NOW Red Mineral Algae

Our assessment

The evidence shows that this product provides calcium from red mineral algae, a source that supports bone health. Our assessment is that calcium is a well-studied mineral for bone mineralization, helping to support bone density and mineral deposition [NIH ODS]. It also plays a role in neuromuscular relaxation and nerve signaling [NIH ODS]. However, you should be aware of the specific risks and interactions associated with calcium supplementation, which we detail below.

How it works

Think of calcium as a structural building block for your bones. It works by depositing into your skeleton to maintain strong, dense bones [NIH ODS]. Additionally, calcium is critical for your muscles and nerves — it helps your muscles relax after contraction and supports proper nerve signaling throughout your body [NIH ODS]. Without adequate calcium, your body will pull it from your bones, which can weaken them over time.

Safety profile

FDA received a total of 592,059 adverse event reports for all products. For calcium specifically, safety data indicates that high intakes might increase the risk of heart disease and prostate cancer [NIH ODS]. Very high levels of calcium in the blood and urine can cause poor muscle tone, poor kidney function, low phosphate levels, constipation, nausea, weight loss, extreme tiredness, frequent need to urinate, abnormal heart rhythms, and a high risk of death from heart disease [NIH ODS]. You should also know that calcium can reduce the absorption of several medications, including bisphosphonates, tetracycline antibiotics, fluoroquinolone antibiotics, levothyroxine, and phenytoin [NIH ODS]. Data on side effects specific to this product is not available.

Our recommendation

Our recommendation is to use this calcium supplement only if your diet does not provide enough calcium. Start with a low dose and be mindful of your total intake from all sources, including food. Because of the potential for interactions, take calcium at least two hours apart from any medications you use, especially thyroid medication or antibiotics [NIH ODS]. If you have a history of kidney stones, heart disease, or prostate cancer, consult your doctor before use. This product is a reasonable option for supporting bone health when used appropriately, but it is not a substitute for a balanced diet.

Supplement labels contain several key sections regulated by the FDA:

• Serving Size — The recommended amount per dose. Always check this — some products require multiple capsules per serving.
• Amount Per Serving — Shows the quantity of each nutrient in the product, typically in IU (International Units), mg (milligrams), or mcg (micrograms).
• % Daily Value (%DV) — Indicates how much a nutrient in a serving contributes to a daily diet. 5% DV or less is low; 20% DV or more is high.
• Other Ingredients — Lists inactive ingredients like fillers, binders, and capsule materials (e.g., gelatin, cellulose, magnesium stearate).
• Suggested Use — The manufacturer's recommended directions for taking the supplement, including timing and dosage.

Source: FDA Dietary Supplement Labeling Guide