protein (0.82) have a comparable score (7, 8).

Hemp seeds are also a great source of protein for vegans. The PDCAAS differ based on how you consume hemp seeds. For example, whole hemp seed scored 90.8-97.5, hemp seed meal scored 84.1-86.2, and hemp seeds scored 63-66%.

There are no studies yet on hemp seed protein, but we imagine the score to be similar to soy or pea protein. Hemp protein also offers a unique benefit by being highly absorbable and containing both essential fatty acids and minerals! (9)

Do I need to combine plant proteins?

It was once thought that we need to combine different types of plant-based proteins with each meal to get enough essential amino acids, a process known as ‘protein combining’. 

While eating a variety of plant foods with each meal can complement each other by balancing amino acids, we now know that doing this every meal is unnecessary so long as you’re getting enough energy from foods and eat a variety of plant proteins each day (10, 11).

The reason why is that our bodies maintain a pool of free amino acids that can be used to complement the lack of certain amino acids with each meal (12). 

How can I get enough protein on a plant-based diet?

Most plant foods contain some protein, with the best sources including legumes, soy products, nuts, and seeds. Grains and vegetables also contain protein, but in smaller amounts. 

When you eat enough quality plant-based protein, you’re also helping to increase your consumption of other important nutrients such as iron, zinc, and calcium.

To get enough protein on a plant-based diet you should include a large variety of these foods:

- Legumes: soybeans, chickpeas, lentils, kidney beans, cannellini beans, split peas, pinto beans, navy beans, black beans
- Whole-grains: brown rice, quinoa, oats, buckwheat, amaranth
- Soy products: tofu, tempeh, seitan
- Nuts: almonds, walnuts, brazil nuts, cashews, pistachios, peanuts
- Seeds: hemp seeds, sunflower seeds, pumpkin seeds, chia seeds
- Plant-based milks: soy milk, almond milk, oat milk
- Dairy products and eggs: for those who are vegetarian

If you are concerned about getting enough lysine, incorporate 2-3 servings of legumes and other proteins a day to easily get your lysine requirements. Serving sizes are:

- Chickpeas, kidney beans, pinto beans, navy beans (125-150 g)
- Lentils (100 g)
- Split peas (100 g), green peas (80 g)
- Edamame (80 g)
- Tofu (125 g)
- Tempeh (165 g)
- Soy milk (1 cup or 250 mL)
- Soy meats (85 g)       
- Peanuts (35-40 g)
- Seitan (85 grams)
- Quinoa 1 cup cooked (185 g)
- Pistachios 1/4 cup (30 g)
- Pumpkin seeds 1/4 cup roasted (35 g)

Take-home message

Getting enough protein is essential for any type of diet. Despite many believing it’s not possible, you can easily consume enough protein if you do a plant-based diet properly.

While general recommendations are around 0.8g/kg of bodyweight, you should aim for around minimum 1 g/kg of bodyweight if you live a sedentary life and 1.6g - 2.2 g/kg of bodyweight if you live an active lifestyle.

When consuming a plant-based diet you should eat a variety of plant-based sources of protein while also including sources of high lysine such as legumes. Hemp seeds are a great way to increase your protein intake and also supply high amounts of essential fatty acids, vitamins, and minerals.

If you have any questions or need support with your health, feel free to email our head nutritionist Ben at ben@13seeds.com.au

Disclaimer:

This article does not constitute medical advice and does not take into consideration your personal circumstances. Please see your medical professional before implementing the above

References:

1. https://lettucevegout.com/vegan-nutrition/protein-amino-acids/
2. https://pubmed.ncbi.nlm.nih.gov/18330140/
3. https://www.ncbi.nlm.nih.gov/books/NBK557845/
4. https://pubmed.ncbi.nlm.nih.gov/19841581/
5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6893534/
6. https://pubmed.ncbi.nlm.nih.gov/19562864/
7. https://pubmed.ncbi.nlm.nih.gov/2198245/
8. https://pubmed.ncbi.nlm.nih.gov/19562864/
9. https://pubmed.ncbi.nlm.nih.gov/20977230/
10. https://pubmed.ncbi.nlm.nih.gov/19562864/
11. https://pubmed.ncbi.nlm.nih.gov/8172124/
12. https://pubmed.ncbi.nlm.nih.gov/9706230/