A presentation of the physiopathological mechanisms linking hydration and digestive issues and potential recommendations

Approximately 11% of the world’s population suffers from irritable bowel syndrome (IBS) (3). A number of digestive issues of varying prevalence are multifactoral, and hydration can be one of those factors.

Constipation is a digestive issue that affects between 14% and 30% of the population (13, 15, 19). Based on various criteria, constipation is described as being chronic or occasional (15). Constipation is a multifactoral disorder and a number of lifestyle habits, including hydration and fibre intake, can play a role (15).

Indeed, hydration serves a number of functions in the digestive system and is a key element of bowel management. Water is absorbed by both the ileum—one of the three parts of the small intestine—and the colon. When someone is insufficiently hydrated, these systems reabsorb more fluids, which can lead to less frequent bowel movements and smaller stool quantities (1). Inversely, proper hydration leads to better gastrointestinal motility (2).

An observational study of more than 10,000 adults found that low fluid intake (less than 1,800 ml per day) is a predictor of constipation in both men and women (13). Another study found consuming 2 L of water per day increased bowel movement frequency and reduced the use of laxatives in adults (1).

Fibre is also a factor in constipation. Fibre is classified as being either soluble or insoluble (5, 6, 9, 14).

Soluble fibre (5, 6, 14):

• When mixed with water, soluble fibre creates a gel-like substance that is digested by bacteria and increases stool viscosity (texture)

• Dietary sources: psyllium, oats (flakes, bran), fruit (oranges, grapefruit, mangoes), vegetables (asparagus, beans, green peas, carrots), barley, flaxseed and chia seed

Insoluble fibre (5, 6, 9, 14):

• Reduces bowel transit time

• Stimulates peristalsis

• Increases stool volume

• Dietary sources: whole wheat (germ), vegetables (cauliflower, kale, spinach, turnip), fruit (raspberries, apples, pears, bananas, blueberries), nuts, peanuts

When constipation occurs, insoluble fibre should be consumed according to individual tolerance (2, 15) and combined with proper hydration. In cases of bloating and digestive discomfort, however, soluble fibre is generally easier to tolerate (6, 15, 16). Fibre supplements such as psyllium, flaxseed, and “laxative” fruit such as kiwis, mangoes, prunes, and figs can also be considered as part of a nutrition-based approach (2, 5, 15, 16).

Certain clienteles, including seniors, are more at risk of constipation (13, 19); the prevalence of constipation increases with age (13, 15). Causes of constipation among seniors include illness, the side effects of some drugs, pelvic floor issues, decreased fluid and fibre intake, and decreased physical activity (19, 20). People who are bedridden and those with low mobility are also more at risk of constipation caused by decreased intestinal peristalsis. Constipation in children is frequent, with more than 90% of cases classified as a functional gastrointestinal disorder (1, 4). Multiple factors are at play here, including psychosocial and dietary factors such as water and fibre intake and certain pathologies (1, 4).

Hydration and the way we hydrate can have an impact on gastroesophageal reflux (GER). That’s because the types of beverages we drink and the way we drink them can either contribute to GER or help manage it.

The idea that drinking water can help relieve acid reflux by reducing stomach acidity is a common myth with no scientific basis (17). Drinking large quantities of fluids during meals can actually make acid reflux worse, as can eating large quantities of food (10, 11). Both cause gastric distension, which puts more pressure on the lower esophageal sphincter (LES) (10, 11). The goal is rather to absorb small quantities of fluids during meals, ideally at the end. Drinking water between meals is recommended to aid digestion without causing gastrointestinal symptoms.

Sparkling and carbonated beverages, drinks containing citrus fruit, tomatoes, or mint (orange juice, tomato juice, lemonade, mint tea), as well as alcohol, coffee, and tea should all be consumed in moderation when experiencing GER, since they are irritants and cause the LES to relax in some people (10, 11, 12). Obviously, individual tolerance is a factor here.

For adults, Health Canada recommends a total daily fluid intake of 3.7 litres for men and 2.7 litres for women, all sources combined (coffee, tea, soup, juice, food) (7).

Aiming for 4 to 6 cups of water per day generally helps meet those targets (8). However, the ideal amount varies depending on the individual and situation. Needs increase in hot weather and during physical activity (8). Medication use and certain health conditions can also influence water retention and excretion (8).

If someone wants to make sure they’re getting enough fluids, they should check the colour and amount of their urine throughout the day (18). Dark yellow urine with a strong odor may indicate insufficient fluid intake. The goal is light yellow urine (18).

It’s important to remember that thirst is a sign that dehydration has already begun (18).

Hydration is essential for optimal digestive health. Water is the best choice, along with coffee and tea (in moderation for those with GER, and not exceeding recommended amounts to avoid increased stress, irritability and insomnia), as well as homemade herbal teas and infusions. The important thing is to try to reduce consumption of sugary drinks (juices, sodas, cocktails).

Carrying a water bottle or cup throughout the day helps increase intake. Setting specific goals for each part of the day can also be a helpful strategy. Flavouring water with frozen fruit or organic vegetables (strawberries, blueberries, cucumbers) and fresh herbs (basil, mint) is a great way to “zhuzh up” water!

Having a good hydration routine, getting enough fibre, and engaging in regular physical activity are all important strategies for optimal intestinal health.

In addition to assessing individual fluid needs and quantities, a nutritional evaluation should also consider hydration as a means of managing gastrointestinal symptoms.