The link between diet and depression: 5 important facts
Depression is a debilitating and potentially life-changing condition. If you receive a diagnosis, you can expect to be treated with medications that alter brain chemistry, or prescribed some form of talking therapy. But the traditional approach may be about to change: the real medicine of the future might just be food.
Mental health issues such as depression and anxiety now feature more prominently in the media than ever before. That’s a good thing — the stigma that once deterred sufferers from openly discussing their issues is fading fast. We read about celebrities who speak frankly of their battle with their internal demons, and realise that it is ok to talk about these matters.
This new understanding is a welcome move in the right direction. However, less welcome is the alarming rise in the number of people diagnosed with depression and anxiety.
According to the World Health Organization, depression is now the leading cause of disability in the world. In the US, 13% of the population take anti-depressants. One in four people will experience a mental health disorder in any given year, according to the National Alliance on Mental Illness.
Diet: the link hiding in plain sight
Depression is a disease of the brain, and the brain is, despite its mysterious complexity, a wobbly, three-pound mass of fat, protein, cholesterol, and water.
Nutrients from food pass in and out of the brain, directing activity and maintaining balance. While scientists look for ever more effective treatments to medicate those with depression (and other mental health issues), the real cause of the problem is often hiding in plain sight.
Diet and nutrition can influence mood and cognitive function in two ways. First, through an excess of harmful dietary components, and second, through deficiency of essential nutrients. Here are five main ways that diet affects mood.
1. Sugar intake
Last year (2017), the journal Scientific Reports published a study which looked into the link between sugar intake and depression. The researchers found that men who consumed 67 grams or more of sugar every day were 23% more likely to suffer from depression over the following 5 years, than men who consumed less than 40 grams of sugar each day.
It’s not difficult to consume the amount of sugar associated with depression. Just one can of sugar-sweetened soda may contain around 10 teaspoons — 40 grams — of added sugar.
Sugar and sugary foods are a significant factor in the onset of type 2 diabetes, and it is now well established that type 2 diabetes is associated with depression. Depression is common, even at the pre-diabetic stage, when blood sugar starts to go awry.
“Depression is at least twice as common among those with diabetes compared to the general population”
In 2015, the World Health Organization issued guidelines that sugar should make up no more than 10% of total daily calorie intake. The WHO added that better still, aim for no more than 5%, or around 25 grams (6 teaspoons) maximum per day.
2. Fish gives you brains
Certain fats are essential to the normal functioning of the brain, which is 60% fat. This organ is rich in fatty acids, one in particular.
That fatty acid is docosahexaenoic acid (DHA). It is required for brain growth and function, and is the most abundant fatty acid in the brain. Lack of DHA is associated with a number of psychiatric disorders, including depression.
DHA is part of the omega-3 family of fatty acids. Although some plant foods, mainly nuts and seeds, contain omega-3 fats, they do not contain DHA. Some DHA is found in meat from grass-fed animals and free range eggs, but nothing like the amount in oily fish.
Oily is good
The only meaningful source of DHA is oily fish, such as salmon, mackerel, herring, trout, anchovies and sardines.
Therefore, without a regular diet of oily fish, or taking fish oil supplements, deficiency is quite likely.
3. SAD without vitamin D
Vitamin D also plays an important role in regulating mood. It is called the sunshine vitamin because the skin makes it in the presence of sunlight.
Most people associate vitamin D with calcium absorption and bone health. Less well known is the role that this vitamin plays in brain health — deficiency can cause depression, and in later life may also cause memory loss.
There is also an association with seasonal affective disorder (SAD), a type of depression that occurs more commonly during the dark winter months. Although this vitamin can be stored in the body, storage capacity is limited and does not extend through the winter.
Although the body makes most of its vitamin D supply, there are some dietary sources that can be useful during the winter months. Oily fish such as salmon provides reasonable amounts, and eggs and cheese can also make a small contribution.
Unsurprisingly, deficiency of vitamin D is rife. A study of nearly 7,500 British people revealed that almost 90% were affected by lack of vitamin D during winter and spring. All year-round, 60% had suboptimal levels. Because lack of this vitamin is so common, the experts now advise that everyone takes vitamin D supplements during the winter months.
For more information about the important role of vitamin D, see this article — Ten reasons why you must take vitamin D.
4. The role of zinc
Another significant nutrient when it comes to diet and depression is the trace element zinc. Zinc is highly concentrated in the brain, yet the World Health Organization estimates that around a third of the global population is zinc-deficient.
Studies have shown that zinc supplementation can be effective in improving the symptoms of depression. It makes sense, considering that researchers believe zinc deficiency plays a role in the development of the disease.
“.. there is increasing evidence linking depression or depression-related changes in brain function or cognitive performance to zinc ion availability.”
The best dietary sources of this mineral are meat, seafood and eggs. Beware a diet high in cereal grains, especially wheat. That’s because these grains contain phytates, chemicals that prevent the absorption of zinc and other minerals in the digestive system. Instead of entering the blood, much of the mineral content passes straight through the gut.
5. Vitamin B12 deficiency: Beware homocysteine
You may have heard of homocysteine, an amino acid which, at high levels in the blood, is a risk factor for cardiovascular disease. Unfortunately, it’s a risk factor for much more, and plays a key role in the link between diet and depression.
High homocysteine arises when there is a deficiency of vitamin B12 and folate, both of which are crucial to the brain. Vitamin B12 and folate deficiency are commonly found in patients with psychiatric disorders. Folate is widely found in leafy green vegetables, such as spinach, cabbage and broccoli. Vitamin B12 is found exclusively in animal based foods: meat, fish, eggs, dairy. Meat and fish have much higher concentrations of B12 than eggs and dairy, so it is important that both vegetarians and vegans supplement their diets with this vitamin.
It is widely acknowledged that chronic conditions such as heart disease, type 2 diabetes and cancer are often rooted in diet. Never before have we consumed so much processed, sugar-laden, nutrient-deficient junk food. Yet bizarrely, although it is now widely acknowledged that depression is a serious, debilitating health condition, the link with diet is rarely made. Although the causes of mental ill-health are many and complex, it may be time to acknowledge that if diet is the cause, it may also be the solution.