Most of us are aware of the important role food plays in protecting our physical health. But we don’t tend to think as much about its role in supporting our brain and mental health — at least not until something goes wrong. Chartered Psychologist and author of How To Build A Healthy Brain, Kimberley Wilson, discusses the key role omega-3 fats play in brain health.

Article written for The Thriva Newspaper

Despite only making up about 2% of your total body weight, your brain is the hungriest organ in your body — it uses up around 25% of your calorie intake when your body is at rest. This high demand for energy comes with a high demand for nutrients. Some nutrients, like omega-3 fats, are particularly important for the healthy structure and function of your brain. 

What are omega-3s?

Omega-3s are a family of fats that are crucial for health. The 3 main omega-3s are:

  • alpha-Linolenic acid (ALA)
  • docosahexaenoic acid (DHA)
  • eicosapentaenoic acid (EPA)

Each of these fats plays a variety of important roles in your body. Technically, ALA is the only one of these that’s an essential nutrient — meaning your body can’t make it, and it must come from your diet. This is because your body can convert ALA into EPA and DHA. But, the rate of conversion is very low, so it doesn’t provide you with what you need. This means it’s still really important to make sure you get enough of all 3 from your diet, or through supplements if necessary.

What foods are rich in omega-3s?

ALA is found in seeds like flaxseed (linseeds), chia, and hemp, as well as walnuts.

DHA and EPA are most abundant in cold-water oily fish like salmon, mackerel, anchovies, sardines, herring, pilchards, and trout. Algae is another excellent source and is what’s used to produce vegan omega-3 supplements.

How exactly do omega-3s support brain health?

ALA is found inside the mitochondria (the ‘powerhouse’) of your cells where it helps cells to generate energy. But, in terms of brain health, it’s DHA and EPA that we need to focus on. These fats, particularly DHA, are thought to have played an important role in the evolution of the brain and the development of human intelligence

DHA makes up 36% of the membrane (outer wall) of your brain cells, where its unique shape helps to maintain flexibility in the cell wall — allowing essential molecules (including water) to flow in and out of your cells. DHA also regulates the behaviour of neurons and cell signalling. 

Cell signalling is the transmission of chemical and electrical messages from one brain cell to another — a process underlying all our emotions, thoughts, ideas, and decisions. Signalling occurs at the synapse, which is the point of communication between brain cells. And DHA supports the formation of healthy, strong synapses. This means that nutrient status, particularly nutrient deficiency, can affect your emotions, thoughts, and so on. 

DHA also influences the activity of certain genes, particularly those involved in fat metabolism in your liver — helping reduce the levels of unhealthy fats in your blood. Through this action, DHA helps to maintain healthy blood vessels, which is important for your brain health.

DHA is also crucial for healthy vision. It makes up 50-70% of the fats in the light receptors in your eye and helps to maintain the shape of your retina. And an adequate supply of DHA during pregnancy and breastfeeding is required for healthy brain and eye development and function in infants.

Both DHA and EPA transform in your body to produce compounds that help to resolve inflammation. Inflammation is how your body responds to illness or injury. And in normal circumstances, it’s essential to your survival — fighting off harmful bacteria and viruses and helping you recover from injury. But, left unchecked, inflammation can start to attack your body’s healthy tissues, including your brain. This can contribute to mental health conditions like depression and neurodegenerative disorders like Multiple Sclerosis and Alzheimer’s disease.

Depression and omega-3s

Depression is the leading cause of global disability — which means that worldwide more people suffer loss of quality of life due to depression than diseases like cancer and stroke. 

Depression is a complex disorder with many different causes and contributing factors. But, recent research suggests that the availability of healthy fats in the brain might play a role in depression — at least for some people. A recent meta-analysis  (where the results of several studies are pooled to look for overall trends) found a beneficial effect of EPA supplements on depressive symptoms. Specifically, around 1g per day of EPA was found to effectively reduce depression, likely due to its anti-inflammatory action.

Building a bigger, better brain 

In the past, it was thought that you were born with pretty much all the brain cells you would ever have. But, in the last decade or so, animal and human studies have shown that the adult brain is capable of creating new brain cells — a process called neurogenesis. This is important for overall brain health (low levels of neurogenesis are associated with more severe depression) but in particular for brain ageing. 

As we age, from our late 40s, it’s common for our brains to shrink by about 1-2% per year. This is considered normal brain ageing and is linked to the poorer memory and cognitive performance commonly seen in older adults. But, DHA has been shown to promote neurogenesis in an area of the brain called the hippocampus — think of the hippocampus as the seat of memory and learning. Indeed, it’s the area of the brain first and most severely damaged in Alzheimer’s disease. 

Consistently, clinical trials of omega-3 supplements have shown increases in hippocampal neurogenesis in the adult brain. And people who eat diets rich in fish and seafood have larger hippocampi and overall brain volume compared to people who don’t eat much of these. 

Top takeaways

Omega-3 fats are essential for the healthy development and function of your brain, as well as delaying brain ageing. DHA plays a unique and indispensable role in the formation and activity of brain cells, while EPA has important anti-inflammatory actions. 

EPA and DHA aren’t efficiently produced in your body, but you can get them already preformed in oily fish. So aim for 1-2 servings of oily fish per week. If you don’t eat a lot of fish or if you’re vegan or vegetarian, you might need to think about taking a supplement that contains both EPA and DHA as you’re unlikely to get enough from plant sources (which only contain ALA).

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References

Bradbury, J. (2011). Docosahexaenoic acid (DHA): an ancient nutrient for the modern human brain.Nutrients,3(5), 529-554.

Calder, P. C. (2016). Docosahexaenoic acid.Annals of Nutrition and Metabolism,69(Suppl. 1), 8-21.

Dyall, S. C. (2015). Long-chain omega-3 fatty acids and the brain: a review of the independent and shared effects of EPA, DPA and DHA.Frontiers in aging neuroscience,7, 52.

Liao, Y., Xie, B., Zhang, H., He, Q., Guo, L., Subramaniapillai, M., ... & Mclntyer, R. S. (2019). Efficacy of omega-3 PUFAs in depression: a meta-analysis.Translational psychiatry,9(1), 1-9.

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Kimberley Wilson C Psychol, MSc Nutrition

Written by Kimberley Wilson C Psychol, MSc Nutrition

3rd Nov 2021 • 6 min read