Mastering Calcium Intake: The Key to Strong Bones and More

We have all heard about the importance of calcium for strong bones and teeth, but it does much more than that! Let’s dive deeper and uncover the versatility of calcium, along with the roles of supporting vitamins and minerals for bone health.

In this exploration of calcium, we’ll reveal its hidden roles, essential vitamins and minerals for bone health, foods beyond dairy that contain calcium, how much you need, how to test for it, and whether you need a supplement.

Calcium: Its Role in the Body

Bone and Teeth Health: Calcium is best known for its role in building and maintaining strong bones and teeth. It provides the structural integrity necessary for bone formation and mineralization.

Blood Clotting: Calcium is essential for the process of blood clotting. When you get injured, calcium helps in the formation of blood clots to prevent excessive bleeding.

Muscle Contraction: Muscles, including your heart, rely on calcium ions for contraction. Calcium facilitates the interaction between muscle proteins, allowing muscles to contract and function properly.

Nervous System Function: Calcium ions are involved in transmitting signals within the nervous system. They play a key role in nerve cell communication and the release of neurotransmitters.

Hormone Secretion: Calcium is necessary for the secretion of various hormones, including insulin, which regulates blood sugar levels, and certain hormones in the parathyroid glands, which control calcium balance in the body.

Blood Vessel Function: Calcium is involved in the constriction and relaxation of blood vessels, which helps regulate blood pressure.

Cell Signaling: Calcium ions act as important secondary messengers in many cellular processes, helping to transmit signals and regulate cell functions.

Enzyme Activation: Calcium is a cofactor for several enzymes, assisting in various biochemical reactions within cells.

 Bone Health: Vitamins and Minerals Beyond Calcium

Vitamin K: activates specific bone associated proteins that are important for bone formation and mineralization.

Vitamin D: regulates the above activation and is crucial for calcium absorption.

Vitamin A: controls which bone building gene responds to vitamin D. Vitamin A is essential for cell development and skeletal growth.

Vitamin C: is essential for collagen formation and collagen is the main protein in bone.

Magnesium: required for bone mineralization (component of bone / mineral crystals) and improves bone strength.

Phosphorus required for bone and teeth mineralization (component of bone / mineral crystals). Vitamin D improves phosphorus absorption.

Calcium: Dietary Sources

Calcium is found a variety of plant foods such as kale, broccoli, mustard greens, Chinese cabbage, okra, almonds, figs, oranges, white beans, sesame seeds (tahini), calcium set tofu, tempeh, and calcium fortified products (plant milks, orange juice, and cereal). The calcium content of a food is not the amount of calcium absorbed (1). Calcium absorption is also affected by factors in foods such as fiber, oxalates, and phytates. For example, spinach is high in calcium, but also high in oxalates so only 6 mg of an 85-gram serving is absorbed.

Food	1 Serving Size	Calcium Content (mg)	Absorbed (mg)
Milk	240 grams	300	96
Tofu w/ calcium	126 grams	258	80
Bok Choy	85 grams	79	43
Kale	85 grams	61	30
White beans	110 grams	113	21
Broccoli	71 grams	35	25

Food Examples	Approx. Absorption Rate
cauliflower, brussels sprouts, kale, watercress, turnup greens, mustard greens, broccoli, cabbage, and bok choy	50%
milk, calcium fortified soy milk, calcium set tofu, yogurt, cheese, and calcium fortified foods and beverages	30%
almonds, sesame seeds (tahini), pinto beans, and sweet potatoes	20%
spinach, rhubarb, Swiss chard	5%

 Calcium: How Much

The recommended daily allowance (RDA) for calcium in Singapore is per the chart below (2). Calcium recommendations are made to account for a 30% absorption rate. 

Infants (7 – less than 12 months)	400 mg
Children (1 – 3 years)	500 mg
Children (4 – 6 years)	600 mg
Children (7 – 9 years)	700 mg
Adolescents (10 – 18 years)	1000 mg
Adults (19 – 50 years)	800 mg
Adults (51 years and above)	1000 mg
Breastfeeding / pregnant	1000 mg

 Calcium: Blood Testing

A question I am frequently asked is, “Why don’t physicians conduct blood tests to check for all nutrient deficiencies?” This approach could become expensive, and nutrient tests are not always reliable, especially when it comes to calcium. Blood calcium levels do not accurately reflect dietary calcium intake because the body tightly regulates serum levels.

It is essential to body function to maintain blood calcium balance. To maintain this balance, the body will leach calcium from the bones. Consequently, inadequate calcium intake can lead to bone health issues. To assess bone health and the risk of osteoporosis, a DEXA scan is the recommended option.

 Wrap-up

Bone metabolism remains active throughout the entire life cycle, encompassing phases of active growth, peak bone mass, and eventual bone loss, underscoring the importance of obtaining sufficient calcium. For individuals following vegan or vegetarian diets, calcium supplementation is typically unnecessary, given the abundance of plant-based and fortified calcium sources available. However, if your diet is mostly processed foods and you don’t drink fortified products or you have an aversion to leafy greens, you may be at risk of insufficient calcium intake.

Research, such as the EPIC-Oxford study (3), has shown that vegans exhibit a 30% higher fracture rate compared to nonvegans. However, this discrepancy disappears when both groups consume a minimum of 525 mg/day of calcium. Adjusted incident rates for fractures in individuals meeting this calcium threshold are as follows: 1.05 (0.90-1.21) for fish eaters, 1.02 (0.90-1.15) for vegetarians, and 1.00 (0.69-1.44) for vegans. This suggests that if individuals, regardless of their dietary choices, consume at least 525 mg/day of calcium, there is no significant difference in fracture rates.

If you are considering calcium supplement, it’s essential to consult with a medical professional because excessive calcium intake can lead to adverse side effects. Additionally, it’s important to note that vitamin D plays a crucial role in calcium absorption. A deficiency in vitamin D can impair calcium absorption, so it’s advisable to spend time outdoors to ensure adequate exposure to the “sunshine vitamin.” Always prioritize a balanced diet and consult with a healthcare provider for personalized guidance on calcium intake.

References

1. Rozenberg, S., Body, J. J., Bruyère, O., Bergmann, P., Brandi, M. L., Cooper, C., Devogelaer, J. P., Gielen, E., Goemaere, S., Kaufman, J. M., Rizzoli, R., & Reginster, J. Y. (2016). Effects of Dairy Products Consumption on Health: Benefits and Beliefs–A Commentary from the Belgian Bone Club and the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases. Calcified tissue international, 98(1), 1–17. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703621/

2. HealthHub. (2023). Retrieved from https://www.healthhub.sg/live-healthy/192/recommended_dietary_allowances

3. Appleby, P., Roddam, A., Allen, N., & Key, T. (2007). Comparative fracture risk in vegetarians and nonvegetarians in EPIC-Oxford. Eur J Clin Nutr, 61(12), 1400-1406.Retreived from https://pubmed.ncbi.nlm.nih.gov/17299475/