Everybody knows that dietary fiber (vegetables, fruits, beans, and other plant-based foods) is good for health, but how many people actually voluntarily eat it?
Fried chicken, barbecue, and hot pot are the favorites of young people, focusing on eating meat. When it comes to eating vegetables, some people say, “Doesn’t the lettuce in my burger count?” As for eating fruits, it’s even more rare; have you seen many men voluntarily munching on an apple?
Some people wonder why it seems like there are more people with depression these days. Is it because of increased life stress and improper diet? This is not unfounded; many studies have found that low intake of dietary fiber may indeed be related to the risk of depression.
▍Is this food generally not liked by the Chinese people? [1-4, 6]
When it comes to the intake of dietary fiber by Chinese people, the simple phrase is: Nobody meets the standard!
According to the “Chinese Residents’ Dietary Fiber Intake White Paper 2016,” the average daily per capita intake of dietary fiber is about 13g (recommended amount is 25g/day), with over 95% of people having an intake lower than the recommended level!
The “Healthy China Action (2019-2030)” also points out that on average, Chinese women consume 13g of dietary fiber per day, while men consume 14g per day, which is still insufficient. Elderly people are the main group lacking in dietary fiber.
Eating dietary fiber prevents depression?
A 2022 Australian study examined the relationship between dietary fiber intake and depression and anxiety, conducted a meta-analysis (integrating and analyzing the results of multiple independent studies to provide more reliable conclusions).
Systematic searches were conducted on data up to May 2021, focusing on depression. The study compiled 15 studies on adults and 3 studies on adolescents.
This meta-analysis found that if adults consume enough dietary fiber, the incidence of depression can be reduced by 10% (equivalent to 10 fewer cases of depression per 100 individuals).
For adolescents, the effect is even more pronounced, with a 57% reduction in the incidence of depression (equivalent to 57 fewer cases per 100 individuals).
So, how much dietary fiber should one consume? Research shows that for every additional intake of 5g of dietary fiber, the risk of depression in adults can be reduced by 5%. Among these, vegetable fiber and soluble fiber have the best effects, with vegetable fiber reducing the incidence of depression by 27% and soluble fiber by 20%.
However, cereal fiber, fruit fiber, and insoluble fiber have slightly less effect on depression, but they still have some impact.
In conclusion, consuming more dietary fiber, especially vegetables and soluble fiber, helps reduce the risk of depression in adults, and this effect increases with higher intake levels.
▍Domestic studies have also found a link between dietary fiber and depression[7-8]
A domestic study aimed to explore the relationship between total dietary fiber intake, vegetable fiber, fruit fiber, cereal fiber intake, and depression.
A study conducted at Qingdao University selected data from the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2014.
(Don’t be surprised why American data was used for the study; the data collection method is strict and publicly available, whereas some countries’ health and nutrition data are not public, and data acquisition requires a complex application process.)
This study included 16,807 adults aged 20 and above, with a 9.41% depression prevalence rate. The data was collected through questionnaires, physical measurements, and laboratory tests, including demographic information, lifestyle characteristics, physical conditions, blood pressure, blood sugar, and medical history. Dietary information was obtained through two 24-hour dietary recall interviews, and depression symptoms were evaluated using the Patient Health Questionnaire Depression Scale.
The researchers compared the initial characteristics differences between depression and non-depression patients using statistical methods such as χ² test, t-test, or rank-sum test.
Further, univariate and multivariate logistic regression analyses were used to explore the relationship between total dietary fiber, vegetable fiber, fruit fiber, cereal fiber intake, and depression. Restricted cubic spline models were also used to assess the dose-response relationship between these dietary fiber intakes and depression.
To delve into the relationship between various fibers and depression, the study grouped the population according to different age groups (<45, 45-64, >64 years), gender (male and female), and total energy intake levels (low, normal, high energy intake groups) for subgroup analysis. The aim was to determine whether total dietary fiber and different sources of dietary fiber are associated with depression in these different subgroups.
The results showed that consuming more dietary fiber, vegetable fiber, fruit fiber, and cereal fiber is associated with a reduced risk of depression.
Specifically, in univariate analysis, individuals who consumed dietary fiber and other fibers had their depression risk reduced by 35%, 42%, 42%, and 56%, respectively.
In multivariate analysis, including ethnicity, marital status, education level, income, body mass index, daily energy intake, smoking, alcohol consumption, work and leisure activities, hypertension, and diabetes.
The results showed that increased intake of total dietary fiber, vegetable fiber, and fruit fiber was still associated with a reduced risk of depression by 59%, 58%, and 64%, respectively. This trend remains significant even after considering factors such as age and gender.
However, the relationship between cereal fiber intake and depression risk was not significant (P=0.46, typically, results are considered statistically significant if P<0.05).
In addition, analyzing results based on different age, gender, and daily total energy intake levels in 6 groups:
– <45 years group, 45-64 years group, male group (all age groups of males), female group (all age groups of females), low energy intake group, and normal energy intake group, showed that increased total dietary fiber intake was associated with a reduced risk of depression.
– <45 years group, >64 years group, female group, low energy intake group, and normal energy intake group, an increased intake of vegetable fiber was also associated with a reduced risk of depression.
– For the >64 years group, female group, low energy intake group, and normal energy intake group, an increased intake of fruit fiber was also associated with a reduced risk of depression.
The study indicated a linear relationship between total dietary fiber intake and the risk of depression. Here, “linear relationship” means that with every additional intake of dietary fiber, the risk of depression decreases, though the impact of cereal fiber on depression may not significant.
Specifically:
Total dietary fiber
As the intake of total dietary fiber gradually increases, the risk of depression decreases rapidly. When the intake reaches 23g per day, the risk of depression reaches a relatively low level. Compared to lower levels of dietary fiber intake, individuals consuming 23g of total dietary fiber per day experienced a 57% reduction in the risk of depression.
Subsequently, with further increase in total dietary fiber intake, the decrease in the risk of depression slows down.
Vegetable fiber
Individuals consuming 6g of vegetable fiber per day had a 38% reduction in the risk of depression compared to those with lower vegetable fiber intake.
Fruit fiber
Individuals consuming 5g of fruit fiber per day had a 35% reduction in the risk of depression compared to those with lower fruit fiber intake.
In summary, consuming more dietary fiber, especially vegetable and fruit fiber, may help reduce the risk of depression.
▍How do you know if you have consumed enough dietary fiber? [3-7]
Total dietary fiber includes two major types:
1. Soluble dietary fiber
Sourced from fruits (such as apples, citrus fruits), vegetables, oats, legumes, and some seeds (such as flax seeds, chia seeds). Its function is to form a gel-like substance in water, helping to lower blood sugar and cholesterol levels.
2. Insoluble dietary fiber
Sourced from whole grains (like whole wheat bread, brown rice), nuts, seeds, vegetables (especially leafy greens). Its function is to increase stool volume, promote intestinal peristalsis, and prevent constipation.
How to calculate dietary fiber intake?
To calculate your daily total dietary fiber intake, you can follow these steps:
1. Keep a food diary using a dietary record tool or app
There are many apps and websites available that can help you track all the food you eat each day and automatically calculate your dietary fiber intake.
2. Check the fiber content of foods
Use food labels (most packaged foods and beverages provide dietary fiber content on the nutrition facts label) or refer to nutrition databases to find the fiber content of each food item. For example, a cup of cooked black beans (about 172g) may contain 15g of dietary fiber.
3. Calculate the total amount
Add up the fiber content of all foods you consume in a day to get your daily total dietary fiber intake.
Example: Calculating the total dietary fiber intake for a day
Breakfast: 1 bowl of oatmeal (4g fiber) + 1 apple (4g fiber) = 8g
Lunch: Whole wheat bread (4 slices, 3g fiber per slice) = 12g
Dinner: 1 bowl of brown rice (3g fiber) + 1 serving of cauliflower (2g fiber) = 5g
Total: 8g (breakfast) + 12g (lunch) + 5g (dinner) = 25g
How to calculate 6g of vegetable fiber?
Here are the fiber contents of some common vegetables (per 100g):
Broccoli is about 2.6g, carrots about 2.8g, spinach about 2.2g, peas about 5.7g, celery about 1.6g, tomatoes about 1.2g, cabbage about 3.6g
We can calculate how much of these two vegetables are needed:
Assuming we consume 50g of broccoli and 100g of carrots:
50g of broccoli: 50g * 2.6g/100g = 1.3g fiber
100g of carrots: 100g * 2.8g/100g = 2.8g fiber
The total fiber intake is: 1.3g + 2.8g = 4.1g
If this is less than the target of 6g fiber, increase the intake of carrots and peas:
50g of broccoli: 50g * 2.6g/100g = 1.3g fiber
150g of carrots: 150g * 2.8g/100g = 4.2g fiber
50g of peas: 50g * 5.7g/100g = 2.85g fiber
The total fiber intake is: 1.3g (broccoli) + 4.2g (carrots) + 2.85g (peas) = 8.35g
This exceeds the goal of 6g of fiber. By adjusting the intake of different vegetables, you can precisely meet the 6g fiber target.
How to calculate 6g of fruit fiber?
Here are the fiber contents of some common fruits:
Apple: A medium-sized apple (about 182g): 4.4g fiber
Pear: A medium-sized pear (about 178g): 5.5g fiber
Orange: A medium-sized orange (about 131g): 3.1g fiber
Banana: A medium-sized banana (about 118g): 3.1g fiber
Strawberry: One cup of strawberries (about 152g): 3g fiber
To reach a daily goal of 6g of fruit fiber, you can achieve it with the following combinations:
One apple (about 4.4g fiber) + half an orange (about 1.55g fiber)
One pear (about 5.5g fiber) + a few strawberries (about 0.5g fiber)
These are rough estimates, and the actual fiber content may vary depending on the size or variety of fruits. By consuming a variety of fruits, you can not only meet your daily fiber intake goal but also get more vitamins and minerals, which are beneficial for your health.
References:
1. “Chinese Residents’ Dietary Fiber Intake White Paper 2016”
2. “Healthy China Action (2019-2030)”
3. Interpretation and analysis of the consumption of vegetables and fruits by Chinese residents, Qingpu Health, May 17, 2019
4. “Chinese Residents’ Dietary Guidelines (2022).” Chinese Nutrition Society.
5. Cao, Q., Wang, W., Zhang, L., et al. (2022). Implementation of a Balanced Diet Pattern for Chinese Residents-Interpretation of “Chinese Residents’ Dietary Guidelines (2022).” Food and Machinery, 38(06), 2229. DOI: 10.13652/j.spjx.
6. Saghafian, F., Hajishafiee, M., Rouhani, P., & Saneei, P. (2022). Dietary fiber intake, depression, and anxiety: a systematic review and meta-analysis of epidemiologic studies. Nutritional Neuroscience, 26(2), 108–126. https://doi.org/10.1080/1028415X.2021.2020403
7. Xu, H. (2018). A study on the relationship between adult dietary fiber intake and depression. Qingdao University.
8. Fang, L. (2021). Dietary fiber may reduce the risk of depression. Family Medicine, (06), 33.
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