This article presents a personal review of existing scientific literature and is shared for educational and informational purposes only. It does not constitute medical advice.
Introduction
The ‘calcium paradox’ is the observation that hip fracture rates are higher in developed countries where calcium intake is higher than in developing countries where calcium intake is lower (1).
According to WHO, hip-fracture rates are highest in Caucasian women living in temperate climates, are somewhat lower in women from Mediterranean and Asian countries, and are lowest in women in Africa (1). This paradox calls for an explanation. The data point to one possible answer: the adverse effect of protein, in particular animal (but not vegetable) protein, may outweigh the positive effect of calcium intake on calcium balance.
My research PICO is: Consumption of Dairy Products versus Plant-Based Calcium Alternatives and Its Effect on Hip Fracture Risk in People living in Developed Countries.
How the Literature Was Explored
I made a research of articles published in PubMed and Google Scholar. I used following key-words in English: osteoporosis, hip fracture, dairy intake, dairy products, milk, bone fractures, bone density, calcium rich food, calcium supplementation, calcium intake guidelines, WHO, animal and vegan proteins on hip fracture risk, plant based diets and calcium. Initially I prioritised the articles published since 2014, however, the research showed that some important studies were done before this period of time too and I included them in the current literature review. I also searched references in these articles and used them in my research. I doubled checked all these referenced articles if they were published in respected medical journals. I included studies focused on humans. I reviewed mainly cohort studies because of long-term nature of the topic. According to Hanieh Malmir et al. even though cross-sectional and case-controlled studies showed an inverse relationship between the dairy intake and hip fracture risk, no such association was found in cohort studies (2).
What Long-term Studies Have Observed
Let’s have a closer look and review a META analysis covering only cohort studies done on this topic. The first META analysis (3) I selected is focused on humans and was done in 2023. It excluded individuals with pre-existed bone disease and analysed only cohort studies. The panel included 13 studies from 16 unique study populations involving 486,950 humans and 15,320 hip fractures distributed with genders: 2 cohorts only men, 4 cohorts only women, 2 cohorts for men and women separately and 5 cohorts not separated by gender. In following countries: 7 USA, 2 Sweden, 2 Norway, 1 Denmark, and one covering Japan, France and Europe.
The results showed that higher milk intake was associated with higher hip fracture risk. Risk rose by 7% with each additional 200 g/d of milk, and people who took 400 g/d had a 15% higher risk than those who took 0 g/d. The lowest risk was among those with no milk intake.
Regarding other dairy products, yogurt, fermented milk and cheese were analysed in relation to hip fracture risk. Only five studies were available for each, and many did not adjust for socioeconomic status, which is linked to higher yogurt and cheese consumption. Yogurt and fermented milk intake of 250 g/d was associated with 15% lower hip fracture risk, and cheese intake of 43 g/d was associated with 19% lower risk. One study of cheese intake (any versus no cheese) found no association. Because of the small number of studies and the lack of socioeconomic adjustment in many of them, these findings should be interpreted with caution.
The mechanisms behind the higher risk with milk intake are not entirely clear. One proposed explanation is D-galactose, a breakdown product of lactose, which has been linked to oxidative stress and inflammation, potentially increasing the risk of fracture and mortality.
It is very important to mention that in the Nurses’ Health Study and the Health Professionals Follow-up Study, the lower fracture risk with total dairy intake was seen only in participants with higher BMI. In the rest of the sample (other cohorts or normal BMI) total dairy intake showed no protective association with hip fracture risk. According to Carrie M Nielson et al. low BMI is associated with high bone fracture risk (4). I will explain this later in our analysis.
Vitamin D is another important factor. In one of the largest cohorts done in the US, Nurses’ Health Study, where milk is fortified with vitamin D, higher milk intake was associated with lower hip fracture risk, while in a large Swedish cohort, where milk is mostly not fortified, it was associated with higher risk. Across individual studies the results were inconsistent: one showed higher risk with milk, seven showed no association, and three showed lower risk. The authors suggested that differences in age, body weight and vitamin D fortification may partly explain this.
The authors concluded that higher milk intake is associated with higher fracture risk, while total dairy intake overall was not associated with hip fracture risk.This is one of the largest meta-analyses on this topic, and its results support my hypothesis that a lack of dairy in the diet does not necessarily increase the risk of hip fracture. It did not, however, directly compare dairy products with non-dairy plant-based alternatives, i.e. population that takes dairy products vs these who do not (for example vegans) and hence, I continued my research.
413,914 participants were followed for 12 years in the UK biobank cohort study (5). While this research did not study vegans, it showed elevated hip fracture risk among vegetarians compared to meat eaters and pescatarians. This increase in risk was partially explained by low BMI among vegetarians. The research also brought up factors like vitamin D and IGF-1, however, not enough information was available to analyse these factors. Most vegetarians consume dairy, yet they had higher hip fracture risk. This suggests that calcium from dairy does not on its own protect against hip fracture when other risk factors, such as low BMI, are present.
Swedish Mammography Cohort (6) is an interesting cohort study that was done in 2017. It studied 61,000 women for 22 years. While this study lacks the information on women who did not consume dairy products at all, it is still interesting because it considered the intake of fruits and vegetables together with dairy products. Compared with a low intake of milk (<1 glass/day) and a high intake of fruits and vegetables (≥5 servings/day), a high intake of milk (≥3 glasses/day) with a low intake of fruits and vegetables (<2 servings/day) was associated with a HR of 2.49. This means that women having high intake of milk and low intake of vegetables had 2.49 times the rates of hip fracture. It also showed that a moderate intake of fermented milk products (dairy products like cheese, yogurt etc) paired with high intake of fruits and vegetables is associated with lower hip fracture risk. In this study, high intake of fruits and vegetables was associated with lower risk in all groups.
In these cohorts, high intake of milk was associated with higher hip fracture risk. High intake of fruits and vegetables combined with low intake of milk was associated with lower hip fracture risk. These cohort studies and META analysis brought up factors which are interesting and I will research each of them here to be able to make a better conclusion regarding the overall dairy and hip fracture risk.
BMI
Vegetarians and vegans generally have lower BMI than meat eaters (7)(8), and previous studies have reported an inverse association between BMI and some fractures, particularly hip fractures, possibly due to reasons including the cushioning against impact force during a fall, enhanced oestrogen production with increased adiposity, or stronger bones from increased weight-bearing (9)(10).
Findings suggest that the association of low BMI with high hip fracture risks potentially is not dependant on calcium intake.
Calcium and Vitamin D
Vicky Tai et al.(11) in their META analysis concluded that increasing calcium intake from dietary sources or by taking calcium supplements produces small non-progressive increases in BMD (bone mineral density), which are unlikely to lead to a clinically significant reduction in risk of fracture. Big majority of these studies used milk or dairy as dietary supplements for calcium.
Heike A Bischoff-Ferrari et al. in their META (12) analysis studied 7 cohort studies with 170,000 women and concluded: prospective cohort studies found no significant association between dietary calcium intake and hip fracture risk in women or men. Randomised controlled trials showed no reduction in hip fracture risk with calcium supplementation, and an increased risk is possible.
A clinical trial (13) was done on 36,000 women, 50-79 years of age in the United States which assigned supplement of calcium carbonate 1000mg plus 400 IU of vitamin D3 to one group and placebo to another. Among healthy postmenopausal women, calcium with vitamin D supplementation resulted in a small improvement in hip bone density, did not significantly reduce hip fracture, and increased the risk of kidney stones.
Dietary patterns
500 Australian women participated in a study (14) done to measure the association of dietary patterns and bone health measured by Bone Mineral Content (BMC). The study found that a diet characterised by high consumption of high energy, nutrient-poor foods such as refined cereals, soft drinks, deep-fried potatoes, sausages and processed meat, vegetable oils, beer, and take-away foods was inversely associated with total body BMC. In addition, a diet similar to a Mediterranean diet and consisting of high consumption of vegetables and vegetable dishes, legumes, seafood, seeds and nuts, wine, rice and rice dishes was directly associated with total body BMC, hip Bone Mineral Density BMD, and spine BMD.
Deborah E Sellmeyer et al. (15) conducted a cohort study of 7 years on 1035 white post-menopausal women and concluded that elderly women with a high dietary ratio of animal to vegetable protein intake (these who eat more animal proteins and less plant based proteins) have more rapid femoral neck bone loss and a greater risk of hip fracture than do those with a low ratio. This suggests that an increase in vegetable protein intake and a decrease in animal protein intake may decrease bone loss and the risk of hip fracture.
The authors proposed that diets rich in animal foods and low in vegetable foods may create a net acid load that can negatively affect calcium balance, and that with age the kidneys excrete this load less efficiently, so bone may act as a buffer.
Eva Warensjo Lemming et al conducted a longitudinal cohort study (16) following 82,000 men and women for 12 years regarding their dietary calcium intake and adherence to Mediterranean Diet. They concluded that individuals who took on average 800 mg of calcium through food a day combined with high adherence to mediterranean diet had the lowest hip fracture rates. These who took low calcium or high calcium rich foods a day (up to 1200 mg/day) with a low adherence to Mediterranean diets had increased hip fracture risks (HR 1.54 and 1.50 respectively).
International Guidelines
WHO (1) has identified green vegetables high in calcium (e.g. broccoli, kale), legumes and by-products of legumes, tortillas processed with lime, as sources for calcium.
Although firm evidence is lacking, prudent dietary and some lifestyle recommendations developed in respect of other chronic diseases may prove helpful in terms of reducing fracture risk. These include:
- increase physical activity;
- reduce salt intake;
- increase consumption of fruits and vegetables;
- maintain a healthy body weight;
- avoid smoking; limit alcohol intake.
Academy of Nutrition and Dietetics in their January 2025 guidelines (17) states that appropriately planned vegetarian and vegan diets can be nutritionally adequate and can offer long-term health benefits.
Summary of Observed Patterns in the Literature
My conclusion: in the long-term studies I reviewed, total dairy intake was not clearly associated with hip fracture risk. Higher milk intake was associated with higher risk, while yogurt and cheese were associated with lower risk, although these findings should be interpreted with caution. The evidence does not support the idea that dairy is needed to protect against hip fracture, and calcium is available from plant sources. These are observational studies, which show associations, not cause and effect.
Low BMI was reported in several cohorts and may explain part of the higher hip fracture risk in vegetarians.
It is not only calcium, vitamin D is also essential for bone health and a diet rich with fruits, vegetables, leafy greens, grains and plant-based proteins.
Some studies suggest calcium supplementation may carry risks and is generally evaluated on an individual basis in clinical settings.
This literature review covers population living in industrialised countries only. There is some research, but limited, done for other parts of the world, however, osteoporosis /hip fracture rates are low there.
Discussion of the Conclusion with an Outlook
This topic is complex, and I have attempted to address most of the elements of this sophisticated puzzle; however, two pieces remain that I would like to discuss here in order to open the way for further reflection:
Silica
Silica, or dietary silicon, was examined in a cohort study including 1,200 men and 1,500 premenopausal and postmenopausal women from the Framingham Offspring cohort (aged 28–87 years) (18). Silicon intake was positively correlated with bone mineral density (BMD) at all four hip sites in men and premenopausal women. A substantial difference of 10% in bone mineral density (BMD) was observed between the highest (>40 mg silicon/day) and lowest (<14 mg silicon/day) quintiles of silicon intake.
Silica is thought to contribute to collagen synthesis and bone mineralization and may have a positive effect on bone mineral density (BMD).
Vitamin C
Within the Framingham Osteoporosis Study (19), 366 men and 592 women were followed for 15 to 17 years. The results suggest that higher vitamin C intake is associated with lower hip fracture risk.
References
(1) Diet, Nutrition and prevention of chronic diseases, WHO technical report series, Geneva 2003.
(2) Consumption of milk and dairy products and risk of osteoporosis and hip fracture: a systematic review and Meta-analysis, Hanieh Malmira, Bagher Larijanic and Ahmad Esmaillzadeh, 2019. https://www.tandfonline.com/doi/full/10.1080/10408398.2019.1590800
(3) Dairy intake and risk of hip fracture in prospective cohort studies: non-linear algorithmic dose-response analysis in 486 950 adults. Suruchi Mishra, Kavitha Baruah, Vasanti S. Malik and Eric L. Ding. Published by Cambridge University Press on behalf of The Nutrition Society, 2023
(4) ‘Obesity and Fracture in Men and Women: An Epidemiologic Perspective’ by Carrie M Nielson, Priya Srikanth, and Eric S Orwoll. Journal of Bone and Mineral Research, Vol 27, Jan 2012.
(5) Risk of hip fracture in meat-eaters, pescatarians, and vegetarians: a prospective cohort study of 413,914 UK Biobank participants. James Webster, Darren C. Greenwood and Janet E. Cade, BMC Medicine (2023)
(6) Intake of milk or fermented milk combined with fruit and vegetable consumption in relation to hip fracture rates: A cohort study of Swedish women: Karl Michaëlsson, professor; Alicja Wolk, professor; Eva Warensjö Lemming, PhD; Håkan Melhus, professor; and Liisa Byberg, associate professor. Journal of Bone and Mineral Research 2017.
(7) Tong TY, Key TJ, Sobiecki JG, Bradbury KE. Anthropometric and physiologic characteristics in white and British Indian vegetarians and nonvegetarians in the UK Biobank. Am J Clin Nutr. 2018;107:909–20.
(8) Spencer EA, Appleby PN, Davey GK, Key TJ. Diet and body mass index in 38 000 EPIC-Oxford meat-eaters, fish-eaters, vegetarians and vegans. Int J Obes. 2003; 27:728–34
(9) Armstrong MEG, Cairns BJ, Banks E, Green J, Reeves GK, Beral V. Different effects of age, adiposity and physical activity on the risk of ankle, wrist and hip fractures in postmenopausal women. Bone. 2012; 50:1394–400.
(10) De Laet C, Kanis JA, Odén A, Johanson H, Johnell O, Delmas P, et al. Body mass index as a predictor of fracture risk: a meta-analysis. Osteoporos Int. 2005;16:1330–8.
(11) Calcium intake and bone mineral density: systematic review w and meta-analysis: Vicky Tai, William Leung, Andrew Grey, Ian R Reid, Mark J Bolland. 2015.
(12) Calcium intake and hip fracture risk in men and women: a meta analysis of prospective cohort studies and randomised controlled trials. Heike A Bischoff-Ferrari, Bess Dawson-Hughes, John A born, Peter Burckardt. Am J Clin Natur 2007
(13) Calcium plus Vitamin D Supplementation and the Risk of Fractures. Rebecca D. Jackson, M.D., Andrea Z. LaCroix, Ph.D., Margery Gass, M.D., Robert B. Wallace, M.D., John Robbins, M.D., Cora E. Lewis, M.D., Tamsen Bassford, M.D. The New England Journal of Medicine, February 2006.
(14) Study An Energy-Dense, Nutrient-Poor Dietary Pattern Is Inversely Associated with Bone Health in Women. Sarah A. McNaughton, Naiyana Wattanapenpaiboon, John D. Wark, and Caryl A. Nowson. American Society for Nutrition, 2011
(15) A high ratio of dietary animal to vegetable protein increases the rate of bone loss and the risk of fracture in postmenopausal women. Deborah E Sellmeyer, Katie L Stone, Anthony Sebastian, and Steven R Cummings for the Study of Osteoporotic Fractures Research Group. Am J Clin Nutr 2001
(16) Combinations of dietary calcium intake and mediterranean-style diet on risk of hip fracture: A longitudinal cohort study of 82,000 women and men. Eva Warensjo Lemming, Liisa Byberg, Jonas Hoijer, Susanna C. Larsson, Alicja Wolk, Karl Michaelsson. Clinical Nutrition Journal, January 2021
(17) Vegetarian Dietary Patterns for Adults: A Position Paper of the Academy of Nutrition and Dietetics. Sudha Raj, PhD, RDN, FAND, Nanci S. Guest, PhD, RD, Matthew J. Landry, PhD, RDN, FAND, FAHA, A. Reed Mangels, PhD, RDN, Roman Pawlak, PhD, RDN, Mary Rozga, PhD, RDN. Journal of the Academy of Nutrition and Dietetics, Vol 125, Issue 6, June 2025.
(18) Dietary silicon intake is positively associated with bone mineral density in men and premenopausal women of the Framingham Offspring cohort. Ravin Jugdaohsigh, Katherine L Tucker, Ning Quia. Journal of Bone and Mineral Research, Volume 19, Issue 2, 1, February 2004.
(19) Protective effect of total and supplemental vitamin C intake on the risk of hip fracture – A 17-year follow-up from the Framingham Osteoporosis Study. Shivani Sahni, Marian Hannan, David Gagnon. Osteoporosis Int. 2009 November.