Thinking of going vegan? What you need to know
Moving to a plant-based diet has been shown to benefit the planet as well as your health. However, before you start swapping your beef burgers for kale smoothies, there are a few things you need to know, says nutritionist Pattie O’Keeffe
Plant foods are abundant in many nutrients that are essential for us to live healthily, but not all sources are the same. Animal-derived foods like milk or meat are rich sources of certain essential nutrients that are easily absorbed by the human body. These same nutrients are present in many plants, but can sometimes be less available to the human body to digest and absorb. A select few essential nutrients are generally under-consumed when following a strictly plant-based diet. However, good planning, cooking and processing methods, and in some cases, supplementation, can eliminate these concerns.
●CALCIUM
Commonly recognised plant sources of calcium include kale, legumes, figs, bok choy, and broccoli. However, the quantity and bioavailability of calcium within these foods is far lower than dairy products or calcium-fortified foods. This is due to several factors such as the presence of oxalic acid and phytates, which bind to calcium and reduce absorption across the gut. Alternatively, vitamin D aids calcium absorption across the gut, so the higher your vitamin D stores, the more calcium you will absorb. Individuals that avoid dairy and other calcium-rich animal foods should eat more plant calcium sources to compensate or should consider calcium-fortified foods.
●PROTEIN
Plant protein is a hot topic these days, especially in relation to a more sustainable planet. But if you do not consume animal-sourced protein, such as eggs, dairy and meat, it is essential to know that we need a variety of plant protein sources to meet our body’s needs.
Protein is made of amino acids, some of which are referred to as essential because the human body cannot make them. Animal protein sources contain adequate levels of these essential amino acids; however, plant sources are often lacking in one or more. Nevertheless, individuals who eat a variety of plant protein sources such as legumes, nuts, grains, and seeds in enough quantities can meet optimum protein needs. Interestingly, the body has the capability of storing amino acids, so this variety does not need to be incorporated into every meal.
●VITAMIN D
Vitamin D comes in two forms: vitamin D2 and vitamin D3. The body uses vitamin D3 far more efficiently than D2. Vitamin D3 is produced by human skin in the presence of ultraviolet light from the sun or sourced from animal products. Plant sources provide vitamin D2 only.
Due to Ireland’s geographical position, people living here make little vitamin D3 from the sun during the months of October to April. Consequently, food sources of vitamin D are crucial for good health. Vitamin D is best sourced from animal sources such as liver, egg yolks, red meat, and oily fish; therefore, a daily supplement or fortified foods are advised for a plant-based diet.
●ESSENTIAL FATTY ACIDS
Omega-3 and omega-6 fatty acids are both essential for the human body to function optimally. The most efficient sources are oily fish, and eating two portions a week is recommended. For some individuals, fish may not be part of a plant-based diet; therefore, levels of these fatty acids are generally suboptimal. The body can convert plantsourced fatty acids into essential fatty acids; however, the conversion efficacy is low. Depending on the plant source, it will be converted to omega-3 (such as chia seeds, flaxseeds, hemp seeds) or omega-6 (such as sunflower oil, sesame oil, almonds). The body typically needs fatty acids in a ratio 3:1 omega-3 to omega-6. A good quality plant-based diet will aim to meet this ratio, but avoid them within the same meal due to competition for absorption.
●VITAMIN B12
The primary dietary sources of vitamin B12 are products derived from ruminants, such as cows, because microorganisms present in their digestive tracts produce this nutrient. Vitamin B12 is generally not present in plant foods; therefore, individuals following a plant-based diet are advised to consume foods fortified with vitamin B12 or to take a supplement. Absorption of vitamin B12 is easily saturated, so
ideally consume vitamin B12 fortified foods on more than one occasion throughout the day.
●IRON
Iron is present in two forms: haem and non-haem iron. Haem iron is more readily absorbed across the gut compared to non-haem iron. Red meat and other animal-derived foods are rich sources of haem iron. Plant sources contain non-haem iron only, such as green leafy vegetables, legumes, nuts, seeds, and grains.
Iron bioavailability can vary significantly due to inhibitors within the same or other foods in a meal.
Phytates, which are abundant in legumes and grains, are inhibitors to non-haem iron absorption. However, common cooking and preparation methods such as soaking, fermenting, germinating and dehulling legumes, can counteract this and thus increase iron absorption.
Tea and coffee are rich in tannins and polyphenols, which also reduce iron absorption, so it is advised to avoid drinking tea and coffee within the hour before and after a meal rich in iron.
Calcium also competes with iron for absorption in the gut, so separating a calcium-rich meal from an iron-rich meal can improve a strictly plantbased diet. Vitamin C enhances iron absorption, so it is ideal to include vitamin C-rich foods in an iron-rich meal. However, bear in mind vitamin C potency is reduced when cooked at high temperatures.
●VITAMIN A
There are two forms of vitamin A available in the human diet. The most abundant form in plants is betacarotene, and provides fruits and vegetables, such as mangos, oranges, carrots, and beetroot, with a yellow/ orange/red colour. The form present in animal products such as liver, fish oils, milk, and eggs, is more efficiently used by the body. However, a healthy plant-based diet is abundant in fruit and vegetables that are rich in betacarotene, so the risk of inadequate intake is not high. Heating vegetables in a little oil or adding acidulants or antioxidant spices such as lime, tamarind, onion or turmeric can increase the absorption of betacarotene.
●IODINE
Iodine is an essential trace element imperative for brain development, normal growth and metabolism. Plant foods can be insufficient and unreliable iodine sources.
In Ireland, the UK, and most of Europe, the primary source of iodine is from milk and milk products, followed by fish and meat. The high content in milk is a result of iodine addition in cow feed and iodinecontaining disinfectants used during milking.
Therefore, it is important to note that vegetarians who swap dairy milk to a plant-based alternative may be at risk of inadequate iodine intake.
Seaweed is a very rich source of iodine, particularly kelp. However, the iodine content can be too high, and excessive iodine intake can have adverse health effects. For this reason, it is advised to limit seaweed consumption to once a week, particularly if you are pregnant.
‘Tea and coffee are rich in tannins and polyphenols, which reduce iron absorption, so it is advised to avoid drinking tea and coffee within the hour before and after a meal rich in iron’