What is a Vegan Diet?
A vegan diet is a plant-based diet that excludes all the animal products such as meat, dairy, and eggs, in its plan. Plenty of fruits, vegetables, beans, nuts, and seeds are the main contents of a vegan diet. People following the vegan diet are called vegans. There is a very slight difference between the vegans and vegetarians, i.e., vegetarians can eat dairy products, eggs, or both while vegans avoid dairy products as well. Vegans opt for soy-based dairy substitutes for obtaining the nutrition received from dairy products.
Compared with other diets, vegan diets are rich in fiber content, folic acid, vitamin C and E, potassium, magnesium, and many phytochemicals. The extra nutritious contents, along with the lower saturated fat and cholesterol, make the vegan diet more healthy and popular. A vegan diet is experiencing more adoption, especially by teenage and adult females, as vegans tend to be thinner with lower serum cholesterol and lower blood pressure. It reduces the risk of chronic diseases such as cardiovascular disorders, type 2 diabetes, obesity, and cancer and aids in weight loss in vegans. The amazing health results of the vegan diet were inferred in the 2018 Gallup poll which reported for 3% of the population of the US being vegans and the increased sale of the plant-based foods in the country.
However, the elimination of all animal products from the diet also increases the risk of a few nutritional deficiencies. Vitamin B12, vitamin D, calcium, and long-chain n-3 (omega-3) fatty acids are of particular concern for micronutrient deficiency in vegans. The remaining nutrition value of the vegan diet can be compensated with the consumption of optimum supplements if the regular food does not fortify the calculated nutrition. In a few cases, the iron and zinc status of vegans may also become a matter of concern due to the limited bioavailability of these minerals. 
In the following article, you will find the summarized health effects of vegan diets and discussion over nutritional shortfalls of the vegan diet. In the end, some practical dietary recommendations to compensate for the nutritional concerns have been discussed.
Health Benefits Associated with the Vegan Diet
In a recent report of the World Health Organization and Food and Agriculture Organization (WHO/FAO), several plant foods were related to their metabolic-epidemiologic evidence for influencing chronic disease reduction.
- The rich intake of fruit and vegetables was rated as probable or possible for cancer risk reduction
- Consuming whole grains was assessed as possible for reducing the risk of colorectal cancer and probable for type 2 diabetes and CVD
- Intake of nuts was rated as probable for reducing the risk of CVD
Optimum Heart Health
Consumption of fruit and vegetables is far more in vegans than omnivores. Fruit and vegetables being rich in fiber, folic acid, antioxidants, and phytochemicals, vegans experience lower blood cholesterol concentrations, reduced incidences of stroke, and decreased risk of mortality from stroke and ischemic heart diseases. The added consumption of whole grains, soy, and nuts provide significant cardioprotective effects in vegans.
Lower Cancer Risk
The Adventist Health Study reports have conveyed the substantially increased risk of colorectal and prostate cancer in non-vegetarians than in vegetarians. Control of obesity was found as a critical factor behind this result. The mean BMI of vegans is found considerably lower than that of non-vegetarians which proves to be a prominent protective factor for lowering cancer risk.
- Fruits and vegetables are considered to be protective against lung, mouth, oesophagus, and stomach cancer
- Regular intake of legumes are proven to protect against stomach and prostate cancer
- Allium vegetables are proven for preventing stomach cancer
- Garlic is known to protect against colorectal cancer
- Lycopene rich foods, such as tomatoes, can protect against prostate cancer
The maintenance of acid-base balance is essential for bone health. A single drop-in extracellular pH can lead to bone resorption as bone calcium will buffer the pH drop. Due to this reason, the acid-forming diet can increase urinary calcium excretion. A vegan diet, being rich in fruit and vegetables, can create a positive effect on the calcium economy. The rich content of potassium and magnesium in fruits and vegetables creates an alkaline environment in the stomach that prevents bone resorption. Moreover, the higher consumption of potassium is found to be associated with the more upper bone mineral density of the femoral neck and lumbar spine in premenopausal women.
2015 studies on several diets by the researchers reported that vegan diets were more effective for weight loss and highly beneficial in terms of macronutrients compared to omnivorous, semi-vegetarian, and pesco-vegetarian diets. The high fat and calories rich animal food are replaced with a low-calorie plant-based food in vegan diets which is a crucial reason behind the weight management in vegans.
Dangers Associated with the Vegan Diet: Potential Nutritional Shortfalls in the Vegan Diet
One question that arises in every person’s mind is: how to decide whether the diet proposed to them is nutritionally adequate? The solution to this query is getting appropriate knowledge of the constituents of a nutritionally adequate diet. Then, check for accessibility, i.e., whether the foodstuffs are available or what could be the substitutes of the unavailable foods to balance the nutritional values. In the following section, the nutrients lacking in the vegan diet and are essential to maintain health are discussed:
n-3 Polyunsaturated Fat
The diets which do not include fish, eggs, or sea vegetables (seaweeds) are insufficient in long-chain n-3 fatty acids, eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). These fatty acids are essential for good cardiovascular health, a better eye, and brain functions. In contrast, plant-based diets are rich in n-3 fatty acid ??- linolenic acid (ALA; 18:3n-3) which can be converted into EPA and DHA but with reasonably low efficiency.
In the EPIC-Oxford study, it was observed that vegans consume the lowest amount of vitamin D (o.88 µg/d ), the one-fourth value of the omnivorous diets. The vitamin D status depends upon sun exposure and vitamin-D fortified foods for a vegan person. Vitamin D supplements can become a requirement in the regions where fortified vitamin D foods are unavailable. The status of vitamin D is also unpredictable for the people who live at high altitudes due to inadequate sun exposure for several months in those regions. The dark-skinned, older people who cover their bodies extensively or the ones who commonly use sunscreens are also at an increased risk of vitamin D deficiency. Another issue of concern for the vegans is that vitamin D2, the form of vitamin D consumed by vegans, is substantially less bioavailable than an animal-derived vitamin D3.
Heme iron absorption is prominently higher than non-heme iron obtained from plant foods. Despite this, the haemoglobin amount and the risk of iron deficiency anaemia are the same for vegans, omnivores, and vegetarians. 
Vegans experience lower plasma vitamin B12 (causing deficiency) and higher plasma homocysteine. Elevated homocysteine levels are known to be the risk factors for CVD and osteoporotic bone fractures. In contrast, vitamin B12 deficiency can cause abnormal and neurologic psychiatric symptoms such as ataxia, psychoses, paresthesia, disorientation, dementia, mood and motor disturbances, and difficulty in concentration. 
Phytates are standard components of grains, seeds, and legumes which bind zinc and decrease its bioavailability. Due to this reason, vegans and vegetarians are often at a high risk of zinc deficiency. The problem becomes further complicated due to the discovery of sensitivity markers to measure human zinc status is still not done.
The studies suggest the absence of difference between the bone mineral density of omnivores and lacto ovo vegetarians. In contrast, postmenopausal Asian women following a vegan diet showed significantly lower spine or hip BMD. The Asian women were found to consume low calcium and protein quantities that resulted in bone loss and fractures at the hip and spine in the elder ages. The higher risk of bone fracture in vegans is assumed to be a consequence of lower mean calcium intake. 
Dietary Recommendations for Optimal Vegan Diets
To overcome vitamin B12 deficiency, vegans are advised to consume daily fortified vitamin B12 foods such as fortified soy, rice beverages, cereals, and meat analogues, and B12 fortified nutritional yeast. A daily supplement vitamin B12 is also appreciable. Fermented soy products and leafy vegetables are not considered as a reliable source for active vitamin B12.
To manage calcium content in a vegan diet, calcium-fortified plant foods such as ready-to-eat cereals, calcium-fortified soy, rice beverages, orange juice, and apple juices. The bioavailability of calcium carbonate in soy beverages and the calcium citrate malate in apple or orange juice is the same as that of calcium in milk.
To ensure optimum vitamin D status, vegans shall consume vitamin- D fortified foods such as soy milk, rice milk, orange juice, breakfast cereals, and margarine. A daily supplement of 5-10 µg vitamin D is also advisable, especially for elderly vegans.
Vegans have better health in terms of lower serum cholesterol and blood pressure, decreased risk of CVD. However, the relation between vegan diets and the risk of cancer, diabetes, and osteoporosis requires further research. Also, due to the lack of dairy products in vegan diets, deficiency of Vitamin B12, vitamin D, calcium, n-3 polyunsaturated fats, iron, and zinc in vegans are commonly found. Such nutritional problems can be avoided with appropriate food choices and dietary supplements. Overall it can be concluded the health status of vegans appears to be better than vegetarians and non-vegetarians.
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