Vegans don’t get enough of this essential thing in their diets

By Stephen Beech

Vegans don't get enough essential amino acids in their diets, suggests a new study.

Even people on a strict vegan diet who eat enough total protein may fall short of the required levels of lysine and leucine, say scientists.

Researchers in New Zealand found that three out of four vegans ate sufficient protein, but half didn’t meet daily lysine and leucine requirements.

The study of people on long-term vegan diets, published in the journal PLOS One, found that most ate an adequate amount of total daily protein.

However, a "significant" proportion did not meet the required levels of lysine and leucine.

A vegan diet is a plant-based one that excludes all animal products - including meat, fish, dairy, eggs, and honey. I

The strict form of vegetarianism is focused on incorporating a variety of fruits, veg, grains, legumes, nuts, and seeds for optimal health.

Study author Dr. Patricia Soh said that proteins are made up of molecular “building blocks” known as amino acids.

She explained that while the human body can synthesize most of the amino acids we need to live, we completely rely on the food we eat to provide the nine “indispensable amino acids” we cannot make ourselves.

Dr. Soh says plant-based foods usually have more varied levels of indispensable amino acids that the body can use, as compared to animal-sourced foods, so they are of particular concern in vegan diets.

Most previous research on protein in vegan diets didn't consider specific amino acids nor the digestibility of different foods, which accounts for the fact that not all of what we eat, including amino acids, is fully utilized by the body.

To help deepen understanding of amino acid intake in vegan diets, Dr. Soh and her colleagues at Massey University analyzed detailed, four-day food diaries kept by 193 long-term vegans living in New Zealand.

Dr. Soh said: “Vegan diets are the most restrictive form of plant-based eating, relying entirely on plant sources for all nutrients.

"Achieving high protein quality on a vegan diet requires more than just consuming enough protein - it also depends on the right balance and variety of plant foods to supply all the amino acids in the quantities that our body needs.

"Prolonged deficiencies in these essential nutrients can negatively affect overall protein balance, muscle maintenance and other physiological functions, especially in more vulnerable populations.”

The research team used information from the New Zealand FoodFiles database and the United States Department of Agriculture to calculate the participants’ intake of different amino acids from the food they ate.

Dr. Soh said the analysis showed that about three-quarters of the participants met daily total protein requirements.

Accounting for body weight, intake of all indispensable amino acids also met requirements.

However, when considering digestibility, only around half of the participants met daily requirements for lysine and leucine levels, making them the most limiting indispensable amino acids in the study.

Among the food types consumed by participants, Dr. Soh said legumes and pulses were the biggest contributors to overall protein and lysine intake.

She says the findings underscore that meeting total daily protein requirements does not necessarily mean meeting indispensable amino acid requirements.

Dr. Soh added: “In our study, lysine and leucine were the most commonly under-consumed amino acids in our vegan cohort and fall below the daily requirements needed by our body.

"This is because many plant foods generally contain lower quantities of these amino acids that can be absorbed and utilized by the body.

"However, the inclusion of legumes, nuts and seeds emerged as valuable plant sources – not only to support overall protein intake but also to specifically increase lysine and leucine quantities in a vegan diet.”

The research team called for further studies to explore how intake of leucine and lysine could be boosted for vegans in a nutritionally balanced manner.