Nutritional rewards and risks revealed for edible algae in Hawaii

Some algae, like the one shown here, are a source of essential nutrients, but they can also expose consumers to unsafe levels of heavy metals. Credit: ACS Food Science and Technology (2024). DOI: 10.1021/acsfoodscitech.3c00476

From sushi to soups, seaweed is a popular food around the world because it adds delicious flavors and beneficial nutrients to dishes. However, it could also expose consumers to heavy metals that accumulate in the fronds before they are harvested. Given the importance of seaweed in the Hawaiian Islands, a recent ACS Food Science and Technology publication reports a comprehensive analysis of essential nutrients and heavy metals for six species of algae collected from around Hawaii.

Algae accumulate elements from the environment where they are grown. Scientists know that factors such as species or growing conditions affect essential minerals, nutrients, and non-essential or toxic heavy metals in a serving of seaweed. However, not much is known about the balance of useful and potentially harmful compounds in many of the varieties traditionally eaten in Hawaii.

In addition, the US has not established safe regulatory limits for toxic substances such as arsenic and lead in whole pieces of edible seaweed, meaning that some products available for sale may not be tested for these compounds. So Kacie Ho and her colleagues decided to analyze the key nutrients and metals in seaweed species grown around Hawaii.

The researchers obtained six types of algae that were cultivated or collected from the wild. They measured the beneficial nutrients and toxic elements in each species and used statistics to differentiate the samples. They found that:

  • Four of the six seaweeds tested were excellent sources of at least one essential mineral with more than 20% of the recommended daily value per serving for iron, manganese, or calcium and magnesium.
  • The amounts of protein, fat, carbohydrate, and fiber varied significantly among the species tested and generally aligned with previous nutritional assessments of three of the algae.
  • Two wild species that are not commonly consumed, S. aquifolium and S. echinocarpum, had the highest levels of arsenic-containing compounds, far exceeding safe consumption limits set by other countries.
  • Two cultivated species, H. formosa and G. parvispora, contained high levels of lead, which are above those recommended for safe food in Taiwan.

Overall, the researchers found that Hawaiian seaweed provides many essential minerals and nutrients, but may also expose consumers to unsafe levels of heavy metals, depending on factors such as the type of seaweed and growing conditions. Previously published studies suggested that boiling or rinsing other species of algae, which were not included in this work, could remove some harmful substances.

But these techniques can also remove beneficial nutrients. So Ho and his colleagues are working with seaweed growers to study the impact of growing location and common cooking practices on heavy metal and nutrient levels in Hawaiian seaweed. Their findings could inform future regulations and ensure safe and nutritious algal food products.

More information:
Samuel T. Kim et al, Determination of Nutrient and Toxic Element Content of Wild-Collected and Cultivated Seaweeds from Hawaii, ACS Food Science and Technology (2024). DOI: 10.1021/acsfoodscitech.3c00476

Provided by the American Chemical Society

Summons: Nutritional rewards and risks revealed for edible algae in Hawaii (2024, March 26) Retrieved March 26, 2024, from seaweed.html

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