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Calcium & Vitamin D: Why They Matter for Your Health

Written by: Consultant Dietitian from Global Precision Wellness

Calcium and vitamin D are essential nutrients that play key roles in supporting our health, especially when it comes to strong bones and muscles. Calcium is the most abundant mineral in the body. 99% of calcium is found in our bones and teeth, where it provides strength and structure [1,2]. The remaining 1% is found in our blood, where it is involved in several important functions like helping muscles move, sending signals between your brain and body, blood circulation, and the release of hormones that help control different processes in the body [1,2]. Vitamin D, on the other hand, is unique as it can be produced by the body when exposed to sunlight and can also be obtained from certain foods. Vitamin D helps the body absorb calcium, it is like the ‘key’ that unlocks calcium’s ability to strengthen our bones. Just like calcium, it also helps with muscle movement and sending signals between your brain and body [3]. It also plays an important role in supporting a strong immune system to protect against illnesses [3].

The Calcium – Vitamin D Connection

Calcium and vitamin D are closely connected when it comes to bone health. Vitamin D helps your body absorb calcium more effectively. Without enough vitamin D, you may not get the full benefits of calcium, even if you’re eating calcium-rich foods. That’s why both nutrients are essential for developing and maintaining strong bones, and together, they help prevent conditions like osteoporosis (brittle bones), osteomalacia (soft bones), and fractures [4].

How Genetics Play a Role in Calcium & Vitamin D

Ever wondered why you might struggle with calcium or vitamin D deficiency, even if you eat foods that contain them? Well, your genes could be a factor, as genes may affect how the body processes or absorbs certain nutrients. Some people are genetically predisposed to process or use these nutrients less efficiently. This is where nutrigenomics, the study of how our genes influence the way our body responds to nutrients, comes in. It sounds complicated, but don’t worry! This article will explain how certain genes may affect your calcium and vitamin D levels, and what you can do about it:

1. Calcium – Average Calcium Absorption

The GC gene is a gene responsible for producing a protein that helps in regulating calcium levels by transporting vitamin D to where it’s needed [5].  If your GC gene functions normally, your body will absorb calcium from food as effectively as most people. This means you are likely to need the standard amount of calcium recommended for your age and gender to maintain bone health.

2. Calcium – Low Calcium Absorption

Variations of the GC gene can lead to altered levels of this protein, potentially impairing vitamin D metabolism and consequently reducing calcium absorption [5]. This means that your body may struggle to get enough calcium from food, which can increase your risk of calcium deficiency. This could lead to symptoms like muscle cramps, dry skin, coarse hair, and brittle nails [6]. Over time, insufficient calcium can lead to more serious conditions, such as osteopenia or osteoporosis, which can increase your risk of fractures [1].

3. Vitamin D – Average Vitamin D Status

The CYP2R1 gene helps produce an enzyme that converts vitamin D into the most abundant form of vitamin D in the bloodstream [7]. Additionally, the GC gene helps transport vitamin D to the tissues where it’s needed, ensuring that it is processed and used efficiently [7]. If these genes function normally, your body will process vitamin D well. With adequate sunlight exposure and right foods, you’re likely to get enough vitamin D.

4. Vitamin D – Low Vitamin D Status

Genetic variations in genes like DHCR7, CYP2R1, and GC can contribute to low vitamin D status by affecting its production or activation [7]. Even if you get enough sunlight or consume vitamin D-rich foods, your body may not use it as efficiently. Symptoms of vitamin D deficiency include muscle weakness and bone pain [8]. Long-term deficiency can lead to conditions such as rickets in children, osteomalacia, and osteoporosis [3].

However, keep in mind that genetic tests only indicate how your body may respond to nutrients; they do not reflect your current nutritional status. Therefore, it is recommended to  complement nutrigenomic testing with blood tests for a more comprehensive understanding of your nutritional status.

Improving Calcium & Vitamin D Health: Simple Steps You Can Take

Here are some simple steps you can take to improve your calcium and vitamin D health, especially if you have a genetically higher risk of deficiency:

1. Eat More Calcium-Rich Foods

Calcium can be found in dairy products like milk, yogurt, and cheese, or plant-based sources like kale and bok choy [1]. For Malaysians, the Recommended Nutrient Intake (RNI) value for calcium is 800-1000 mg per day for adults [9].

Here’s the calcium content for some common calcium-rich foods:

  • 1 glass of milk (250 ml): 270 mg calcium (~27-34% of RNI)
  • 1 serving of yogurt (150ml): 190 mg calcium (~19-24% of RNI)
  • 1 slice of cheese: 90 mg calcium (~9-11% of RNI)
  • 1 cup of kale, chopped, uncooked (around 60 g): 110 mg calcium (~11-14% of RNI)
  • 1 cup of bok choy, chopped, uncooked (around 90 g): 90 mg calcium (~9-11% of RNI)

To meet the daily RNI for calcium, aim for at least 3 servings of calcium-rich foods per day, such as a combination of milk, yogurt, and plant-based sources.

2. Include More Vitamin D-Rich Foods

Foods such as fatty fish (salmon, mackerel, and sardines), egg yolks, fortified dairy products, and fortified plant-based milks are good sources of vitamin D [3]. The RNI for vitamin D in Malaysia is 5-10 mcg per day for adults [9].

Here’s the vitamin D content for some common vitamin D-rich foods:

  • Salmon, cooked (85 g): 14 mcg vitamin D (~140-280% of RNI)
  • Egg yolk from 1 large egg, scrambled: 1 mcg vitamin D (~10-20% of RNI)
  • 1 glass of milk, vitamin D fortified (250 ml): 3 mcg vitamin D (~30-60% of RNI)

Including 1-2 servings of vitamin D-rich foods daily can help meet the RNI for vitamin D. If consuming these foods is challenging, consider pairing them with moderate sunlight exposure (see Tip #4 below).

3. Healthy Fats Help Absorption

Since vitamin D is a fat-soluble vitamin, eating it with healthy fats can help improve its absorption in the body [3]. Foods like avocado, olive oil, nuts, and seeds are excellent sources of healthy fats [10]. Pairing these foods with vitamin D-rich items can enhance the effectiveness of vitamin D and help your body absorb the nutrient more efficiently [11].

4. Get Some Sunshine

Vitamin D is often called the “sunshine vitamin” because the body produces it in response to sunlight exposure [3]. Spending time outdoors, particularly in the morning or late afternoon, allows your skin to synthesise vitamin D. Usually, around 30 minutes of sunlight exposure is sufficient to meet daily vitamin D needs [9]. However, it is essential to be cautious about sun exposure between 10 AM and 4 PM, as this is when harmful UV radiation is most intense [12].

5. Consider Supplements If Needed

If your dietary intake cannot meet your calcium and vitamin D needs, supplements can be an option. As mentioned earlier, the RNI values for calcium and vitamin D are 800-1000 mg and 5-10 mcg per day for Malaysian adults, respectively [9]. With a wide variety of supplements available in the market, here are some key considerations to help you choose the right ones:

i. Choosing Between Calcium Supplements:

Calcium Carbonate vs. Calcium Citrate

Supplement Form Calcium Carbonate Calcium Citrate
Pros
  • Most common & cost-effective form of calcium supplements
  • Contains about 40% elemental calcium, meaning fewer tablets are needed to meet your daily requirements [13].
  • Best absorbed when taken with food, as it requires stomach acid for optimal absorption [13].
  • More easily absorbed than calcium carbonate [13].
  • Can be taken on an empty stomach, making it convenient for those with lower stomach acid (e.g., older adults) [13].
  • Contains about 21% elemental calcium, which can be beneficial for those needing a gentler supplement [13].
Cons
  • May not be suitable for individuals with lower stomach acid levels or those who prefer taking supplements on an empty stomach [13].
  • Typically more expensive than calcium carbonate.
  • May need to take more tablets to meet your calcium needs [13].

Both forms of calcium supplements have their advantages and disadvantages. For individuals with normal stomach acid levels who prefer a cost-effective option and want to take fewer tablets, calcium carbonate is generally recommended. For those with lower stomach acid levels, such as older adults or individuals who prefer taking supplements without food, calcium citrate may be the better choice.

ii. Choosing Between Combination Supplements:

Calcium + Vitamin D vs. Calcium + Vitamin D + Vitamin K

Supplement Form Calcium Carbonate Calcium Citrate
Pros
  • Vitamin D enhances calcium absorption in the body, making this combination useful for making sure that your body gets enough calcium.
  • A straightforward option for those primarily focused on improving calcium absorption.
  • In addition to enhancing calcium absorption, vitamin K helps direct calcium to the bones while preventing its accumulation in soft tissues, potentially reducing cardiovascular risks [14].
  • This combination may be particularly beneficial for individuals at risk of osteoporosis or those looking to maximize overall bone health.
Cons
  • Does not address the potential issue of excess calcium accumulating in soft tissues without the regulatory effects of vitamin K.
  • Generally more expensive than combinations that include only calcium and vitamin D.

Choosing between these two supplement combinations depends on your individual health needs and goals. For those primarily focused on improving calcium absorption, Calcium + Vitamin D may suffice. However, if you are concerned about bone health and the potential risks of excess calcium in soft tissues, opting for Calcium + Vitamin D + Vitamin K could provide additional benefits.

While supplements can help fill nutritional gaps for those with deficiencies, they should be used with caution. Excessive calcium supplementation can increase the risk of heart disease due to calcification of the arteries [15]. It is crucial to consult with a healthcare professional before starting any supplementation regimen. Supplements can help address nutrient deficiencies, but it is always best to prioritise meeting your nutrient needs through food sources whenever possible.

In a nutshell, calcium and vitamin D are essential for maintaining strong bones, muscles, and overall health. While your genetic makeup can influence how your body processes and uses these nutrients, other factors such as diet and sun exposure also play an important role. Whether your genetic profile indicates average or low absorption rates, it’s never too late to make positive changes. Always consult a healthcare professional before making major changes to your diet or starting any supplements. A balanced approach to nutrition is key for long-term wellness.

Reference List

    1. National Institutes of Health Office of Dietary Supplements. Calcium [Internet]. National Institutes of Health. 2019. Available from: https://ods.od.nih.gov/factsheets/Calcium-Consumer/
    2. Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary reference intakes for calcium, phosphorus, magnesium, vitamin D, and fluoride. Washington (DC): National Academies Press (US); 1997. 4, Calcium. Available from: https://www.ncbi.nlm.nih.gov/books/NBK109827/
    3. National Institutes of Health Office of Dietary Supplements. Vitamin D [Internet]. National Institutes of Health. 2019. Available from: https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
    4. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Calcium and vitamin D: important for bone health [Internet]. National Institutes of Health. 2023. Available from: https://www.niams.nih.gov/health-topics/calcium-and-vitamin-d-important-bone-health
    5. Fang Y, van Meurs JB, Arp P, van Leeuwen JP, Hofman A, Pols HA, Uitterlinden AG. Vitamin D binding protein genotype and osteoporosis. Calcif Tissue Int. 2009 Aug;85(2):85-93. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC2729412/ doi: 10.1007/s00223-009-9251-9
    6. Lewis III JL. Hypocalcemia (low level of calcium in the blood) [Internet]. MSD Manual. 2023. Available from: https://www.msdmanuals.com/home/hormonal-and-metabolic-disorders/electrolyte-balance/hypocalcemia-low-level-of-calcium-in-the-blood
    7. Slater NA, Rager ML, Havrda DE, Harralson AF. Genetic variation in CYP2R1 and GC genes associated with vitamin D deficiency status. J Pharm Pract. 2017 Feb;30(1):31-36. Available from: https://journals.sagepub.com/doi/10.1177/0897190015585876doi: 10.1177/0897190015585876
    8. Johnson LE. Vitamin D deficiency [Internet]. MSD Manual. 2024. Available from: https://www.msdmanuals.com/home/disorders-of-nutrition/vitamins/vitamin-d-deficiency
    9. National Coordinating Committee on Food and Nutrition. Recommended nutrient intakes for Malaysia. 2017
    10. Wein H. Weighing in on dietary fats [Internet]. NIH News in Health. 2011. Available from: https://newsinhealth.nih.gov/2011/12/weighing-dietary-fats
    11. Dawson-Hughes B, Harris SS, Lichtenstein AH, Dolnikowski G, Palermo NJ, Rasmussen H. Dietary fat increases vitamin D-3 absorption. J Acad Nutr Diet [Internet]. 2015 Feb;115(2):225-30. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25441954/ doi: 10.1016/j.jand.2014.09.014
    12. United States Environmental Protection Agency. Ultraviolet (UV) radiation and Sun Exposure [Internet]. United States Environmental Protection Agency. 2018. Available from: https://www.epa.gov/radtown/ultraviolet-uv-radiation-and-sun-exposure
    13. Corliss J. Choosing a calcium supplement [Internet]. Harvard Health Publishing. 2020. Available from: https://www.health.harvard.edu/nutrition/choosing-a-calcium-supplement
    14. Hu L, Ji J, Li D, Meng J, Yu B. The combined effect of vitamin K and calcium on bone mineral density in humans: a meta-analysis of randomized controlled trials. J Orthop Surg Res. 2021 Oct 14;16(1):592. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC8515712/ doi: 10.1186/s13018-021-02728-4
    15. Morelli MB, Santulli G, Gambardella J. Calcium supplements: good for the bone, bad for the heart? A systematic updated appraisal. Atherosclerosis [Internet]. 2020 Mar;296:68-73. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC7276095/ doi: 10.1016/j.atherosclerosis.2020.01.008
Calcium & Vitamin D Why They Matter for Your Health