Any of us who have ever turned to junk food over a stretch of time came to realize it doesn't make us feel our best.
Whether our poison is salty potato chips or indulgent candy, cakes or other sugary desserts, we know it's not good for us physically. And we now know, too, that it's not good for us emotional and mental health either.
And now a new study from Columbia University that was published in the American Journal of Clinical Nutrition shows a link between eating junk food and depression.
Yes. Constantly munching on candy bars, drinking sugar-laden soda, and eating foods high in carbs can alter our moods without us even realizing it. This is in addition to fats and sugars causing cognitive impairment, which we learned from another study this week.
The Columbia study looked at post-menopausal woman, but James Gangwisch, an assistant professor at Columbia's department of psychiatry, says he always suspected that eating a lot of sugars affected men as well.
"We expected that people who are depressed are more likely to eat more sweets and are known to crave sweets, and we excluded all the people who are depressed already," Gangwisch says of the study. "We were looking at the relationship of the glycemic index of the diet to new cases of depression."
The index measures how much people's blood sugar is raised by the particular foods they eat.
Gangwisch's team took measurements from a food study of 70,000 women, none of whom were depressed at the start. It looked at their diets and levels of depression based on the questionnaire and then a three-year follow-up.
The results were clear that those who ate foods with a higher glycemic index were at risk of developing depression, and those who ate foods with lower levels of sugars had a lower rate of depression, Gangwisch says.
Lactose from dairy products has a low glycemic index and was associated with being protective against depression, he says. The biggest trigger was added sugars rather than just total sugars and carbs.
"Eating a higher fiber intake with fruits and whole foods, vegetables and grains were protective of developing against depression," Gangwisch says. "Refined grains increased the risk of developing depression."
What happens if you eat foods with a lot of sugar or drink a soft drink with a lot of sugar that will raise your blood sugar that prompts the body to release insulin to lower the level, Gangwisch says. The body releases counter measures to help increase the blood sugar, and if the sugar supply to the brain isn't enough, it can affect your mood.
Fruits have sugars but are low in the glycemic index. The fiber associated with it compared to fruit juices slows down the rate blood sugar is released in the blood stream. That keeps the blood sugar at an even keel and prevents spikes and troughs, he says.
"When people eat candy it leads to craving to more candy," Gangwisch says. "Your blood sugar can go out too high, and insulin is sent out. It can make you feel hungry once the blood sugar goes low again and lead to cravings for more. You end up on a rollercoaster."
Eating a bad diet high in sugars can also trigger cardiovascular disease that's linked to depression. That is also the cause for resistance to insulin.
So when it comes to your mood, leave out the candy bars, Danishes, cakes, and other foods that you can check on for their high glycemic index even though some studies have found benefits in chocolate regarding heart health.
As for those people who are already depressed and weren't part of a controlled study, Gangwisch says you can't draw the conclusion that the diet is definitely the cause. But when you see new cases added over time to those who became depressed from that junk food diet, it strengthens the argument that diet may be causing depression in people.
"There have been experimental studies that found that when given higher GI diets, it negatively affect mood pretty quickly," Gangwisch says. "There is a mouse model study that induced low blood sugar with insulin - the depression began in a few hours and lasted 24 to 48 hours."
Gangwisch says the advice we've gotten for years still holds true: Eat a healthy and balanced diet, and that not only leads to better physical health but mental health as well.
"Most any nutritionist will tell you avoid too many sweets and higher refined carbohydrates, and so the results of our study add to that," Gangwisch says. "We should have a good, balanced, and healthy diet with whole fruits and vegetables that are natural and seasonal."