If you've eaten a green vegetable, you've gotten some chlorophyll in your diet. Chlorophyll is the substance that makes plants green. Some people take chlorophyll supplements in the hopes of losing weight, lowering their risk or cancer or eliminating internal odors that cause bad breath or smelly gas. (ref 1) Check with your doctor before taking chlorophyll supplements, as the research on their beneficial effects is still preliminary and they may not be safe for everyone, especially if taken in large amounts. (ref 2,3)
Dark green, leafy vegetables tend to be good sources of chlorophyll, with a cup of spinach providing about 24 milligrams. However, other green vegetables also provide this nutrient. For example, a cup of green beans has more than 8 milligrams of chlorophyll and the same amount of sugar peas has almost 5 milligrams. You can also get chlorophyll in the form of a supplement. Some chlorophyll supplements are made from green algae, including chlorella, but these tend to be more expensive so most supplements you buy actually contain chlorophyllin, which is a semi-synthetic material made from chlorophyll that is more stable, according to the Linus Pauling Institute. (ref 2)
Check with your doctor to determine the best dose for you based on your condition. A typical dosage is between 100 and 300 milligrams split into three daily doses. (ref 2 supplements chlorophyllin, with ref 4 for backup) Eating a moderate to high amount of green vegetables will allow you to get this same amount of chlorophyll in your diet without resorting to supplements, according to an article on the Linus Pauling Institute website. (ref 5)
Optimal Dosage Uncertain for Cancer
An animal study published in "Food and Chemical Toxicology" in February 2012 found that chlorophyll may help limit the spread of cancer up to a point by limiting the bioavailability of certain carcinogens. However, once the doses of the carcinogen get too high, it may actually make the problem worse. (ref 6 and ref 7 abstract) Further research is necessary to determine whether this same effect occurs in people and what the best dose is for limiting cancer risk.
Side Effects and Contraindications
Chlorophyll is generally considered nontoxic and isn't associated with many severe side effects. In some cases, people's urine may turn green or their tongue may turn black or yellow. Taking chlorophyllin supplements can cause diarrhea or a false positive on some tests for blood in the feces. (ref 2) Very large doses of chlorophyll may also cause stomach cramps or loose bowels. (ref 3) Pregnant and nursing women should avoid chlorophyll supplements because their safety hasn't been well studied in these populations. (ref 2)