Chlorophyll is a naturally occurring pigment found in plants and algae that creates their characteristic green color. Its primary function is to facilitate photosynthesis, whereby sunlight is used to generate chemical energy for the plant.^[4] There are several types of chlorophyll that are together considered the most abundant pigments on Earth, but chlorophyll a and b account for over 99% of naturally occurring chlorophyll.^[5] Chlorophyll is a phytonutrient, meaning it is a biologically active but non-nutritive substance found in plants that may contribute to health. Some food sources particularly rich in chlorophyll include spinach, arugula, broccoli, green beans, and peas.^[5] Natural chlorophyll is highly unstable and prone to degradation; therefore, most chlorophyll supplements (including those used in studies) actually contain a semisynthetic derivative of chlorophyll called sodium copper chlorophyllin (SCC), which has been chemically modified to increase its stability and solubility.^[5] While chlorophyll has demonstrated potential health benefits in preclinical research, its effects in humans are poorly understood.

In vitro and animal studies suggest that chlorophyll and its derivatives may have anti-inflammatory,^[6] antioxidant,^[7][8] anticarcinogenic, anti-obesity,^[9] and anti-diabetic properties.^[10] However, none of these effects have been confirmed in human clinical trials.

Chlorophyll and its derivatives have demonstrated cancer-preventative effects in animals, and this remains an area of active research in humans.^{[11][12][13][14]} Chlorophyll seems to be able to tightly bind to various carcinogenic compounds (e.g., polyaromatic hydrocarbons, heterocyclic amines, aflatoxin),^[15][16][17] potentially preventing their gastrointestinal absorption and interaction with body tissues. Two clinical trials have found that chlorophyll supplementation (as SCC) reduced the absorption of aflatoxin, a carcinogenic mold and food contaminant.^[18][1] Still, it’s unknown if this translates to a reduced risk of cancer in the long-term.

Chlorophyll is generally considered to be safe and well-tolerated, although proper safety analyses have not been done. According to case reports, oral use has been associated with green-colored stool and increased skin sensitivity to sun exposure (photosensitivity),^[19][20] and topical use may cause dermatitis.^[21]

The effects of chlorophyll are complex and poorly understood. In vitro studies suggest that chlorophyll can act as an antioxidant directly by acting as an electron donor to stabilize reactive species, and can also activate the transcription factor NF-E2-related factor 2 (Nrf2), leading to an increased production of the body’s own antioxidant enzymes.^[22][5] Accordingly, in animals chlorophyll has been shown to reduce oxidative stress and prevent oxidative damage following exposure to pro-oxidant compounds.^[8][5] Chlorophyll could have cancer-preventative effects by tightly binding (chelating) to carcinogenic compounds, preventing their absorption and interactions with the body, and has been found in animals to protect against DNA damage and mutations induced by certain compounds.^[5] However, how chlorophyll works in the human body is largely unexplored.

While it was previously thought that chlorophyll was not absorbed by the human body, research now suggests that upon ingestion, chlorophyll is rapidly degraded into different derivative compounds that may be subsequently absorbed into the bloodstream with varying degrees of bioavailability.^[23][24] Natural chlorophyll consists of a ring structure with a magnesium atom in the center and a hydrophobic (i.e., insoluble in water) side chain. Through exposure to different temperatures, pH, or food processing techniques, chlorophyll can be converted into many possible derivatives; these can involve replacing the central magnesium atom with another metal (e.g., zinc, iron, copper), removing it altogether, or removing the side chain.^[5] All of these potential changes alter the properties of chlorophyll. It has been suggested that chlorophyll’s potential positive effects are likely due to its derivatives, not the unaltered compound.^[5][25] Ultimately, a lot more research is needed to understand the complexities of chlorophyll and its derivative compounds.