Seaweed

Seaweed is traditionally an important source of food in several countries, especially Asian ones. Its consumption has spread to other regions of the world.
It contains amino acids, unsaturated fatty acids, docosahexaenoic acid (DHA), omega 3, mucilages, vitamins and numerous minerals and essential trace elements, among which is found iodine in very variable quantities but large in some of them (EC 2018, Romarís 2012 , Kikuchi 2008, Moon 1999), so much that its excessive consumption can produce symptoms of hyperthyroidism: anxiety, insomnia, tachycardia, palpitations (Leung 2012, Picco 2006, Salas 2002).


Consumption of algae increases the levels of iodine in plasma, urine and breastmilk (Moon 1999, Kim 1998).
There have been reports of hypothyroidism in infants of East Asian mothers who include in their diet significant amounts of marine algae rich in iodine such as Undaria Pinnatifida, Laminaria japonica or others (Hulse 2012, Emder 2011, Rhee 2011, Nishiyama 2004).

The maximum daily intake of iodine should not exceed 600 micrograms (μg) per day in adults and 200 μg/day in children under 3 years of age, which is 0.6 and 0.2 mg of iodine respectively (EC 2018).

Bear in mind that the bioavailability of iodine contained in algae is very low, meaning that the total iodine that reaches plasma circulation after being cooked, digested and metabolized in the liver is much less than that contained in algae. For example (Romarís 2012):
• Spirulina (Spirulina platensis), Agar-agar (from Gelidium sesquipedale), canned seaweed (prepared from Himanthalia elongata and Saccorhiza polyschides), nori (Porphyra umbilicalis), sea lettuce (Ulva rigida) and dulse (Palmaria palmada): contain less than 100 μg/g of iodine of which less than 6 μg/g are bioavailable
• Sea spaghetti (Himanthalia elongata): 120 μg/g of iodine, bioavailable 4 μg/g
• Wakame (Undaria pinnatifida): 300 μg/g, 9 μg/g bioavailable
• NIES 09 Sargasso: 525 μg/g, 23 μg/g bioavailable
• Kombu (Laminaria ochroleuca): 6,000 μg/g, 1,000 μg/g bioavailable

It is advisable to inquire about the composition of each particular algae and avoid them or consume moderately if the amount of iodine is large: Kombu algae in particular, Sargasso and, in general, dried algae products containing more than 20 mg of iodine per kilo (20 μg/g) of dry matter.

Algae can also contain heavy metals such as arsenic (Lynch 2014, Farré 2009), cadmium, iodine, lead and mercury (EC 2018, Romarís 2012).

The FAO and WHO have established a Provisional Tolerable Weekly Intake (PTWI) for inorganic arsenic at 15 μg/kg body weight (Farré 2009).

The most toxic form of arsenic is inorganic. Most algae contain the organic form, except for Hiziki or Hijiki brown alga (Sargassum fusiforme, Hizikia fusiformis) which contains very high concentrations of inorganic arsenic (80,000 μg/Kg) and its consumption has not been recommended (EFSA 2014, Farré 2009). Other algae contain an average of 270 μg/ Kg, with Wakame (Undaria spp.) having the highest content with 280 μg/Kg and Kombu (Laminaria spp.) with 350 μg/Kg (EFSA 2014).

Nevertheless, arsenic is ubiquitous and is present in water and all the foods we consume in varying quantities: 2 μg/L of water, 5 μg/kg in tomato, potato and apple, 100-150 μg/kg in rice, some mushrooms, molluscs and thyme, and 260 μg/Kg in ginger.
It should be noted that many dietary products labeled as nutritional supplements containing minerals, pollen, algae, fibre, etc. contain more than 1,000 μg/Kg of arsenic (EFSA 2014).

It is advisable to consume algae of known and reliable origin, with correct labeling and from companies which meet all the requirements of existing legislation, in particular the recommendations of the European Commission (EC 2018) regarding the concentration of iodine and heavy metals, with periodic analyses transmitted regularly to the EFSA (European Food Safety Authority).
Do not consume quantities above those indicated by the manufacturer, which range between 3 and 6 grams per day.

The levels of docosahexaenoic acid (DHA) in breastmilk increased when mothers consumed a nutritional supplement of algae (Jensen 2000).

Although in some cultures it is used as a galactogogue, there is no evidence of its effectiveness in increasing milk production. The best galactogogue is frequent on demand breastfeeding with correct technique in a mother who is self-confident (Mannion 2012, Forinash 2012, ABM 2011).

External treatments with algae, whether in the form of massages or body wraps on the skin, involve no or very little systemic absorption and are compatible with breastfeeding.

See below the information of these related products:

• Chlorella (Fairly safe. Mild or unlikely adverse effects. Compatible under certain circumstances. Follow-up recommended. Read Commentary.)
• Fucus (Unsafe. Moderate/severe adverse effects. Compatible under certain circumstances. Follow-up recommended. Use safer alternative or discontinue breastfeeding from 5 to 7 T ½ . Read Commentary.)
• Spirulina (Fairly safe. Mild or unlikely adverse effects. Compatible under certain circumstances. Follow-up recommended. Read Commentary.)