Proteins, fiber, and lipids: Age-proof the gut with diet

Highlights:

• The aging process negatively influences all parts of the gastrointestinal tract, causing changes in the structure and function of most organs
• Plant-derived proteins are better options compared to ones derived from animal sources, like red meat  
• Saturated and trans fats accelerate the process of gut damage and promote age-related diseases, like cardiovascular disorders
• Sugars damage the intestinal wall and promote inflammatory mediators and harmful microflora growth

Introduction

Like other bodily functions and organs, the aging process negatively influences the gastrointestinal tract (GIT). According to research, age-related decline affects the structure and function of the GIT. Examples of the latter include changes in the sense of taste, gastric emptying, esophageal sphincter function, and others. The said changes impact the way nutrients are processed and absorbed from the GIT. In addition, the aging process causes changes in the gut microbiome and mucosal barriers, promoting oxidative stress, inflammation, and reduced immunity. These factors combined damage the absorptive intestinal surface, making the elderly more susceptible to malnutrition, dysphagia (swallowing difficulties.), and other conditions. In this article, we will provide nutrition solutions to tackle aging GIT.

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How does aging affect the gastrointestinal tract?

The GIT is fundamental for many functions, like nutrient and medication absorption and protection against pathogens. In the elderly, the function of the GIT declines, which affects the capacity to ingest, digest, and tolerate nutrients (1). Also, the defensive mechanisms of the GIT, like antioxidants production, alkaline mucus secretion, and autophagy, are impaired. Oxidative stress and chronic low-grade inflammation, hallmarks of the aging process, are the main drivers responsible for decreased GIT health and functionality (1). Compromised GIT integrity (including the microbiome) has been linked to an increased rate of systemic, age-related diseases, like diabetes, neurodegenerative disorders, and others.     

The impact of the aging process has been found to affect all parts of the GIT, starting from the tongue. According to the literature, the aging process causes a decline in the tasting sense, which could contribute to a decrease in food intake, promoting malnutrition (1). The esophagus is another part of the GIT that is impacted by aging  (1, 2).

Reduction in gastric acid secretion is also impacted by the aging process. In this context, research indicates that there is about a 30% decrease in gastric acid secretion in the elderly population (3). Consequently, this could result in reduced capacity to digest food, less protection against invasive pathogens, and intestinal harmful bacteria overgrowth. The latter leads to low body weight and causes decreased absorption of micronutrients, like vitamin B2, B6, B9, and some minerals (1). The small intestine is another organ impacted by aging.

Protein: How it influences GIT and the overall health

Protein is an essential nutritional component of everyday diet. The literature indicates that it interacts with the gut microbiome, a critical player in the longevity equation (4). Protein type and source have been found to contribute to the gut microbiome type and diversity. In this context, research shows that people who consume large quantities of meat have a higher pathogenic gut microbiome count than those on a meatless diet (4).

Similarly, red meat intake was found to promote microbial gut genera that produce compounds with proatherogenic (compounds that promote atherosclerosis) properties, increasing the risk of cardiovascular diseases (5). Examples of these compounds include trimethylamine-N-oxide, which is formed by the action of gut microbiota on precursors found in high quantities in eggs, red meat, and saltwater fish (6). Further research showed that protein from dairy products (like whey) and plant sources (like peas) increased beneficial bacteria, while only whey reduced pathogenic ones. In addition, pea-derived protein has also been found to support gut barrier health and to possess anti-inflammatory properties (4).

Overall, the literature indicates that plant-derived protein consumption was linked to lower mortality compared to the animal-based source. In a study by Levine et al., subjects on a high-protein diet were found to have higher overall mortality rates, but this effect was attenuated or eliminated if the source was plant-based (7). Also, higher protein intake in old adults possibly optimized the healthspan and longevity.

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Fats and GIT health

Most Western diets are rich in saturated and trans fats, which promote cardiovascular diseases due to the elevated low-density lipoprotein (bad cholesterol) levels (4, 8). On the contrary, mono- and polyunsaturated fats promote health and alleviate the risk of chronic diseases.

A high-fat diet (optimal intake is 20–35% of total calories, with <10% of the latter being saturated fat and <1% trans fat) has been found to promote inflammation in the gut, among other organs and systems (9, 10). In this context, research has shown that a diet rich in trans and saturated fats increases the production of pro-inflammatory cytokines and elevated oxidative stress (11). The latter process disrupts the gut barrier, promoting increased permeability, which predisposes the host to diseases (12). Also, this occurs by enriching the gut microbiome with barrier-disrupting microflora species, which thrive due to the high lipid component. All these factors promote faster GIT aging.

In addition to the above, clinical studies have demonstrated that a high-fat diet increases pathogenic bacteria, promoting age-related conditions like heart diseases (4). On the contrary, reducing dietary intake of fats promoted beneficial bacteria and other favorable outcomes, like reduced fasting glucose and cholesterol. Moreover, implementing the latter will likely attenuate the age-related gut damage caused by microflora and inflammatory cytokines (12).

Carbohydrate consumption and gut health

Carbohydrates are among the most widely studied dietary components. They exist in two forms: digestible (degraded in the digestive tract and includes starches and sugars) and non-digestible (not degraded enzymatically in the digestive tract and includes fiber and resistant starch) (4).

According to the literature, a diet high in sugar and low in fiber has been found to promote gut barrier disruption and inflammation (13). Also, such a diet increases gut oxidative stress as a result of increased energy input (13, 14). The latter contributes to intestinal epithelium damage associated with accelerated gut aging.

The value of dietary fiber to the gut and the overall health has been mentioned in the literature. In this context, research indicates that they produce favorable metabolic outcomes, like reduced LDL cholesterol, triglycerides, and hemoglobin A1c (a measure of glucose control over three months) (4). Also, fiber inclusion in diets decreased inflammatory and promoted anti-inflammatory markers. 

Diet as a solution for the aging GIT

The literature indicates the importance of protection against malnutrition in the elderly, as it could negatively influence gut health. The daily intake of  30–40 kcal/kg and 1.0–1.5 g protein/kg body weight was proposed to fight frailty and promote GIT health (15). However, the latter is amenable to change according to individual health status. Also, the importance of micronutrients has been highlighted for general and GIT health, as their deficiency could contribute to gut damage and the development of age-related diseases (15).

In the elderly, dairy products represent a good source of energy, protein, micronutrients, and more. Yogurt containing probiotics (microorganisms that confer health benefits) were found to reduce GIT mutagenicity and promote anti-inflammatory effects, reducing the impact of aging on the gut (15). Also, dairy products help fight frailty and constipation, diluting the effects of aging on the GIT. It is important to note that dairy products do not suit all individuals, as some suffer from lactose intolerance.

Histidine-containing dipeptides (HDPs) (soluble peptides found in the mammalian skeletal muscle) have been suggested to be a valuable nutritional option for the elderly, as they have many health benefits (15, 16). Examples of the latter include antioxidant and anti-inflammatory properties, which are essential to fight gut aging and provide other health benefits. Poultry meat has been found to have high levels of HCDs, providing a viable option for GI health (17). Oily fish is another type of meat that carries benefits that help fight the GIT aging process due to unsaturated fatty acids' anti-inflammatory and antioxidative properties (15). Moreover, fish oil confers benefits to overall health. Many of these beneficial effects are attributed to omega-3 polyunsaturated fatty acids, which support the gut microbiota and enhance immunity (18).

The recommended daily consumption of fiber to maintain general and GIT health is 25–35g per day (of which 6 g is of soluble fiber) (15). Non-digestible dietary fibers, like resistant starch (found in beans, lentils, and other sources), were found to be utilized by the gut microbiome (15, 19). The latter process produces short-chain fatty acids that promote intestinal wall integrity and have anti-inflammatory properties (4, 15). This preserves the integrity of the gut against the effects of the aging process.

Flavonoids, found in many vegetables and fruits, have also been highlighted as an important dietary component to promote gut health and slow down the impact of aging (15). These phytochemicals have a variety of biological actions, like antioxidant, anti-inflammatory, and anti-mutagenic properties (20).

Suboptimal hydration in the elderly has been associated with negative gastrointestinal and systemic outcomes (15). Therefore, it is essential for gut health that the elderly consume 1.7 liters of fluids or more over 24 hours. The latter should be increased by an additional 500 milliliters for every degree above 38°C in case of fever (15).

Tips

Many factors play a role in the GIT health equation. You can implement a few tips to help your clients preserve their gut function and reduce the impact of aging (4, 5, 15, 21).

• Encourage your clients to consume plant-derived proteins and reduce animal sources, especially red meats. However, explain that animal proteins from dairy products carry value when consumed in moderation.
• Recommend your clients to follow a diet rich in legumes, fruits, and vegetables, like the Mediterranean and flexitarian diets..
• Highlight the importance of maintaining proper hydration levels by drinking fluids like water.
• Tell your clients about the importance of reducing trans and saturated fats in their diet and encourage them to use mono- and polyunsaturated fatty acids, like fish oil.
• Encourage your clients to eliminate sugars from their diet. Recommend they add fiber to their diets by consuming more whole grains, berries, or beans.

Conclusions

The aging process affects all parts of the GIT, starting from the mouth. As individuals age, the GIT function and structure begin to deteriorate. These effects result from an imbalance in the gut microbiome, oxidative stress, epithelium damage, and other causes. These adverse effects could be attenuated by utilizing approaches like controlling dietary components to promote gut health.

References

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2.            Shim YK, Kim N, Park YH, Lee J-C, Sung J, Choi YJ, et al. Effects of Age on Esophageal Motility: Use of High-resolution Esophageal Impedance Manometry. Journal of neurogastroenterology and motility. 2017;23(2):229-36.

3.            Feldman M, Cryer B, McArthur KE, Huet BA, Lee E. Effects of aging and gastritis on gastric acid and pepsin secretion in humans: a prospective study. Gastroenterology. 1996;110(4):1043-52.

4.            Singh RK, Chang H-W, Yan D, Lee KM, Ucmak D, Wong K, et al. Influence of diet on the gut microbiome and implications for human health. Journal of Translational Medicine. 2017;15(1):73.

5.            De Filippis F, Pellegrini N, Vannini L, Jeffery IB, La Storia A, Laghi L, et al. High-level adherence to a Mediterranean diet beneficially impacts the gut microbiota and associated metabolome. Gut. 2016;65(11):1812.

6.            Velasquez MT, Ramezani A, Manal A, Raj DS. Trimethylamine N-Oxide: The Good, the Bad and the Unknown. Toxins. 2016;8(11):326.

7.            Levine ME, Suarez JA, Brandhorst S, Balasubramanian P, Cheng CW, Madia F, et al. Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population. Cell Metab. 2014;19(3):407-17.

8.            Stamler J, Daviglus ML, Garside DB, Dyer AR, Greenland P, Neaton JD. Relationship of baseline serum cholesterol levels in 3 large cohorts of younger men to long-term coronary, cardiovascular, and all-cause mortality and to longevity. Jama. 2000;284(3):311-8.

9.            Duan Y, Zeng L, Zheng C, Song B, Li F, Kong X, et al. Inflammatory Links Between High Fat Diets and Diseases. Frontiers in immunology. 2018;9:2649-.

10.          Liu AG, Ford NA, Hu FB, Zelman KM, Mozaffarian D, Kris-Etherton PM. A healthy approach to dietary fats: understanding the science and taking action to reduce consumer confusion. Nutrition journal. 2017;16(1):53-.

11.          Basson AR, Chen C, Sagl F, Trotter A, Bederman I, Gomez-Nguyen A, et al. Regulation of Intestinal Inflammation by Dietary Fats. Frontiers in immunology. 2021;11:604989-.

12.          Rohr MW, Narasimhulu CA, Rudeski-Rohr TA, Parthasarathy S. Negative Effects of a High-Fat Diet on Intestinal Permeability: A Review. Adv Nutr. 2020;11(1):77-91.

13.          Satokari R. High Intake of Sugar and the Balance between Pro- and Anti-Inflammatory Gut Bacteria. Nutrients. 2020;12(5):1348.

14.          Aragno M, Mastrocola R. Dietary Sugars and Endogenous Formation of Advanced Glycation Endproducts: Emerging Mechanisms of Disease. Nutrients. 2017;9(4):385.

15.          Cristina NM, Lucia dA. Nutrition and Healthy Aging: Prevention and Treatment of Gastrointestinal Diseases. Nutrients. 2021;13(12):4337.

16.          Menon K, Marquina C, Hoj P, Liew D, Mousa A, de Courten B. Carnosine and histidine-containing dipeptides improve dyslipidemia: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews. 2020;78(11):939-51.

17.          Barbaresi S, Maertens L, Claeys E, Derave W, De Smet S. Differences in muscle histidine-containing dipeptides in broilers. Journal of the Science of Food and Agriculture. 2019;99(13):5680-6.

18.          Fu Y, Wang Y, Gao H, Li D, Jiang R, Ge L, et al. Associations among Dietary Omega-3 Polyunsaturated Fatty Acids, the Gut Microbiota, and Intestinal Immunity. Mediators of inflammation. 2021;2021:8879227-.

19.          Ramdath DD, Lu Z-H, Maharaj PL, Winberg J, Brummer Y, Hawke A. Proximate Analysis and Nutritional Evaluation of Twenty Canadian Lentils by Principal Component and Cluster Analyses. Foods (Basel, Switzerland). 2020;9(2):175.

20.          Panche AN, Diwan AD, Chandra SR. Flavonoids: an overview. Journal of nutritional science. 2016;5:e47-e.

21.          Catterson JH, Khericha M, Dyson MC, Vincent AJ, Callard R, Haveron SM, et al. Short-Term, Intermittent Fasting Induces Long-Lasting Gut Health and TOR-Independent Lifespan Extension. Current Biology. 2018;28(11):1714-24.e4.

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