Longevity Briefs: What Is The Best Diet For A Long, Healthy Life?

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Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem:

The global population is ageing rapidly, and with that comes a surge in chronic health conditions among older adults. Research suggests that the ageing process is malleable – it can be accelerated, slowed down and even reversed in some organisms. While there’s currently no treatment proven to slow ageing in humans, research shows that diet plays a crucial role in preventing many age-related diseases and extending healthspan (the number of years spent in good health). Yet the relationship between diet and ageing as a whole has been extremely challenging to study, due to the complex interplay between diet, genetics and other lifestyle factors. Nevertheless, some common themes have emerged.

The discovery:

In this study, researchers investigated the link between long-term dietary patterns and healthy ageing using data from two large, long-term US studies: the Nurses’ Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS). The study followed 105,015 participants for up to 30 years, starting in 1986. Participants’ dietary intake was tracked using questionnaires administered every four years to build a picture of long-term dietary habits. They used statistical analysis to study the relationship between healthy ageing (which encompassed survival to age 70, absence of major chronic diseases and cognitive and physical health) and adherence to eight different healthy dietary patterns. These were as follows:

The Alternative Healthy Eating Index (AHEI)
The Alternative Mediterranean Index (aMED)
The Dietary Approaches to Stop Hypertension (DASH)
The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND)
The healthful plant-based diet (hPDI)
The Planetary Health Diet Index (PHDI)
The empirically inflammatory dietary pattern (EDIP)
The empirical dietary index for hyperinsulinaemia (EDIH)

They found that higher adherence to all eight dietary patterns was significantly associated with a greater likelihood of healthy ageing. However, some were more strongly associated than others. The Alternative Healthy Eating Index (AHEI) showed the strongest association – the top 20% of adherents to the AHEI had 86% greater odds of healthy ageing (at age 70) compared to those in the lowest 20%. The AHEI is primarily based on American dietary guidelines for reducing the risk of chronic disease. AHEI also had the strongest association with physical function and intact mental health, while the Planetary Health Diet Index (PHDI, which aims for both human health and environmental sustainability) has a slightly stronger association with cognitive health and probability of living to age 70.

The odds ratio for different aspects of health ageing for different dietary patterns by age 70. The odds ratio is the ratio of people in good health among the top 20% of adherents to the diet, relative to the bottom 20%. For example, if a diet has an odds ratio of 2 for intact cognitive health, that means that the 20% of people who adhere the closest to that diet are twice as likely to have intact cognitive health as the 20% of people who adhere the least to that diet.
Optimal dietary patterns for healthy aging

Specific foods and nutrients linked to greater odds of healthy ageing included fruits, vegetables, whole grains, unsaturated fats, nuts, legumes, and low-fat dairy. Conversely, higher intakes of trans fats, sodium, sugary beverages and ultra-processed foods were inversely associated with healthy ageing.

They also found that not everyone benefited from these diets to the same extent. Women generally benefited more, as did smokers, those with a BMI of over 25 (overweight) and those with lower physical activity levels, for example. However, these disparities weren’t always consistent between different diets. For example, the associations between health and aMED, DASH and PHDI were not significantly different between those with BMI above or below 25, whereas the associations with EDIP and EDIH was significantly stronger for BMIs above 25.

Odds ratio of health ageing for different sub-categories of participants. This time the odds ratio represents the likelihood of health ageing for the top 10% of adherents vs the bottom 10%.
Optimal dietary patterns for healthy aging

The implications:

This research highlights the difficulties of trying to put together a single, ‘optimal’ longevity diet – there is no one size fits all approach as people with different risk factors are going to benefit differently from different approaches. This shouldn’t really be that surprising. However, it’s worth emphasising that most of the benefits from these diets are coming from the overall dietary strategy. This study and many others consistently show that prioritising plant-based foods, avoiding processed foods, choosing unsaturated fats over trans and saturated fats, and consuming red meat only in moderation is associated with reduced risk of age related disease. Most people would probably benefit more by tightening their adherence to these broad recommendations, rather than trying to fine-tune their diets based on evidence that is still rather limited and often conflicting.