Digestion problems and aging
How does digestion work?
The digestive system is a normal part of health and well-being, because it is critical for allowing the absorption of nutrients into the body, by breaking down protein, fats, carbs, and fibre, and extracting micronutrients.
The muscular walls of the stomach create “motility” that drives the process in one direction through a continuous tube (the alimentary canal), consisting of the mouth, esophagus, stomach, small and large intestines, and rectum.
Nutrients are absorbed into the body through the small intestine, as soon as food leaves the stomach. The liver and pancreas also help to produce enzymes that break down and transport fats, while any remaining undigested carbohydrates (fibre) and fats are taken up by microflora in the colon before stools are formed.
Changes to digestion with age
It has been reported that the stomach of older adults has a natural reduction in its ability to contract its muscle walls, making it less effective to digest solid food . The stomach is also less responsive to appetite signals from the brain and is less able to repair itself if it gets damaged .
This may partly explain why older people generally eat less  and develop intolerances to some foods, such as those higher in saturated fats, protein, sugars, spicy foods, and food additives. Problems such as liver disease may other problems, including difficulties in digesting fats properly, leading to higher levels of fat in the feces (steatorrhea).
The ability of the small intestine to absorb nutrients may also decline with age , but this may be combined with a lower intake of nutrient-rich foods as well. This gradually empties micronutrient stores in the body, leading to undernutrition.
New research is even shedding light on how the microbiome of the large intestine age, showing that even some families of bacteria become altered or lost . Interestingly, one study found that older people with less healthy microbiome profiles had lower survival rates over a 4 year period.
What are the health risks of weight gain in later years?
A key to longevity is believed to be to maintain a balanced diet with age, especially one that is rich in micronutrients and low in saturated fats. This pattern of eating is routinely observed in countries with the best life expectancies and reduces the likelihood of becoming overweight. Having a more plant material in the diet has even been linked to preventing the shortening of telomeres 
Being overweight or obese is one of the most important risk factors for many health issues, including diabetes, heart and blood vessel problems, liver problems, immune system problems and even cognitive function. Older adults may have more difficulty controlling their weight owing not just to the digestive changes described here, but other factors like lower mobility and energy levels.
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