Use Caution with Seaweed Consumption

"Under the sea / Darling it's better / down where it's wetter." And if you're a fish or even a Little Mermaid, that's probably true. But for those of us with two legs firmly planted on land, not everything is better under the sea. Some foods from "down where it's wetter" might be better left to the crustaceans. A study published in the European Journal of Cancer Prevention reports that seaweed consumption has been linked to increased risk of thyroid cancer in post-menopausal women. 

In Japan, 80% of iodine intake comes from seaweed. The Japan Public Health Center-based Prospective Study followed 679 women ages 40 - 69 for over 14 years. In that length of time, there were 134 new cases of thyroid cancer; 113 of those were papillary carcinoma, which is the most common form of thyroid cancer. Post-menopausal women who reported eating seaweed daily were 3.8 times more likely to develop thyroid cancer than those who ate seaweed two times a week or less. A high content of iodine in seaweed is suspected as the cause of the increased risk for thyroid cancer in this population.

Although many respected health advocates correctly say that seaweed is a valuable source of nutrients, there is reason to be cautious. Registered dietician Jeff Novick, MS, has long warned that seaweed consumption poses health risks. Here are Jeff's recommendations for which seaweeds to include in our diet and which ones to stay away from:

• HIJIKE - Avoid   Hijike can contain high levels of arsenic. Several health organizations have warned against consuming it.
• KOMBU and KELP - Avoid   Kombu and kelp are concentrated sources of iodine; there is no way to know how much iodine is in the product we purchase.
• WAKAME - Watch for sodium   Like other seaweeds, wakame can be very high in sodium. One brand reports 660 mg of sodium per 25 calorie serving. That is well over the recommended 1:1 ratio of sodium to calories for a main dish or 4:1 for a condiment.
• SPIRULINA - Don't waste your money   Spirulina can contain toxins. Further, it is an expensive way to get nutrient-dense food. Since it is taken in such small quantities anyway, there is little benefit for those eating a diet of whole plant foods.
• NORI - Look for vegan or 'fish free'   Nori seems to be low in iodine and sodium, but may have small shellfish ground up in it.

Consumption of seaweed is growing in the United States as sushi becomes an increasingly popular meal across the country. Low-fat, whole plant eaters can enjoy this trend, which relies on nori for wrapping the bite-sized portions of rice and vegetables. Chef Cathy Fisher offers a version of sushi that stars trumpet mushrooms at her site, StraightUpFood.com. Susan Voisin of Fat Free Vegan Kitchen figured out how to make grain-free sushi as well as a whole-food version of sushi featuring brown rice; she calls these 'Non-Traditional Sushi.' You might just call them "yummy." And for anyone who loves sushi but is intimidated by the thought of wrapping the ingredients into a tight roll, Susan offers a Sushi Salad recipe that tosses brown rice, edamame, and mushrooms with traditional sushi ingredients in an easy one-bowl meal.

As we expand our palate to include new textures and flavors from different cuisines, we need to make sure that the whole plant foods which we add to our diet actually increase our health. Unfortunately, in the case of seaweed, we need to be cautious. I thank Jeff for offering us clear guidelines so that we can wisely enjoy this food from under the sea while still optimizing our health.

For additional information:

(1) Toxin Contamination of Spirulina Supplements

(2) Too Much Iodine Can be as Bad as Too Little

(3) Do Cruciferous Veggies Impair Thyroid Function?

(4) Some Sense about Seaweed!