Much of the information that is presented around a vegan diet (a diet that excludes all forms of protein from animals) ignores some basic nutrition elements that may have significant health impacts. There are nutritional considerations to be aware of when excluding animal protein to ensure optimal health and wellbeing.
Even though protein is in a wide variety of foods, omnivores and those following a plant-based diet still struggle to meet recommendations. The most recent adult nutrition survey (ANS) showed an average of 73-79g of protein was consumed by women aged 19-51years.
While we don’t have good New Zealand data, international literature consistently reports that people following a plant-based diet consume up to 30 percent less than their omnivore counterparts. This may be because it takes a considerably larger number of calories (and therefore food) to get the same amount of protein that would be found in animal-based foods, which can be tricky for those with small appetites.
The recommended daily intake according to the New Zealand Dietary Guidelines is 0.8g per kg body weight of protein, which would place the amount reported from the ANS within range.
However, the nutrient reference values (NRV) document, a resource created by both Australian and New Zealand Government experts, has an acceptable macronutrient distribution range (ADMR) of 15-25 per cent of daily calorie intake coming from protein.
This places protein requirements much higher, and is more in line with academics who research protein needs for populations and advocate for levels of approximately 1.5g per kg body weight for optimal health outcomes.
The discordant recommendations come from a new understanding of protein’s role in the body such as the regulation of body composition and bone health, gastrointestinal function and bacterial flora, glucose homeostasis, cell signalling, and satiety.
The RDI of 0.8g per kg bodyweight was based just on nitrogen balance and protein turnover. If we consider an "average" weight of 68kg for females, putting their protein intakes at around 102g, 90 per cent of them will fall below adequate intakes, according to ANS data.
The quality of protein also needs to be considered. Protein-containing food provides 22 amino acids to the body, nine of these are considered essential or "indispensable" — they can’t be produced by the body and must be provided in the diet.
All animal-based sources contain these nine essential amino acids, however, vegetable sources of protein (including nuts, seeds, legumes, flours, vegetables) are missing at least one of them. Experts agree we need to also account for protein’s role in the many other functions I listed earlier.
There is also increased recognition that digestibility of protein needs to account for the presence of "antinutrient" factors present in plant-based foods. This has led to the creation of a new method that assesses protein quality (called the Digestible Indispensable Amino Acid Score (DIAAS) to replace the older Protein Digestibility Corrected Amino Acid Score (PDCAAS).
When comparing plant versus animal protein sources using PDCAAS, some proteins were rated almost equal in their quality, (ie soy and whey protein).
Now, though, the DIAAS reduces the plant-based proteins by a considerable amount due to the presence of phyticacid, trypsins and alpha-galactosides in nuts, seeds and legumes which reduce digestibility of protein and other mineral absorption.
Make protein the first nutrient you consider
It’s difficult to say how much of a problem this poses. Many of the potential pitfalls may not be apparent in the short term and could take years to develop.
Research investigating the relationship between amino acid content of a vegan diet and the association between gastrointestinal function, gut microbiome and glucose homeostasis hasn’t been conducted over the long term in clinical trials, so we can’t establish risk.
And environmental and genetic differences in every body mean that what we see as problematic for one person may be the reasons another person thrives.
My advice is to make protein the first nutrient you consider. While it may not be in the most bioavailable form in most plant-based forms, ensuring a variety of whole grains, legumes, nuts and seeds will help increase the variety of amino acids needed and keep protein levels high.
Quinoa is a pseudo-grain that has a higher protein content than most grains and makes it a good, gluten freechoice for many people.
Soak your grains
Soaking any grains may benefit from adding an acid medium (such as apple cider vinegar) to help break down the phytic acid.
Edamame beans (soy beans) and fermented soy (such as miso or natto) are complete protein sources and are either minimally processed or produced in such a way that helps reduce the anti-nutrient factors present in legumes.
A grain bread that is made from soaked and sprouted grains (such as buckwheat) will have more bioavailable nutrients than other types of bread.
Ensure you soak legumes for at least 12-24 hours, adding a pinch of bicarbonate of soda to the water for kidney shapedbeans — this is said to reduce the cooking time considerably. For other legumes (such as black beans), soak in water (with or without 1 Tbsp of apple cider vinegar for each cup of legumes), refreshing the water every few hours to help enhance the digestibility.
Soaking nuts for 12-18 hours and then drying them in a low oven for a long time (100C for 6-8 hours) will enhance the absorption of nutrients, including protein.
Read the label
Look for meat substitute products, such as the Sunfedrange, that are made with pea protein and have minimal ingredients. These are some of the higher protein options out there. Other substitutes are made predominantly of wheat, contain vegetable oils, additives, flavours and colours, are low in protein, and are effectively more "junk" foods than quality substitutes. Check the ingredients list before purchase.
Follow the recipe
You will find plenty of recipes for vegan dishes made with quality ingredients by authors Megan May and Aaron Brunet in our plant based collection