Is chlorella safe during pregnancy?

What does the evidence say about chlorella during pregnancy?

1. In a small trial of 22 pregnant women, the 10 who took 6 grams of chlorella daily from 12 to 18 weeks gestation through delivery had no serious adverse maternal or newborn effects and had significantly less constipation than the untreated group. 1
2. A separate study found that chlorella pyrenoidosa supplementation during pregnancy lowered the level of dioxins later found in breast milk and raised its immunoglobulin A content, though this reflects one small study rather than broad safety data. 2
3. Testing of commercial chlorella supplements has detected metals like aluminum, manganese, and strontium along with pharmaceutical residues such as caffeine, reflecting environmental contamination that can end up in an unregulated algae product. 3
4. Dietary supplement makers aren't required to test their ingredients for safety before selling them, and reports on algae supplements like chlorella can be missing information on purity or contaminant testing, which is part of why an unstudied supplement deserves caution in pregnancy. 4
5. Chlorella can also cause nausea, diarrhea, abdominal cramping, gas, and green-tinted stools, along with rare allergic reactions, so starting at a low dose and watching for side effects is reasonable if your provider is on board. 2

Is chlorella safe in each trimester?

• First trimester. There's no chlorella-specific research on first-trimester use, and since early pregnancy is when organs are forming, this is the point where checking with your provider before starting any new supplement matters most.
• Second trimester. The small pregnancy study that exists started chlorella between 12 and 18 weeks and continued it to delivery, reporting no serious adverse effects in that group, though the trial was too small to be the final word on safety.
• Third trimester. If you're using chlorella for a specific reason like constipation, ask your provider whether a better-studied option makes more sense this late in pregnancy, since supplement quality and contaminant testing vary by brand.