know the risks and benefits of a predominantly plant based diet
Lilli M Clemens ND
Reasons for dietary change is generally for better health, but no matter what diet we choose the challenge is in understanding what foods and nutrients we need to maintain health and wellness. The five food groups (vegetables, fruit, grain, meat and dairy) contain valuable nutrients for our daily requirements. When we choose to omit certain food groups we also miss out on certain essential nutrients. This report aims to provide evidence-based information in the type of nutrient deficiencies vegetarians and vegans are most likely to experience and the signs and symptoms that can present with these deficiencies. The report also provides some guidance in alternative food sources and supplements to avoid nutrient deficiencies, but also food for thought for the dietary endeavours we choose to take.
The popularity of the Vegetarian movement is undoubtedly gaining momentum, and for the last three decades, the Internet has fostered a well-informed society, with an increasing conscience for environmental sustainability, animal welfare and aspirations for better health and well-being.
It has also brought with it a large number of social media advocates promoting the benefits of a plant-based diet. However, there is much misinformation and conflicting views in the realm of a predominantly plant-based diet, and it can be confusing for any aspiring vegetarian or vegan to seek the right knowledge.
Government and media are also informing us to eat more vegetables and fruit, and that the current over-consumption of meat, sugar and processed products is pushing the population’s health status to epidemic proportions from obesity to cardiovascular diseases, diabetes and cancers.1
Dietary choices do not just play a big part in how we live our life’s, but also forge new opportunities in the food market, as growing awareness and demand bring opportunities. Including improvements in ethical food standards, the growth of boutique organic and biodynamic farmers, farmer’s markets and homegrown products
Fortunately, science provides us with a large body of literature that allows us to identify the advantages and limitations of an exclusively plant-based diet (vegan diet). Epidemiological studies and randomised controlled trials provide evidence in how nutrition and individual nutrients affect our biological systems and how certain nutritional deficiencies lead to disease. Science can also demonstrate how nutrients can affect other nutrients (nutridynamics) and what role nutrients play in the body, and how they contribute to our overall health and well-being.
There is much misinformation suggesting that humans are herbivores and that we should not be consuming any animal proteins. However, from an evolutionarily perspective we need to understand that humans have evolved as omnivores and this is evident in how we anatomically and physiologically have adapted to the food sources around us. Our teeth have incisors to rip and tear (carnivore) and molars for chewing (herbivore). Our digestive system has uniquely adapted to both meat and plant-based diet with a highly acidic stomach and an unusually long herbivorous digestive tract to break down and ferment plant fibers. 2 Unlike herbivores we have a highly acidic stomach (pH1-2.5), as the risk of foreign microbes is higher with meat consumption, but also to help break down meat fibers and release nutrients for digestion. 2 Our stomach and pancreas also produce protease and pepsin which are specific enzymes aiding in protein digestion and indicative to a highly acidic environment. 2
consume meat if we choose not to
Unlike the carnivore, we have an unusually long digestive tract that has adapted superbly to digest plant fibre and metabolise and absorb the nutrients through the extensive microflora of the gut.
Does a plant-based diet affect digestion?
Unfortunately, low stomach acid (hypochlorhydria) is a common manifestation for those on a long-term vegan diet and those that choose a vegetarian diet with little animal protein and fats. The digestive system uniquely adapts to food habits, and it is primarily animal proteins that regulate stomach acid. 2
Therefore, the absence of animal protein can naturally reduce the acid volume in the stomach and subsequently increase the risk of pathogens (bacteria and parasites) causing digestive problems and typical symptoms of low appetite, aversion of animal proteins and fats, nausea, headaches, fatigue and generally not feeling right. Similar digestive problems occur when vegans or vegetarians revert to animal proteins too quickly. The untrained stomach does not have sufficient acid to digest the proteins, causing pain, cramping, heartburn, migraines, headaches, constipation, diarrhoea or nausea.
Those that have difficulty in re-introducing or increasing protein intake should seek clinical advice. The certified Naturopath or Nutritionist can assess your current digestive status and recommend a personalised treatment plan to help you maintain optimal digestive function.
The benefits of plant-based foods
Plant-based foods are fundamental to health and well-being, and there is indisputable evidence that a plant-based diet reduces the risk of disease and morbidity.3–5 Many studies have implicitly demonstrated the benefits in reducing bodyweight, cardiovascular diseases,4,6 reduction of high blood pressure, 6 diabetes 7 and certain cancers.1
The daily consumption of plant-based foods such as leafy greens, root vegetables, coloured vegetables, fruit, fungi, legumes, seaweed, nuts and seeds are highly nutrient dense foods packed with minerals, vitamins, antioxidants, amino acids, fats and fiber. These natural foods are fundamental for metabolic function, providing the body with energy, mental health, optimal bowel flora and digestion, healthy immune function, blood sugar regulation, removal of metabolic waste and healthy sleep. Furthermore, a plant-based diet is alkalising by removing metabolic acids that the body typically produces through daily cellular respiration and other cellular processes. Maintaining the ideal body tissue pH will provide optimal enzymatic activity and cellular function and reduce the risk of disease.
Can a vegetarian diet sustain optimal health and longevity?
In short, a vegetarian diet is sustainable, but a healthy vegetarian needs to be discerning and aware that some nutrients are not available or in suboptimal quantities in an exclusively plant-based diet. The lack of knowledge in food choices and nutrient requirements is a primary factor why vegetarians are at risk of some common nutrient deficiencies including iron, zinc, calcium, B12, essential fatty acids, and protein, 8,9 nutrients predominantly found in animal protein. Therefore, reducing the variety and quantity of animal products and not sourcing a wide range of plant-based foods can significantly affect the optimal amount of these nutrients.
What we also need to consider is that nutrient requirements differ during our life stages and the lifestyles we lead. The body will have a higher demand for nutrients during pregnancy and lactation, menstrual cycle, childhood and adolescence growth spurts and increased physical activity, but also during trauma, injury and illness when the body needs to heal. The primary nutrient that the body is in need of is protein, and it is during these occasions that we need to consider how we will supplement protein. From a scientific and clinical perspective sourcing, a natural animal-based protein is the healthiest option. Why? Because animal proteins come naturally with all the nutrients that a vegetarian generally may be at higher risk of deficiency, including B12, zinc, iron, calcium and certain fatty acids.
Protein is a vital macronutrient that makes up every cell of your body. Proteins build muscle and regulate all chemical reactions to preserve life. Of the twenty amino acids that the body needs to create protein, nine are essential amino acids (EAAs) which can not be synthesised by the body and need to be regularly supplemented in foods to meet protein requirements. The nine EAAs are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Most plant proteins present in smaller quantities and lack one or several essential amino acids. It is therefore important that we eat a wide variety of plant-based foods to deliver all EAAs for our bodily needs. The few plants that contain a complete protein include soybean, chia, quinoa and buckwheat.
Many vegetarian and vegan Internet resources will talk about protein combining, which means that you need to eat specific protein sources together to create a complete protein (all 20 amino acids), such as brown rice with chickpeas or barley with lentils. However, protein combining is old science and sourcing your proteins should not be a complex task in food preparation. The body has ample protein and amino acid stores to support any immediate dietary amino acid insufficiencies. It is, however, vital that you maintain an optimal amino acid pool in your body by maintaining a broad dietary intake of plant-based foods.
We also need to keep in mind that not all proteins are equal in digestibility and bioavailability. 10 Animal proteins have the better bioavailability because they contain a complete protein (contain all 20 amino acids). Of all the animal proteins eggs, milk and whey powder have the highest digestibility and bioavailability. 10,11
All plants contain antinutrient factors such as phytates, glucosinolates, tannins, isothiocyanates and digestive enzyme inhibitors. Antinutrient factors bind with proteins or inhibit enzymes to assimilate proteins. 11 Considerable amounts of antinutrient factors are present in seeds, cereals, nuts, pulses and legumes. The good news is that many of these inhibitors can be diminished with either heat (as in cooking or baking), soaking, sprouting and fermenting. With proper preparation plant protein, availability is approximately 50-80%. You can also supplement your protein from vegetable protein powders which mostly come in a concentrated form with a digestibility of more than 95%. 11 If you are one of these people that needs some extra protein you can always supplement your diet with some dairy or plant-based protein powder. Supplementation can also include calcium, iron, B12 and zinc and will be discussed under each nutrient section.
The symptoms of insufficient protein or specific essential amino acids may show as muscle wasting or difficulty in gaining muscle mass and underweight. Also, mood changes including depression and anxiety, loss of menstrual cycle, anorexia, anaemia, muscle weakness, fatigue, malabsorption and digestive issues, reduced liver function, brittle nails, dull hair, frequent infections, pale or pasty complexion and lack of appetite.(Many of these symptoms are not exclusive to protein deficiency and it is recommended to seek professional advice if you experience any of these symptoms)
Fats or fatty acids are a major source of energy and an important macronutrient for the vegetarian and vegan as a low-fat diet will inversely affect muscle mass. Unfortunately, the common consensus on fats is that they are bad for us and that fats makes us fat and are the cause of cardiovascular disease, which is still highly contentious amongst scientists and researchers. Nevertheless, what we do know is that fatty acids are essential for health. They play a crucial role in the structure and function of all cells, hormone production, disease prevention, 12 and support the absorption of fat-soluble vitamins A, E, D and K. The storage of fats in and around the body is an evolutionary survival mechanism and also essential for organ protection and thermal regulation. The primary fatty acids are saturated fats and omega 3, 6 and 9, and each is equally important for health and wellness. So why is it that omega 3 is always in the limelight and not saturated fat? Because saturated fat and omega 6 which is a common polyunsaturated fat, are more readily available in our general diet compared to omega 3. Both omega 6 and 3 play a pivotal role in the production of intermediate fatty acids that help to regulate the immune system response to inflammation.
Most foods contain a bit of every fatty acid, but there is always a predominant fatty acid that rules the food. The more obvious are the plant oils including sunflower, peanut, canola, safflower and corn oils which are predominantly omega 6. Olive and canola oil are predominantly omega 9, and saturated fats can be found in coconut oil, palm oil and butter and other dairy products.
Of course not all fats are equal. Processing oils from seeds and grains require heat that can damage the fatty acids. The oils and fats that go through the least process are those that are cold pressed, which include olive, avocado, almond, macadamia and coconut oil. The healthy vegetarian should include a variety of fats in their diet to maintain a good source of energy, maintain muscle mass and healthy immune function.
The symptoms of insufficient fatty acids include muscle wasting, acne, bruising, dry, itchy skin, dry, brittle hair, menstrual dysfunction and reproductive failure, gall stones, diabetes, neuralgia, poor wound healing, pancreatic problems, inflammatory disorders, miscarriage, high cholesterol and skin disorders.(Many of these symptoms are not exclusive to fatty acid deficiency and it is recommended to seek professional advice if you experience any of these symptoms)
Iron is available in most plant foods including wholegrain cereals, almonds, pine nuts, parsley, spinach, avocado, sunflower and pumpkin seeds and red wine :). However, non-heme iron in plants is poorly absorbed compared to animal heme iron.11,13 Other plant compounds such as calcium, zinc, proteins and phytic acid found in grains, nuts, legumes, seeds and polyphenols (colour compounds) also have an inhibiting effect on iron availability. Fortunately, other compounds such as organic acids and bitters found in many foods increase the availability of non-heme iron. Some examples of foods that are sour and or bitter include citrus, including lemons and limes, tomatoes, tamarind, fermented vegetables, apples, mango, bitter melon, yoghurt, vinegar, tea, dandelion tea, coffee and dark chocolate.
Individuals who will have an increased risk of iron deficiency will be athletes,14 menstruating women, during rapid growth, frequent blood donations, pregnancy, lactation and a poor diet.
Iron deficiency may exhibit symptoms of fatigue or lack of energy, impaired immunity, low blood pressure, dizziness and fainting, brittle nails and hair, reduced cognition, poor appetite, headaches, a sore inflamed tongue (stomatitis), restless leg syndrome and pale complexion.(Many of these symptoms are not exclusive to iron deficiency and it is recommended to seek professional advice if you experience any of these symptoms)
B12 is essential for DNA and cellular reproduction, cardiovascular, skin, nerve function, blood production and gut mucosa. It is naturally only available in animal protein. We can argue that B12 is also present in some plants such as mushrooms, algae, which is due to bacterial action from soil or insect contamination. 11,13 Statistics show that the Australian population sources up to 50% of their B12 from milk and dairy products. 13 Eggs are also a good sources of B12. 13 Alternative B12 supplementation includes tablets and sublingual spray, and individuals who may not respond to oral application due to poor absorption can obtain B12 injections.
Individuals who are likely to be at a higher risk of B12 deficiency include those with chronic digestive issues, long-term vegans and vegetarians and those with genetic disorders of B12 metabolism. B12 deficiency may exhibit symptoms including mouth ulcers, stunted growth, neuropathy, poor sleep, digestive issues, bleeding gums, high homocysteine, high blood pressure, cardiovascular disease, gastric of duodenal ulcers, sore mouth and tongue, depression, dementia, restlessness, pernicious anaemia, numbness in hands and feet, moodiness, memory loss and insomnia.(Many of these symptoms are not exclusive to B12 deficiency and it is recommended to seek professional advice if you experience any of these symptoms)
Calcium is required for bone growth and bone turnover, 15,16 healthy teeth, and the function of muscles and cardiovascular system. 17 According to the Australian Bureau of statistics, more than half of the Australian population has inadequate calcium intake, with the higher percentage (75%) in females compared to males. 18 Calcium is found in all plant products with significant amounts in grains, cereals, legumes, almonds and green leafy vegetables. Milk and dairy products have the most significant amounts of calcium, ranging from 380 – 1220mg per 100gm. Another good source is bony fish 460mg/100gm, which would be tinned sardines and salmon, where the bones are soft and easily digestible. The overall recommended intake of calcium is 1000mg per day, and that demand will increase to 1300 - 1500 mg during adolescence and the elderly due to reduced absorption capacity. 13
Counting the milligrams of calcium will give us some indication if we are consuming enough calcium per day, but that does not mean that we are digesting that same amount. Although calcium is relatively easily absorbed plant-based calcium contains a number of compounds that have shown an inhibitory effect on absorption of calcium. Phytates from legumes, cereals, nuts, grains, and oxalates in spinach, rhubarb, beets, chard and kale 19 have a tendency to form insoluble calcium compounds. Another less known calcium loss is through perspiration (up to 60mg/day). 13 It is therefore prudent that calcium based foods are a part of your daily diet. Individuals that are at a higher risk of calcium deficiency include those that have a high alcohol intake, regular consumption of soft drinks (high phosphate intake), vegans and vegetarians, pregnancy and lactation, magnesium or vitamin D deficiency and a poor diet. Calcium deficiency may exhibit symptoms of cramps, bone pain, lower backache, high blood pressure, arthritis, frequent bone fractures, osteoporosis, anxiety, nocturnal muscle cramps, restless legs, menopausal symptoms and menstrual cramps.(Many of these symptoms are not exclusive to calcium deficiency and it is recommended to seek professional advice if you experience any of these symptoms)
Below is a table that depicts the different vegetarian types. In general, the vegetarian avoids meat and mostly fish, and may supplement their diet with dairy and eggs. However, there should be no hard and fast rules of a vegetarian diet as it is the individual’s choice in how they would like to supplement their plant-based diet.
- Oyebode O, Gordon-Dseagu V, Walker A, Mindell JS. Fruit and vegetable consumption and all-cause, cancer and CVD mortality: analysis of Health Survey for England data. J Epidemiol Community Health. 2014;68(9):856-862. doi:10.1136/jech-2013-203500
- Beasley DE, Koltz AM, Lambert JE, Fierer N, Dunn RR. The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome. 2015. doi:10.1371/journal.pone.0134116
- Clemens L. Literature Review and Research Proposal The health benefits of vegetable and fruit how much do consumers know ? 2016:1-9.
- Esposito K, Giugliano D. Diet and inflammation: A link to metabolic and cardiovascular diseases. Eur Heart J. 2006;27:15-20. doi:10.1093/eurheartj/ehi605
- Slavin J, Lloyd B. Health Benefits of Fruits and Vegetables. Adv Nutr. 2012;3(4):506-516. doi:10.3945/an.112.002154.506
- Alonso A, de la Fuente C, Martín-Arnau AM, de Irala J, Martínez JA, Martínez-González MA. Fruit and vegetable consumption is inversely associated with blood pressure in a Mediterranean population with a high vegetable-fat intake: the Seguimiento Universidad de Navarra (SUN) Study. Br J Nutr. 2004;92(2):311-319. doi:10.1079/BJN20041196
- Viguiliouk E, Kendall CW, Kahleová H, et al. Effect of vegetarian dietary patterns on cardiometabolic risk factors in diabetes: A systematic review and meta-analysis of randomized controlled trials. Clin Nutr. June 2018. doi:10.1016/J.CLNU.2018.05.032
- Walsh,S Deriemaeker, P Hebbelinck,M Clarys P. Nutritional Profiles of elderly Vegetarians. In: Vegetarian AndPlant-Based Diets in Health and Disease Prevention. ; 2017:599-617.
- Clarys P, Deliens T, Huybrechts I, et al. Comparison of Nutritional Quality of the Vegan, Vegetarian, Semi-Vegetarian, Pesco-Vegetarian and Omnivorous Diet. Nutrients. 2010;6:1318-1332. doi:10.3390/nu6031318
- Hoffman JR, Falvo MJ. Protein - Which is Best? J Sports Sci Med. 2004;3(3):118-130. http://www.ncbi.nlm.nih.gov/pubmed/24482589. Accessed January 26, 2019.
- Agnoli C, Baroni L, Bertini I, et al. Position paper on vegetarian diets from the working group of the Italian Society of Human Nutrition. NMCD. 2017;27. doi:10.1016/j.numecd.2017.10.020
- Calder PC. The relationship between the fatty acid composition of immune cells and their function. Prostaglandins Leukot Essent Fat Acids. 2008;79:101-108. doi:10.1016/j.plefa.2008.09.016
- Australian Government D of H and A. Nutrient Reference Values for Australian and New Zealand.; 2005. https://www.nhmrc.gov.au/guidelines-publications/n35-n36-n37.
- Barr SI, Rideout CA. Nutritional Considerations for Vegetarian Athletes. doi:10.1016/j.nut.2004.04.015
- Bhatia V. Dietary calcium intake - A critical reappraisal. Indian J Med Res. 2008;127(3):269-273. http://icmr.nic.in/ijmr/2008/march/0309.pdf.
- Heaney PR, Abrams S, Dawson-Hughes B, et al. Peak Bone Mass. Osteoporos Int. 2000;11(12):985-1009. doi:10.1002/cncr.26410
- Salehi-Abargouei A, Maghsoudi Z, Shirani F, Azadbakht L. Effects of Dietary Approaches to Stop Hypertension (DASH)-style diet on fatal or nonfatal cardiovascular diseases-Incidence: A systematic review and meta-analysis on observational prospective studies. Nutrition. 2013;29(4):611-618. doi:10.1016/j.nut.2012.12.018
- Australian Bureau of Statistics. Calcium. 4364.0.008 - Australian Health Survey: Usual Nutrient Intakes, 2011-12. http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by Subject/4364.0.55.008~2011-12~Main Features~Calcium~401. Published 2015.
- Sanders K, Nowson CA, Kotowicz MA, Briffa K, Devine A, Reid IR. Calcium and bone health: Postion paper for the Australian and New Zealand bone and mineral society (ANZBMS), Osteoporosis Australia and the Endocrine Society of Australia. Med J Aust. 2007;190(6):316-320. doi:san10083_fm [pii]