How to spot the outward signs of a fat-deprived brain

Maria Cross MSc
Sep 1 · 9 min read

When Alicia came to see me for dietary advice for various physical health problems, she made no mention of her extreme anxiety. I had my suspicions — it didn’t take a genius.

I asked her what health issue she most wanted to address. Her answer was unequivocal. “It’s my husband. He’s a fucking bastard”.

This could go one of two ways, I thought.

Alicia was certainly different, but she was typical in one regard: she had a combination of physical and mental symptoms. And, as it turned out, there was one underlying cause. Alicia’s brain lacked fatty acids, and this deficiency was manifesting in other parts of her body.

Physical signs and symptoms of essential fat deficiency include:

  • Dryness — skin, eyes
  • Asthma
  • Premenstrual syndrome
  • Dysmenorrhea (painful periods)
  • Infertility
  • Aching joints
  • Cardiovascular disease
  • Inflammatory bowel disorder

Alicia had very dry skin and eyes.

I worked as a nutrition consultant for over 15 years, during the 1990s and 2000s. My standard approach was to focus on the most likely dietary cause of a client’s health problems, and work from there. As Alicia was talking, I wrote down: low DHA?

DHA is a type of fatty acid that is essential to the whole body, including the brain. Without sufficient DHA, possible mental health problems include depression and anxiety.

One month later, back came a different person. When I asked Alicia how she was, to my surprise she replied that never in her life had she felt so “unanxious”. She revealed that, for as long as she could remember, she had been in a state of high anxiety. She never mentioned this before because she thought it was just part of her make-up. This novel, quite exhilarating absence of anxiety was quite a revelation to her.

Getting fat into Alicia’s system turned out to be the key to solving Alicia’s physical health problems too (though not her troublesome spouse).


The human brain is made of fat, cholesterol, protein and water. The dry weight of the brain is 60 per cent fat, making it the fattiest organ of the body. Different types of fat — lipids — are involved in the structure and function of the brain, including nerve transmission and signalling.

The brain’s requirement for fat begins in the womb and continues throughout life. The most important fats in the brain are the long-chain polyunsaturates (PUFAs).

There are two families of PUFAs: omega-6 (linoleic acid) and omega-3 (alpha-linolenic acid). They are metabolically and functionally distinct — one cannot replace the other — and are required in more or less equal amounts.

The two omega-3 fatty acids that are most important to the brain are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). EPA is converted to DHA, the most abundant omega-3 fatty acid in the body. Cells that have a lot of electrical activity, such as the brain, have higher proportions of DHA.

Where do you get these fats from?

Algae and phytoplankton are the primary sources of EPA and DHA. Micro algae are eaten by small fish, which are eaten by larger fish. Thus, for humans, fish and other seafood are the only meaningful source of these fatty acids, although both are also found in small amounts in meat and to a lesser extent eggs. Offal is a good source, albeit an acquired taste.

DHA is found abundantly in oily fish, including salmon, mackerel, trout, sardines, herring and fresh (not tinned) tuna.

Alicia did not eat any fish, and flatly refused to do so. The only way to get large amounts of EPA and DHA quickly into her system was via fish oil capsules, which fortunately she agreed to take. This did the trick for both her dry skin/eyes and depression.

Unlike Alicia, Ellie was accutely aware that her depressed mood was not normal. Depression was the main reason for her booking a nutrition consultation. A 26-year-old marketing executive in a stable relationship, her life was pretty much on track and she couldn’t understand why she felt so depressed. On further investigation, it turned out she also suffered from premenstrual syndrome and dysmenorrhea, which is extreme period pain. She also had permanently dry lips, another important clue.

I should point out at this juncture that it is not enough to consume adequate levels of omega-3 fats. It is important to avoid over-consumption of omega-6 fatty acids.

Humans evolved on a diet with more or less equal amounts of omega-6 and omega-3. Nothing about our biology has changed, even if our diets have changed beyond recognition. The modern Western diet now provides around 15 times more omega-6 fat than omega-3. The main source of these omega-6 fats is vegetable cooking oils: corn, soya, sunflower. These are the oils commonly used in cheap spreads, processed foods and even home cooking.

The problem is that omega-3 and omega-6 fats compete with each other for absorption in the body, including the brain - where excessive omega-6 displaces omega-3.

Excessive omega-6 can create dissonance elsewhere in the body, including the reproductive system. DHA is a precursor to hormone-like substances called eicosanoids. They are particularly important for male and female reproductive health. With insufficient DHA, brought on either by lack of DHA in the diet or excessive omega-6, women might experience premenstrual syndrome and/or dysmenorrhoea.

Dysmenorrhoea is something that, like Ellie, I had first-hand experience of.

The pain of this condition is severe, with labour-like uterine contractions. It is — or was, in my case - accompanied by simultaneous vomiting and diarrhoea, shaking, numbness of the hands and feet and occasional fainting. I lived in fear from one month to the next of the inevitable, until I was finally prescribed high strength anti-inflammatory drugs. The low-strength drugs did nothing.

Years later, as I grew interested in nutrition and discovered the therapeutic effect of fish oil, I was able to stop taking the anti-inflammatory drugs.

“Increased intake of omega-3 FA can reverse the symptoms in this condition by decreasing the amount of omega-6 FA in cell membranes.” (Saldeen & Saldeen)

In Ellie’s case, I asked her to eliminate vegetable cooking oils and processed foods, and eat lots of oily fish. I also recommended fish oil supplements, just for the short-term. When she returned, several weeks later, she said there had been a “huge difference”. Even though she had had only one period since our first appointment, she experienced no PMS and most importantly for her, no pain.

And no depression.

Essential fats are crucial for male reproductive health too. Omega-3 fats are a significant component of sperm, and in one particular trial of infertile men who received either EPA and DHA or a placebo for 32 weeks, in those receiving the fatty acids testing revealed a significant improvement in sperm quality — count, motility and form.

Omega-3 fatty acids are also a key component of the retina of the eye, and too little DHA may affect your vision. Eating fish at least twice a week is associated with reduced risk of developing age-related macular disease and can also help with dry eye syndrome.

Lack of omega-3 fatty acids is linked to coronary heart disease and high blood pressure. You can add, to that list, asthma, rheumatoid arthritis, and Crohn’s disease.

The key word when it comes to many of these physical ailments is inflammation. Interestingly, it is increasingly acknowledged that depression is an inflammatory disorder of the brain. Omega-3 fats are anti-inflammatory agents.

One inflammatory condition that Charles, a fifty-year old journalist, was all too familiar with was joint pain. He also lived with mood fluctuations and had done so for years. He described one bout of depression as “extreme”. Dry skin on his hands and feet was just a minor irritation by comparison.

I can’t say for sure that consuming oily fish and cutting out excessive omega-6 is what eliminated Charles’s joint pain and depression — he also cut out gluten, which in some cases can cause severe mental illness and numerous physical symptoms. But his dry skin cleared up well too. I suspect that it was the combination of eating oily fish and eliminating gluten that worked for him.

Mental signs and symptoms of omega-3 fatty acid deficiency include:

Bipolar disorder. DHA has been shown to be significantly lower in patients with bipolar disease and major depressive disorder compared to healthy controls.

“Several laboratories have provided evidence that depressed patients have, on average, lower plasma levels of n-3 PUFAs than non depressed controls; furthermore, there are relationships within these populations between severity of depressive symptoms and lower plasma levels of the n-3 PUFAs.” (Kiecolt-Glaser et al).

Attention deficit hyperactivity disorder. Children with ADHD also report symptoms that are typical of fatty acid deficiency, including thirst, dry skin, dry hair, dandruff, brittle nails.

Autism. Autistic children have been found to have levels of DHA that were “particularly decreased”, compared to non-autistic controls.

Schizophrenia. Post-mortem studies have revealed low DHA in the frontal lobes of schizophrenia patients.

What’s going on?

We once ate a lot of fish, the main dietary source of these incredibly important fatty acids.

“It is our contention that the movement in the 19th to 21st centuries away from traditional use of sea foods and increased emphasis on land based food supply is a likely cause in the rise in brain disorders including mental ill-health, stress, and other psychiatric disorders.”(Crawford et al 2014).

Fish consumption today, certainly in the UK, is alarmingly low. Without a regular intake of oily fish and seafood, or taking supplements, deficiency of DHA is virtually a given. We Brits love our fish and chips, but that is a far cry from the herring and salmon that were once a staple of the poor.

Food writer Colin Spencer describes in his book British Food: An Extraordinary Thousand Years of History how, after the Romans left Britain (in the early 5th century) and before the land enclosures, “The marshlands were crammed full of eels, the rivers had plenty of salmon and trout, and other fish such as perch, pike, tench, carp and bream.” Rivers, streams and lakes were also “stuffed” with freshwater fish, such as trout. The shoreline offered free and abundant treasures, including whelks, periwinkles, limpets and mussels.

During the Middle Ages, monks on their monastic diets did exceptionally well, consuming fish on average around 215 days a year, as part of their ‘fasting’ regime. Not so monastic after all.

In the 18th century, herring — and oysters — were cheap and plentiful.

“Just over a century ago, oysters were gathered and presented on the bar table in the East end of London free for those who bought beer.” (Crawford et al 2014).

The National Diet and Nutrition Survey provides information on the dietary habits of all four UK countries. In 2012/13 and 2013/14, oily fish consumption in all age groups remained “well below” the recommended weekly amount, at 13g-29g in children and 54–87g in adults.


In the US, the recommended consumption for fish is two 2.5oz servings weekly, preferably oily. However, the reality is that “a large percentage of the US adult population is not meeting recommendations for omega-3 fatty acid consumption”.

Without regular fish and seafood, it is difficult to obtain sufficient DHA (unless, like our grandparents, you eat a lot of offal, including brawn. Even I can’t envisage doing that).

Having said that, meat (and eggs) from animals that are pasture-fed contain much higher proportions of DHA than meat from intensively farmed animals. Better still, meat from wild animals (venison and buffalo) contains significantly more DHA than pasture-fed or organically reared animals.

Nuts and seeds and other plant foods are often suggested as a suitable vegetarian source of omega-3 fats. Although it is true that the body can make some limited DHA (and EPA, its precursor) from plant sources, its ability to do so is poor, and effectively meaningless. The liver converts less than 0.5% of the omega-3 fat in plant sources to DHA. That’s on a good day: in many studies, that conversion rate has been shown to be less than 0.1%, making it “negligible”.

Of course, there are many possible dietary causes of imbalances in the brain leading to mental health issues, some of which I cover in other articles in my publication Feed Your Brain. Neither is mental ill-health necessarily diet-related.

But it might be.

Feed Your Brain

Exploring the link between diet and mental health

Maria Cross MSc

Written by

I’m a nutrition science writer, specialising in diet and mental health. Subscribe to for free brain food guide. @MariaXCross

Feed Your Brain

Exploring the link between diet and mental health

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