Irish Dietitian Orla Walsh: Can a plant protein diet ever be as good as a meat one?
We are bombarded by conflicting information about our health - even more so when it comes to food. Now that a plant-based diet is becoming more popular, we ask our resident dietitian Orla Walsh if a meat-free diet can provide the same nutrients as a meat-based one
To understand the pros and cons of plant proteins, it’s important to understand protein in general.
It’s imperative not to underestimate the power of protein. It is more than just food for our muscles. The human body has over 10,000 different proteins that are integral in the normal functioning of the body.
Nonetheless, protein is famous for feeding the body’s muscles. When people think of their muscles they’ll often picture the muscles found in their arms and legs. However a large chunk of our overall muscle tissue is found internally (heart, diaphragm, gut etc). Muscles and bones are similar in that they are constantly breaking down and rebuilding. Not drastically, it’s a slow process, but it is constantly happening. If you do not give your muscles and bones the necessary building blocks to rebuild after breaking down, you end up losing these precious tissues over time. This would obviously impact your quality of life and how long you live for.
The more muscles and bone tissue you have, the faster your metabolism runs. This is why men often need to eat more than women, as they tend to be taller and stronger. Protein needs to be fed to the body regularly to keep the metabolism running as fast as it should, in the same way you need to keep throwing kindling on a fire to keep it from going out. Additionally, if you don’t feed your muscles and bones protein regularly, you’ll lose them, slowing your metabolism down as you age.
Do we all need to go on a high-protein diet?
What is clear when it comes to protein is that it’s not the case of the more the merrier, but we definitely shouldn’t under eat it. In fact, it’s a bit of a Goldilocks scenario where there is a recommendation that is just right. (See panel A)
The important point to note is that we can only absorb and use a certain amount of protein at each meal. Therefore the protein that we eat should be spread evenly across the day. At each mealtime the aim is to achieve about 20g of protein as this is the number of grams that has been shown to stimulate most adults’ muscles to their maximum.
The age of the person eating the protein matters.
Protein requirements increase with age. When it comes to being ‘older’, the research on protein is rather offensive! Sarcopenia is the loss of muscle mass and muscle function with age. It is estimated that you lose about 1pc of your muscle per year after the age of 40. Fortunately we now know, thanks in part to Irish researcher Dr Caoileann Murphy, that we are in control of this process. Exercise and the right amount of protein at each meal being the ingredients needed for success.
Muscles of both young and older people are always breaking down and rebuilding. However, the muscles of older people need more protein than a younger person at each meal to maximally stimulate their muscles to rebuild. To put numbers on it, an older person needs about 40g of protein at each meal while a younger person needs about 20g. Additionally, calorie needs decline with age. Therefore older people need to choose more protein-dense foods. Reaching these targets for protein is challenging as older people can develop a reduction of appetite-regulatory hormones and eating protein increases the fullness feeling and reduces hunger. It’s even harder to achieve when focusing on plants as they tend to have lower amounts of protein per bite of food.
To use the examples from, 1 drained tin of kidney beans is 240g of kidney beans. Therefore if kidney beans are your protein source at a meal, more than 1 tin of beans would be required to hit the 20g mark for protein. The likes of poultry, fish and meat are richer sources of protein. Approximately half a large chicken breast is all that is required to meet your protein needs at mealtime. In other words, there tends to be more protein in one bite of animal protein compared to one bite of plant protein.
Although overall quantity and pattern of intake are incredibly important, it is crucial to consider the quality of the protein.
Are plant proteins high quality?
A common question that a dietitian might be asked would be whether plant proteins are “incomplete”? And whether or not it’s necessary to combine different plant proteins to make them “complete”?
To understand what this means it’s important to grasp the basic structure of protein. Proteins are made of building blocks called amino acids. Some of these amino acids can be made within the body, while others can’t. As you can’t produce certain amino acids within the body, you need to eat them. These are often referred to as essential amino acids.
Animal proteins contain all these essential amino acids. While all plant proteins contain at least some of the essential amino acids, they tend to be lacking in one of them. For example, legumes tend to be lower in an amino acid called methionine while other plant proteins are lower in an amino acid called lysine. It’s therefore important for someone eating a 100pc plant-based diet to ensure they consume a variety of plant proteins throughout the day.
Previously people were encouraged to eat “complementing proteins” such as beans and grains to ensure they eat all the essential amino acids at each meal. However, the current thinking is that due to the liver stores of essential amino acids, you just need to eat all the essential amino acids over the course of the day.
Therefore it is possible to meet your protein requirements while following a plant-based diet, but it does involve a little bit of thought and planning.
There are many positives that come with eating plant protein
There are many positives that you could expect from introducing more plant protein into your diet. Animal proteins are low in fibre and can be high in saturated fats with processed versions often having added sugars and salts. Switching some of the animal proteins in your diet to protein-containing plants could increase your overall fibre, phytocompounds and healthy sources of fat intake. This change would be enough to significantly improve the average Irish diet. The changes would translate to improvements in health as diets richer in plants are associated with lower risks of common conditions and diseases like obesity, heart disease, high blood pressure, type 2 diabetes and even certain types of cancer. Simple switches would therefore go a long way.
Is a plant-based diet nutritionally complete?
If you were to remove animal proteins from your diet completely, what nutrients might you struggle to eat enough of? Some nutrients are more challenging to absorb into the body when eaten in the plant rather than the animal form. Additionally, some nutrients are found predominantly in animals rather than plants. Therefore a vegan diet isn’t advisable until a plan to meet these requirements is in place. Here are some examples of the nutrients you may need to replace below:
Iron — A crucial component of red blood cells. They carry oxygen around our bodies giving us energy.
- Non-plant sources — Liver, kidney, duck, venison, beef, black pudding and octopus.
- Plants sources — Beans, peas, lentils, green leafy vegetables and dried fruit.
- Challenge — Iron isn’t as easily absorbed from plant sources as it is from meat sources. To help you absorb iron from these foods it’s important to eat vitamin C-rich foods at the same time, such as strawberries, citrus fruits, tomatoes, cabbage and broccoli.
Calcium — This is essential for the development of healthy bones and teeth.
- Non-plant sources — Oily fish, milk, yoghurt, cheese.
- Plants sources — Dark green vegetables, nuts, peas, beans, lentils, tofu and dried fruit.
- Challenge — One glass of milk contains the same calcium as nearly two large tins of baked beans, ¼kg of almonds, 6 tbsp tahini or 1kg (24 spears) of broccoli.
Vitamin D — This is needed for healthy bones and immune system.
- Non-plant sources — Oily fish and eggs.
- Plants sources — Some mushrooms.
- Challenge — Vitamin D requirements would need to be met with foods fortified with vitamin D or with supplements.
Omega 3 — These fatty acids are great for your heart health.
- Non-plant sources — Oily fish such as salmon, mackerel, kippers, herring and fresh tuna.
- Plants sources — Rapeseed oil, walnuts, flaxseeds, chia seeds and soy beans.
- Challenge — The omega 3 found in plants is not the same as the omega 3 found in oily fish. Therefore a supplement is required.
Vitamin b12 — Essential for brain function and a healthy nervous system.
- Non-plant sources — Eggs, milk, cheese, yoghurt, meat, fish and poultry.
- Plants sources — Yeast extract.
- Challenge — Vitamin B12 requirements would need to be met with foods fortified with vitamin B12 or with supplements.