It’s not uncommon to crave particular foods when a certain mood strikes. Whether it’s a coffee on waking or a 3pm chocolate hankering, most of us experience food cravings at one time or another. While there’s little evidence to account for any deeper meaning for these cravings – other than perhaps a drop in blood sugars – can the foods we choose to eat actually impact our emotions?
A bit of background on the brain
Last year, one of the most interesting units I studied covered the connection between diet and the brain. Even without delving into the specific evidence, it does make logical sense: given the myriad ways our brains can be affected by alcohol, caffeine and other substances, it’s reasonable to assume that diet may also make an impact.
The human brain is a lipid-rich, fuel-hungry machine, consuming 20% of the energy we take in, and just like our bodies, it can show signs of nutrient deficiencies. Not only that, but the neurotransmitters released by the brain (dopamine, serotonin) are influenced by diet. These chemical messengers can directly affect our mood, sleep quality and cognitive ability, so good nutrition is just as important for our bodies as it is for our minds.
So, which are the most influential nutrients for our brain?
The main contenders
Iodine: In my previous post on iodine, I highlighted the potential links between deficiency in children and poor school results. This is a very real concern, however even more worrying is the cognitive effects such deficiency could have on pregnant women’s unborn babies. Professor Creswell Eastman, vice chairman of the International Council of Iodine Deficiency, says up to 50% of pregnant women could be iodine deficient, which can cause a significantly reduced IQ in children. One major step is being taken to eradicate iodine deficiencies worldwide, in the form of universal salt iodisation; however, a decrease in salt usage, along with a growing preference for unfortified sea salt, put a question mark over the seemingly logical initiative’s success.
Omega 3 Fatty Acids: A huge proportion of the brain is made up of fatty acids – up to 60%, in fact. These mainly consist of the two polyunsaturated fatty acids, Arachidonic Acid (AA, or Omega 6) and Docosahexaenoic Acid (DHA, or Omega 3), and research has shown many links between their levels and mental health.
Until recently, AA was the big focus, with many pushing for people to increase the amount of Omega 6 in their diets. However, when it was discovered that a high level of DHA was concentrated in human grey matter, the paramount importance of the Omega 3 fatty acid became apparent. In examining the effects of animals lacking in dietary Omega 3, it was found that levels of the DHA in the brain were significantly reduced. These same animals also showed neurons of decreased size; changes in learning, memory, hearing and smell; and an increase in depression and aggression.
Evidence has shown that the body’s reaction to a lack in Omega 3 is similar to the physical effects of depression: in both cases, the body exhibits decreased dopamine expression, blood flow and glucose metabolism, as well as an increase in the production of pro-inflammatory chemicals in the brain. Not only that, but the addition of DHA to the diet has shown the ability to counteract these symptoms.
Interestingly, the mechanisms of traditional antidepressant medications and Omega 3 are similar. They both compete with AA (Omega 6) to reduce the production of chemicals that increase inflammation and other symptoms of depression.
Discoveries such as this, as well as statistics demonstrating a link between worldwide seafood consumption and lowered depression rates, have prompted research into the efficacy of using Omega 3 as an additional treatment. One double blind, placebo-controlled trial on 30 medicated bipolar patients aged between 18-65 showed that depressive and manic episodes were reduced with the aid of Omega 3 supplementation.
Obviously further research is required before a piece of salmon will be prescribed over traditional medication, but it’s clear that the current recommendation to consume oily fish (a great source of Omega 3) twice a week is well warranted.
Carbohydrates: Consuming a high-carbohydrate meal leads to heightened levels of the amino acid tryptophan in the brain. This amino acid is then converted into the neurotransmitter serotonin, resulting in a relaxed, sleepy, calm mood. Choose good quality carbohydrates such as whole grains, legumes and vegetables.
Glycaemic Index: Not all carbohydrates are created equal, and it appears that certain types are better others in terms of sustained energy and mental capacity. Glycaemic Index (GI) describes the rate at which the carbohydrates are digested and absorbed. Ranking between 1-100, those of a high GI; such as most processed foods, potato, many popular breakfast cereals, white bread, rice and pasta, rapidly raise blood sugar, while those of a low GI such as porridge, grainy breads, rice noodles, beans, yoghurt and milk impart a slower released energy. One recent study compared the cognitive functions of adolescents a low-GI breakfast, a high-GI breakfast, and nothing, with results supporting the idea that low GI may positively influence the brain. The study showed that a low GI breakfast enabled faster response rate and accuracy than both high GI and breakfast omission, suggesting that certain carbohydrates may bear superior cognitive effects than others.
Protein: Conversely, chowing down on a meal high in protein such as turkey, fish, chicken and eggs, leads to heightened tyrosine (amino acid) levels, signalling increased dopamine and/or epinephrine levels in the brain. An increase in these neurotransmitters elevates the rate of mental alertness and concentration. However, its also been said that a high protein meal will decrease tryptophan levels (those increased by carbohydrate consumption), which can lead to a negative mood and decreased learning!
Cocoa: Despite overblown reports of chocolate’s ‘health benefits’, natural compounds in cocoa, called flavanols, have proven not only cardioprotective, but also beneficial in cognitive health. Cocoa first became a food of interest when researchers noticed the unexpectedly good health of the Kuna Indians of Panama. The low incidences of cardiovascular disease, cancer, blood pressure and diabetes were decidedly not a result of genetics, as the Kuna Indians living on the mainland showed a significant rise in these lifestyle-related diseases. Admittedly, the islanders’ diet is of better quality, consisting of more plant foods and fish and less meat; however, another noteworthy difference is the high rate of cocoa drunk by islanders, who consume on average around 4 cups of cocoa a day made with raw cacao beans.
It’s been shown that this cocoa consumption increases blood flow to brain, theoretically leading to positive moods. Studies have also demonstrated improved mental performance and decreased fatigue during periods of intense mental concentration following cocoa consumption. But before you stock up on Freddo Frogs, it’s worth mentioning that these benefits are only significant when cocoa is consumed in the raw form of cacao, which is present in higher amounts in dark chocolate. Once high levels of milk and sugar are added to the ever-popular dairy milk, the benefits are next to none.