Vegetarian, vegan or flexitarian: for, against or what's it all about?

Critical micronutrients in the vegetarian and vegan diet

Vegetarian and vegan diets have become increasingly popular over the last decade. When switching to a more plant-based diet, the question arises as to what effects this has on the micronutrient balance.

Definition of a vegetarian and vegan diet

The various forms of vegetarian diets differ in terms of which animal products are still consumed. The name indicates which food is still eaten. "Ovo" stands for eggs and "lacto" for dairy products.

  • Ovo-lacto-vegetarian diet (eggs and dairy products, but no meat or fish)
  • Ovo-vegetarian diet (eggs, but no meat, fish or dairy products)
  • Lacto-vegetarian diet (dairy products, but no meat, fish or eggs)
  • In the flexitarian diet, meat or animal products are generally reduced without eliminating them completely. The focus here is on conscious consumption.
  • In the vegan diet, the consumption of animal products such as meat, fish, milk, eggs and honey is completely avoided.

Vegetarian and vegan: impact on health

The impact of nutrition on health depends on various factors such as food selection, nutritional planning, personal health and life situation. A vegetarian or vegan diet consisting of a high proportion of fruit and vegetables can have a positive effect on the prevention of lifestyle diseases such as obesity, diabetes and cardiovascular disease.

In particular, the higher intake of dietary fibre from fruits, vegetables, legumes such as lentils or chickpeas or whole grains could have a preventive effect. Vegetarian and vegan diets also contain less saturated fatty acids from animal products. Together with a higher consumption of dietary fibre, this could have a positive effect on the blood lipid profile.

Micronutrient supply in the vegetarian and vegan diet

By eliminating entire food groups, vegetarian and vegan diets require careful planning and consideration of the foods consumed to ensure that an adequate intake of all necessary nutrients is guaranteed.

People who follow a vegetarian or vegan diet should ensure that they eat a varied and balanced diet and supplement critical nutrients that are not or insufficiently absorbed through the diet.

Critical micronutrients

One question that is often discussed is whether an adequate supply of nutrients is guaranteed despite the absence of animal products. A balanced plant-based diet consisting of a high proportion of vegetables, fruit, legumes and complex carbohydrates has a good supply of folate, vitamin B1, vitamin B6, vitamin C, potassium and magnesium as well as dietary fibre and phytochemicals. However, studies show that iron, vitamin B12, omega-3 fatty acids, vitamin D, calcium, zinc, iodine, selenium and vitamin B2 are critical micronutrients. The supply of individual essential amino acids, which are only found in small quantities in plant sources (especially lysine and methionine), can also be critical.

Difference in micronutrient supply between vegetarian and vegan diets?

In a vegetarian diet, the micronutrient's calcium, vitamin B2 and vitamin B12 can also be obtained through the consumption of milk, dairy products and eggs.


The trace element iron is contained in plant-based foods, but in the less bioavailable form of non-heme iron. Secondary plant substances from cereals or pulses as well as polyphenols, which are found in coffee or black tea, for example, significantly reduce iron absorption by binding the iron molecules. Vitamin C, on the other hand, promotes the absorption of non-haem iron.

Omega 3 fatty acids

Omega-3 fatty acids are polyunsaturated fatty acids that cannot be sufficiently produced by the body itself. They must therefore be taken in with food. Alpha-linolenic acid (ALA) from tree nuts or linseed oil can only be converted into the important eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to a limited extent in the body.

With a plant-based diet, omega-3 fatty acids cannot be sufficiently absorbed or converted through food and must therefore be supplemented with preparations containing EPA and DHA, e.g. from algae oil.


In a balanced vegetarian diet, the calcium requirement can often be covered by milk and dairy products. A vegan diet contains less calcium and the calcium contained in plant-based foods is less readily available to the body because the oxalic acids (nuts, spinach) and phytates (cereals, pulses) also contained in these foods reduce absorption in the intestine. An additional intake can therefore make sense.

An inadequate calcium supply results in suboptimal bone density, which can manifest itself in early osteoporotic changes.


In a balanced plant-based diet, phytates and dietary fibres, e.g. from legumes and whole grain products, inhibit the absorption of zinc in the intestine. By soaking, sprouting or fermenting seeds and grains, the proportion of phytates can be reduced, thereby improving zinc absorption from these foods.

Vitamin B12

As part of a purely vegan diet, vitamin B12 cannot be sufficiently absorbed through food, as it is found almost exclusively in animal foods. An additional intake in the form of a supplement is therefore a necessary addition to a balanced diet.

Vitamin D

Vitamin D can be produced by the body in the skin with the help of sunlight. In our latitudes, however, the sun is only strong enough for this in the summer months unless sun protection is used - unprotected exposure to the sun increases the risk of skin cancer. It is not possible to obtain sufficient vitamin D from food, regardless of diet, as only a few (animal) foods contain significant amounts.

Adequate supplementation is therefore advisable for the general population regardless of diet, especially in the winter months or all year round according to laboratory values.


A plant-based diet does not provide enough iodine to cover requirements due to iodine-poor soils. For this reason, salt in Switzerland and Austria is fortified with the vital trace element iodine. Fish, milk and dairy products are important sources of iodine in the diet; if these are not available, iodized table salt should be used in the kitchen. Iodine supplementation is particularly recommended during pregnancy and breastfeeding, as the requirement increases.

Vitamin B2 (Riboflavine)

With good meal planning and suitable food choices, such as pulses, wholegrain products, nuts and seeds and mushrooms, the vitamin B2 requirement can be met through a plant-based diet. As vitamin B2 is water-soluble, cooking water should be reused wherever possible and food should be cooked in as little water as possible.


The selenium content in many foods depends on the content in the soil, which is low in the Alpine region. Among other things, selenium is important for the immune system, a component of antioxidant systems and normal thyroid function. Selenium also supports sperm formation and contributes to the maintenance of healthy hair and nails. It therefore makes sense to take an additional selenium supplement.

Plant-based nutrition during pregnancy and breastfeeding

The developing child obtains its nutrients exclusively from the mother. This increases the intake recommendations for various micronutrients by 50 - 100 %, such as folic acid. In a plant-based diet, certain nutrients cannot be adequately covered by the diet and are therefore particularly critical during pregnancy and breastfeeding. These include iodine, omega-3 fatty acids (DHA and EPA), calcium, iron and vitamin D. This increased requirement should be covered by a balanced diet in combination with a suitable multivitamin and mineral supplement.

During pregnancy and breastfeeding, the following nutrients should be taken in addition to a balanced diet:

  • Multivitamin-mineral supplement with folic acid, iron, iodine and vitamin D
  • Omega-3 fatty acids DHA and EPA
  • Calcium and magnesium
  • Iron depending on requirements and blood values

You can find detailed information on nutrition and critical nutrients during pregnancy here:

Nutrition during pregnancy 

A vegetarian or vegan diet in old age - what to look out for?

Compared to healthy adults, the energy requirement decreases with age. However, the nutrient requirements remain the same or even increase, such as the need for proteins. In addition, the body's properties and functions change. For example, the activity of many enzyme systems and digestive organs decreases, which reduces the absorption of vitamin B12.

In addition, more and more medication is being taken, which also makes a micronutrient deficiency possible. This makes an adequate supply of macro- and micronutrients particularly important to prevent a nutrient deficiency. With a vegan diet in old age, particular attention should be paid to vitamin D, vitamin B12, zinc, calcium and protein intake.

Tips for everyday life

  • Use iodized table salt for cooking
  • Incorporate calcium-rich foods into your daily diet
  • Vitamin B12 must be taken in with a dietary supplement if you follow a vegan diet. Supplementation can also be useful with a vegetarian diet if little milk and dairy products or eggs are consumed
  • Supplement vitamin D during the winter months, regardless of your diet
  • Omega-3 fatty acids (DHA/EPA) should also be supplemented with a vegetarian and vegan diet.
  • A long-term low-dose iron supplement makes a significant contribution to covering your daily requirements if you consume few iron-rich foods
  • Make sure you eat a varied diet in line with the balanced plate in a vegan diet.



With good food and nutritional knowledge, many nutrients can be covered with a well-planned plant-based diet. Critical nutrients that are not or insufficiently absorbed through the diet or for which a shortage is identified must be supplemented in order to avoid deficiencies and their health consequences. Critical micronutrients in a vegetarian diet are: Iron, zinc, iodine, selenium, omega-3 fatty acids and vitamin D. In a vegan diet, vitamin B12, vitamin B2 and calcium are also critical micronutrients.


The "green line" at Burgerstein.