At first glance, it might not look like much. But seaweed and kelp are gaining recognition as highly nutritious foods for both humans and animals. And it’s no wonder!
Seaweed and kelp, as a class of plants, have the broadest spectrum of trace minerals and vitamins of any plant group in the world. The reason seaweed and kelp contains this wide range of nutrients is because of their ability to absorb minerals directly from ocean water. Unlike land plants, kelp and seaweed do not have root systems to absorb minerals. Instead, they absorb minerals directly through the plant tissue from the mineral-rich seawater they are living in.
Aren’t all kelps the same?
Over 300 species of kelps and seaweeds are found in the world’s oceans. Each has a different mineral and vitamin profile. In fact, using the word “kelp” or “seaweed” is sort of like using the word “fruit” to describe apples and oranges. Trace mineral and vitamin levels vary significantly, depending on the species, growing conditions, water temperature and exposure to air.
Another thing a lot folks don’t realize is that the location the kelp grows in is critical to how safe it is. Basically, since seaweeds and kelps absorb all their mineral content from the ocean, the more pristine the source of ocean water, the higher the quality of the trace minerals in the plant. Unfortunately, much of the kelp used as ingredients in pet foods are sourced out of mass-produced commercial fi rms in China, Southeast Asia, or northwest Russia (i.e. the Baltic Sea). Also, kelps harvested from more polluted waters will have a tendency to have higher levels of contaminants such as heavy metals.
Seaweed vs. kelp – what’s the difference?
“Seaweed” and “kelp” are often used interchangeably. However, while there is no formal scientific distinction between the two terms (they are all members of the algae family), it is generally accepted that kelps are marine plants that are always submerged in seawater and consequently have a higher trace mineral content. On the other hand, seaweeds are generally regarded as marine plants that are partially or fully exposed to air during low tides. These plants usually have a lower mineral content, are more commercially accessible, and as a result are more often used in food ingredients. However, these terms can be blurred, often for marketing purposes. For example, the commonly used Norwegian kelp (Ascophyllum nodosum) is a very abundant seaweed that is completely exposed at low tide and extensively harvested around the world. However, the term “Norwgeian” conjures up visions of deep, pure cold waters and remote fjords.
Because kelps are submerged in mineral-rich seawater for most of their life cycle, they tend to have higher levels of iodine than partially submerged seaweed species. D. Laminaria probably has some of the highest levels of iodine of any kelp species. As well, the part of the kelp used will often determine the iodine level. For example, experiments we have done with D. Laminaria show that the stipe of the plant (the thin part between the kelp blade and the plant’s holdfast) has almost 1,000 ppm of iodine content – two to three times greater than the iodine content in the blade alone.
Questions to ask when buying kelp
1. Where is the kelp harvested? Nova Scotia, Iceland and New Zealand are all good sources because of the unpolluted cold ocean water in these areas.
2. What species of kelp is it, and what is the mineral and vitamin content in that species?
3. How finely ground is the dried kelp? Kelp is a fibrous plant, so the finer it is ground, the more absorbable the minerals and vitamins in it are, especially for a dog or cat’s short digestive system. A rough “cracked pepper” grind may have as little as 5% to 10% mineral and vitamin absorbability.
4. Is the kelp dried at ambient or high temperatures? High temperature drying will break down most of the vitamin content in any food, including kelp.