Nguyen-Hoang A, Dhadra M. Improvement in calcium intake in the Asian population: A narrative review. HPHR. 2021;41.
Calcium intake may play an important role in bone health. Low serum calcium is associated with bone disorders and abnormal growth as well as improper functions of muscles, nerves, and certain organs such as the heart. Evidence suggests that Asian populations have been at a high risk of calcium deficiency across studies in the last decade. The narrative review investigated factors affecting the dietary calcium intake among Asian populations, such as traditional non-dairy based diets in many Asian countries, and the high prevalence of milk tolerance. In addition, calcium supplements and fortified foods as well as the related innovative strategies in biotechnology were considered to improve calcium intake in Asian population.
Around 99% of calcium is found in bones and teeth, with the remaining found in blood, muscles, and tissue. A healthy diet rich in calcium improves bone health, especially during early years of life. Those with poor calcium intake during childhood may suffer from fractures and rickets, as well as not reaching their potential adult height and maximum bone mass.1 Evidence also shows that calcium deficiency is also associated with improper functions of muscles, nerves, and organs such as the heart.2 According to a database in 2011 directed by Kumssa and coworkers3, a number of countries in Asia, particularly Southeast Asia, South Asia and West Asia, found 50%-90% of people at risk of calcium deficiency because of inadequate dietary intake of calcium. Notably, a more recent study demonstrated that average dietary calcium intakes in Asian countries did not meet the daily recommendation for calcium intake and were far lower than those in Western countries even though the daily recommendations were the same for adults.4 To date, this trend remains unchanged.5 This review aims to document various aspects of calcium intake in this population.
Calcium widely presents in a variety of dietary sources including dairy foods (e.g., milk, cheese, yogurt), and non-dairy foods (e.g., meats, fish, eggs, tofu, soy, vegetables, and legumes). Of these sources, milk and dairy products are well-recognized as the optimum food source of dietary calcium,6-7 which accounted for 40-75% of calcium intake among Western populations.8-9 On the contrary, milk and dairy products are not the main food sources of dietary calcium in many countries in Asia. Instead, vegetables and fish consumed with bones are commonly consumed as a calcium source.6,10 An example of this is demonstrated in a Chinese study where only 6.7% of calcium was acquired from milk and dairy products.11 The authors emphasized that vegetables and legumes contribute to nearly 50% of dietary calcium intake in this population.
Some vegetables, such as kale, watercress, and broccoli were well-reported in Western population diets12 and are high in calcium, providing 100-150mg of calcium per 100 g. Plant sources of calcium in the Asian population remains unclear. Moreover, anti-nutrients, such as oxalate and phytate, which are mainly found in some leafy green vegetables, might have inhibitory effects on calcium absorption. When these high-affinity complexes are combined with calcium and consumed at the same time, they can form insoluble complexes. As a result, they may decrease the amount of calcium available for absorption of by the body. The inhibitory effect of phytate and oxalate on calcium absorption has been well-recognized by animal as well as human studies.13 Inadequate vitamin D levels also reduce calcium absorption. People with gross vitamin D deficiencies absorb only 10%–15% of calcium from food.32 Notably, vitamin D deficiency is prevalent in Asia, according to a recent systematic review and meta-analysis.39 Deficiencies can be caused by inadequate vitamin D intake through diet or supplements or by insufficient sun exposure.
In addition, milk and dairy products, such as cheese, yoghurt, contain lactose. An enzyme called lactase, is produced to digest lactose in milk and dairy products. There is evidence that the activity of this enzyme reduces with age, making adults more susceptible to lactose intolerance compared to children. Notably, Asian adults were more likely to experience symptoms of lactose intolerance than European populations. It was estimated that the prevalence of lactose intolerance in Asia is estimated to be 67% while it is 28% and 36% in Western Europe and the US, respectively.14 Genome-wide association studies have partly shed light on how lactose intolerance varies between ethnicities. To date, at least 23 genetic variants (in relation to the lactose persistence state), have been identified across different ethnic backgrounds, mainly in populations of European descent.15 However, it was worth noting that genomic data in the study from people of non-Caucasian ancestry are comparatively lower to their Caucasian counterparts. Further genetic studies involving ethnically diverse populations, particularly Asian populations would be beneficial to address the diversity gap in lactose intolerance studies. This would also allow a wider pool of data to be analyzed. Lactose intolerance in adulthood may prevent an individual from consuming calcium-rich foods such as milk and dairy products. A systematic review also revealed that people from Asia avoided consuming milk and dairy products because of concerns about developing lactose intolerance-related symptoms.16 A qualitative study on adolescent females demonstrated that Asian adolescents were more likely to report lactose intolerance-related symptoms as a reason for avoiding milk and dairy products from their diet, compared to European populations.17
A consensus among global health organizations and societies is that calcium supplements may be helpful in preventing or treating calcium deficiency when dietary calcium intake is inadequate.18-19,32 Calcium requirements vary across the human lifespan. However, calcium supplements could be implemented to ensure calcium requirements are met in people where calcium deficiency is suspected or diagnosed. This may be particularly helpful during periods of increased calcium requirements, such as adolescence, pregnancy, and breastfeeding, as well as older age groups (50 years and over).12 For example, the dietary demands of a developing fetus and child may cause an increase in transitory bone mineral loss in women. Not all mother’s recover from this despite increased intestinal calcium absorption and increased calcium intake during pregnancy and breastfeeding.20 Moreover, calcium deficiency during pregnancy is associated with pre-eclampsia and its related complications. The Cochrane systematic review demonstrated that calcium supplementation was beneficial to prevent pre-eclampsia during pregnancy.21 An updated recommendation from the World Health Organization22 also emphasized that calcium supplementation should be advised to women before or during early pregnancy. This would aid in reducing or preventing hypertension and other related complications during pregnancy in the absence of adequate dietary calcium intake.
In addition, evidence from randomized controlled trials (RCTs) revealed that calcium supplementation has a positive effect on increasing bone mass in adolescents.23-26 A Cochrane meta-analysis of 19 RCTs also emphasized the effect of calcium supplementation for increasing bone density in children, but the analysis had a few limitations such as small effects being measured as well as reduced diversity with Caucasian dominant databases.27 The significant difference in the mean calcium dietary intake between Caucasians and Asians has been well-reported within a number of studies3-5. It is likely to limit our knowledge of the cause-effect relationship in diverse populations and could increase health inequity. A further need for studies involving ethnically diverse populations is needed to address this issue.
Calcium supplements come in various salt forms, such as calcium carbonate, calcium phosphate, calcium lactate and calcium gluconate. Calcium salts can be also used as fortificants in foods. Like calcium supplements, food fortified with calcium salts is considered a potential approach to prevent and treat calcium deficiency at a population level. Palacios and colleagues suggested that a food fortification strategy may be feasible to address calcium deficiency in Asian countries with low dietary calcium intake.28 However, food vehicles should be carefully considered to reach the whole population.29 Weaver et al. investigated the absorption of calcium from tofu fortified with calcium chloride and calcium sulphate among Asians and Caucasians.30 The findings demonstrated that the calcium absorption effect is the same for fortified tofu when compared with calcium absorption of milk.
In addition, studies on calcium supplements and fortified foods have shown that different calcium salts demonstrate varied absorption rates as well as their amounts of elemental calcium.32 Calcium lactate and calcium gluconate are more soluble in water than calcium carbonate and phosphate, but they are not considered practical for oral supplements because they contain less elemental calcium.31 Considerably more tablets would need to be consumed to reach the same dose as calcium phosphate or calcium carbonate. Calcium carbonate and calcium phosphate are forms of calcium containing the highest amount of elemental calcium (39-40%) compared to other salts and are also a less expensive source of calcium on the commercial market.32 However, absorption of calcium from these calcium salts largely depends on whether they are taken on an empty stomach or with meals.32-33 Moreover, their bioavailability is also affected by particle size in the supplements.34 Innovative strategies in biotechnology have been employed for calcium salts to increase the amount of elemental calcium in supplements and food products, as well as improve their bioavailability. For example, two studies used microencapsulation biotechnology to increase calcium absorption from soy milk and soy yogurt, given their low calcium content. The microencapsulation technology can significantly reduce the particle size as well as improve the stability of certain calcium salts and minimize excessive urinary excretion of calcium.35-37 Soy milk is naturally low in calcium; it contains about 12mg of elemental calcium per 100g. Schrooyen and colleagues showed that soy milk with calcium lactate encapsulated with lecithin provides an increase of 110mg elemental calcium per 100g of soy milk.37 Moreover, Planas and Garriga38 studied the bioavailability of the commercially available product LipocalTM. This product is composed of micronized tricalcium phosphate encapsulated with lecithin. During the study, subjects were fed soy yoghurt alone, or soy yoghurt fortified with either non-encapsulated tricalcium phosphate or LipocalTM. Plasma Ca2+ concentrations were then measured every ten minutes for 50 minutes following consumption. The results demonstrated that plasma Ca2+ concentrations increased significantly higher for the subjects administered LipocalTM compared to non-encapsulated tricalcium phosphate. Similarly, plasma Ca2+ levels also increased at a faster rate for the subjects fed soy yoghurt fortified with LipocalTM than those fed soy yoghurt fortified with tricalcium phosphate.38 When directly compared, both sets of results would suggest that the microencapsulation technology applied to the LipocalTM product leads to an improved bioavailability of calcium and, more importantly, improves blood plasma Ca2+ levels. The microencapsulation technique and its application are not only applied to calcium absorption but also to the absorption of other natural bioactive compounds, such as antioxidant rich Rubusulmifolius extracts.35
Asian populations are likely to be calcium deficient. This could be partly attributable to the traditional non-dairy diets consumed in many Asian countries as well as the high prevalence of lactose intolerance in this continent. Studies in calcium-rich non-dairy foods in Asia are needed. In addition, calcium supplements and foods fortified with calcium seemed to be an effective strategy to prevent and treat calcium deficiency for individuals in whom calcium dietary intake is suspected or confirmed. The bioavailability of calcium salts in supplements and fortified foods is low and largely affected by many factors, such as particle size and gastric solubility. There is evidence that innovative biotechnologies, such as microencapsulation technology, have been effective to increase the amount of elemental calcium in supplements and food product matrices, as well as, improving their bioavailability.
Mona Dhadra, a full-qualified nutritional therapy practitioner and a registered Five-Element acupuncturist in Birmingham, United Kingdom. As a member of the British Acupuncture Council, all her treatments adhere to the highest standards of safety and competency. She has a keen interest in natural health. She qualified as a nutritional therapist from the University of Worcester and has since gone on to receive her degree equivalent qualification in Traditional Chinese medicine and five element acupuncture from The Acupuncture Academy. Mona has recently opened her clinic to administer acupuncture treatments in Birmingham. Her practice interests are mental health and chronic pain.
Anh Nguyen-Hoang is a Registered Nutrition Practitioner and Consultant in genomic medicine who works in the intersection of nutrition and genomics to treat and prevent chronic diseases. He serves as clinical nutrition director at Children & Women Health Centre, Edinburgh, UK. He has been honored as a Fellow of the British Association for Nutrition and Lifestyle Medicine. His work focuses on patient-oriented research projects on precision nutrition and genomics. He is also known for the efforts to explain profound concepts in personalized nutrition and lifestyle medicine between European and Asian children. Recently, he is leading a funded research project on nutrition therapy for long COVID. He is also elected for Ambassadorial Scholar to the Genetics Society, one of the oldest learned societies in the UK devoted to genetics, in order to promote education and research on nutritional genomics for healthcare professionals in the UK and Asia. He is a professional member of the Complementary and Natural Healthcare Council, the Association of Genetic Nurses and Counsellors, and the British Society of Genetic Medicine.
With a strong interest in teaching and academic service, he serves as the guest faculty of the European Lifestyle Medicine Organization’s lifestyle medicine certificate program for medical doctors across the Europe. As Guest Speaker at The Economist, he has participated in workshop series on nutrition, health, genomics, and mindfulness for policymakers, healthcare CEOs, and thought leaders across the globe. He has also performed as panel speaker at the Asia Summit Global Health 2021 on public health issues in Asia, organized by The Hong Kong Trade Development Council.