Spirulina

Spirulina earns a strong-recommend at 7.0 because it delivers a replicated cluster of cardiometabolic benefits at food-grade safety and an unusually low cost. The practical verdict: if you have elevated blood pressure, lipids, or fasting glucose, a certified spirulina product is a cheap, low-risk add-on worth a measured 12-week trial. If your markers are already optimal, expect little, and if you have phenylketonuria or active autoimmune disease, it is not for you. The score tier is justified by the breadth of meta-analytic support and the benign risk profile, tempered to moderate confidence because individual trials are small and antioxidant outcomes are mixed. The sourcing caveat is the whole game: the algae is safe, but uncertified product is not.

✅ Best for: People with elevated blood pressure who want a cheap evidence-backed adjunct, given the several-mmHg pooled effect in Machowiec 2021; people with high LDL or triglycerides looking for a food-grade lipid nudge; people with prediabetes or type 2 diabetes targeting fasting glucose specifically; cost-conscious supplement users who want a dense nutrient base of protein, iron, and carotenoids; allergic rhinitis sufferers willing to run a personal trial after Cingi 2008; and measurement-minded people who will pick one marker, dose for 12 weeks, and re-test.

❌ Avoid if: You have phenylketonuria, since spirulina contains phenylalanine and is contraindicated; you have active autoimmune disease such as lupus or rheumatoid arthritis, where immune stimulation could theoretically trigger a flare; you are pregnant or breastfeeding without clinician guidance; or you cannot verify your product. The contamination findings in Rhoades 2023 mean uncertified open-pond product can carry microcystins or heavy metals, so a current certificate of analysis showing microcystins below 1 ppm is mandatory, especially for children.