You've probably heard the saying "you are what you eat" and until recently I simply took if for that; if you eat healthy foods you'll be healthy and if you eat unhealthy foods your health will suffer.
Let's start by saying that IS completely true, but today I wanted to take a deeper dive into how what you eat can affect every cell in your body.
Which, by the way, you have approximately 30 TRILLION of .
An Introduction To You
Every living thing is built from cells. There are many different types of cells that fulfil many different roles, including immune cells that help fight foreign invaders and muscle cells that have sliding filaments responsible for muscular contractions. In terms of nutrition, though, our cells have two basic functions:
Get nutrients from the food we eat
Use materials to build new raw materials and fuel to keep us alive
And it's quite accurate to say that how our body works depends upon how well our cells are functioning. To do their above jobs cells go through a lot, including:
Grow, mature and die
Exchange gases like oxygen and carbon dioxide
Absorb and metabolise nutrients
Regulate fluids and exchange solutes
Get rid of waste
Reproduce (although not ALL cells reproduce)
Figure 1: A typical animal cell
Now you may recognise some of these alien-like parts of the cell known as organelles. Organelles refer to membrane-bound structures that have specific jobs to help maintain the cell. I'll give a brief breakdown of those labelled above before we talk about how what we eat affects their function:
Mitochondria - Involved in the biochemical processes of respiration and energy production
Nucleus - The largest organelle, control centre, home to our DNA wrapped up in chromosomes.
Endoplasmic Reticulum - A network of tube-like structures within a cell that is involved in protein and lipid synthesis.
Golgi Apparatus - A structure within a cell involved in secretion and intracellular transport.
Peroxisome - Contains enzymes that help metabolise nutrients
Cell Membrane - The boundary of the cell (more on this later)
Lysosome - Contains enzymes that help to break substances down.
An Introduction To Cell Signalling
So this is a little bit of the nitty-gritty, but important, information about the process of how our body responds to every chemical introduced into our circulation.
Cells get information about what's happening around them through cell signalling. This process, also known as signal transduction, starts via receptors that are embedded in the cells plasma membrane. They take specific information from passing molecules and pass the information onto second messengers inside the cell.
The second messenger may pass this information on again until the information is in the right place that the body can make an appropriate response. The organelles we mentioned earlier can all process and respond to different types of information.
Think of it this way: the cell has sensors sat on the outside of its walls which send signals to messengers on the inside.
Sometimes the body will need to make a particular protein for a specific job. For example, to repair muscle tissue it has to take a particular set of instructions from your DNA.
Your DNA is inside chromosomes which are inside the nucleus of your cells.
Figure 2: A receptor on the outside of the cell membrane and the location of your DNA in the nucleus of the cell.
The process of taking information and our body expressing a functional product is known as gene expression. What we eat interacts with our DNA by causing hormonal cascades (signalling pathways) that influence it.
Genetics + Environment = Product
As mentioned above, your DNA dictates which proteins are made by the body. Ultimately, your genetic code determines everything from how your body develops to your risk of a particular illness. And although you cannot edit your DNA (yet) you CAN affect which genes are expressed!
For instance, your genes might suggest you could grow to anywhere between 5'10" and 6'1". But your actual height is an interaction between genes and environment since everything we introduce into the body will cause a response. If you were to grow up malnourished you'd never reach the maximum height your genes are coded to (6'1" in this case).
What you eat early in life and what your mother ate during pregnancy can affect your genes and regulate your traits - including the development of disease in later life.
Our genes can be influenced by a number of things, including:
Nutrient deficiencies or excesses
Dietary components (eg omega-3 fats)
Sunlight and vitamin D
Toxins (industrial chemicals, pesticides etc)
Bacteria and viruses
Exercise and activity
Alcohol and other drugs
Stress and trauma
So like I alluded to earlier, we cannot control what genes we have, but we can control their expression to some degree. We can influence which genes get "switched on or off" by controlling the signalling pathways that interact with our DNA.
Example - Omega-3 Fatty Acids
So hopefully you're getting the picture, that what you eat affects signalling pathways and gene expressions which ultimately shape how you'll look, develop and your overall health.
Although this next example isn't an example of gene expression, it highlights another way in which nutrition plays a role in keeping our bodies functioning optimally.
Cell membranes (the boundary that's responsible for passing information from outside the cell to inside the cell) has a bilayer that is flexible and fluid. It's mostly made up of phospholipids, which are a type of molecule that has a phosphate head and fatty acid tail.
Because of this lipid structure, the types of fat we eat can change how fluid or flexible the cell membrane can be, thereby affecting its ability to pass on information.
Too much saturated fat can cause the membrane to be too rigid 
Too much polyunsaturated fat may cause the membrane to be too fluid 
And to tie it all in together nicely studies such as [2,3,4] all highlight the importance of Omega-3 fatty acid consumption for healthy and well functioning cell membranes, and ultimately health in general. Study  in particular highlights these key points:
• "Omega-3 fatty acids are essential nutrients that cannot be synthesized in the body and must be obtained from the diet."
• "Dietary omega-3 fatty acids are incorporated into cellular membranes of all tissues. The extent of incorporation into tissue membranes is dependent on dietary intake."
• "The enrichment of membranes with omega-3 fatty acids can modulate cellular signalling events, membrane protein function and gene expression."
• "Consumption of recommended intakes of omega-3 fatty acids may lead to a general increase in the overall health and well-being of the population."
Figure 3 : Cell membrane showing omega-3 fatty acids incorporated into the phospholipid bilayer. Omega-3 fatty acids can modify gene and protein expression, modulate membrane protein activity and act as a reservoir for bioactive molecules. Image by: Lianne Friesen and Nicholas Woolridge
Just to clarify - you HAVE to get omega-3 fatty acids from your diet. They are present in all membranes of all our cells and are directly related to our dietary intake. When membranes have omega-3 fatty acids present, cell signalling, protein function and gene expression are improved. Consuming omega-3 fatty acids will improve your health - most likely for the reasons above.
Now, you may be reading this thinking 'Well I know Omega-3 fatty acids are good for me' but hopefully now you understand why! I believe that creating an understanding will help reinforce peoples actions and decision making.
After all, if I simply told you that eating your fish would help you to "unlock your genetic potential" then you'd probably start listening. By the way, that is essentially what I'm saying, we've just gone into the details above.
Our cells are complex structures that contain organelles, such as the nucleus (home to our DNA), mitochondria (used in energy production) and more.
Cell signalling is the process of our cells gathering information about what’s entering our body and passing on that information to gain an appropriate response.
Sometimes, if a functional product is required (often a protein), then information is needed from our DNA and gene expression occurs.
The clarity of these signalling pathways can be affected by our cell membrane’s ability to let information in and out of a cell.
Omega-3 fatty acid consumption will directly affect our bodies ability for cell signalling and gene expression due to the cell membrane being made up of phospholipids. Gene expression is also affected by a host of other factors including nutrient deficiencies and excesses, toxins such as pesticides, exercise, stress and alcohol.
And that, my friend, is why I consume 3 x fish oil tablets and 1 x vitamin D tablet every single day, even if I am eating fish that day. Of course, you can get perfect amounts of omega-3 fatty acid and vitamin D from your diet (and the sun) but it's a fail-safe. It's also shown that those exercising more intensely will require higher amounts of both the above mentioned for normal cellular function. So, on the days you exercise it's arguably more important to make sure you you get these two in.
Along with that and other staples of a healthy life, such as mental wellbeing, physical activity and high quality, nutrient-dense foods - you are giving yourself the best chance to unlock your genetic potential!
 The Science Of Nutrition, Chapter 7, Systems and Cells, The Essentials of Nutrition and Coaching 4th Edition.
 Surette ME. The science behind dietary omega-3 fatty acids.CMAJ. 2008;178(2):177–180. doi:10.1503/cmaj.071356
 Ferreri C, Masi A, Sansone A, et al. Fatty Acids in Membranes as Homeostatic, Metabolic and Nutritional Biomarkers: Recent Advancements in Analytics and Diagnostics.Diagnostics (Basel). 2016;7(1):1. Published 2016 Dec 22. doi:10.3390/diagnostics7010001
 Hutchins-Wiese, H. (2013). The impact of supplemental n-3 long-chain polyunsaturated fatty acids and dietary antioxidants on physical performance in postmenopausal women. The Journal of Nutrition, Health & Aging, 17(1), 76-80.