You are what you eat. And so are your cells.
Each of the tiny 100 trillion cells in your body has an outer layer called the membrane. The machinery inside each cell has a membrane, too.
That membrane is kind of important. It holds your cell together so the things inside it can do their job and don't just float off. It protects the cell from things outside of it. It filters the messages and deliveries to that cell from the blood stream. It lets cells talk to each other.
To do this, the cell membrane needs to be just the right structure. Not too rigid that nothing can pass in or out, stopping that cell from talking to other cells. But not too flexible that nutrients might escape or gate crashers could enter.
Or, take your mitochondrial membrane. The mitochondria makes energy to fuel all of the things that the cell does. If it has a flimsy or clogged membrane, it's not going to be able to do that properly because its security gate and supply channel is compromised.
Eating fats changes the structure of the cell membrane because any of the fats you eat can set up shop there.
Omega 3 fats are the building blocks for a healthy cell membrane. You've probably read that omega 3 fatty acids do all sorts of good things in the body, from promoting heart health to neuron function. The common thread here is membrane fluidity. Omega 3 fatty acids like EPA and DHA help to build a healthy membrane, not too rigid, not too permeable.
And that's not all they do. Omega 3 fatty acids also play a vital role in anti-inflammation, neurological function, cognitive capacity and mental health.
But your body can't make omega 3 fats. So if you don't eat or supplement them because you're too busy chasing the latest super food trend, you're body isn't getting them.
There's three routes you can take to supply omega 3s to your body.
First, you can eat the precursor omega 3 called alpha linolenic acid (ALA). It's found in foods like linseed, walnuts and chia seeds. After consuming ALA, it takes a number of steps to turn it into EPA and then DHA in the liver. This is a biochemically inefficient process - on average,< 15 % of ALA actually makes it into EPA and only < 5 % becomes DHA. So, you really need to eat EPA and DHA directly from foods or supplements to boost it in the body.
Second, you can eat foods that contain the omega 3s in the forms that your body can use, called EPA and DHA. EPA and DHA are predominantly marine forms of omega 3s and you'll find both in fatty fish, like salmon, mackerel, tuna, herring and sardines. Remember, that's fatty fish, not just fish full stop. Leaner fish, like bass, tilapia and cod, and also shell fish like scallops or shrimp, contain far less fat, ie far less omega 3s (because it's a kind of fat!)
The Australian Guide to Healthy Eating plate says to eat 'lean meats and poultry, fish, eggs, tofu, nuts and seeds,' but that's a bit confusing because at least for omega 3, you really need to eat fish that is fattier or you're not going to meet it.
It's easier to see this if you equate for protein and look at the omega 3 content of salmon, canned sardines and canned tuna.
Salmon, Atlantic: 150 g (uncooked weight): 31 g protein, 1.22 g EPA, 1.5 mg DHA.
Sardines, wild in spring water, 2 cans drained: 34 g protein, 1.1 g EPA and 1.34 g DHA.
Compare that to tuna, light, 2 cans drained: 32 g protein, 0.08 g EPA 0.38 g DHA.
Ie, you'd have to eat 12 tins of tuna to consume the same total amount of omega 3 that's in 150 g of salmon, or 10 tins to equate to the omega 3 in 2 tins of sardines.
Third, you can supplement. If you're not eating enough fatty fish, take a fish or krill oil. Make sure it's high quality, packaged in a glass, opaque bottle and that you keep it in the fridge to protect it from light and heat.
Translating this into foods
To keep it simple, I eat sardines for lunch and salmon for dinner at least 1 x each in 7 days. I might add a fish oil to that to supplement my nutrition and support my health state at a particular time.
If you're not a huge fan of sardines, you can double up on salmon 2 x instead, or add fried eggs or smashed avocado to the sardines - the yolk or the avocado's flesh does a decent job at disguising the taste and texture.
Think of your cell membranes.