A 10-year study of more than 1,500 adults aged 65 and older found that persistently limited dietary variety was associated with greater depressive symptoms, while retaining more than 20 natural teeth was linked to lower depression scores.
By yourNEWS Media Newsroom
A decade-long study of older adults in China has identified connections among dietary variety, oral health and depressive symptoms, suggesting that what people are able to eat — and whether they retain enough natural teeth to eat comfortably — may be associated with mental well-being later in life.
Researchers followed 1,538 adults aged 65 and older using data from the Chinese Longitudinal Healthy Longevity Survey, or CLHLS, beginning in 2008 and continuing for 10 years.
The findings, published in Frontiers in Nutrition, showed that participants who began the study eating a relatively limited variety of foods and increased that variety only modestly over time finished the study with higher depressive symptom scores and significantly greater odds of experiencing depressive symptoms.
Dental health emerged as another important factor.
Participants who retained more than 20 natural teeth had notably lower depressive scores than those with fewer teeth, according to the researchers.
The results do not establish that eating a wider assortment of foods or maintaining a particular number of teeth prevents depression. The study was observational, meaning researchers identified associations but could not determine whether one factor directly caused another.
The findings nevertheless add to evidence that nutrition, chewing ability, oral health and psychological well-being can become closely interconnected as people age.
Researchers Followed Dietary Changes Over a Decade
The CLHLS is a continuing research project that tracks health and lifestyle characteristics among older adults throughout China.
For the current analysis, researchers selected 1,538 participants who were at least 65 years old when they entered the study in 2008.
Food intake information was collected repeatedly during subsequent follow-up periods.
Rather than concentrating primarily on calories or individual nutrients, researchers measured dietary diversity by counting how many different categories of foods participants consumed regularly.
That approach allowed them to examine whether people maintained varied diets, lost variety as they aged or began with a narrow selection of foods and gradually expanded it.
Researchers then compared those long-term patterns with standardized measurements of depressive symptoms.
The analysis identified three major dietary trajectories.
One group maintained relatively consistent dietary variety throughout the study.
Another began with greater diversity but consumed a progressively narrower range of foods as the years passed.
A third group started with comparatively little dietary variety and showed only a modest increase over time.
The third group demonstrated the clearest unfavorable association with depressive symptoms.
Those participants had higher depressive scores by the end of the study and significantly greater odds of experiencing depressive symptoms compared with participants following more consistently varied dietary patterns.
The results suggest that simply adding a small number of additional foods after years of limited variety may not produce the same nutritional pattern as maintaining broader food diversity over a longer period.
Researchers emphasized, however, that the study cannot determine why those associations appeared.
One Dietary Pattern Produced an Unexpected Finding
Not every result followed the pattern researchers anticipated.
Participants whose diets became less varied over time actually recorded lower depressive symptom scores than those whose dietary variety remained consistently stable.
The authors said they could not clearly explain that result.
The unexpected finding underscores the complexity of drawing conclusions about mental health from dietary behavior alone.
Changes in food consumption among older adults may reflect many other circumstances, including income, living arrangements, chronic illness, appetite, family support, cultural habits and changing physical abilities.
A person might reduce the number of foods eaten while still consuming nutritionally adequate meals, for example, while another person with a wider nominal variety could still have an overall less nutritious dietary pattern.
Depression itself can also influence appetite and food choices, raising the possibility that mood affects diet rather than dietary changes being solely responsible for mood differences.
Because the study recorded associations rather than experimentally controlling participants’ diets, researchers could not completely separate those possibilities.
Greater Food Variety May Provide Broader Nutritional Support
Researchers said there are several plausible reasons why dietary diversity could be associated with mental and physical health.
Eating foods from a wider range of categories generally increases exposure to vitamins, minerals, fiber, proteins and naturally occurring plant compounds.
A diverse diet can also provide a broader range of amino acids, which the body uses to manufacture neurotransmitters involved in mood regulation and other neurological functions.
Fruits, vegetables, legumes, nuts, whole grains and other plant foods additionally contain polyphenols and fiber that have been examined in previous research for possible relationships with cognitive function, inflammation and mental health.
Protein-containing foods supply amino acids needed for maintaining muscle and producing important biological compounds.
No single food category, however, can account for the relationship researchers observed.
The study’s broader implication was that older adults who eat repeatedly from only a small selection of foods may be more vulnerable to nutritional gaps than those whose diets include multiple food groups.
Such deficiencies could potentially interact with other age-related changes affecting physical function and mental well-being.
Number of Natural Teeth Was Associated With Depression Scores
The study also identified a relationship between oral health and depressive symptoms.
Adults who retained more than 20 natural teeth showed substantially lower depressive scores.
Researchers noted that dental health can affect nutrition in practical ways that may not be immediately apparent when dietary behavior is studied separately.
Loss of teeth, loose teeth, dental pain and impaired chewing can make many nutritious foods difficult or uncomfortable to consume.
Raw vegetables may become challenging to bite and chew.
Whole nuts and seeds can become impractical.
Certain meats and other firm protein sources may also be avoided.
Over time, those limitations can lead people to rely increasingly on softer, easier-to-chew foods, potentially reducing dietary variety and changing nutrient intake.
Dental problems may therefore influence mental health indirectly by narrowing the range of foods someone is physically able or willing to eat.
Oral health can also affect daily comfort, social interaction and quality of life independently of nutrition.
Previous research has identified chewing function and dental status as factors associated with nutritional health and the ability of older adults to carry out routine daily activities.
The latest findings suggest those relationships may extend to depressive symptoms as well.
Diet and Dental Health May Reinforce One Another
The study highlights how oral health and nutrition can become intertwined during aging.
Someone with healthy teeth may find it relatively easy to eat raw vegetables, fruits, nuts, whole grains and varied sources of protein.
An older adult experiencing tooth loss or pain may gradually eliminate many of those foods without consciously deciding to adopt a more restricted diet.
That shift can make meals repetitive and potentially reduce exposure to certain nutrients.
At the same time, poor nutrition can affect broader health, including tissues involved in oral health.
Researchers therefore cautioned against treating dietary diversity and dental status as completely independent factors.
The association between having more than 20 natural teeth and lower depressive scores could reflect, at least in part, the ability to maintain a broader and more satisfying diet.
It could also reflect overall health differences among people who retain more of their teeth.
People with better dental health may differ in socioeconomic status, health care access, lifestyle practices or chronic disease burden from people who have experienced substantial tooth loss.
Those potential confounding factors are among the reasons the study cannot prove causation.
Softer Preparation Can Preserve Variety When Chewing Becomes Difficult
The researchers emphasized practical ways older adults can maintain dietary diversity even when chewing ability changes.
Rather than eliminating difficult foods entirely, preparation methods can often be modified.
Vegetables can be steamed or cooked until tender instead of eaten raw.
Nuts can be finely chopped, ground or incorporated into other foods.
Tougher proteins can be slow-cooked, shredded or prepared in softer forms.
Fruits can be selected or prepared based on texture.
Those adaptations may allow people with dental limitations to continue consuming foods from multiple nutritional categories rather than gradually narrowing their diets.
Researchers recommended incorporating variety across vegetables, fruits, protein sources, dairy products, nuts and whole grains rather than repeatedly relying on a small number of familiar foods.
They also stressed the importance of regular dental care.
Loose or painful teeth, poorly fitting dental appliances and other oral problems should be addressed promptly when possible so that chewing difficulties do not unnecessarily restrict food choices.
Findings Add to Broader Research on Healthy Aging
The study contributes to a growing body of research examining aging as the result of interconnected physical, nutritional and psychological factors rather than isolated medical conditions.
Depressive symptoms in older adults can be influenced by chronic illness, reduced mobility, social isolation, bereavement, financial pressures, medications, cognitive changes and numerous other circumstances.
Nutrition and oral health represent only part of that broader picture.
The decade-long follow-up strengthens the study by allowing researchers to observe patterns over a substantial period rather than relying on dietary information collected at a single point.
Still, the observational design prevents researchers from concluding that increasing dietary variety will directly reduce depressive symptoms.
Similarly, the finding that people with more than 20 natural teeth had lower depression scores does not prove that tooth retention itself prevents depression.
Future research will be needed to determine whether interventions that improve diet quality, preserve chewing function or address dental problems can produce measurable improvements in mental health.
For now, the findings point to two relatively practical aspects of healthy aging that may warrant attention together.
Maintaining access to varied, nutrient-dense foods and preserving the ability to comfortably chew them could support more than nutritional status alone.
Over the 10-year study period, older adults who began with restricted diets and achieved only limited improvements in dietary variety were more likely to show depressive symptoms, while those retaining more than 20 natural teeth tended to have lower depressive scores.
The results suggest that preserving both dietary flexibility and oral function may be important components of maintaining overall well-being as people age.
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