Limu is the Hawaiian name for a type of brown algae high in a potentially beneficial substance called fucoidan. A review article published in "Marine Drugs" in 2011 noted that fucoidan acts as an anti-inflammatory and may help reduce the pain from arthritis. However, there are some potential side effects from taking limu supplements, including lethal poisoning if the supplements are contaminated, so speak with your doctor before adding these to your daily routine.
Potential High Levels of Iodine
The iodine content of seaweed and algae can vary quite a bit and can be as much as 4,500 micrograms in 1/4 ounce of dried seaweed, which is well above the tolerable upper intake level of 1,100 micrograms per day. Excessive iodine could cause an increase in your thyroid hormones and lead to goiter, an enlarged thyroid or intestinal effects like diarrhea, nausea and vomiting. Excessive iodine consumption can also cause a rash that looks like acne.
Limu may also be high in vitamin K, so you don't want to consume large amounts of it, or it may interfere with blood thinners, such as warfarin and heparin. The "Marine Drugs" article noted that fucoidan also appears to decrease blood clotting times when taken at higher doses, but increase the amount of time for blood to clot at lower doses. It may increase the effect of blood thinners, according to the Memorial Sloan-Kettering Cancer Center.
Contamination With Heavy Metals
Only purchase limu from a reputable company that has tested it and certified it is free from heavy metal contamination. Depending on where algae or seaweed is grown, it can become contaminated with substances such as arsenic. This can cause diarrhea, nausea, numbness, tingling or weakness and lead to death if you continue to get too much of these substances in your diet.
Some people may experience an allergic reaction to limu or other types of algae or seaweed. Symptoms can include rash, hives and difficulty breathing. Seaweed and algae, such as limu, can be high in sodium, which may increase your blood pressure and your risk for heart disease if you also eat a lot of other foods high in sodium.