Classification of diets can be based on the level of vegetarianism based on the type of animal products included from raw vegan to semi-vegetarian (flexitarian) and non-vegetarian. Another way of grouping the PBDs is based on the plant-based dietary index that grades the PBDs into healthy and less healthy or unhealthy types. Healthy food includes whole grains, fruits, vegetables, legumes, nuts, vegetable oils, coffee, and tea, while unhealthy food is for example fruit juice, refined sugar, potatoes, sweetened beverages, and dessert. Animal products are scored negatively in this system. A healthy plant-based dietary index is associated with reduced CVD morbidity and mortality, while unhealthy food groups seem to increase total and CVD mortality. A Mediterranean diet containing the mentioned kind of healthy food in addition to fish and low-fat dairy (in contrast to a Western diet with red meat, refined sugars and full-fat dairy) is shown to lower total and CVD mortality, probably due to high poly- and mono-unsaturated fats, low saturated fats, high omega-3FAs, and high dietary fibres.
Gut microbiota is defined as the sum of all groups of microorganisms inside the human gut (bacteria, viruses, fungi, protozoa, archaea). Diet has documented effects on microbiota, and so-called dysbiosis (change in composition and function) is related to atherosclerotic CVD, mediated by systemic inflammation. The authors summarise the most important studies on the association of PBD and CVD, balancing the knowledge that both PBDs and their effects on health and disease are heterogeneous. While many PBD diets have preventive effects, others may have opposite effects. Questions like acceptability, adherence, duration of eating PBDs, when in a lifetime to start, and quality of studies such as length of follow-up are covered. Animal welfare, intensified animal cultivation, food safety and overfishing, as well as climate change and environmental damage due to food production, are also discussed.
Although PBDs have been extensively studied for their possibility to prevent CVD, many questions are still unanswered. The authors conclude that the best PBD for good CVD health is not yet defined, and nor is the time it takes for PBD to have a positive impact on CVD health.
Longevity is not solely about eating healthy and PBDs. Two articles from a general population, based on data from the Norwegian Tromsø Study, investigated what could be learnt from adults who had participated in several surveys from 1974 (men) and 1978 (women) to 2016 and followed up for all-cause deaths (3,4). The authors demonstrate the importance of having no, or few, risk factors in midlife with respect to longevity (diet was not assessed). Non-smoking and physical activities were most important, and beneficial changes in these lifestyle factors increased life expectancy in both sexes.