CHAPTER 13
Your Brain is Built on Fat
PART 1
Fat for Thought
“A fat baby is a cute baby,” says Tom Brenna, professor of nutritional sciences at Cornell University. “And the real question is, why do humans make fat babies? Chimpanzees don't, baboons don't. Humans are the only primates born with fat. And we put that fat on for very good reasons.” We do it for our brains.
As important as fats are throughout life, they may be most critical to fetal and infant development, especially when it comes to the brain and the rest of the nervous system. The most rapid brain growth occurs during the first year of life, with the infant’s brain tripling in size by the first birthday. “Humans have been called the animals with the runaway brains,” says Brenna. READ MORE
Our Brainy Appetite for Fats
When it comes to brains, fat is also a critical building block. “The human brain is the fattiest organ in the body,” says Brenna. “More than 50% of the dry weight of the human brain is fat. That surprises people, but it's true.” Probably not so surprising is that brain fat is not inert fat. It is structural fat contained in the membranes of neural cells and a key component of the synapses, or connections, between neural cells.
Not only is the brain a metabolically active and therefore hungry organ, it is also a picky eater. DHA and ARA are two specific fatty acids that are critical to neurological development. They are both polyunsaturated fatty acids found in breast milk. Neither are strictly “essential” fatty acids since they can be produced in the human body. DHA can be made from the omega-3 fatty acid ALA (alpha-linolenic acid) and ARA from the omega-6 fatty acid LA (linoleic acid). But they are produced in such low quantities that dietary sources are critical, which is why breast milk contains both.
Evidence of the fats’ function can be found in the locations in which they are concentrated: DHA and ARA make up a third of the fatty acids found in brain grey matter and up to two-thirds of those found in the eye's retina. As important as they are, they still actually make up only a miniscule fraction of breast milk. LESS
PART 2
DHA in Early and Late Life Stages
Researchers have also discovered that the amounts of these fatty acids found in breast milk can vary by region. Breast milk levels of DHA, which is found in fish oil, are believed to be due to differences in maternal diet. Breast milk with the highest concentrations of DHA came from women who lived in such seafood-eating places as Japan and coastal China. Women who lived in countries such as the Sudan and the U.S. had much lower levels of DHA in their breast milk.
Research has shown that infant diets deficient in DHA are linked to problems or delays in brain development. Increased intelligence of breastfed infants has been linked to the increased DHA content of human milk. Other studies suggest that children with poor school performance (due to attention deficit disorders) have insufficient essential fatty acids in their diet.
Though there is still a great deal to learn about exactly how fatty acids are important in brain development, the evidence is persuasive enough that most infant formulas are now fortified with both DHA and ARA. READ MORE
Brain Health in the Elderly
At the same time that researchers are striving to find out what dietary elements are important for enhancing brain growth and development in the beginning a person’s life, they are also trying to discover what dietary elements might prevent or at least delay the deterioration of cognitive function at the end that person’s life.
Key fatty acids are also believed to be involved, particularly the omega-3 fatty acid DHA, which is the reason that fish oil supplements are being aggressively marketed these days as a way to stave off brain aging. Can omega-3 fatty acids prevent or treat cognitive decline and dementia?
Many experts believe there is reason for cautious optimism. But the scientific jury is still out and the research results are mixed so far. A recent study conducted by the National Institute on Aging found that DHA did not slow the progression of cognitive decline and therefore did not support the routine use of DHA in patients Alzheimer’s. Another study showed a positive result on one test of memory and learning, but the effect was in healthy older adults, not people with Alzheimer's.
In some studies, it appears that certain individuals with mild forms of Alzheimer’s disease did respond to treatment. One reason might be that these individuals were deficient in these key fatty acids. Another reason might be genetics. As in breast cancer, some forms of Alzheimer’s might have a very strong genetic component and therefore be more difficult to treat. LESS
PART 3
Fish Oil and Depression
Omega-3 fatty acids have also been investigated as a treatment for psychiatric disorders such as depression, psychosis and bipolar disorder. Here too, while the research is promising, the results so far are not conclusive. Interestingly, depression is less common in countries with higher fish consumption. READ MOREStudies have found that fish oil seems to improve symptoms of depression, but as with studies of omega-3s and Alzheimer’s, it is isn’t clear whether treatment with fish oil is effective for depressed patients in general or only for those with abnormally low levels of these omega fatty acids. It is also unclear whether fish oil supplements work on their own or are effective only with conventional antidepressant treatment.
So are omega fatty acids the magic brain food? No. And it’s not very likely that there will be a single super brain food or brain supplement. Many recent studies, in fact, are exploring the possible benefit of combinations of fatty acids and vitamins. Which also points to a broader principle: when it comes to a healthy diet, there is rarely “one” reason to eat a particular food. Eat this vegetable for your liver, that fruit for your thyroid, this fat for your hair, or that vitamin for your skin.
The bottom line will likely remain to be that you have a whole body of reasons to eat according to sound, healthy principles. LESS