(Vegetarian) nutrition and depression

Lifestyle illnesses have an obvious connection with nutritional choices. It's not so far-fetched that also nutrition and depression might have a strong correlation. It's logical to think that improper nutrition can lead to poor brain function, as the brain relies on sufficient nutrition like the rest of the body. There are many reports that people with clinical depression suffer from malnutrition as they can't take proper care of themselves. Nutrient deficiencies themselves could also lead to abnormal brain function. So why don't health care professionals pay more attentions to patients' eating habits? 

The neurobiological base of depression is not well known, albeit it has been detected that the metabolism of the neurotransmitter serotonin is closely linked to depressive symptoms. A lower level of serotonin activity has been detected in those who suffer from a major depressive disorder. Thus substances that selectively increase the neurotransmission of serotonin have been ascertained to been effective antidepressants.

Serotonin synthesis of the brain is dependent on tryptophan, a precursor molecule to serotonin, found in plasma. Dr. P. J. Cowen and his crew concluded in their research over 20 years ago that there might be a strong correlation between tryptophan intake and depressive symptoms. Sleeplessness, anxiety or irritability may indicate low tryptophan levels. The recommended daily intake (RDI) of tryptophan is about 240 mg. 100 grams of meat protein contains 1300 mg of tryptophan. Legumes contain about 2 % of protein, but for a vegetarian to satisfy the RDI of tryptophan they should eat about 1 kg of legumes a day. This arouses the question of incidence of depression in those following a special diet. The best sources of tryptophan for a ovo-lacto-vegetarian are TVP and cheese.

Carbohydrates play an indirect, yet important role in brain function. Food rich in carbohydrates triggers the release of insulin in the body, which simultaneously triggers the entry of tryptophan to the brain, which needs sugar to work normally. It is suggested that low glycemic index (GI) foods are more likely to provide a moderate but lasting effect on brain chemistry due to more stable insulin release.

Depression has also been linked with low tyrosine levels. Tyrosine is another amino acid, a precursor to neurotransmitters and hormones, forming catecholamines such as dopamine, noradrenaline and adrenaline. The lack of tyrosine can cause symptoms such as lethargy, fatigue, sleeping too much or feelings of immobility. Tyrosine occurs naturally in high protein foods, which again might be an issue with a poorly constructed vegetarian diet.

There have been numerous studies on the benefits of two omega-3 fatty acids, DHA and EPA in treating and preventing brain related disorders. EPA is conversed to leukotrienes, prostaglandins, and other chemicals required by the brain. Both EPA and DHA influence neuronal signal transduction. The best source of omega-3 fatty acids is fish oil. Flaxseed oil and nuts are the best choice for a vegetarian.

Also many other micronutrient deficiencies have been linked with depression. Low levels of especially B6- vitamin and folate have been detected in depressed subjects, though it's not yet clear whether poor nutrition, as a symptom of depression, causes folate deficiency or primary folate deficiency produces depression and its symptoms. Lower levels of iron, zinc, and selenium tend to be more common among depressed than non-depressed persons. Vegetarians are at risk of vitamin B deficiencies due to the lack of meat in their diets, meat being the highest source of B-group vitamins. Vegetarians also have often lower iron levels than omnivores, as haem iron is absorbed more easily by the intestine than iron obtained from plants.

A plant-based diet has many health-promoting factors, protecting against chronic diseases such as cancer, cardiovascular disease and diabetes, so in no way should vegetarianism be connected to poor nutritional value. Nor should it be seen as a possible cause for bodily disfunction. The above text only shows that vegetarians should pay extra special attention to what they consume (noting this aspect only after my research). It should be believed that sufficient eating habits help in healing and preventing depression. Thus health care professionals should be educated in nutrition intervention, as it could be an inexpensive, safe and easy way to cut the increasing number of statistical cases of depression.