How eating more fat can improve your memory
The ketogenic diet is about much more than weight loss
Your brain is the most advanced, sophisticated nerve centre on the planet. Or — depending on how you look at it — a crinkly lump of fat, housed within your skull. Either way, it is the accumulation of millions of years of human evolutionary biology.
No other organ contains so much fat, or needs it so much. Without it, the brain simply cannot function. Memory loss is one sign of that.
The dry weight of the brain is 60% fat. It’s all there: saturated, monounsaturated and polyunsaturated fat. There’s also a good deal of cholesterol, a fat-like substance. As well as forming part of the structure of the brain, and providing fuel, these fats play a role in maintaining memory and other aspects of cognitive function.
By the same token, lack of the right fats plays a role in cognitive dysfunction, including poor memory and ultimately dementia.
Perhaps that’s why fat is so appealing. “Fat gives food flavor”, as chef and TV personality Julia Child once famously put it. Fat is filling, and instantly lights up your brain’s reward centres.
Doesn’t the brain run on glucose, not fat?
Yes, and no, is the answer to that question.
Although the human brain normally uses glucose as its main source of fuel, it can switch to burning substances called ketones, when glucose is in short supply. Times of short supply include fasting, endurance exercise and when on a low carbohydrate diet. Carbohydrate is the body’s main source of glucose.
When glucose levels dwindle, fatty acids are released from your adipose tissue — your fat store. Ketones are made in the liver from these fatty acids.
Fatty acids cannot cross into the brain via the blood-brain barrier, but ketones can, and do.
It’s a ketogenic thing
You may have heard of the ketogenic diet as a weight loss strategy. It is, basically, a very low carbohydrate, high fat diet, and is effective because when glucose runs out, you start dipping in to your fat stores.
The ketogenic diet is the latest in a long line of popular diets. But don’t be mistaken — this is not a new, or fad diet. Weight loss is just an added bonus; it’s not what the diet was originally about.
The ketogenic diet is a scientifically proven treatment for drug-resistant epilepsy. It was first used in the 1920s when it was found to be an effective way to control seizures.
Studies have found that half of children experience at least 50% reduction in seizures after 6 months on the ketogenic diet, and one third achieve over 90% reduction.
Now, the focus of attention is on memory, and brain function.
Epilepsy is a brain disorder — there’s your first clue.
Your second clue is the fact that there is a higher incidence of seizures in patients with Alzheimer’s disease than in people without the condition.
Researchers are optimistic that the ketogenic diet could be used as an effective dementia prevention strategy. A low carbohydrate diet has already proved effective in the treatment of mild cognitive impairment (MCI), a condition that precedes dementia and is considered a risk factor for the disease.
In 2012, the journal Neurobiology of Aging published the results of a study into the effects of a very low carbohydrate diet on memory loss. The 23 participants, who were elderly and all had MCI, were given either a very high or a very low carbohydrate diet for six weeks. At the end of the trial period, improved verbal memory performance was observed in the low carbohydrate group, but not in those following the high carbohydrate diet. The low carbohydrate, ketogenic group also experienced reductions in weight and waist circumference.
How does it work?
People with Alzheimer’s have impaired brain glucose uptake — use of glucose by the brain deteriorates.
That is why type 2 diabetes increases the risk for dementia. Diabetics do not produce enough insulin, or cannot use insulin properly. A ketogenic diet circumvents this problem — ketones provide an important, non-glucose source of energy to the brain. The liver can produce enough ketones, per day, to meet the brain’s needs.
Ketosis occurs when the body is producing ketones. Ketosis can be induced on a dietary regimen of 20g-50g of carbohydrate per day. Such a regimen produces a shift from glucose to ketone metabolism, and is indicated by the presence of ketones in urine.
There is another way to burn ketones for fuel, other than restricting carbohydrates.
Some saturated fatty acids — the medium-chain triglycerides (MCTs) — are easily metabolised by the body and converted into ketones. For that reason, scientists believe that these MCTs may be beneficial to people who have Alzheimer’s or some form of memory impairment. If they can’t use glucose, they can use MCTs instead.
The coconut is an especially rich source of MCTs. In fact, it has been singled out as a ‘potential cognitive strengthener’ for people with Alzheimer’s.
When a group of 20 people with either Alzheimer’s or mild cognitive impairment were given an oral dose of MCTs, or a placebo,
But is ketosis natural? Or even safe?
You did it in the womb; you just don’t remember.
Babies use ketones as brain fuel, before they are even born. Ketones supply as much as 30% of the brain’s energy requirement, pre-birth.
After birth, breast-feeding babies are in a sustained, mild ketogenic state, because human breast milk contains medium-chain fatty acids — just like coconuts.
It does you no harm as an adult, either. In 2003 a systematic review found no adverse effects of a ketogenic diet on blood fats, blood pressure or fasting glucose levels. Instead, trials resulted in improved health and significant weight loss.
There’s nothing new about a high fat diet. We humans developed a taste for fat around 3 million years ago, when we started to leave our tree homes, and abandoned our fruit-based diet. There’s your third clue.
We started off with small brains, and weren’t especially bright. But change is inevitable, and change we did.
First, we scavenged. Then, as we got smarter, we packed our tools and went a-hunting. The bigger and fatter the prey the better, as far as early humans were concerned.
Of course we didn’t know it at the time, but the change in lifestyle from fruit-eating to hunter-gathering is credited with triggering the most extraordinary, rapid expansion of the brain, for which we humans are so famous. The brain went on to almost triple in size — an exceptional feat, by any standards.
Mark Sisson, American former endurance athlete and now best-selling nutrition author and blogger, sums up the ketogenic diet as “A reset… a return to the ancestral metabolic state, the metabolic state we were born into.” I think that sums it up quite nicely.
Beyond ketones: DHA
Ketones are not the only fat that the brain loves, and needs. Ketones provide fuel, but when it comes to function, there are other fats. Perhaps the most important of those is the omega-3 fatty acid, docosahexaenoic acid (DHA).
Only two mammalian species have disproportionately large brains and advanced cognition — humans and bottlenose dolphins. Both depend on DHA.
You need DHA for neurotransmitter function and the development of your cognitive skills. Neurons just won’t fire without it, and memory retrieval is a struggle.
In fact, without DHA you couldn’t even grow a brain in the first place.
Dependency on DHA begins before you are born, and doesn’t end until you die. During pregnancy, a mother will pass more DHA to her baby than she keeps for herself. That supply is normally enough to last for the first three months of life.
After that, it all depends on diet. And that’s the worry: children who lack DHA are more likely to have increased rates of neurological disorders, including attention deficit hyperactivity disorder (ADHD), and autism.
Young and old alike
Deficiency of DHA can affect memory, even in young adults. A team of researchers investigated whether supplemental DHA could improve cognitive performance in young people who ate little fish. Fish is the main source of DHA.
In their study, reported in The American Journal of Clinical Nutrition in 2013, A total of 176 healthy adults aged 18–45 who had a low intake of DHA were given either a daily DHA supplement, or a placebo, for six months. At the end of the study period, they were tested for cognitive performance. The researchers concluded that:
“DHA supplementation improved memory and the RT (reaction time) of memory in healthy, young adults whose habitual diets were low in DHA.”
The issue is not that taking DHA supplements improves memory - it’s that lack of DHA worsens memory. This could lead to more serious problems later in life.
In old age, deficiency could lead to dementia. That’s because DHA accumulates in areas of the brain involved in memory and attention, such as the cerebral cortex and hippocampus.
The bad news is that although high DHA intake has been shown in studies to have a clear protective effect against risk of developing Alzheimer’s disease, supplementing with DHA once the disease has taken hold appears to have no benefit.
The only good, reliable source of DHA is seafood and oily fish. Oily fish includes salmon, trout, herring, sardines, fresh tuna, and anchovies. Meat and eggs make a small contribution, but only from pasture-fed animals.
Although some plant foods, most notably nuts and seeds, contain fats that can be converted into DHA, the conversion rate is so low it is considered negligible, and insufficient to meet the brain’s requirements.
So if you are not eating a lot of fish and seafood, or free-range, pasture-fed meat, what’s your source of DHA? I don’t wish to scare you, but perhaps it’s good to be a little scared at times.
It’s worth making sure you have a plentiful supply of DHA now, because
It’s all gone horribly wrong
There is no cure for dementia, including Alzheimer’s disease, the most common form. Cases are rising exponentially: death from dementia increased by almost 40% from 2005 to 2015.
It is estimated that the number of people across the globe living with dementia is 46.8 million, and this is predicted to double by 2030. Furthermore, cases of early-onset diagnosis — under the age of 65 — are also on the rise.
These statistics have nothing to do with genetics, or living longer.
The evidence suggests that the alarming rise in dementia figures has everything to do with diet, and some decidedly dodgy dietary advice.
It all began in the 1950s, when American biologist and pathologist Ancel Keys proposed a theory that saturated fat was the cause of heart disease. In 1952 he presented his “diet-heart hypothesis”. He blamed saturated fat (and cholesterol) for just about every chronic disease known to humanity, and promoted vegetable oils as a healthy alternative.
In 1961, Keys, now on the nutrition committee of the American Heart Association, convinced the other committee members that his diet-heart health theory provided the way forward for the good of the nation. From 1961 onwards, the AHA recommended that saturated fat should be substituted with vegetable oils made from corn or soya.
Look at any fast food product, snack or ready-meal and you will most likely see the presence of these vegetable oils on the label.
These oils are highly processed, and high in omega-6 fatty acids. Consumption of these omega-6 fatty acids has sky-rocketed, since they replaced saturated fat in our diet.
And therein lies the problem.
They replaced saturated fat in the diet, and they displaced DHA in the brain. It is generally accepted that we evolved on a diet containing more or less equal amounts of both groups. They compete for absorption, and when omega-6 exceeds omega-3, DHA is knocked out.
If you’re scared of saturated fat, don’t be. The evidence against saturated fat has always been more speculative than factual. That is why the British Medical Journal published, in 2015, a review of the most robust studies into the assumed harmful effects of saturated fat — including risk of death — and concluded that there was no evidence to support claims that saturated fat was in any way a risk factor.
As Julia Child also famously said: “If you’re afraid of butter, use cream.”
Humans are the only land mammals born fat. That makes us rather special. (Dolphins, like us, are born fat, and they are pretty intelligent too.) The fat is there to serve as a reservoir for fuel and growth for the rapidly developing brain.
(The role of cholesterol, a fat-like substance, is also important. So much so that I’ve written a separate article on the subject — see below ).
It may have had a bad rap for the last 50 years, but fat is still essential to the healthy functioning of the brain. You can change dietary advice as often as you like, but you cannot change human biochemistry.
In the meantime, remember that you have a magnificent specimen of evolutionary biology housed within your skull. Please look after it, and reconsider the fat-free option.