Calcium and Vitamin D Deficiency

Calcium and vitamin D deficiency is more common than many people realise, even among those who believe they eat a balanced diet. Calcium is the most abundant mineral in the body — 99% is stored in bones and teeth, while the remaining 1% supports muscle movement, nerve signalling and hormone release.

Vitamin D is unique because the body can produce it from sunlight as well as obtain it from food. It acts like a “key” that unlocks calcium’s ability to strengthen bones, while also supporting muscle function and immune health. Together, these two nutrients form one of the most important partnerships for long-term bone health.

How Calcium and Vitamin D Work Together

Vitamin D helps the body absorb calcium more effectively. Without enough vitamin D, you may not get the full benefit of calcium even if you eat calcium-rich foods regularly. This partnership helps prevent osteoporosis (brittle bones), osteomalacia (soft bones) and fractures.

The Role of Genetics

Some people struggle with low calcium or vitamin D levels despite a healthy diet. Genes can influence how efficiently the body processes and absorbs these nutrients. This is the field of nutrigenomics — the study of how genes affect nutrient response.

The GC Gene and Calcium Absorption

The GC gene produces a protein that helps transport vitamin D and regulate calcium levels. When this gene functions normally, calcium absorption is typically average. Certain variations, however, can reduce absorption efficiency and increase the risk of deficiency symptoms such as muscle cramps, dry skin, brittle nails and, over time, osteopenia or osteoporosis.

CYP2R1, DHCR7 and Vitamin D Status

Genes such as CYP2R1 and DHCR7 influence how the body produces and activates vitamin D. Variations in these genes can lead to lower circulating vitamin D levels even with adequate sunlight or dietary intake. Long-term deficiency may contribute to muscle weakness, bone pain, rickets in children, or osteomalacia and osteoporosis in adults.

Genetic tests indicate predisposition, but they do not show current nutrient status. Combining genetic insights with blood tests gives a clearer picture.

Practical Steps to Improve Levels

1. Eat More Calcium-Rich Foods

The Malaysian Recommended Nutrient Intake (RNI) for calcium is 800–1000 mg per day for adults. Good sources include:

• 1 glass of milk (250 ml) ≈ 270 mg
• 1 serving of yogurt (150 ml) ≈ 190 mg
• 1 slice of cheese ≈ 90 mg
• 1 cup chopped kale ≈ 110 mg
• 1 cup chopped bok choy ≈ 90 mg

Aim for at least three servings of calcium-rich foods daily.

2. Include Vitamin D-Rich Foods

The RNI for vitamin D in Malaysia is 5–10 mcg per day for adults. Useful sources include fatty fish (salmon, mackerel, sardines), egg yolks and fortified milk or plant-based alternatives.

3. Pair with Healthy Fats and Get Safe Sunlight

Vitamin D is fat-soluble, so consuming it with healthy fats (avocado, nuts, seeds, olive oil) improves absorption. Moderate morning or late-afternoon sunlight (around 30 minutes) also helps the body produce vitamin D. Avoid prolonged exposure between 10 AM and 4 PM when UV intensity is highest.

4. Choose Supplements Wisely if Needed

When diet and sunlight are insufficient, supplements can help. Calcium carbonate is cost-effective and best taken with food. Calcium citrate is better absorbed and can be taken without food. Combinations with vitamin D (and sometimes vitamin K) may further support bone health. Always consult a healthcare professional before starting supplements, as excessive calcium can increase cardiovascular risk.