The Calcium Contest: Raw Numbers vs. Bioavailability
When comparing the calcium content of different foods, the raw numbers on the nutrition label can be misleading. For years, milk has been a cornerstone of dietary calcium, but what about smaller, nutrient-dense foods like sesame seeds? A direct comparison of the calcium content per 100 grams initially suggests sesame seeds are the clear winner. However, this simple calculation fails to account for a critical factor: bioavailability, which refers to the proportion of a nutrient that is absorbed from the diet and used for normal body functions. Milk is known for its excellent calcium bioavailability, while compounds naturally present in sesame seeds can impede absorption, altering the outcome of the comparison.
Raw Calcium Content: A Numbers Game
To understand the full picture, we must first look at the crude numbers before diving into the nuances of absorption. Different sources provide slightly varying figures, but a consistent trend emerges.
Milk's Calcium Profile
- Cow's milk (1 cup / 237 mL): Approximately 300-325 mg of calcium, depending on fat content.
- Milk per 100g/mL: Roughly 125-170 mg.
- Key takeaway: Milk provides a reliable and substantial amount of calcium in a standard serving.
Sesame Seeds' Calcium Profile
- Whole, dried sesame seeds (100g): Up to 975-1450 mg of calcium, with some sources listing slightly different ranges.
- 1 tablespoon (9g): Approximately 87.75 mg of calcium.
- Key takeaway: On a per-gram basis, whole sesame seeds contain significantly more calcium than milk.
The Bioavailability Factor: What Your Body Actually Absorbs
The raw numbers tell only part of the story. The true nutritional value depends on how much of that calcium can be absorbed by the body. This is where the competition between milk and sesame seeds gets interesting. The presence of certain compounds in food, often referred to as 'anti-nutrients,' can bind to minerals like calcium and prevent their absorption.
The Challenge with Sesame Seeds
Whole sesame seeds, particularly the unhulled variety, contain anti-nutrients called oxalates and phytates. Oxalic acid binds to calcium, forming calcium oxalate, an insoluble compound that the body cannot absorb. One Instagram post even explicitly states, "sesame seeds are very high in oxalic acid... a substance that binds both calcium and iron, rendering it unavailable for the human body". This drastically reduces the actual amount of usable calcium despite the high raw numbers. While hulling the seeds removes some of these inhibitors, absorption remains notably lower than that from dairy.
The Advantage of Milk
Milk is a superior source of bioavailable calcium for several reasons.
- No Oxalic Acid: Unlike sesame seeds, milk does not contain oxalic acid, so the calcium is readily available for absorption.
- Ideal Ratio: Milk has an excellent calcium-to-phosphorus ratio, which is beneficial for efficient calcium absorption.
- Enhancing Compounds: The natural presence of lactose and casein phosphopeptides (CPP) in milk further promotes calcium absorption.
Bioavailability Research: A Supporting View
Scientific studies confirm the superior absorption from milk. One in vitro study comparing the bioaccessibility of calcium found that cow's milk was significantly higher than both almond and sesame seeds. Another study using a rat model showed that milk had a higher calcium bioavailability than sesame seeds, even when the seeds were ground into powder.
A Head-to-Head Nutritional Comparison
| Feature | Milk (1 cup, ~240 mL) | Whole Sesame Seeds (100g) |
|---|---|---|
| Raw Calcium Content | Approx. 300 mg | Approx. 975–1450 mg |
| Calcium Bioavailability | High (approx. 30%) | Low (approx. 65% relative to milk) |
| Anti-nutrients | None | Oxalates and Phytates |
| Absorption Enhancers | Lactose and Casein Phosphopeptides | Grinding or hulling helps, but not fully |
| Serving Volume | 1 cup (easy to consume) | Small amount (high calorie density) |
| Dietary Suitability | Not suitable for lactose intolerance or dairy allergy | Excellent for vegan/dairy-free diets, with considerations |
Practical Considerations for Your Diet
Understanding the difference between raw calcium and bioavailability allows you to make more informed dietary choices, whether you consume dairy or follow a plant-based diet.
For Dairy Consumers
For those who tolerate dairy, milk remains one of the most efficient and easily accessible sources of calcium. Incorporating milk, cheese, and yogurt into your diet is a straightforward way to meet a significant portion of your daily calcium needs. Its high bioavailability means less volume is required to achieve the desired absorption.
For Plant-Based Eaters
If you avoid dairy, don't despair. Sesame seeds can still be a valuable part of your diet, but strategizing is essential:
- Use Tahini: Tahini is a paste made from ground sesame seeds, which can increase the calcium absorption compared to eating whole seeds.
- Hulled Seeds: Using hulled sesame seeds reduces the presence of anti-nutrients.
- Balanced Diet: Combine sesame seeds with other plant-based sources like fortified plant milk, tofu, and leafy greens to ensure a wider range of nutrient intake.
- Fortification: Relying on calcium-fortified plant-based milks and juices is an effective strategy, as these often contain easily absorbed forms of calcium.
Conclusion: Milk or Sesame Seeds? The Final Answer
So, which has more calcium, milk or sesame seeds? On a weight-for-weight basis, sesame seeds have a higher raw amount of calcium. However, considering the crucial factor of bioavailability, the calcium in milk is significantly better absorbed by the body. Milk offers a more efficient delivery system for this essential mineral due to its lack of anti-nutrients and the presence of absorption-enhancing compounds. For those who can't or don't consume dairy, incorporating sesame seeds into a varied and balanced diet that includes other fortified plant-based sources is the best approach to ensuring adequate calcium intake.
Ultimately, the 'better' source depends on individual dietary needs and preferences, but understanding the difference between raw content and usable content is key to promoting optimal bone health. For a detailed study on calcium bioavailability, see this comparison of calcium bioaccessibility.
