Vitamins A, B12, Selenium, D & Iodine – What pregnant women with a plant-based diet should know – Medically sound, evidence-based and safe
By Dr. Valesca Proske, physician specializing in functional medicine & founder of NUTRILAB MUNICH
More and more women are choosing a plant-based or even purely plant-based diet while trying to conceive, during pregnancy, and while breastfeeding. However, it is precisely during this sensitive phase of life that the need for certain micronutrients is increased – and adequate intake is often far from guaranteed. In this blog post, as a physician and developer of high-quality supplements, I explain what really matters when it comes to key nutrients – especially vitamin A, vitamin B12, selenium, vitamin D, and iodine. The information is well-founded, scientifically proven, and explained in an easy-to-understand way.
Vitamin A during pregnancy: Why retinyl palmitate instead of beta-carotene?
Vitamin A is indispensable for cell division, growth, eye development and the baby's immune system.
However, women who follow a plant-based diet usually only consume beta-carotene – a precursor that the body must first convert into active vitamin A. The conversion rate varies considerably from person to person and can be severely limited in cases of genetic variants (e.g., the BCO1 mutation). Studies show that approximately 40% of people have this reduced conversion rate. Furthermore, the conversion efficiency decreases even further with high beta-carotene intake.
Therefore, we rely on retinyl palmitate – directly effective vitamin A – in a safely low dose of 225 µg.
This is well below the internationally established upper limit of 3000 µg per day (EFSA), but ensures a basic supply for all women, even those with reduced conversion capacity. Diet (vegetables, fruit) continues to provide beta-carotene – we supplement only selectively and safely. The critical period for teratogenic risks is between days 15 and 60 post-conception – our low dosage carefully takes this into account. During breastfeeding, vitamin A intake is adjusted, as the risk of direct fetal exposure no longer exists.
Sources: EFSA 2015, WHO 2020, DOI: 10.3945/ajcn.2009.27993D, DOI: 10.1093/ajcn/nqac106, PubMed ID: 28328354
Vitamin B12: Why 100 µg is beneficial during pregnancy
Vitamin B12 is THE critical factor in vegan or vegetarian diets. The official recommendations for pregnant women (e.g., DGE: 4.5 µg/day) apply to omnivorous diets – but women following a plant-based diet often have lower stores.
Italy, for example, recommends 50 µg of vitamin B12 per day for pregnant vegetarians. Studies show that 100 µg/day is optimal to replenish stores and minimize risks to the baby (e.g., neurological damage, developmental delay, anemia). Vitamin B12 has no known threshold for side effects; it is absorbed as needed, and excesses are simply excreted. Absorption is limited—of a 100 µg dose, only 2–3 µg are effectively absorbed.
Therefore, our products contain 100 µg of methylcobalamin – for maximum safety, even in cases of absorption problems.
Conclusion: Current research shows that vitamin B12 supplementation with 100 µg during pregnancy in women with a plant-based diet has a clearly positive benefit-risk ratio, as there is no upper limit for B12, dosages up to 1000–2000 µg are considered safe, while a B12 deficiency can cause serious consequences such as neural tube defects and developmental disorders in the child.
Sources: Rizzo 2016, EFSA 2015, DOI: 10.1002/14651858.CD013823.pub2, DOI: 10.1136/bmjopen-2020-034987, PubMed ID: 28974367
Selenium: Why we rely on sodium selenite instead of selenium yeast
Selenium supports thyroid function, the immune system, and antioxidant defense mechanisms. Plants often provide little selenium because the content in the soil varies greatly.
Selenium yeast contains selenium in organic form (selenomethionine), which can accumulate in the body – especially with long-term use. Sodium selenite, on the other hand, is absorbed quickly, utilized efficiently, and excreted in excess. Animal and human studies show that sodium selenite is used more efficiently for selenoprotein synthesis and is better regulated.
Our decision: Sodium selenite – safe, bioavailable and without risk of accumulation.
Sources: WHO 2004, EFSA 2014, DOI: 10.1007/s12011-018-1618-1, DOI: 10.1016/j.jtemb.2018.11.002, PubMed ID: 15136966
Why no vitamin E?
Vitamin E is considered a classic antioxidant, but the research on supplementation during pregnancy is sobering:
Lack of efficacy: Extensive Cochrane reviews involving over 21,000 pregnant women show that routine vitamin E supplementation during pregnancy offers no benefit. No improvements were observed in preeclampsia, premature births, intrauterine growth restriction, or other important pregnancy outcomes.
Potential harms: Vitamin E supplementation was associated with an increased risk of abdominal pain (RR 1.66) and premature rupture of membranes at term (RR 1.77). These side effects outweigh the only proven benefit of reduced placental abruption.
Adequate intake through diet: Additional vitamin E supplementation is not considered necessary during pregnancy, as the daily requirement can be easily met through a balanced, healthy diet. Studies have not been able to demonstrate any positive effect from additional vitamin E supplements.
Evidence-based decision: The AOK fact box confirms that there is no evidence of benefit from routine vitamin E intake during pregnancy. In fact, it may even contribute to abdominal pain.
Against this background, NUTRILAB consciously omits vitamin E from its formula. This decision follows the evidence-based principle: "No additive without proven benefit." Mother and child are adequately supplied with vitamin E through a good diet – an extra supplement offers no scientifically proven advantage.
Sources: Cochrane 2015, Miller et al. 2005, DOI: 10.1002/14651858.CD004069.pub3, DOI: 10.1002/14651858.CD007176.pub2, PubMed ID: 16210918, AOK-Faktenbox Vitamin E** Cochrane 2015, Miller et al. 2005, DOI: 10.1002/14651858.CD004069.pub3, DOI: 10.1002/14651858.CD007176.pub2, PubMed ID: 16210918
Vitamin D during pregnancy: Why 3000 IU is beneficial and safe
Germany is a region with a pronounced vitamin D deficiency – pregnant women are particularly affected. A large German study showed that over 78% of pregnant women have insufficient vitamin D levels (< 50 nmol/l).
The randomized MUSC trial (Hollis et al.) with 494 pregnant women demonstrated that 4000 IU per day was the most effective and safest dose. 3000 IU daily is within the evidence-based optimal range for good 25(OH)D levels in both mother and child. International organizations such as the WHO, the Endocrine Society, and ACOG consider 4000 IU to be safe.
Here too, we recommend that you test regularly (once per trimester).
✅ Benefits: Reduced risk of preeclampsia, premature birth, gestational diabetes and optimized bone development.
Sources: DOI: 10.1007/s00404-017-4351-1, DOI: 10.1002/jbmr.300, DOI: 10.1002/14651858.CD013446.pub2
Iodine 200 µg: Important for cognitive development – but check thyroid function!
Germany is still considered an iodine-deficient region. Particularly critical is the fact that almost half of women of childbearing age are deficient. Iodine is essential for the brain development of the child – especially in the first trimester, when the baby depends on maternal hormones.
The WHO recommends 250 µg/day during pregnancy, the DGE 230 µg. We deliberately supplement with 200 µg – within safe limits and only for women with a healthy thyroid.
Why check your thyroid beforehand? Too much iodine can be harmful in cases of Hashimoto's or other thyroid disorders. A preconception test (TSH, fT4, TPO antibodies) provides reassurance and allows for targeted therapy.
🧠 Studies show that iodine deficiency is associated with an increased risk of premature birth, growth retardation, and cognitive deficits in children. Controlled iodine supplementation is safer than abstinence in most cases.
Sources: DOI: 10.1089/thy.2016.0457, PubMed ID: 25629356, WHO/UNICEF/ICCIDD (2007)
Conclusion: Greater safety through scientifically sound micronutrients
Women trying to conceive, pregnant, or breastfeeding deserve well-planned, medically validated supplementation. Our products from NUTRILAB MUNICH address precisely this need:
- optimally adapted to a plant-based diet
-
scientifically proven, without unnecessary additives
Because your baby deserves more than the standard. It deserves knowledge. And you deserve trust.
You can find more information and products at: www.nutrilab-munich.com
