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Strong bones aren’t built in a day—or with just any calcium supplement.
While calcium is crucial for keeping your bones healthy and teeth strong, your body can only absorb so much at once.
That’s why finding the right amount—and the right type—matters. So, how much should you really take, and which types deserve a spot on your shelf? Let’s dive into that next.
Source | Absorption Rate | Additional Minerals | No / Little Side Effects | |
| Marine Calcium *Winner* | Marine Algae | High (up to 70%) |  | |
| Calcium Carbonate | Limestone/Rocks | Moderate (40%) |  | |
| Calcium Citrate | Lab-Synthesized | Good (50%) | | |
Marine calcium stands out for its natural origin and superior absorption profile. Derived from marine algae, this form of calcium comes packaged with trace minerals that support overall bone health.
Source & Production: Marine calcium is harvested from living marine algae, primarily species like Lithothamnion calcareum, which naturally accumulate calcium and other minerals from seawater. These algae are sustainably harvested from pristine ocean waters and undergo minimal processing to preserve their natural mineral matrix. The resulting calcium is essentially “pre-digested” by the algae, contributing to its high bioavailability.
Key Benefits:
The most common and economical form of calcium supplementation, calcium carbonate offers a high percentage of elemental calcium but comes with some drawbacks.
Source & Production: Calcium carbonate is primarily mined from limestone quarries or obtained from crushed marble and chalk. The raw materials undergo extensive processing, including crushing, washing, and purification. Some sources include:
The production process involves mining, crushing, and chemical purification to remove contaminants, resulting in a concentrated form containing 40% elemental calcium.
Key Benefits:
Drawbacks:
A popular alternative to calcium carbonate, calcium citrate is known for its gentle nature and good absorption rate.
Source & Production: Calcium citrate is produced through a chemical synthesis process where calcium salts are combined with citric acid. The production typically involves:
Unlike the other forms, calcium citrate is largely manufactured in laboratory settings rather than extracted from natural sources.
Key Benefits:
Drawbacks:
Quick Check:
These vitamins are crucial for proper calcium absorption and use. Vitamin D3 ensures your body can absorb calcium efficiently, while Vitamin K2 directs calcium to your bones, keeping it from building up in your arteries and causing long-term health risks.
Must Have:
Not all calcium supplements are created equal. While some can cause kidney stones or digestive issues when taken over long periods, high-quality formulas—like those made with natural marine algae—are easier on the body.
Best Sources: 🔹 Marine-derived calcium 🔹 Natural mineral co-factors 🔹 Third-party certified
Avoid: ❌ Uncertified limestone sources ❌ Unknown origin ❌ Missing purity certificates
Where your calcium comes from matters. Marine-sourced calcium is harvested sustainably from red algae, providing a cleaner and more natural source compared to mined limestone-based calcium.
If you want a more holistic version of Marine Calcium with D3 + K2, the Bone & Stress is a great choice.
This comprehensive bundle contains two perfectly paired supplements sourced from Lithothamnion spp. and Aquamin Mg™, marine sources that have been extensively studied for their superior mineral content and exceptional absorption rates.
It comes with the addition of Marine Magnesium + B6. Magnesium is a vital mineral your body needs for bone, mental, sleep and nerve health. The magnesium component features vitamin B6, which research shows helps maintain proper magnesium levels in cells. Together with the calcium formula’s D3 and K2, this creates a complete mineral system that supports not just bone health, but overall body function.
The scientifically-backed ratio of calcium to magnesium (2:1) mirrors the body’s natural requirements, as studies show this proportion is optimal for both minerals’ absorption and utilization. Each mineral is carefully portioned to maximize absorption – the calcium at 500mg per serving and magnesium at 250mg.
This marine-sourced mineral bundle delivers multiple benefits:
The bundle takes mineral supplementation further with its dual-source approach, which preserves the natural mineral matrices of both marine sources. This ensures that you get the full spectrum of trace minerals and optimal absorption from each supplement.
With this thoughtfully designed combination of essential minerals and their cofactors, the Cal + Mag Bundle provides the most complete and bioavailable mineral support system available.
If you want a more holistic version of Marine Calcium with D3 + K2, the Bone & Stress is a great choice.
This comprehensive bundle contains two perfectly paired supplements sourced from Lithothamnion spp. and Aquamin Mg™, marine sources that have been extensively studied for their superior mineral content and exceptional absorption rates.
It comes with the addition of Marine Magnesium + B6. Magnesium is a vital mineral your body needs for bone, mental, sleep and nerve health. The magnesium component features vitamin B6, which research shows helps maintain proper magnesium levels in cells. Together with the calcium formula’s D3 and K2, this creates a complete mineral system that supports not just bone health, but overall body function.
The scientifically-backed ratio of calcium to magnesium (2:1) mirrors the body’s natural requirements, as studies show this proportion is optimal for both minerals’ absorption and utilization. Each mineral is carefully portioned to maximize absorption – the calcium at 500mg per serving and magnesium at 250mg.
This marine-sourced mineral bundle delivers multiple benefits:
The bundle takes mineral supplementation further with its dual-source approach, which preserves the natural mineral matrices of both marine sources. This ensures that you get the full spectrum of trace minerals and optimal absorption from each supplement.
With this thoughtfully designed combination of essential minerals and their cofactors, the Cal + Mag Bundle provides the most complete and bioavailable mineral support system available.
AlgaeCal is a plant-based calcium supplement that’s marketed to support bone health.
The type of calcium used in AlgaeCal is marine calcium, which we absolutely love. Their formula also contains vitamin D3 as a booster, along with magnesium as well.
Now, even though we like the clean ingredients and great formulation, we’re not too excited about them not including vitamin K into the mix, as it’s a must-have to prevent calcium deposits in unwanted areas like your arteries.
All in all, a pretty good choice for a calcium supplement only if you’ve got the budget for it, as it costs significantly more than the other choices in this list.
Citracal is a calcium with vitamin D3 supplement that’s marketed to provide essential nutrients for bone health.
Citracal’s calcium type is a mix of calcium citrate and calcium carbonate, which are harder to absorb and may cause more side effects compared to marine calcium. It also contains a dose of vitamin D, which aids in calcium absorption.
Now, we do love the vitamin booster they’ve added, but we’re definitely not fans of the amount of fillers and colors they’ve added to the ingredients, which include talc, titanium dioxide, and magnesium stearate.
Caltrate is a calcium supplement that’s marketed for bone health as well.
The ingredient blend is simple, with 600 mg of calcium with absorbability booster vitamin D. Now, Caltrate uses calcium carbonate, which is the least absorbable type of calcium. Plus, you may experience side effects like an upset stomach or constipation.
Now, while we do appreciate them adding vitamin D to ensure you get the best from the calcium, we’re not too happy about the other ingredients they’ve added.
Even with its affordable price tag, it doesn’t justify having fillers like talc, titanium dioxide, and other food coloring like Red 40 that do not offer any benefits to the formula.
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