How the Food we Eat Makes us Happier
In today’s time, it is so easy to reach for foods high in refined carbohydrates. Thanks to the availability, the huge quantities and low prices, we live in a very different way to our ancestors.
They lived on carbohydrates from seasonal and indigenous vegetables and fruits. As hunter-gatherers, they foraged for natural, whole foods.
However, overindulging in modern, refined foods has led to diabetes and obesity. It may also increase the risk of depression.
The Study of GI
A study was done in the late ‘90s by the Women’s Health Initiative (WHI) in Columbia.
Over 93 000 postmenopausal women between the ages of 50 and 79 took part. Focusing on glycemic load and GI as risk factors for depression, they also looked into other measures of carbohydrate consumption.
Dietary fiber and carbohydrates were all classified separately to determine the effect they have. This included vegetables, legumes, whole grains, non-juice fruits, nuts and seeds and refined grains.
Using the Burnam 8-item scale for depressive disorders and a 3 year follow-up, depressive symptoms were measured.
3 years later the group was classified based on incidence of depression and available carbohydrate.
Those with higher GI quintiles and depressive symptoms were generally younger, less active and consumed a lot of transfat and unhealthy fatty acids.
They had a higher BMI and a lower intake of dietary fiber, fruit, seeds/nuts, legumes and vegetables. They were also associated with lower income, lower education and more stressful life events.
They, generally, also had less social support.
The Culprits
Depressive symptoms increased with intake of high GI foods and added sugars.
Analyses showed that high GI sugars glucose and sucrose increased depression incidence.
Low-GI sugar lactose showed lower odds for depression if eaten more often.
Foods with high fiber content lower the odds of depression because of this.
Where the sugar comes from determines how it affects the body. If the food source is high in fiber the carbohydrate metabolises slowly and the GI is lowered.
Increased consumption of non-juice fruit and vegetables also resulted in less depression incidence. This is due to the low GI content fruit has. Of our top 6 favourite fruits, apples, oranges, peaches and strawberries all have a low GI.
Grapes and ripe bananas have an intermediate GI and watermelon has a high GI.
The study didn’t find a relation between depression and dietary starch. Starches like boiled potatoes and white bread have a high GI.
Other starches like seeds, yams and legumes are rich in fiber and have a low GI. The study found that eating more whole grains led to lower depression incidence.
The opposite was true for refined and non-whole grains. Eating more vegetables also led to decreased depression incidence. This is odd because the potato is the most eaten vegetable in the United States.
The Good Guys
Some vegetables low GI:
- Tomatoes
- Head lettuce
- Leaf lettuce
- Sweet corn
- Onion
- Chili peppers.
(Eating legumes and nuts/seeds made no difference to the incidence of depression. This may be because it is seldom eaten.)
Vicious Cycle
The results could be seen as being contradictory.
Depressed people are thought to self-medicate by consuming carbohydrates. Sweet foods often provide temporary relief to the depressed.
While carbohydrates may help the synthesis of serotonin in the brain, the meal must be only carbohydrates to make this happen. There should also not be any left over protein in the gut.
Protein and sweet foods both blunt the tryptophan from assisting the synthesis of serotonin. Sweetened yogurts, ice cream, pastries, rice and bread can have enough protein to blunt an increase in tryptophan.
Further Studies
The only other study about the effect of GI on depression was done on pregnant women. It focused on those with postpartum depression 2-9 months after birth.
The differing results of this study might be due to the differences in study group. Postpartum depression being more acute in nature might have an influence on the results. The locations of the studies might have also had an influence, because the one focused on western eating habits and the other on a Japanese diet.
37.9% of women from the general UK population report persistent low blood sugar symptoms.
Also, insulin-induced hypoglycemia in mice, which lasted less than 2 hours, was shown to result in depressive like behaviours, which continued for 24-48 hours.
More Findings
By the year 2020, it is thought that depression will be the second-highest burden on society worldwide.
More regions are adopting the western diet and indulging in refined foods.
Consumption of these refined foods is showing a steady increase in the average dietary glycemic index (GI) in the US.
A high-GI diet increases the risk of inflammation, cardiovascular disease and insulin resistance. These conditions have been implicated in the development of depression.
High-GI diets spike and trough blood glucose. This can trigger hormone responses that cause symptoms like hunger, irritability and anxiety. This often manifests in fatigue, mood changes and cognitive impairment.
Conclusion
The results of this latest study suggest that postmenopausal women indulging in high-GI diets could be at risk of depression.
Trials should be done to determine if diets rich in low-GI foods, which are high in fiber, could prevent depression in postmenopausal women.
