Switching to a plant-based diet? Keep an eye on your micronutrients
Thursday, Oct 3, 2019, 05:45 AM | Source: Pursuit
By Ken Ng, Said Ajlouni
Earlier this year, a major United Nations report outlined how switching to a plant-based diet can help fight climate change, saying "the West's high consumption of meat and dairy produce is fuelling global warming".
And it seems Australians are paying attention. The number of people here adopting a plant-based diet is increasing steadily.
The impetus driving these plant-based diet movements is also supported by emerging links with improved health including psychological wellbeing, a reduced risk of chronic conditions including Type-2 diabetes and coronary heart disease (CVD), as well as all-cause mortality.
In fact, the most recent release of the Australian National Dietary Guidelines also features the viability of a nutritionally balanced plant-based diet for maintaining our health.
But many people are making this switch without talking to their GP or other health professionals.
And it's important to note that not all plant-based diets are equal, nor are they necessarily beneficial for everyone. This is particularly true if you are already missing out on the levels of certain essential nutrients required for your life stage.
What is a healthy plant-based diet?
A plant-based diet is characterised by eating patterns that avoid consuming most or all foods of animal origin, emphasises a greater consumption of wholegrains, vegetables and fruits, legumes, as well as nuts and seeds.
The health benefits of plant-based diets are largely attributed to the higher proportion of nutrient-dense food intake.
But there are multiple cross-sectional studies that demonstrate how plant-based diets high in less nutritious foods, like sweetened beverages and refined grains, are actually negatively associated with health biomarkers.
So, ensuring that a plant-based diet is high quality is pivotal for anyone hoping to reap the benefits of going plant-based.
Not all nutrients are equal
Most essential nutrients are present in foods of both animal and plant origin.
However, some nutrients from plants are only present in smaller quantities, and our bodies aren't able to absorb all of them.
We call this bioavailability; in terms of nutrient bioavailability, this refers to the proportion of a nutrient that is absorbed from the diet and used for normal body functions.
So while macronutrients like carbohydrates are less likely problematic as they're present in higher quantities in food, there are others that anyone considering moving to a plant-based diet need to keep an eye on.
Key micronutrients and where to get them
Several metal elements work together to maintain the metabolic processes that our bodies need to function properly.
This includes oxygen transport, the conversion of food into energy, building strong teeth and bones, and many more.
Australia's latest national nutritional survey found that many people have a pre-existing insufficient intake of some these essential elements.
This includes most people, regardless of gender, not getting enough calcium, men not getting enough zinc, and women under 30 not getting their quota of iron.
A chronic calcium deficiency can lead to an increased risk of developing osteoporosis and/or bone fracture, while a lack of iron can cause anaemia and reduced cognitive function. Even mild inadequacies in zinc intake can result in impaired immunity and growth.
Essential elements naturally occur in a range of foods and drinks, although the body can better absorb those from animal sources; for example, calcium from milk is more bioavailable than the same amount from spinach.
However, we can give ourselves an adequate intake of minerals through frequently consuming a diverse range of plant-based foods. Nuts, seeds and legumes contain high concentrations of zinc and iron, while brassica vegetables – like broccoli and kale – are good sources of bioavailable calcium.
There is also the possible role of fortified foods (that have nutrients added to them that don't naturally occur) consumed in moderation.
In Australia, some bread and cereal products are enriched with iron and zinc, while fruit juice and non-dairy alternative milks can contain added calcium.
Vitamin B12, also known as cobalamin, is an essential dietary component needed for the synthesis of nerves, red blood cells, DNA and other factors in blood and neurological function.
Low blood cobalamin levels can lead to the development of blood-related conditions like anaemia, and elevations in homocysteine, a risk factor of CVD. There is also an association between low B12 levels and cognitive decline in older adults.
Cobalamin is not required in large amounts as it is stored in the liver for years. However, its predominant dietary sources are foods of animal origin like meat, seafood, egg and dairy.
Plants exposed to bacterial fermentation can contain cobalamin, but not in substantial quantities.
Some bioavailable plant sources of cobalamin include nori seaweed, mushrooms and fermented foods such as legumes and tea.
Here in Australia, Vitamin B12 is also commonly added to foods like yeast products (yes, Vegemite), breakfast cereals, meat analogues, non-dairy milk alternatives and some beverages.
These kinds of fortified foods are considered as highly bioavailable sources of cobalamin.
Choline is a water-soluble, vitamin-like nutrient that plays a chief role in cell signalling, brain development, nerve transmission and liver function.
It's naturally synthesised within the body, but not enough to meet our requirements.
Earlier this year, a modelling investigation based on the most recent dietary survey showed that less than 10 per cent of the Australians are meeting the recommendations for choline intake.
Choline has long been associated with healthy foetal neurodevelopment during pregnancy; a lack of the nutrient is linked to conditions like liver disorders, CVD and some cancers.
More recently, epidemiological studies have found the association between choline intake in our diets and a reduced incidence of developing Alzheimer's disease, as well as enhanced cognitive performance.
Similar to cobalamin, sources of choline are the highest in meat, egg and dairy products.
But there are good sources of plant-based choline; wheat germ, whole grains, nuts, soybeans and their products, and cruciferous vegetables like broccoli and cauliflower.
While choline isn't usually added to foods they some other nutrients are, it is available as a pharmaceutical supplement for people with specific dietary requirements, such as during pregnancy.
More information on dietary guidelines
Nutritional needs can be rather individualised – across age groups, gender, and other conditions that can influence our ability to metabolise certain nutrients.
It's always best to consult a health professional, like your doctor or an Accredited Practising Dietitian when making any major dietary changes.
The Australian Guide to Healthy Eating is a great resource that provides a comprehensive guide on approaching a nutritionally balanced dietary regime, based on food groups and ideal portion sizes.
Information on individual nutrients and their recommended daily intakes can be found on the National Nutrient Reference Values (NRVs) website.
So, if you are thinking of going plant-based, make sure you have the right information and advice to keep yourself healthy and get all the nutrients your body needs.