Many readers are probably aware that the Seventh-day Adventists of Loma Linda, California are considered a blue-zone group. This means that they have one of the largest clusters in the world of people who live to a ripe old age with minimal debility. ￼Seventh-day Adventists, as a rule, do not smoke or drink. This immediately gives them a better than average chance of living a long life. However, they are also an ideal group to perform a dietary patterns study on, because almost half of seventh Day Adventists eat animal products of all types on a regular basis, while the other 50% or so are divided up into subgroups ranging from vegan to lacto-ovo-vegetarian to pesco-vegetarian.￼￼ The latter group includes fish in their diet for those who may be unfamiliar with that term.￼
Mention of the Loma Linda seventh Day Adventist diet in the press often focuses on the plant-based nature of their diet.￼ However, as you can see from the excerpt below of a massive study of 73,308 church members over a period of six years, it appears that it was the fish eaters who did best — and by quite a large margin.￼￼ ￼
There were 2570 deaths among 73,308 participants during a mean follow-up time of 5.79 years. The mortality rate was 6.05 (95% CI, 5.82–6.29) deaths per 1000 person-years. The adjusted hazard ratio (HR) for all-cause mortality in all vegetarians combined vs non-vegetarians was 0.88 (95% CI, 0.80–0.97). The adjusted HR for all-cause mortality in vegans was 0.85 (95% CI, 0.73–1.01); in lacto-ovo–vegetarians, 0.91 (95% CI, 0.82–1.00); in pesco-vegetarians, 0.81 (95% CI, 0.69–0.94) … compared with nonvegetarians.
The plain English way of stating these results is that each of the following groups was less likely to die than frequent meat eaters by the percentage indicated:
- All Vegetarians: 12%
- Vegan: 15%
- Pesco-vegetarian: 19%
- Lacto-ovo vegetarian: 9%￼
￼￼It is what one would expect, given the convincing body of evidence pointing towards the health and longevity benefits of a primarily plant-based diet.￼ That being said, it is actually unclear how meaningful this relative risk is. Let’s consider what’s called the absolute risk.￼ I’m going to compare the absolute risk of dying for the group as a whole versus the absolute risk for the vegan sub group.￼
The mortality rate was 6.05 (95% CI, 5.82–6.29) deaths per 1000 person-years [for the entire group].
The adjusted HR for all-cause mortality in vegans was 0.85
To roughly determine the average number of deaths per thousand person-years for vegans alone, the formula is .85 × 6.05￼. This comes out to 5.14 deaths per 1000 person-years. In other words, there was less than one additional death for vegans per 1000 person-years than for the group as a whole. This discrepancy between relative and absolute risk is a common area for misinterpretation of epidemiological studies￼.￼
Nevertheless, this data is still significant. The Seventh Day Adventists have several lifestyle factors working to their advantage (don’t smoke, don’t drink, supportive community). Some research suggests that these three factors taken together are actually more important than diet (within reason that is)￼. So, diet may not be as differentiating a health factor in their population as compared to the general population.￼
Research recently published in the British medical Journal on the relationship of five healthy habits to morbidity and mortality found that each healthy lifestyle adoption￼ provided incremental benefits.￼￼￼ This research confirms the findings of several other large studies, albeit in largely white and relatively educated populations.￼￼ At least in that group, ￼diet is clearly an important factor that should not be neglected by anyone who has a health goal of maximizing their lifespan with a minimum level of morbidity along the way.￼
With that in mind, I have a few thoughts about why the different types of vegetarian diets fared differently from each other.￼￼
A lacto-ovo vegetarian diet has a much higher possibility of having an excess of saturated fat in it, which could account for that group having the least benefit from adopting such a diet.￼
A vegan diet is more likely than a pesco-vegetarian diet to be lower in fat and higher in carbohydrates. There is no built-in reason that a vegan diet has to over-emphasize carbohydrates. However, because that is the type of vegan diet that has been largely pushed in the popular press up until recently, it was most likely the dominant one in this population at the time of the study￼￼.￼
A strict vegan diet will also eventually lead to a vitamin B 12 deficiency, albeit over a very long period time, unless the person either takes a supplement or uses other more questionable means to obtain vitamin B 12, such as eating unwashed produce.￼ However, even though vitamin B 12 deficiency can take a very long time to manifest, it becomes a critical issue as one ages and is thus directly germane to the focus of this study, which was mortality.￼ We can reasonably expect that some sizable percentage of this group may not have adequately attended to their micronutrient needs. This may have extended to the essential fatty acids that are more easily absorbed from fish oil.￼
It is very possible and even likely that the pesco-vegetarians were influenced by all of the research on the Mediterranean and blue zone diets and consciously chose to include fish as part of an overall health regimen.￼ If they were influenced by this research, they would lack the concern for overall fat in the diet that was held by previous generations of vegans and vegetarians.￼ This would probably shift the balance even further toward high-quality fat and away from carbohydrates of all forms.￼
In case you’re wondering how the various dietary subgroups were defined:￼
Dietary patterns were determined according to the reported intake of foods of animal origin.
Thus, vegans consumed eggs/dairy, fish, and all other meats less than 1 time/mo;
lacto-ovo–vegetarians consumed eggs/dairy 1 time/mo or more but fish and all other meats less than 1 time/mo;
pesco-vegetarians consumed fish 1 time/mo or more but all other meats less than 1 time/mo;
semi-vegetarians consumed nonfish meats 1 time/mo or more and all meats combined (fish included) 1 time/mo or more but no more than 1 time/wk;
and last, nonvegetarians consumed nonfish meats 1 time/mo or more and all meats combined (fish included) more than 1 time/wk.