Algae as nutritional and functional food sources: revisiting our understanding

Abstract

Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.

Keywords: Algal foods; Antioxidants; Arsenosugars; Experimental design; Microalgal supplements; Nutritional minerals; Omega-3-fatty acids; Polysaccharides; Sea vegetables; Vitamins.

Fig 1

a Pyropia spp. being dried in squares in the intertidal zone by First Nations’ people at Pearce Island, British Columbia (2009). Harvesters would traditionally lay the seaweed out to dry on warm rocks while waiting for those fishing to return with the canoes (photo credit, Amy Deveau). b Checking the seaweed squares after transfer to cedar racks for final drying (photo credit, Victoria Wyllie-Echeverria)

Fig 2

a Haematococcus pluvialis cells showing droplets of red astaxanthin within the cells; b Chlorella vulgaris; c Arthrospira maxima SAG 21-99 (also known as spirulina). Scale bar = 15 μm. (photo credits, Maria Zori)

Fig. 3

A comparison of essential fatty acids liberated from 1 g dry weight of Palmaria palmata (raw and boiled for 30 min) wheat, rice, and corn flours in simulated gastrointestinal digestion. The mean values ± 1 SD (n = 5) are shown in mg g⁻¹. Significant differences between species (p > 0.05) are indicated by different letters. (Used with permission from Maehre et al. (2016))

Fig. 4

Structures of some key vitamins and lipids mentioned in review

Fig. 5

Sea vegetables used in European cuisine include marinated kelp (Alaria esculenta) in a cannelloni bean salad (a), laver/nori (Porphyra umbilicalis/Pyropia yezoensis) in chocolate molasses meringues (b), the traditional Welsh laver-bread cakes, with dulse (Palmaria palmata) crisps (c), and dulse-cheese scones (d). These additions add texture, protein, vitamins and minerals, and flavor. (Used with permission of Prannie Rhatigan from The Irish Seaweed Kitchen)

Fig. 6

Examples of sea vegetable use in Japanese cuisine: a “Onigiri” is a Japanese rice ball usually wrapped by nori (Pyropia yezoensis) with several other ingredients: from right to left, rice wrapped in nori, with Japanese apricot (umeboshi) and preserved kombu (tsukudani, Saccharina japonica and other species of the genus Saccharina), wrapped with shredded kombu (torero-kombu), and wrapped in nori; b Tempura soba with wakame (Undaria pinnatifida). Wakame is used in Japan, noodles, soups, salads, pickles, and more. c Traditional Japanese dishes with sea vegetables: preserved kombu (tsukudani) on rice, miso soup with wakame, sliced kombu with vegetables, and sliced raw fishes (sashimi) with wakame and cucumber. d “Kobu-maki” is simmered food, often salmon or herring, wrapped in kombu, which is usually prepared for the New Year’s holidays. Kombu is used in several dishes and soup stock. (Courtesy of Kazuko Sato and Yoichi Sato)