How diet and depression are linked
There are many ways - here are five of the most common
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 there is also a third way.
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Mental health issues are in the spotlight more than ever, and rightly so. Whereas those afflicted with mental ill-health were once also afflicted with the stigma that came with their illness, and were often treated in a derisory or dismissive manner, they are now afforded the same consideration and dignity as those suffering from any physical condition.
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 a leading cause of depression across the world.
In the US, anxiety disorders affect 40 million adults – over 18% of the population. Furthermore, over 7% of the population has had ‘at least one major depressive episode’.
Hiding in plain sight
Depression is a disorder 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 cross the blood-brain barrier, 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 may go unaddressed. The real cause may, or may not, be diet-related. So why not investigate?
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 directly affects mood.
1. Sugar overload
In 2017, the journal Scientific Reports published a study that looked into the link between sugar intake and depression in men. The researchers found that those 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”
2. Fish for 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), part of the omega-3 family of fatty acids. 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.
The best source of DHA is oily fish, such as salmon, mackerel, herring, trout, anchovies and sardines. Grass-fed meat is also a reasonable source. Although nuts and seeds and other plant foods are often cited as an alternative plant source of omega-3 fats, that claim is misleading. Although the body can make some limited DHA from plant sources, its ability to do so is so poor that it is effectively negligible.
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 usually occurs during the dark winter months. Although this vitamin can be stored in the body, storage capacity is limited and does not extend throughout the winter.
Fortunately there are a few 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 see the article below.
4. The role of zinc
Another significant nutrient involved in mood regulation is the trace element zinc. Zinc is highly concentrated in the brain, or should be: the World Health Organization estimates that across the globe, inadequate dietary zinc affects 15%-20% of the global population.
Studies have shown that zinc supplementation can be effective in improving the symptoms of depression.
“.. 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, plant compounds that reduce 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
Homocysteine is an amino acid and raised levels of homocysteine in the blood is an indication of B12 deficiency. The symptoms of B12 deficiency include depression and anxiety.
Homocysteine is created during the metabolism of the amino acid methionine to cysteine. This process is regulated by a trio of B vitamins: B12, folate (B9) and vitamin B6 (pyridoxine), all working together. To lower blood levels of homocysteine, you simply need a regular intake of these three vitamins.
Low levels of B6 are uncommon because this vitamin is widely distributed in food. Folate deficiency is more widespread and can be reversed by eating plenty of leafy green vegetables, such as spinach and broccoli, though the richest dietary source is offal, especially beef liver. Pulses (especially lentils, black-eyed peas, mung beans), avocados, citrus fruits and eggs are also a good source.
Vitamin B12 is the tricky one and the one most likely to cause a rise in homocysteine if it’s missing from the diet. It is found naturally only in animal-source foods: meat, fish, eggs, dairy.
For details of the damage that vitamin B12 deficiency can do, see:
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.
Nevertheless, there is still little, official acknowledgement of the role of diet in the development of mental ill-health. Although the causes of mental ill-health are many and complex, it is wise to consider that that if diet is the cause, it may also be the solution.
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