To investigate correlations between diet and prevalence of constipation among elderly people in Beijing.

A total of 2776 (≥ 60 years) were selected in Beijing region for investigation. Data regarding constipation and diet habits was collected via hierarchical status, segmentation and random cluster sampling. Investigation included constipation-related demographic indicators and diet habits. Door-to-door questionnaires and surveys included daily staple food intakes, frequency of fish, egg, fruits and vegetables consumption. Constipation was defined according to the China Chronic Constipation Diagnosis and Treatment Guideline (2013), with the following constipation judgment indicators: decreased defecation frequency, dry and hard stool, and difficulty in defecation.

The prevalence of constipation among elderly people in Beijing region was 13%. There was a positive correlation between prevalence of constipation and age, but negative correlations between prevalence of constipation and staple food, fish and dietary fibres (fruits and vegetables) intakes. These differences were all statistically significant.

The prevalence of elderly constipation in Beijing region is closely related to diet habits, and is significantly decreased by high staple foods intake, fish eating and high dietary fibres (fruits and vegetables) consumption.

Constipation is a common gastrointestinal disease affecting all age groups, elderly individuals suffer particularly more than younger individuals, among which females have higher prevalence than males[1,2]. High incidence of constipation in older populations not only accounts for change in organ functions with age, but diet habits play an essential role in prevention and treatment. Many studies have suggested that high dietary fiber intake can significantly reduce prevalence and alleviate symptoms of constipation[3-6]. Constipation in older populations should firstly be treated with dietary modifications prior to any medical intervention to minimize side effects of certain drugs. Thus, we conducted an epidemiological study regarding diet habits and prevalence of constipation among elderly people in Beijing to further confirm the significance of diet in treating and alleviating symptoms of constipation without any potential side effects. This research is one of key parts of the special project, which funded by the National Health and Family Planning Commission of the People’s Republic of China. The project consists of two related programs: (1) the study on comprehensive geriatric health evaluation index system; and (2) Multidimensional longitudinal study of aging among the elderly in Beijing.

This study has investigated the prevalence of constipation among elderly people in both urban and rural areas of Beijing. Our results show that the differences between females and males, living in urban or rural areas are not statistically significant (P > 0.05 for both) (Table 1). However, many other studies have indicated that females in general suffer more from constipation than males in all age groups[1,2]. Age is one of the most important risk factors, our results (P < 0.001) are in accordance with other studies which have concluded the prevalence of constipation increased with age (Table 1)[1,2]. The proportion of constipated elderly people increases drastically from 70-year-old group (11.3%) to 75-year-old group (18.8%), so dietary and lifestyle modifications are highly recommended as first line treatment in these age groups prior to any medical interventions. Ageing is a naturally occurring process which implies changes in organ functions with age, previous studies have pointed out that constipated older adults could have normal or delayed colonic transit, caused most commonly by distal colonic or anorectal dysfunction[7-9]. This irreversible process can be partially compensated by establishing a healthy intestinal microbiota. Spinzi et al[10] have suggested that the faecal flora changed markedly with age mostly by a fall in numbers of bifidobacteria. Nowadays, probiotics are commonly prescribed and widely available, probiotics not only promote the growth of bifidobacteria, but shorten bowl transit and soften stools most likely by increased short chain fatty acid concentration and decreased colonal pH[11]. Although the causal relation between intestinal microbiome and constipation remains undefined, remarkable outcomes have been proven by the use of probiotics in alleviating constipation symptoms, probiotics supplement and fermented dairy products are highly suggested to be incorporated into diet due to lacks of side effects and food and drug interactions.

Staple foods in China generally refer to rice and wheat products such as noodles and steamed buns. Our results indicate a clear negative correlation between amount of staple food consumed and prevalence of constipation among elderly populations (Table 2). By increasing staple food consumption from 150 g per day up to 500 g and more per day, the prevalence of constipation decreases from 11.7% to 4.2% (P < 0.05). A Japanese study has found out a clear dose-response relationship between increased intake of rice and a decreased prevalence of constipation among young female dietetic students[12]. Also, increased intakes of rice at breakfast, lunch, and dinner were all associated with a decreased prevalence of constipation[12]. The protective effect of rice on constipation has also been indicated in two previous studies conducted in Asian communities where rice is the main staple food[13,14]. Two possible explanations can be speculated. (1) Elderly people are generally eating less than younger adults, so their caloric intake is also lower than young people. Towers et al[15] have concluded that there was a strong negative correlation between total transit time and number of calories as measured by the daily food diary (r = -0.58, P < 0.0001) and the diet questionnaire (r = -0.28, P = 0.05). Thus, slow transit times are associated with low caloric intake which potentially leads to constipation; and (2) rice and wheat products are main source of vitamins and minerals in China, some of constituents in rice and/or combinations of these constituents might exert a preventive effect on constipation[8]. However, Western countries have different dieting habits where potato, bread and corns are considered staple foods. Protective effects of staple food indicated in our results cannot be directly applied to Western countries due to differences in eating habits, further investigation is required to confirm the beneficial effects of staple food in Western diets.

In this study, we have established a relationship between fish eating, egg eating and prevalence of constipation in older age groups. Although the prevalence of elderly who do not eat eggs is higher than egg-eaters, this result is not statistically significant (P > 0.05). However, a negative correlation between fish eating and prevalence of constipation is demonstrated by our results (Table 3); elderly people who do not eat fish have higher prevalence than those fish eaters (P < 0.01). One study conducted on infants regarding diet and constipation has suggested that the easily digested proteins in breast milk, primarily whey, resulted in soft stools; breast-fed infants tended to have more frequent stools and soft in consistency[16]. Nonetheless, less digestible casein proteins are believed to result in firmer stools, formula-fed infants tended to have more firmer stools and more frequent constipation problems[16]. According to this result, we can speculate that certain proteins in fish might be more digestible than proteins found in eggs, so more digestible proteins promote the formation of soft stools among elderly people. Further study is required to confirm this hypothesis.

To date, many studies have agreed that higher dietary fibers (fruits and vegetables) consumption decreases prevalence of constipation in different age and gender groups. According to our study, elderly people who consume fruits and vegetables frequently have lower prevalence of constipation (P < 0.05) (Table 4). The mechanism of action of fiber on constipation includes: (1) fiber increases stool bulk and accelerates colon transit; (2) fermenting fiber produces short-chain fatty acids (butyrate, propionate, acetate, etc.), which increase osmotic load and accelerate colon transit; (3) short-chain fatty acids change the intraluminal microbiome (mass) directly or indirectly by decreasing luminal pH, which accelerates colon transit; and (4) fiber contains water. All these improve stool consistency and amount[3-5]. Increasing soluble fiber intake by increasing fruits and vegetables consumption resulted in more frequent and softer stools[6]. Meanwhile, fruits and vegetables contain relatively higher amount of water than other food groups, Murakami et al[12] have indicated that low intake of water from foods was independently associated with increasing prevalence of constipation[12]. Therefore, frequent intake of fruits and vegetables is highly recommended to elderly people. Roma et al[17] have conducted a study on children in selected areas of Greece, and have observed that the mean daily fiber intake was lower in the parents of constipated children than in control parents. This implies that constipation is not “inherited” but “passed” in a family where eating habit is essential in both prevention and treatment of constipation. High prevalence of constipation among elderly is not only due to ageing processes, but dieting habit is also a key factor. Increase dietary fibers intake and modify eating pattern can both influence familial health status and potentially reduce incidences of constipation. Moreover, according to Sun Hwan Bae certain fruits such as pear, grape, plump, and apple with peel are useful in treating constipation due to their high fiber content[18]. Green kiwifruits, prune, persimmon and banana are commonly consumed and available in Asia, green kiwifruits and prune have beneficial effects on constipation yet raw persimmon and banana pose negative effects on constipated patients. Green kiwifruit significantly increases defecation frequency, stool volume, softness of bowel motion, and ease of defecation in adult clinical studies[19]. Similarly, prune and Japanese apricot are beneficial to constipation; prune contains large amount of phenolic compounds which aid in laxative effect[20], and Japanese apricot increases defecation frequency and contraction of the rat colon[21]. Nevertheless, unripe persimmon contains high tannin concentration, tannin acid reduces intestinal secretions and inhibits peristalsis, and even healthy individuals experience painful defecation when ripe persimmons are eaten[18], persimmons should be avoided by constipated elderly people. Also, unripe bananas contain 100-250 mg tannins/100 g and have high amylase-resistant starch content; they can cause or aggravate pre-existing constipation[22]. Unripe banana should not be recommended to constipated elderly people, as many other sources of fibers are available. Additional examples in terms of which fruits can aggravate constipation require further study.

Our epidemiological investigation demonstrates that higher staple food (rice, wheat products) intake, frequent fruits and vegetables consumption, incorporation of fish into diet pose beneficial effect on constipation and reduce the prevalence of constipated patients. Increase dietary fibers intake from both fruits and vegetables and whole grains to alleviate symptoms of constipation is one of effective methods. A balanced diet should be promoted and emphasized as first line treatment prior to any medical intervention.