Common mistakes on a vegetarian diet: myths and practical tips

Can a vegetarian diet be deficient?

Not if it is well planned. One of the most persistent myths is that giving up meat and fish inevitably leads to nutrient deficiencies. According to the Academy of Nutrition and Dietetics, well-planned vegetarian and vegan diets are healthy and nutritionally adequate [1]. They may also help prevent and manage some diseases [1]. That document considers them appropriate at every stage of life, including pregnancy, breastfeeding, childhood, adolescence and sport [1]. In childhood, a vegan diet should only be followed with supervision from a paediatrician and a dietitian-nutritionist. Professional support is also advisable from the outset during pregnancy and breastfeeding. If a vegan mother is breastfeeding, B12 supplementation is essential and should be prescribed by her doctor or dietitian-nutritionist. See “Raw vegan diet”.

Diet quality depends on what is on your plate, not on whether it is labelled vegetarian. A diet based on fried food, soft drinks, refined flour and vegan pastries is just as unbalanced as an omnivorous diet based on the same foods. For a full guide to vegetarian diet types, portions and meal plans, see our guide to vegetarian diets. Here, we focus on common mistakes.

How can you get enough plant protein?

Worrying about getting too little protein is one of the questions we hear most often in consultations. People often believe plant protein is “incomplete”. In fact, plant proteins contain all the essential amino acids—the ones your body cannot make [2]. Some are lower in lysine or methionine and may be slightly less digestible [2]. According to the Academy of Nutrition and Dietetics, soy and soy products (tofu, tempeh and textured soy) have an amino acid profile very similar to animal protein [2].

You also do not need to combine pulses and grains in the same meal. With a varied diet and enough energy, you can get all the amino acids you need over the course of the day [1]. What matters is including a protein-rich food at every meal [2].

To estimate portions without weighing food, set aside a quarter of your plate for a protein source. 120 g of tofu or tempeh, 40 g of dry textured soy, or a serving of pulses weighing about 80 g dry provides 15–25 g of protein. If you eat eggs and dairy, two eggs or 100 g of fresh cheese provide slightly less, about 12 g.

Why do you need a B12 supplement even if you eat dairy or eggs?

The most serious mistake is overlooking vitamin B12 (cobalamin), which is needed for the nervous system and red blood cell production. Bacteria produce it, and no unfortified plant food is a reliable source of B12.

Seaweed such as spirulina, unfortified yeast and fermented foods such as tempeh are not reliable sources. They mainly contain inactive forms of the vitamin, which do not meet requirements and can create a false sense of security [1].

Eggs and dairy provide B12, but are often not enough. The European Food Safety Authority (EFSA) sets an adequate daily amount of 4 µg for adults [3]. B12 deficiency is common among vegetarians, especially vegans [2]. Although milk and eggs may meet the recommendation on paper, more may be needed to prevent deficiency. For this reason, B12 supplementation is essential if you are vegan and may also be needed if you eat eggs and dairy [2]. Your doctor or dietitian-nutritionist prescribes the B12 supplement.

Cyanocobalamin is one form of B12 used in supplements [4]. Your doctor or dietitian-nutritionist decides the plan and whether you need a blood test first.

How to get more iron from pulses

It is a myth that only meat prevents anaemia. Iron-deficiency anaemia is no more common among vegetarians than omnivores [1]. However, their iron stores (ferritin) tend to be lower [2].

The difference lies in absorption. According to EFSA, haem iron—the type found in meat and fish—is absorbed at a rate of 15–35% [5]. Non-haem iron, found in pulses, grains and vegetables, is absorbed less efficiently and at highly variable rates [5]. How much you absorb depends on your iron stores and what you eat at the same time.

Phytates (in whole grains and pulses) and tannins (in coffee, tea and cocoa) reduce iron absorption. Vitamin C increases it [5]. In practice, serve pulses with raw red pepper, tomato, citrus fruit, kiwi or strawberries. Have coffee or tea one to two hours after eating.

Vegetarian burgers and processed foods: how to choose them at the supermarket

Supermarket shelves are full of burgers, sausages and other plant-based products. The mistake is assuming they are healthy just because they are plant-based. Many contain a lot of salt, fat, added sugars and additives, according to the Academy of Nutrition and Dietetics [2]. Even so, they can be useful when you are starting out or short on time [2].

Many contain only a small amount of the ingredient they are named after (tofu, lentils or soy), with refined oils, starches, flours and salt making up the rest. A practical rule of thumb we use in consultations is to choose products where the main plant ingredient is first on the ingredients list and makes up at least half of the product. Have them occasionally and prioritise tofu, tempeh, pulses or homemade burgers.

The same applies to drinks. Water should be your usual drink, and it is best to limit juice and sugary drinks [6]. If you drink plant-based milk, choose soy or another option with at least 3 g of protein per 100 ml. Choose one with no added sugar and fortified with calcium, at around 120 mg per 100 ml, similar to cow’s milk. If you are allergic to soy, look for another option that meets the same criteria. Before age one, plant-based drinks do not replace breast milk or infant formula.

Where to get calcium and omega-3

For calcium, especially if you are vegan, two or three daily servings of foods containing well-absorbed calcium are recommended [2]. Examples include fortified soy drink, tofu set with calcium salts, and green vegetables such as kale or broccoli [2]. Sesame (tahini) and almonds also contribute.

The plant-based omega-3 is alpha-linolenic acid (ALA), an essential fat because the body cannot make it. The Academy of Nutrition and Dietetics lists an adequate amount of 1.1 g per day for women and 1.6 g for men [2]. You can meet this with three or four walnuts (about 15 g) or a tablespoon of ground flaxseed. Before age 5, offer nuts ground or as a smooth paste, never whole. This means they can be included from the start of complementary feeding.

What mistakes do we see most often in consultations?

The most common is removing meat and leaving an empty space. The meal becomes pasta with vegetables or a salad, with no pulses, tofu, tempeh or eggs. After a few weeks, people may feel that vegetarian eating is tiring or leaves them hungry. The solution is simple: whenever you remove meat or fish, replace it with one of these protein sources.

The second is making cheese your go-to. Lacto-ovo vegetarians often rely on it every day in sandwiches, salads and hot meals. It provides protein and calcium, but aged cheese is high in saturated fat and salt and can displace other options. For sandwiches and snacks, try avocado with seeds, roasted vegetables or 100% nut butter.

Can you follow a vegetarian diet and do sport?

Yes. According to the Academy of Nutrition and Dietetics, well-planned vegetarian diets are suitable for athletes [1]. In healthy active adults and athletes, a well-planned vegetarian diet can support gains in muscle and strength if it provides enough energy and protein [2]. Protein needs should be adjusted to each athlete and their training.

What makes the difference is eating enough energy and spreading protein intake across the day. Tempeh, tofu, seitan, textured soy and pulses can help you meet your needs. If you train intensely or compete, it is a good idea to tailor your diet to your training load.