Kelp is a type of extremely fast-growing seaweed called leafy algae that prefers the hard packed ocean floor surface. Giant kelp can shoot up about 300 feet per year.[1, 2] It is a dietary staple in Japan, Iceland, Hawaii, and Alaska.[2, 3] Kelp farming helps maintain the nutritive balance of the plant.
The Chinese have used kelp and other seaweed for medicinal purposes since about 3000 B.C., while the Greeks have used it for cattle feed dating back to the first century B.C. In Japan, it was used for kidney, bladder, and prostate problems, as well as health issues associated with the genital tract. And the Europeans used it as fertilizer.
Kelp is often a component of vitamin and mineral supplements. It contains B vitamins, including folic acid (B-9), plus vitamins C, E, D, and K. It's also nutrient-rich, containing protein, carbohydrates, and essential fatty acids. And, it's loaded with the minerals calcium, iron, sodium, potassium, magnesium, zinc, and iodine.[2, 3]
Kelp is used to produce alginates, which add to the smoothness of ice cream, toothpaste, and cosmetics.
Many naturopaths recommend kelp for a number of health issues, including: 
- Thyroid disorder
- High blood pressure
- Poor digestion
- Nervous disorders
Kelp is available as a powder, tincture, tablet, and capsule. As for a dosage, none is set. It's best not to overdo kelp usage, however, as it is high in iodine, which may lead to thyroid problems. The recommended dose of iodine is 150mcg daily from age four and up.[1, 2, 3]
Does kelp work
The iodine in kelp is not recommended for thyroid conditions. If your iodine levels are low kelp may be therapeutic, but deficiency of this trace mineral is not common. And taking too much could actually create thyroid problems.
There also isn't enough evidence that kelp:[1, 2]
- Cuts breast cancer risk
- Helps prevent infections such as flu and HIV viruses
- Improves sensory receptors
- Makes nails and blood vessels healthy
- Lowers blood pressure
- Supports healthy digestion
- Relieves constipation
- Diminishes the chances of hair loss
- Facilitates weight loss
Do not take kelp within a month before scheduled X-rays involving contrast media and do not consume kelp untilwell after the exam, giving the contrast time to be flushed out of your body. Also, avoid taking kelp with thyroid medication.
Safety Concerns and Side Effects
- Consuming too much kelp can contribute to overactive or underactive thyroid.
- Do not take kelp with medication for irregular heartbeat.
- Do not take excessive amounts of kelp unless prescribed by your doctor.
- Large amounts of kelp may cause acne.
- Kelp supplements may contain unsafe amounts of arsenic.
- If you high blood pressure, consult your physician before consuming kelp.
- University of Utah Health Care; "Kelp"
- NYU Langone Medical Center; "Kelp;" Reviewed 2013
- AltMed; Encyclopedia of Alternative Medicine; "Kelp"