Transcript: Antioxidants and Depression
According to the latest from the CDC, the rates of all of our top ten killers have fallen or stabilized except for one: suicide. Accumulating evidence indicates that oxidative free radicals may play important roles in the development of various neuropsychiatric disorders, including major depression.
For example, in a study of nearly 300,000 Canadians, greater fruit and vegetable consumption was associated with lower odds of depression, psychological distress, self-reported mood and anxiety disorders and poor perceived mental health. They conclude that since a healthy diet comprised of a high intake of fruits and vegetables is rich in antioxidants, it may consequently dampen the detrimental effects of oxidative stress on mental health.
But that was just based on asking how many fruits and veggies people ate. If you measure the levels of carotenoid phytonutrients in nearly 2,000 people across the country, a higher total blood carotenoid level was associated with a lower likelihood of elevated depressive symptoms, and there appeared to be a dose-response relationship, meaning the higher the levels, the better people felt.
Lycopene, the red pigment predominantly found in tomatoes, but also present in watermelon, pink grapefruit, guava, and papaya, is the most powerful antioxidant amongst the carotenoid family. In a test tube, it’s about 100 times more effective at quenching free radicals than vitamin E, for example.
And in a study of about a thousand older men and women, those who ate the most tomato products had about half the odds of depression. The researchers conclude that a tomato-rich diet may have a beneficial effect on the prevention of depressive symptoms.
Higher consumption of fruits and vegetables has been found to lead to a lower risk of developing depression, but if it’s the antioxidants, can’t we just take an antioxidant pill? No; only food sources of antioxidants were protectively associated with depression. Not antioxidants from dietary supplements. Although plant foods and food-derived phytochemicals have been associated with health benefits, antioxidants from dietary supplements appear to be less beneficial, and may, in fact, be detrimental to health. This may indicate that the form and delivery of the antioxidants are important. Alternatively, the observed associations may be due not to antioxidants, but rather to other dietary factors, such as folate, which also occur in fruits, vegetables, and plant-rich diets.
In a study of thousands of middle-aged office workers, eating lots of processed food was found to be a risk factor for at least mild to moderate depression five years later, whereas a whole food pattern was found to be protective. Yes, it could be because of the high content of antioxidants in fruits and vegetables but could also be the folate in greens and beans, as some studies have suggested an increased risk of depression in folks who may not have been getting enough.
Low folate levels in the blood are associated with depression, but since most of the early studies were cross-sectional, meaning a snapshot in time, we didn’t know if the low folate led to depression, or the depression led to low folate. Maybe when you have the blues, you don’t want to eat the greens.
But since then, a number of cohort studies were published following people over time, and low dietary intake of folate may indeed be a risk factor for severe depression–as much as a threefold higher risk. Note this is dietary folate intake, not folic acid supplements, so they were actually eating healthy foods. If you give people folic acid pills they don’t seem to work. This may be because folate is found in dark green leafy vegetables like spinach, whereas folic acid is the oxidized synthetic compound used in food fortification and dietary supplements because it’s more shelf-stable, but it may have different effects on the body, as I previously explored.
These kinds of findings point to the importance of antioxidant food sources rather than dietary supplements. But there was an interesting study giving people high-dose vitamin C, also known as ascorbic acid. The vitamin C, but not placebo, group experienced a decrease in depression scores, and also greater FSI. What is FSI? FSI evidently stands for penile-vaginal intercourse, an acronym that makes no sense to me.
But evidently, high-dose vitamin C improves mood and intercourse frequency, but only in sexual partners who don’t live with one another. In the placebo group, those not living together had sex about once a week, and those living together a little higher, once every five days, but with no big change on vitamin C. But for those not living together on vitamin C, every other day! The differential effect for non-cohabitants suggests that the mechanism is not a peripheral one, meaning outside the brain, but a central one—some psychological change that motivates the person to venture forth to have intercourse. The mild antidepressant effect they found was unrelated to cohabitation or frequency, so it does not appear that the depression scores improved just because of the improved FSI.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
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