Fibre-Rich Strawberries For Digestion

Introduction

The digestive system consists of a set of organs in the human body that aid in digesting and absorbing nutrients from food. The digestive system has the role of turning food that is consumed into nutrients and energy for survival. It also functions to remove waste from the body, through bowel movements.

Digestion is crucial for the body to stay healthy and function appropriately, by breaking down and absorbing vital nutrients. These necessary nutrients include carbohydrates, proteins, fats, vitamins, minerals as well as water. This then aids certain processes in the body to perform their role including providing growth, energy and repairing cells.¹

Fibre is necessary for digestion to work normally, by increasing good bacteria in the gut. This supports a positive immune response to inflammatory disorders and allergies. The Association of UK Dieticians have indicated that a high-fibre diet reduces the risk of chronic diseases, including type 2 diabetes, cardiovascular disease and bowel cancer. On a daily basis, adults are recommended to consume 30g of fibre to gain general health benefits.

However, it is reported that in the UK the average adult fibre intake is 18g. Recommendations for children aged two are 15g per day, primary school-aged children are 20g and secondary school-aged children should aim to eat 25g per day. Fibre is found in plants and is consumed and digested primarily by the small intestine. Any leftover fibre will be digested or partially broken down by bacteria in the large intestine.

Combining a variety of types of fibre in the diet can enhance overall immunity, in particular improving the diversity of microbiota, which helps to improve constipation and lactose tolerance, as well as inflammation in the gut.²

Epidemiological data has shown that a diet rich in fruits and vegetables has an association with a lower incidence of various ailments including obesity, cardiovascular and neurological diseases, infections and cancer. Strawberries have been indicated to play an important role due to their high phytochemical content. Strawberries are classified as a relevant source of bioactive compound due to the high levels of vitamin C, folate and phenolic constituents, and hold connotations with digestion.³ 

Understanding fibre and its support in digestion

Fibre is known to be a carbohydrate that the human body cannot break down and digest however it is an ultimate compound essential for digestive health. Fibre promotes the digestive system to function as usual, and helps to prevent constipation. Fibre plays a role in slowing down the digestion process as well as regulating blood sugar levels. The consumption of fibre also keeps the microbes (a collection of bacteria) in the gut healthy as they support energy harvesting, immune defence and digestion. This ultimately protects the gut from ‘bad bacteria’ that can cause problems.

To ensure the gut microbiome benefits the human body it must receive an adequate amount of fibre. Research in Microecology has shown fibre intake to be lower in today's population in comparison to our ancestors, particularly in high-income countries. This is mainly due to industrialisation and an increase in a Westernised diet that is composed of highly processed foods, animal proteins, refined sugars and saturated fats.

According to Havard Health, the recommended daily fibre intake for women aged under 50 is 25g, whereas men are encouraged to consume 38g per day. However, these recommendations do go down after the age of 50, 21g for women and 30g for men. In reality, on average, American adults consume 10g to 15g of fibre per day, so clearly do not meet these targets.

Adopting a low-fibre diet can have a significant impact on gut health, and can cause unintended consequences in the long term. During childhood dietary microbiome patterns develop and can cause changes that are difficult to reverse.

There are two types of fibre - soluble and insoluble. Soluble fibre dissolves in water and aids in lowering cholesterol, stabilising blood sugar levels and slowing the absorption of carbohydrates from food. This type of fibre is found in oats, nuts, seeds, vegetables and fruits such as apples, strawberries and oranges.

Insoluble fibre, in contrast, attracts water to the intestine, adding to stool and promoting the movement of waste products through the digestive system. This type of fibre is beneficial for individuals who struggle with constipation and irregularity. It is found in nuts, wholegrains and vegetables such as green beans, cauliflower, carrots and potatoes.⁴

Nutritional profile of strawberries

Strawberries represent a healthy food choice due to their nutrient profile. Their dietary fibre and fructose levels contribute to the regulation of blood sugar levels by slowing down the digestion process. Their fibre content also contributes to controlling calorie intake. Strawberries are a source of healthful essential fatty acids, as the strawberry seed oil is rich in unsaturated fatty acids. Vitamins such as carotenoids and tocopherols are also identified in the fruit.

The fruit has become an important source of vitamins in human nutrition due to its extremely high content of vitamin C and folate. Research has shown that the intake of folate through consuming 250g of strawberries can supply 30% of the daily European and American folate recommended daily allowances.

These red fruits are also a source of several other vitamins, including riboflavin, niacin, thiamin, vitamin B6, vitamin E and vitamin K. Manganese (a crucial mineral) is also rich in the fruit, a serving of eight medium-sized strawberries (144g) will provide approximately 20% of the daily adequate intake of manganese. Similarly, 144g of strawberries will provide around 5% of an adequate intake for potassium. Strawberries are also a good source of iodine, magnesium, copper, phosphorus and iron.

Strawberries possess antimicrobial, antioxidant, antiallergic and antihypertensive properties. The antioxidant capacity of red berries has an association with the presence of vitamin C and phenolic compounds. Studies have published values of the total antioxidant capacity of numerous foods.

Results have consistently ranked strawberries amongst the highest (4x than other fruits, 10x more than vegetables and 40x more than cereals) in terms of total phenolics and total antioxidant capacity. Moreover, within the same fruit group, strawberries have a more powerful antioxidant capacity in comparison to apples, pears, grapes, peaches, tomatoes, oranges and kiwi. This is because the individual contribution of varying phytochemical compounds in fruits is important to determine their total antioxidant capacity.

There is variation in phenolic content and the total antioxidant capacity in fruits and vegetables, and these factors may be controlled to optimise quality. The polyphenol composition of strawberries varies throughout their growth as well as the stage of ripening. For example, in most cases, an unripe fruit pulp has a higher level of phenolic compounds and antioxidant capacity in comparison to a ripe fruit pulp.³

The characteristics of a strawberry are also due to the genetic background and the environmental conditions, as the micronutrients and phytochemicals vary from cultivar to cultivar, and are dependent upon cultural practices in harvesting. Storage can also play a role in the micronutrient and phytochemical profile of the strawberry. The temperature in which strawberries are stored is a key factor affecting the stability of phenolic antioxidants in fruits during post-harvest storage.

To gain the full potential of consuming strawberries and benefiting from its healthful attainability, strawberries are commonly processed into products such as juice, puree, jam and jellies and are readily available on the market. The processing steps may involve concentration of fruit juice, storing in tank farms, diluting or producing strawberry jam by heating under a vacuum.

It has been reported that processing fruit does influence antioxidant activity, however, research has also shown a decrease in product composition in comparison to fresh fruits. This is in relation to the production time and processing steps such as heat treatment. To maintain the original quality of fruits the food industry could avoid processing steps and product treatments.³ 

Specific benefits of strawberries for digestion

It is important to note the factors affecting the composition of the strawberries, of which include the nutrient and phytochemical contents in the fruits. This allows a greater understanding of the bioavailability and the metabolism of the phytochemicals in strawberries after consumption. Giampieri et al has discussed the research conducted on the bioavailability and pharmacokinetics of strawberry anthocyanins and has shown anthocyanins to be absorbed less well.

Scientific data showed anthocyanins of less than 2% that were ingested were excreted in urine within a 24-hour timeframe as well as lower concentrations in plasma. Larger amounts of ingested anthocyanins escape absorption in the upper small intestine and are thought to enter the colon. This is where they are exposed to a microbial environment which is capable of modifying the anthocyanin structure.

Studies have portrayed that incorporating strawberries in the diet can have a positive effect on the risk factors for cardiovascular disease. The digestive system stimulates the heart via nerve impulses and releases chemicals into the bloodstream. In particular, this improves endothelial function, inhibits inflammation, inhibits platelet aggregation, improves blood cell profile, regulates metabolism and increases low-density lipoprotein (LDL).³ 

A common soluble fibre that is found in strawberries is pectin, which reduces LDL (bad cholesterol) levels. Samee et al have reported findings from a group of healthy participants who had consumed 500 grams of strawberries each day for a month had a drop in LDL levels. Strawberries play a crucial role in stimulating the hormone production of adiponectin and leptin, both of which are fat-burning and metabolic hormones.

This results in an increase in metabolic rate and regulating body weight. Anti-inflammatory enzymes can treat tissue damage and internal injuries. This allows the human body to engage in exercise for a healthy lifestyle. Upon consuming strawberries the body produces further adiponectin when antioxidants such as anthocyanins are present. This then ultimately promotes digestion as well as suppressing cravings and is a possible cause of burning fat. Consuming strawberries with a combined, wholesome, well-balanced diet and exercise can help to maintain weight loss.⁶

Summary

Strawberries are a source of phytochemical compounds, including polyphenols, and hold various vital dietary components such as fibre, folate, vitamins, and minerals. Data on biological activity in accordance with polyphenolic consistency is still limited. It is understood that the constituents in the fruit function alongside each other. However, recent research has shown that strawberry phenolic compounds are great for their antioxidants and anti-inflammatory activities; as well as their bioactivities extending to many other pathways.³

There are various roles fibre plays in digestion, including regulating the digestive process, maintaining blood sugar levels and creating an immune defence.⁴ Consuming strawberries has many health benefits, including aiding digestion, and preventing inflammation, cardiovascular disease, obesity, diabetes and neurodegeneration.³

Further studies are needed on the factors that have an effect on the metabolism and bioavailability of strawberry phytochemicals, which would help in the development of innovative functional food products to enable consumers to gain increased health benefits from strawberry consumption.³