Kelps are seaweeds that grow in particular shallow and nutrient-rich waters around the world. They've been eaten and used medicinally for hundreds of years in various forms, and are processed today, with some by-products commonly used in ice cream, salad dressings and even chocolate milk.
In recent years there's been a sudden increase in sea kelp products and supplements on the market, and as a result plenty of speculation and argument as to whether they're a miracle health booster or a potential health threat.
The benefits of sea kelp:
Nutrients: Sea kelp is a natural source of vitamins A, B1, B2, C, D and E, as well as minerals including zinc, iodine, magnesium, iron, potassium, copper and calcium. In fact it contains the highest natural concentration of calcium of any food - 10 times more than milk.
Weight loss: Iodine is a trace mineral vital for the operation of the thyroid gland which plays an important part in body development and metabolism. It combines with tyrosine - an amino acid - to create T3 and T4, thyroid hormones that regulate metabolism and other physiological functions throughout the body. As sea kelp is the richest natural source of iodine it can help to regulate metabolism and in turn affect weight loss and gain.
Additionally, a University of Newcastle study concluded that alginates - fibres within sea kelp - 'significantly reduce fat digestion' and absorption, much more so than most consumer slimming treatments. However, the findings are only preliminary.
Anti-ageing: The iodine content of kelp also appears to have other benefits. A 2008 study showed that the form of iodine in kelp effectively removed free radicals - chemicals that accelerate ageing - from human blood cells.
Hair growth - There's plenty of anecdotal evidence suggesting taking sea kelp supplements can boost hair growth. Whether or not it actually boosts growth, it contains nutrients involved in hair health and strength, so it may help reduce split ends and breakages.
The risks associated with sea kelp:
As sea kelp contains so many minerals and nutrients in such high quantities it may pose health problems if consumed in an incorrect dosage or by those with particular health issues.
Iodine: Sea kelp is rich in iodine as it rapidly absorbs the high iodine content of the sea, and you might find anecdotal advice to take it for iodine deficiency. In the developed world though this condition is rare, and even if you are a sufferer it's unlikely iodine supplements would be the recommended course of action.
In fact, you'll probably already get between 160mcg and 600mcg of iodine from salt, and taking excess iodine can cause many health problems including hyperthyroidism, Grave's disease and thyroid cancers. Different forms of kelp can vary greatly in iodine content too; another reason to be cautious. For example, the iodine content of different products containing bladderwrack (or seawrack) - a type of kelp - may vary greatly.
Heavy metals: Sea kelp grown in polluted waters may well absorb toxic heavy metals which if ingested can cause major health problems. The potential for this means it isn't recommended to be taken if pregnant or breastfeeding, or by children or people with health issues, especially liver or kidney problems. It should be possible however to make sure a particular supplement comes from kelp grown in clean waters.
Unpredictability: There are a large number of sea kelp supplements available containing a variety of different types of algae that all come under the name 'kelp', which may affect your body in different ways. For instance, bladderwrack can cause or worsen acne, and there is a single reported case of it causing kidney failure.
So, is it a yes or no for sea kelp? As with any supplements of this kind it's definitely best to consult a doctor before taking any; especially if pregnant, breastfeeding or suffering from any ailments. Of course, never exceed the recommended dosage of supplements, or the recommended daily allowance of minerals like iodine.