Calcium: The Overlooked Nutrient on Plant-Based Diets

Those of us who choose to follow a plant-based diet will be very used to questions about where we get protein from, or how we can possibly be eating enough iron. But what if the noise about these nutrients is detracting from others more worthy of our attention? Current evidence tells us we need to be much more mindful of calcium, and that optimising gut health as well as ensuring adequate calcium intake is important. As a Paediatric Dietitian I support families with young children in my clinic to navigate the ‘nutrition noise,’ gaining clarity around which aspects of nutrition actually need their focus. And it all starts with evidence, so let’s take a quick look at what it’s telling us.

Are protein and iron really a concern?

Protein

A recently published systematic review¹ offers new reassurance that all varieties of plant-predominant eating patterns can provide protein intakes well within the recommended 10-35% of daily energy intake. As the body of evidence continues to grow, we can also be confident that plant-based diets can provide more than enough protein for young children² and older children alike³, with many eating more than 2-3 times the recommended amount of protein regardless of dietary pattern.

Iron

And in terms of iron? The lower bioavailability of plant versus animal iron is an important consideration, and would explain why those with plant-based eating patterns may be at higher risk of iron deficiency and associated anaemia⁴. Again, the evidence to date helps reassure us that it is perfectly possible to have an adequate iron intake, and serum ferritin status whilst following a plant-based diet^5–7. And findings from the VeChi studies^{2, 3} demonstrate that iron intakes are generally adequate in vegan children, too. Many vegan children actually eat more iron than their omnivorous counterparts.

Why calcium deserves more attention

What the VeChi studies also tell us, and what we need to be giving much more airtime to, is that children with plant-based eating patterns are often not eating the optimal amount of calcium. In 6-18 year olds it was found that average calcium intake (around 300mg per day) was 25% lower than in omnivorous children. In the UK, recommended calcium intakes for this age group are between 550-1000mg daily⁸. Whilst the VeChi studies were completed in Germany, it is likely that there is significant similarity to other populations. So, it is likely that children with plant-based diets could be significantly under-consuming calcium. When we consider the importance of childhood and early adulthood in growth and the development of strong, healthy bones, this is clearly something that deserves a lot more of our attention. Data from the National Diet and Nutrition Survey, which monitors dietary intakes of a cross-section of the population in the UK⁹ suggests that the issue of low calcium intake may extend beyond plant-based diets, too. It shows us that teenage children are at the greatest risk of inadequate calcium intakes. Parents will know that nutritional concerns are not necessarily the top of the teenage agenda, so a lack of general concern about nutrition is also likely to be a significant factor here, regardless of specific dietary pattern.

Are plant-based adults getting enough calcium?

In 2023, a large review study indicated that adult vegan diets were substantially lower in calcium than vegetarian and omnivorous diets¹⁰. Another recently published review suggests that plant-based diets are associated with a greater risk of osteoporosis, particularly when the diet has been followed for 10 or more years¹¹. The development of osteoporosis is complex and does not relate only to dietary intake, or calcium, but both are important factors. The elephant in the room, of course, is that following a vegan or plant-based diet per se is not the cause of low calcium intake. It is a question of diet planning and diet quality as well as lifestyle habits such as optimising gut health, weight-bearing exercise, Vitamin D intake and ensuring adequate protein intake.

As plant-based eating patterns gain popularity, with people inspired to adopt ‘greener’ eating patterns for ethical, sustainability and economic reasons, it’s important that we don’t allow the ‘where do vegans get protein from’ noise to distract us from calcium, which seems equally, if not more worthy of concern across all age groups.

What is the link between calcium and the gut?

It has been known for decades that calcium plays a crucial role in skeletal development, growth and long-term bone health. But we are learning more about the 2-directional relationship between gut health and calcium. Put simply, calcium plays a range of important roles in supporting good gut health, from the production of digestive enzymes to regulating gut motility^12–14. Equally, a healthy gut and an abundant gut microbiome can help support calcium absorption¹⁵, with specific probiotic supplements shown to enhance absorption¹⁶. Supporting healthy bones throughout the lifespan, therefore, requires optimal calcium intake and a healthy, happy gut, as well as a range of other lifestyle factors.

Calcium: how much we need and where to find it

The good news is that there are many quick and simple ways to boost daily calcium intake, and for most of us, there should be no need for specific calcium supplements. For those who consistently struggle to meet the recommended calcium intake, a supplement would be recommended - be mindful that calcium citrate has been shown to have better bioavailability than other calcium compounds¹⁷.

The tables below summarise age-specific calcium requirements and 7 of my favourite ways, as a Paediatric Dietitian, to make sure the calcium box is checked each day for all ages.

Key takeaways for professionals

• Dairy is not needed for bone health, but calcium, protein and vitamin D are essential.
• Calcium intake should be monitored for everyone, but particularly for those following plant-based diets.
• Calcium requirements are highest during adolescence and breastfeeding, so these life stages need extra special attention.
• A healthy, happy gut can help support calcium absorption.

References 

1. Rolands MR, Hackl LS, Bochud M, Lê KA; Protein Adequacy, Plant Protein Proportion, and Main Plant Protein Sources Consumed Across Vegan, Vegetarian, Pescovegetarian, and Semivegetarian Diets: A Systematic Review. The Journal of Nutrition [Internet]. 2024;155(1). Available from: https://pubmed.ncbi.nlm.nih.gov/39117040/
2. Weder S, Hoffmann M, Becker K, Alexy U, Keller M. Energy, Macronutrient Intake, and Anthropometrics of Vegetarian, Vegan, and Omnivorous Children (1–3 Years) in Germany (VeChi Diet Study). Nutrients. 2019 Apr 12;11(4):832.
3. Alexy U, Fischer M, Weder S, Längler A, Michalsen A, Sputtek A, Keller M. Nutrient Intake and Status of German Children and Adolescents Consuming Vegetarian, Vegan or Omnivore Diets: Results of the VeChi Youth Study. Nutrients. 2021;13(5):1707. doi: https://doi.org/10.3390/nu13051707.
4. Moustarah F, Mohiuddin SS. Dietary iron. [online] PubMed. 2024. Available at: https://www.ncbi.nlm.nih.gov/books/NBK540969/.
5. Henjum S, Groufh-Jacobsen S, Stea TH, Tonheim LE, Almendingen K. Iron Status of Vegans, Vegetarians and Pescatarians in Norway. Biomolecules. 2021;11(3):454. doi: https://doi.org/10.3390/biom11030454.
6. Tong TYN, Key TJ, Gaitskell K, Green TJ, Guo W, Sanders TA, Bradbury KE. Hematological parameters and prevalence of anemia in white and British Indian vegetarians and nonvegetarians in the UK Biobank. The American Journal of Clinical Nutrition. 2019;110(2):461–472. doi: https://doi.org/10.1093/ajcn/nqz072.
7. Haider LM, Schwingshackl L, Hoffmann G, Ekmekcioglu C. The effect of vegetarian diets on iron status in adults: A systematic review and meta-analysis. Critical Reviews in Food Science and Nutrition. 2017;58(8):1359–1374. doi: https://doi.org/10.1080/10408398.2016.1259210.
8. British Dietetic Association (BDA). Calcium. [online] 2021. Available at: https://www.bda.uk.com/resource/calcium.html.
9. Public Health England. NDNS: results from years 9 to 11 (2016 to 2017 and 2018 to 2019). [online] GOV.UK. 2020. Available at: https://www.gov.uk/government/statistics/ndns-results-from-years-9-to-11-2016-to-2017-and-2018-to-2019.
10. Bickelmann FV, Leitzmann MF, Keller M, Baurecht H, Jochem C. Calcium intake in vegan and vegetarian diets: A systematic review and Meta-analysis. Critical Reviews in Food Science and Nutrition. 2022;63(31):1–19. doi: https://doi.org/10.1080/10408398.2022.2084027.
11. Zheng S, Yu T, Hou J, Deng Q, Liu J, Jin M, et al. Plant-based diet and risk of osteoporosis: A systematic review and meta-analysis. Clinical Nutrition (Edinburgh, Scotland). 2025;50:253–262. doi: https://doi.org/10.1016/j.clnu.2025.05.023.
12. Zhu L, Yang L, Liang Z, Shi W, Ma M, Chen J, et al. Association between dietary calcium intake and constipation in a metabolic syndrome population: evidence from NHANES 2005–2010. Frontiers in Nutrition. 2024 Oct 30;11.
13. Kirchhoff P. Role of calcium and other trace elements in the gastrointestinal physiology. World Journal of Gastroenterology. 2006;12(20):3229.
14. Scientific Opinion on the substantiation of health claims related to calcium and maintenance of bones and teeth (ID 224, 230, 231, 354, 3099), muscle function and neurotransmission (ID 226, 227, 230, 235), blood coagulation (ID 230, 236), energy-yielding. EFSA Journal. 2009 Oct;7(10):1210.
15. Hadadi N, Berweiler V, Wang H, Trajkovski M. Intestinal microbiota as a route for micronutrient bioavailability. Current Opinion in Endocrine and Metabolic Research [Internet]. 2021 Oct 1;20:100285. Available from: https://www.sciencedirect.com/science/article/pii/S245196502100082X
16. Wang J, Wu S, Zhang Y, Yang J, Hu Z. Gut microbiota and calcium balance. Frontiers in Microbiology [Internet]. 2022 Dec 20;13. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9881461/
17. Sakhaee K, Bhuket T, Adams-Huet B, Rao DS. Meta-analysis of Calcium Bioavailability: A Comparison of Calcium Citrate with Calcium Carbonate. American Journal of Therapeutics [Internet]. 1999 Nov 1;6(6):313. Available from: https://journals.lww.com/americantherapeutics/abstract/1999/11000/meta_analysis_of_calcium_bioavailability__a.5.aspx