Vegan and Vegetarian Diets: What You Need to Know

In recent years, the practice of going vegetarian or vegan has caught on. Adopting such a plant-based diet is an age-old tradition in certain cultures or religions like Hinduism and Buddhism. However, it has begin to gain popularity these days as it is seen as a more ethical and healthful way to live. 

Pros of a vegan or a vegetarian diet

Some perks of a plant-based diet may include: 

Reduced animal cruelty

  • Less demand for meat translates to less caging and slaughtering of animals

Reduced carbon footprint

Health Benefits

Types of vegan and vegetarian diets

There is a whole spectrum of plant-based diets which vary in what foods are excluded: 

  • Vegan diet: Completely avoiding animal products and even honey.
  • Lacto-Ovo vegetarian diet: Eating eggs and dairy products while avoiding meat, fish, and poultry products.
  • Lacto-vegetarian diet: Eating dairy products while avoiding eggs, meat, fish, and poultry.
  • Pescetarian diet: Avoiding meat and poultry but eating fish, and sometimes egg and dairy products.
  • Flexitarian diet: Semi-vegetarian diet occasionally incorporating meat, fish, or poultry.

Supplements recommended

Although there are many benefits of undergoing a plant-based diet, such a diet may lead to certain nutritional deficiencies.

Depending on the type of diet followed, it may be either impossible or difficult to obtain a few vitamins and minerals in adequate amounts from natural plant foods. Therefore, to maintain good health whilst on a plant-based diet, it is important to eat fortified foods or supplement with the following:

Vitamin B12

Vitamin B12 is necessary for the proper functioning of the brain and nervous system, protein metabolism and also production of oxygen-transporting red blood cells. Deficiency can lead to numbness and tingling, memory loss, anaemia and fatigue.

The reference daily intake (RDI) of vitamin B12 is about 2.4 microgram but a higher amount is required for pregnant and lactating women. Some fruits and vegetables contain traces of vitamin B12 e.g. apple, banana, berries, beetroot, spinach and potato but these minute amounts cannot meet daily requirements of B12.

Non-meat sources of vitamin B12 include:

  • Eggs
    • One large hard-boiled egg contains 25% of the daily requirement of vitamin B12. Eggs are also a good source of protein
  • Fortified foods
    • One serving of fortified cereal contains 25% of the daily requirement of vitamin B12.
    • Fortified juice and tofu are also great sources of Vitamin B12
  • Nutritional yeast
    • One Tablespoon provides 100% of the daily requirement of B12. 
    • Provide cheesy or nutty flavour
    • Can be added in curries, vegetable sauces, chilis, and air-popped popcorn
  • Dairy products
    • A cup of low-fat milk contains half of the daily requirement of vitamin B12
    • A cup (8 ounces) of low-fat yogurt contains 46% of the daily value
    • 1 ounce (2 dice-sized cubes) of swiss cheese contains 38% of the daily value
  • Plant based- milks
    • For vegans, soy and nut milks e.g. almond/macadamia milk are a good alternative to dairy products as a source of B12
  • Others
    • Nori or seaweed is commonly eaten in Asia. Eating 4 grams of dried nori every day is sufficient to meet daily Vitamin B12 requirement.
    • Yeast spreads like Marmite
    • B12 is also available as an injectable drug or oral formulation. 

Long-chain omega-3 fatty acids

These are namely Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA). Adequate dietary levels are important for brain development and function (reducing risk of Alzheimer’s and dementia), reducing the risk of inflammation and heart disease among many health benefits. The RDI is ~200–300 mg per day.  

EPA and DHA are however, mostly found in animal products like fatty fish, seafood and fish oil. Alpha-linoleic Acid (ALA) may be obtained from certain plant foods e.g. flax seeds, chia seeds, walnuts, soya-based foods and converted into EPA and DHA, although in limited amounts. This process is highly inefficient; it has been suggested that only ~5% of ALA gets converted into EPA, and ~0.5% into DHA.

Thus, if you are undergoing a vegan or vegetarian diet, you should consider supplementing with algae oil to meet the daily requirements of EPA+DHA. 

Vitamin D

Vitamin D has many vital functions:

  • Helps regulate mood 
  • Improve immune system function 
  • Aids absorption of nutrients such as calcium and phosphorous, for maintaining healthy bones

The RDI for vitamin D for children and adults is 600 IU (15 mcg) per day. The elderly, pregnant or lactating women need 800 IU (20 mcg) per day. Foods highest in Vitamin D are not vegan-friendly, e.g. salmon, egg yolks, shellfish. 

Vegan sources of vitamin D include fortified cereals, fortified nut milks, fortified orange juice and some types of mushrooms but are usually insufficient to meet daily requirements.

The body can also make vitamin D when it gets enough sunlight – 15 to 20 minutes in the afternoon sun without sunscreen and with skin mostly exposed. However, because of the risk of skin cancer with excess UV radiation, it is advisable to limit sun exposure.

Vegans can consider taking a daily vitamin D3 supplement.


Calcium is another essential nutrient that vegans have been shown to lackIt is involved in bone and teeth formation, muscle function, and heart health. The RDI for calcium is 1,000 mg per day for most adults and 1,200 mg per day for those over the age of 50.

The following are calcium-rich plant-based sources:

  • Dark, leafy greens, such as mustard greens, bok choy, and watercress
  • Legumes, such as chickpeas
  • Fortified foods, which include many types of plant-based milk

If a person is not getting enough calcium from these foods, they should consider supplementation. Taking vitamin D may help boost absorption of calcium.


Iron is crucial for producing healthy red blood cells to carry oxygen throughout the body. Deficiency in iron can lead to anaemia, fatigue, impaired immune function. The RDI is 8 mg for adult men and post-menopausal women. It increases to 18 mg/day for adult women, and 27 mg/day for pregnant women.

It has two different forms:

  • Heme iron which comes from animals and is more easily absorbed/utilised
  • Non-heme iron which comes from plants

Iron-rich plant-based foods include:

  • Nuts and seeds
  • Legumes
  • Whole grains
  • Dried fruits
  • Dark, leafy vegetables
  • Some fortified cereals and foods

Consuming adequate vitamin C also increases absorption of iron. Iron supplementation may be recommended for vegetarians/vegans only if blood levels of haemoglobin and ferritin indicate iron deficiency.


Zinc is a mineral responsible for metabolism, immune function, and the repair of body cells. Deficiency can lead to developmental problems, hair loss, diarrhoea, and delayed wound healing. The RDI for zinc is 8–11 mg per day for adults, 11–12 mg for pregnant women, and 12–13 mg for lactating women.

Few plant foods contain high amounts of zinc. Moreover, zinc absorption from many plant foods is impaired by their phytate content. 

Eat a variety of zinc-rich foods e.g. fermented foods such as tempeh and miso, tofu, whole grains, wheat germ, sprouted breads, legumes, nuts, and seeds. Soaking nuts, seeds, and legumes overnight may lower phytate content. Vegans with zinc deficiency may consider taking a daily zinc supplement.


Iodine is necessary for a healthy thyroid gland, which is involved in metabolism. Deficiency during pregnancy and early infancy can result in intellectual disability. Deficiency can also lead to hypothyroidism, which may manifest as low energy levels, dry skin, tingling in your hands and feet, depression, and weight gain

The RDI for adults is 150 mcg of iodine per day, 220 mcg/day for pregnant women and 290 mcg/day for lactating women. Vegans are considered at risk of iodine deficiency, with studies showing vegans having up to 50% lower blood iodine levels than vegetarians. 

Seafood and dairy products have high iodine content but are unsuitable for vegans. Vegan sources of iodine include: 

  • Seaweed: Eating seaweed a few times a week, such as in sushi, should fulfil necessary iodine requirements.
  • Iodized salt: Half a teaspoon (2.5 ml) of iodized salt is sufficient to meet RDI.

Vegetarians and vegans may have their iodine levels checked for deficiency and obtain necessary supplementation as advised by their healthcare practitioners.

Concluding thoughts on vegan and vegetarian diets

Plant-based diets offer many benefits but may present with challenges in meeting nutritional needs as certain nutrients may be difficult to achieve through diet and fortified foods alone. 

Vegetarians or vegans can consider discussing with their healthcare providers on how best to supplement their diet to ensure they stay healthy.

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