Even though total lipid content is generally low, seaweeds are still a good source of health promoting PUFA's compared with other foods derived from plant and animal sources (Rajapakse and Kim, 2011).
For the micro-algae it is a different story and there are several reported cases where the lipid content is considerable higher than soybeans or sunflowers. These studies where done to estimate the value of growing these micro-algae on waste land. They have to be grown in pounds or closed parts of the tidal harbours. From a technical point of view more complex and expensive but the products won also.
Lipids content and composition.
The mean lipid content of seaweed is low, between 0.2 and 4% of the dry mass and varies with environmental conditions (Patarra et al., 2012). The seasonal variation in lipid content however differs between seaweed species. It has been suggested that the omega-3 marine fatty acids, especially EPA (C20:5 n-3), are the predominant fatty acids in seaweed (Holdt and Kraan, 2011).
However, a summary of data in their review indicate a large variation between seaweed species with EPA being 1-15% of total fatty acids as in Ulva and Laminaria / Saccharina up to almost 50% in Palmaria. Only Palmaria and Sargassum seem to contain a relevant amount of EPA, Ulva contains a relatively high amount of oleic acid (van Ginneken et al., 2011).
In contrast to other plants, seaweeds contain a small amount of C18:4 n-3, which is said to influence the immune system. In addition, seaweeds contain a small amount of phospholipids, contributing to the emulsification and digestion of dietary fat.In conclusion, macro algae are in general relatively low in lipid content. Only specific species as Palmaria may significantly contribute to the supply of omega-3 marine fatty acids (EPA). In a small proportion of compound animal diets marine fatty acids are included because of expected benefits on the health and immune competence of (young) animals or in order to enrich the end product (eggs) with these fatty acids. Specific benefits of other components included in the lipid fraction like glycolipids and sterols.