Nutrition and Omega-3 fatty acids: What do ALA, EPA and DHA mean?
What do salmon, herring and mackerel have in common with walnuts, hemp and linseed? It's simple: they contain omega-3 fatty acids, the benefits of which have been confirmed in numerous studies. Because you've probably heard: not all fats are created equal. Omega -3 fatty acids are a special subgroup of fatty acids . They not only contribute to energy production, they also play a role in regulating inflammatory reactions, they are necessary for the formation of certain hormones and they help build cell membranes, especially in the nerve cells in the brain. Omega-3 fatty acids receive special attention not only because of their vital function, but because, as some of the nutrients are essential, they cannot be produced by the body itself. They must be ingested with food. We give you an overview of the most important omega-3 fatty acids and explain which foods contain them.
Fatty fish contains particularly high levels of omega 3 fatty acids.
The three most important omega-3 fatty acids
Omega-3 fatty acids form a whole class of long-chain, polyunsaturated fatty acids – eleven different types are currently known. The name can be explained by a brief excursion into chemistry: they consist of chains of 16 to 24 carbon atoms. Polyunsaturated means that there are so-called double bonds between several carbon atoms. At the beginning of the chain is the so-called carboxyl group, which as a functional unit determines the properties of the fatty acid. The last carbon atom in the chain is called omega – analogous to the last letter of the Greek alphabet (ω). The last double bond in the chain is on the third carbon atom in the chain (counting from the omega end). Hence the name omega-3 fatty acid. The most important omega-3 fatty acids for humans are α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). They are involved in some vital processes and are therefore well researched.
ALA – alpha-linolenic acid
Linolenic acid is a component of many vegetable oils and fats. The fatty acid consists of a chain of 18 carbon atoms and has three double bonds. The linseed oil that gives it its name contains a good 50 to 70 percent ALA. Some vegetable oils, such as olive oil, contain less than one percent ALA. Here you can see an overview of the ALA content in vegetable oils:
- linseed oil – 56-71%
- dragon head oil – 60%
- Chia oil – 60%
- hemp oil – 28%
- Perilla oil – 31-42%
- walnut oil – 12%
- rapeseed oil – 10%
- soybean oil – 8%
- Sunflower oil, olive oil, grape seed oil – less than 1%
ALA is the only essential of the most important omega-3 fatty acids. EPA and DHA can be formed in the body from ALA. The biosynthesis of EPA and DHA is also the most important function of ALA. In addition, ALA has a regulating effect on the activity of certain enzymes that are involved in the formation of tissue hormones, the so-called eicosanoids.
The chemical structure of ALA shows the double bond at the third position.
EPA – eicosapentaenoic acid
EPA consists of 20 carbon atoms and contains five double bonds. EPA is found in all living things, but especially in fish and seafood. Fatty sea fish such as salmon, herring and mackerel in particular have a high EPA content, as do krill, phytoplankton and some types of algae. EPA is important as a precursor for the biosynthesis of DHA, and important eicosanoids are formed from EPA. Eicosanoids influence the permeability of certain types of tissue to large molecules such as white and red blood cells or plasma proteins. They therefore help to initiate or reduce inflammatory processes.
DHA – docosahexaenoic acid
DHA consists of 22 carbon atoms and six double bonds. The smallest sea algae are able to form DHA and are therefore responsible for the accumulation of DHA in the marine food chain, from plankton and krill to the large sea fish, which in turn serve as a rich source of DHA for humans. DHA is an important component of the cell walls of nerve cells. In the nerve cells of the retina, DHA makes up 93 percent of the omega-3 fatty acids present, and in the nerve cells of the brain, it makes up as much as 97 percent. In humans, DHA is synthesized by the mammary glands of the breast, among other things. This enriches breast milk with DHA. Since the need for DHA is particularly high during pregnancy and breastfeeding, the German Nutrition Society recommends including at least one to two fish meals per week in the diet during this time.
How much omega-3 fatty acids do I need?
The heart, brain and eyes in particular need the omega-3 fatty acids EPA and DHA to function normally. To achieve this, around 0.5 percent of daily energy requirements should be covered by omega-3 fatty acids. This corresponds to around 1.25g for an adult. However, more than 5g should not be consumed daily, as this could affect the flow properties of the blood. At least 250 mg of DHA are required daily to contribute to maintaining normal brain and eye function. Foods that are suitable for contributing to this should contain at least 40 mg of DHA per 100 g. Pregnant women and breastfeeding mothers are recommended to consume an additional 200 mg of DHA to promote the development of normal brain and eye function in their children.
Omega-3 in relation to Omega-6
However, it is not just the amount of omega-3 fatty acids that are consumed through food that is important, but also the ratio to other fats, especially omega-6 fatty acids. In many cases, omega-3 fatty acids are precursors for the biosynthesis of other building blocks of life. This is made possible by certain desaturases. These are enzymes that build additional double bonds into the fatty acid chains, which then enable further reactions. The same desaturases are also involved in the metabolic processes of omega-6 fatty acids. The metabolic processes of omega-3 and omega-6 fatty acids therefore compete with each other, and not just in the enzymes required. While the eicosanoids formed from EPA reduce inflammatory processes, eicosanoids formed from omega-6 fatty acids are involved in initiating inflammatory processes. The ratio of omega-6 to omega-3 should ideally be between 1:1 and 5:1. Since most foods that contain omega-3 fatty acids also contain omega-6 fatty acids, this ratio can hardly be balanced by increasing the consumption of omega-3-containing foods, but only by avoiding foods that contain particularly high levels of omega-6. Sunflower oil, for example, contains 70 times more omega-6 than omega-3 fatty acids and thus ruins the fatty acid balance of any fish that is fried in it. In this sense, oils with an omega-3 content of more than 10 percent are more suitable for cooking.
