Research has been conducted in Australia to study the association between poor diet and the development of depression and anxiety in women. The study showed that there was “an association between habitual diet quality and the high-prevalence mental disorders”. 
The SAD diet, otherwise known as the Standard Australian Diet is one of high energy and low nutrient content that is becoming increasingly prevalent in today’s society. Characteristically, it contains high levels of processed and refined foods and saturated fats, sugar and soft drinks. It is this pattern of poor eating that has been linked to the development of depression and anxiety.
Research studies prove that a diet high in sugar, fat and processed foods will lead to obesity, and is likely to lead to depression. With obesity come other chronic illnesses too, including cardiovascular disease, diabetes and cancer.
A balanced diet on the other hand, has been shown to improve the risk of developing depression, and is often a recommendation to help improve the outcomes of treatment for depression and anxiety once diagnosis has been confirmed.
Soft drinks are one of the major contributors to obesity, and energy drinks seem to be the worst of a bad bunch. With their high caffeine content, they appeal particularly to teenagers, and some sources are reporting them as a ‘gateway’ to other forms of drug dependence. In Australia, there have been calls for regulation on these drinks and for the packaging to include warning labels, not unlike alcohol.
An American paediatric endocrinologist has discovered that fructose (a sugar that is found in particularly high amounts in soft drinks and confectionary) may create habitual dependence, similar to alcohol. In fact, fructose has been called “alcohol without the buzz” by researchers. It may have the ability to adversely affect our mood, emotions and behaviour.
It is important to remember however, that we control the food we put in our mouths. A bad diet does not necessarily have to be a death sentence. We all have the ability, once properly informed, to make good choices that will help to promote better health and lifestyle for us and for our families. A balanced diet, one that includes fresh fruit and vegetables, nuts, lean meat, fish, wholegrains and legumes, provides our body with not only the nutrients it needs to keep us functioning well physically, but also mentally and emotionally too.
Am J Psychiatry.  J Adolesc Health. 2013 Apr 30. pii: S1054-139X(13)00141-9. doi: 10.1016/j.jadohealth.2013.03.007  Adv Nutr. 2013 Mar 1;4(2):226-35. doi: 10.3945/an.112.00299
2010 Mar;167(3):305-11. doi: 10.1176/appi.ajp.2009.09060881. Epub 2010 Jan 4