"A plant-based diet is based on foods derived from plants, including vegetables, wholegrains, legumes, nuts, seeds and fruits, with few or no animal products."
Introduction:
A plant based diet is one that focuses on only or mostly foods from plant sources. This way of eating may have benefits for both a person’s health and the planet.Some people interpret it as a vegan diet, which involves avoiding all animal products.
For others, a plant based diet means that plant foods, such as fruits, vegetables, whole grains, nuts, and legumes, are the main focus of their diet, but they may, occasionally, consume meat, fish, or dairy products.
A plant based diet also focuses on healthful whole foods, rather than processed foods. Western societies notice an increasing interest in plant-based eating patterns such as avoiding meat or fish or fully excluding animal products (vegetarian or vegan). In 2015, around 0.4−3.4% US adults, 1−2% British adults, and 5−10% of German adults were reported to eat largely plant-based diets1,2,3,4, due to various reasons (reviewed in ref. 5). Likewise, the number of scientific publications on PubMed (Fig. 2) and the public popularity as depicted by Google Trends (Fig. 3) underscore the increased interest in plant-based diets. This increasing awareness calls for a better scientific understanding of how plant-based diets affect human health, in particular with regard to potentially relevant effects on mental health and cognitive functions.
People choose a plant-based diet for a variety of reasons including concern about the treatment of animals, health reasons, environmental concerns or because of taste and social pressure. Plant-based diets are becoming more popular and if they are wellplanned, can support healthy living at every age and life-stage.
Types of plant-based diets include:
• Lacto-ovo vegetarians – eat dairy foods and eggs but not meat, poultry or seafood.
• Ovo-vegetarians – include eggs but avoid all other animal foods, including dairy.
• Lacto-vegetarians – eat dairy foods but exclude eggs, meat, poultry and seafood.
• Vegans – don’t eat any animal products at all, including honey, dairy and eggs. Many shop bought ready-made products may contain animal ingredients so the labels of all manufactured products do need to be read carefully.
Variations of plant-based diets include:
• Pescetarians – eat fish and/or shellfish.
• Semi-vegetarians (or flexitarians) – occasionally eat meat or poultry.
Eating for optimum health:
Diets centred on a wide variety of plant foods offer affordable, tasty and nutritious options. Plant-based diets which are rich in beans, nuts, seeds, fruit and vegetables, wholegrains such as oats, rice, and cerealbased foods such as breads, and pasta can provide all the nutrients needed for good health. This includes essential fats, protein, vitamins, minerals and plenty of fibre too.
Well balanced plant-based diets, that are also low in saturated fat, can help you manage your weight and may reduce your risk of type 2 diabetes, cardiovascular disease and some cancers. However, as with any diet, plant-based nutrition needs to be planned.
Most nutrients are abundantly available in plant-based diets, but if you are avoiding all or minimising your consumption of animal-derived foods there are a few nutrients that you need to pay attention to.
• Calcium - Calcium is essential for bone health, along with weightbearing exercise and a healthy diet. An adult requires approximately 700mg per day.Thus, figs, nuts such as almonds, leafy green vegetables, red kidney beans, sesame seeds, tahini and tofu should be taken to lower the risk of bone fractures.
• Omega 3 fatty acids - These fats have been shown to be important for health and are commonly found in oily fish. However if you are not eating fish, plant sources of omega 3 include walnuts, flax (linseed), hemp seeds, chia seeds and soya beans.
• Vitamin D - Vitamin D is needed to keep bones, teeth and muscles healthy and is made in our bodies when our skin is exposed to appropriate sunlight. Plant-based sources of vitamin D include sun-exposed mushrooms and fortified foods such as vegetable spreads, breakfast cereals and plantbased dairy alternatives.Since it’s difficult to get enough vitamin D from food alone, everyone should consider taking a daily supplement of 10mcg/ day during the autumn and winter months. Some vitamin D supplements are not suitable for vegans. Vitamin D2 and lichen-derived vitamin D3 are suitable.
• Iodine - The major sources of iodine in our diet are dairy products and fish. The iodine content of plant foods depends on the iodine content of the soil which is variable. Foods grown closer to the ocean tend to be higher in iodine. Where soils are iodine deficient, iodised salt and seaweed provide iodine which is needed in moderation.As the iodine content of seaweed is variable, and sometimes too high, guidance is not to consume sea vegetables more than once a week. An excess of iodine is also unhealthy.
• Vitamin B12 - We need vitamin B12 for many reasons. Too little can result in fatigue, anaemia and nerve damage and increase homocysteine levels leading to cardiovascular disease. Suitable B12-fortified foods include some breakfast cereals, yeast extracts, soya yoghurts and non-dairy milks.To make sure you get enough vitamin B12, either eat fortified foods at least twice a day, aiming for 3mcg of vitamin B12 a day, or take a supplement, 10mcg daily or at least 2000mcg weekly.
• Iron - Plant sources of iron include dried fruits, wholegrains, nuts, green leafy vegetables, seeds and pulses. Eat plenty of fruits and vegetables rich in vitamin C to help the iron to be absorbed e.g. citrus fruits, strawberries, green leafy vegetables and peppers.
• Zinc - Phytates found in plant foods such as wholegrains and beans reduce zinc absorption, so it’s important to eat good sources of zinc-containing foods. Eat fermented soya such as tempeh and miso; beans (soak dried beans then rinse before cooking to increase zinc absorption); wholegrains; nuts; seeds and some fortified breakfast cereals.
• Selenium - Plant sources of this mineral include grains, seeds and nuts. Just two brazil nuts daily will provide you with your daily requirement of selenium.
• Protein - Plant-based sources of protein include lentils, beans, chickpeas, seeds, nuts and nut butters (e.g. peanut butter), and tofu. Eggs, and dairy are also good sources if you are eating these. Meat substitutes like vegetarian burgers, soya sausages, and other meat alternatives can be useful for those adapting to a plant-based diet and can provide a source of protein. However as with any processed foods, these can often be high in salt and fat so should be used in moderation.
Sustainable eating:
In the UK, it is estimated that well-planned completely plant-based, or vegan, diets need just one third of the fertile land, fresh water and energy of the typical British ‘meat-and-dairy’ based diet. With meat and dairy being the leading contributor to greenhouse (GHG) emissions, reducing animal based foods and choosing a wide range of plant foods can be beneficial to the planet and our health.
The effects of plant-based diets on the body and the brain:
Western societies notice an increasing interest in plant-based eating patterns such as vegetarian and vegan, yet potential effects on the body and brain are a matter of debate. Therefore, we systematically reviewed existing human interventional studies on putative effects of a plant-based diet on the metabolism and cognition, and what is known about the underlying mechanisms. Using the search terms “plant-based OR vegan OR vegetarian AND diet AND intervention” in PubMed filtered for clinical trials in humans retrieved 205 studies out of which 27, plus an additional search extending the selection to another five studies, were eligible for inclusion based on three independent ratings. A causal impact of plant-based diets on cognitive functions, mental and neurological health and respective underlying mechanisms has yet to be demonstrated.
Health benefits:
Following a plant based diet offers many possible health benefits, including:
Better weight management:
Research suggests that people who eat primarily plant based diets tend to have a lower body mass index (BMI) and lower rates of obesity, diabetes, and heart disease than those who eat meat.
Plant based diets are high in fiber, complex carbohydrates, and water content from fruit and vegetables. This may help to keep people feeling fuller for longer and increase energy use when resting.
Lower risk of heart disease and other conditions:
A 2019 study from the Journal of the American Heart Association found that middle aged adults who ate diets high in healthful plant foods and low in animal products had a lower risk of heart disease.
According to the American Heart Association, eating less meat can also reduce the risk of:
• stroke
• high blood pressure
• high cholesterol
• certain cancers
• type 2 diabetes
• obesity
• Diabetes prevention and treatment
Plant based diets may help people prevent or manage diabetes by improving insulin sensitivity and reducing insulin resistance.
Of the 60,000 people studied in 2009, only 2.9% of people on a vegan diet had type 2 diabetes, compared to 7.6% of those eating a nonvegetarian diet.
People eating vegetarian diets that included dairy and eggs also had a lower risk of type 2 diabetes than meat eaters.
IS A VEGETARIAN DIET BAD FOR YOUR BRAIN?
If creatine is important for brain functioning and vegetarians have lower creatine levels, could a vegetarian or vegan diet have a negative impact on cognitive function?
Creatine is a non-essential amino acid, which means that our bodies have the ability to manufacture it from other amino acids.
Observational data suggest that lifelong vegetarians and vegans actually have a lower risk of dementia than meat eaters. Now, this may not have to do directly with the amount of animal products they do or don’t consume. It could be due to a higher intake of vegetables or legumes, for example. Or it could have to do with the fact that vegetarians are statistically more likely to exercise and less likely to smoke or any number of other lifestyle factors. That’s the difficulty with observational data; it’s impossible to prove cause and effect. There’s little evidence to suggest that a vegetarian or vegan diet impairs brain function or increases the risk of cognitive decline.
Conclusion:
Well-planned plant-based diets can support healthy living at every age and life-stage. Include a wide variety of healthy whole foods to ensure your diet is balanced and sustainable. --- by Swati Gupta