What are the dietary sources of calcium for vegetarians and non-vegetarians?

Dietary Sources of Calcium for Vegetarians and Non-Vegetarians

Consumption of calcium-rich foods and beverages is the preferred approach to ensuring adequate calcium intake for both vegetarians and non-vegetarians, with dairy products being the primary source for non-vegetarians and fortified foods plus specific plant sources being critical for vegetarians. 1

Calcium Requirements by Age and Sex

The Institute of Medicine establishes clear daily calcium targets that apply to both dietary patterns 1:

• Women aged 19-50 years and men aged 19-70 years: 1000 mg/day
• Women over 50 years and men over 70 years: 1200 mg/day
• Upper safety limit: 2500 mg/day for adults under 50 years; 2000 mg/day for those over 50 years 1

Non-Vegetarian Dietary Sources

Primary Sources (Dairy Products)

More than 70% of dietary calcium in typical Western diets comes from dairy products, which remain the most concentrated and bioavailable sources 1:

• Milk (whole or skimmed): 200 mL provides approximately 240 mg calcium 1
• Each dairy serving typically provides 200-300 mg elemental calcium 2
• Yogurt and cheese: Additional concentrated sources 1

Secondary Non-Dairy Sources

Most adults consume approximately 300 mg of calcium daily from non-dairy sources including various vegetables and grains 1. These sources are equally important for non-vegetarians to reach recommended intakes.

Vegetarian and Vegan Dietary Sources

Critical Consideration for Plant-Based Diets

Vegetarians and vegans face greater challenges meeting calcium requirements and may be at higher risk of lower bone mineral density and fractures 3. Vegetarians and vegans in observational studies were more likely than meat eaters to have low calcium intakes 1.

High-Bioavailability Plant Sources

Certain plant foods provide well-absorbed calcium, with some vegetables showing higher absorption rates than supplements 1:

• Broccoli and kale: Higher proportion of calcium absorbed compared to supplements 1
• Green leafy vegetables: Important sources when consumed regularly 1, 4
• Legumes and soya beans: Provide moderate calcium content 1

Fortified Foods

Calcium fortification of processed foods and beverages is variable, requiring careful label checking to determine calcium content per serving 1. Fortified plant-based milks, orange juice, and other products can help vegetarians meet requirements 1.

Nuts and Seeds

Nuts provide supplementary calcium, though in less concentrated amounts than dairy 1.

Practical Estimation of Daily Intake

To estimate daily calcium intake 1:

1. Assume 300 mg from non-dairy sources (vegetables, grains) as baseline
2. Add dairy contributions: Each serving = 200-300 mg
3. Check fortified food labels for additional calcium content
4. Calculate total to compare against age-specific requirements

Bioavailability Considerations

The bioavailability of dietary calcium is substantially lower in vegetarian diets than meat-based diets, which is particularly concerning given the growing interest in veganism 1. This means vegetarians may need to consume higher absolute amounts of calcium-containing foods to achieve equivalent absorption.

When Supplementation Becomes Necessary

Supplements should be considered when dietary intake is inadequate, but food sources remain preferred 1. For vegetarians unable to meet the 1000-1200 mg daily requirement through diet alone:

• Calcium carbonate: 40% elemental calcium, most economical, must be taken with meals 1, 2
• Calcium citrate: 21% elemental calcium, can be taken without food, preferred for those with low stomach acid 1, 2
• Divide doses: No more than 500-600 mg elemental calcium per administration to maximize absorption 2

Special Populations at Higher Risk

Particular attention should be given to postmenopausal women and elderly individuals who require higher calcium intake (1200 mg/day) and commonly have inadequate dietary intake 1. Vegetarians and vegans in these age groups face compounded risk and require careful dietary planning or supplementation 3.

Common Pitfalls to Avoid

• Assuming all plant foods provide adequate bioavailable calcium: Only specific vegetables like broccoli and kale have high bioavailability 1
• Relying solely on supplements without maximizing dietary sources first: Food sources are preferred and associated with fewer adverse effects 1
• Ignoring fortified foods: These can be critical for vegetarians but require label verification 1
• Exceeding upper limits: Intake above 2000-2500 mg/day should be avoided due to increased risk of nephrolithiasis and potential cardiovascular concerns 1