Investigating Nutrition, Diet and Gut Microbes in Healthy Older Danes

Research output: Book/ReportPh.D. thesisResearch

As the global population continuous to grow older, so does the incidence of age-related diseases such as neuro-degenerative and cardiovascular diseases, several cancers as well as sarcopenia and osteoporosis. Proper diet and nutrition are important parts of maintaining a healthy body throughout the aging process. Newer research is furthermore indicating a role of gut bacteria in healthy aging.

The overall aim of the current PhD project was to investigate risk of nutrient inadequacy as well as dietary intake in relation to musculoskeletal health in 184 community-dwelling older Danes (65-82 year). Additionally, to investigate potential effects of different macronutrient supplements and resistance exercise on gut microbiome composition and the fecal metabolome.

In the project, dietary intake was assessed by 3-day food diaries and study participant’s estimated nutrient intake was compared to average requirements or recommended intake references in order to assess risk of nutrient inadequacy. Determinants of nutrient intake was investigated by comparing the registered intake with information related to, for instance, study participant’s age and their attitudes toward dietary guidelines and healthy eating.

The PhD project investigated relationships between diet and musculoskeletal health represented by bone mineral density (BMD) and muscle function (e.g. hand grip strength and 400 meter walking tests). This was accomplished by reviewing the scientific literature for specific food groups previously associated with BMD and muscle function and subsequently testing the intake of these food groups against different BMD and muscle outcomes in a group of older Danes.

Macronutrient and exercise-dependent effects on gut bacteria were investigated in a one year intervention study where participants were randomized to receive either 40g/day of collagen protein, 40g/day of whey protein or 40g/day of easily digestible maltodextrin. The whey intervention arm was further divided into three groups: no exercise, mild intensity resistance exercise and heavy intensity resistance exercise. Lastly, the PhD project further explored different biological and lifestyle-related factors that associate with gut bacteria in relatively active and healthy older adults. Attempts to resolve these scientific inquiries were performed in three separate studies upon which this PhD is based.

From the collective findings of this PhD project it can be concluded that nutrient
inadequacy likely is a minor issue in otherwise healthy community dwelling older Danes. However, low intakes of vitamin D (compared to recommendations) were a potential nutritional concern. Although protein inadequacy can be assessed with different cut-off values based on different methodologies, results from the current PhD project indicate that protein intake is sufficient for the vast majority of community-dwelling older Danes. These findings were supported by the study participant’s relatively good performances in physical strength and functionality tests. Obtaining adequate amounts of energy in the diet and caring about dietary guidelines and nutrient quality was found to be important for nutrient risk in older Danes.

Several previous studies indicate that diet is an important aspect of building and
maintaining bone strength throughout the human lifespan. Adherence to a suggested “bone healthy” diet consisting of high intakes of coarse (whole) grains, fruits, vegetables, dairy products, legumes and nuts, fish and seafood and low intakes of red and processed meats and confectionery was not found to be associated with bone mineral density in this PhD project. Adherence to this dietary pattern was however found to be associated with better physical performance, particularly with faster 400 m walking speeds, which is supporting
previous findings.

The addition of purified animal protein or easily digestible carbohydrates to the diet of older individuals was found to have subtle effects on the gut microbiome. The specific implications for host health were however difficult to assess in the current project and warrants further studies. Heavy resistance exercise did also affect the gut microbiome, but generally to a smaller degree than dietary supplementation. Based on the results of this PhD project, subtle shifts in gut bacteria should be expected from macronutrient and resistance exercise interventions in older adults, particular in dietary interventions. Furthermore, the results of the current project indicate the gut metabolome likely will change accordingly, which could prove relevant for host health.

In addition to diet and physical exercise, the gut microbiomes of community-dwelling older adults seem to be shaped by age, sex and pharmaceutical drug use. The findings of this PhD project cooperates previous findings demonstrating that the gut microbiome of humans are highly individualized. This was found to be true for older healthy Danes living within the same geographical area.

In summary, the collective findings of this PhD suggest that the average diet of older Danes are of moderately good nutritional quality and that diet may be an important factor in maintaining physical performance in older people. Furthermore, protein supplementation (particularly collagen) and heavy resistance exercise can exert subtle effects on the gut microbiome and their metabolites in older individuals.
Original languageEnglish
Place of PublicationCopenhagen
PublisherDepartment of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen
Number of pages140
ISBN (Print)978-87-7209-440-3
Publication statusPublished - 2022

    Research areas

  • Faculty of Science - Nutrition, Diet, Gut microbes, Aging, Older adults, Healthy, Community-dwelling older adults, Denmark

ID: 300915722