olive oil and decreased mortality

 a recent article based on 2 long-term large observational studies found that consuming olive oil was associated with decreased total and cause-specific mortality (see mortality dec with olive oil JACC2021 in dropbox, or doi.org/10.1016/j.jacc.2021.10.041) 

 

Details:

-- databases:

    -- 60,582 women in the Nurses’ Health Study (NHS), from 1990-2018

    -- 31,801 men from the Health Professionals Follow-up Study (HPFS), from 1990-2018

        -- all were free from baseline cardiovascular disease or cancer

        -- diet was assessed by semiquantitative food frequency questionnaires every four years, consisting of >130 food items, and questioning how often, on average in the preceding year, participants consumed specific foods as well as the types of fats, oils, and brand or type of oil used in cooking

            -- for olive oil consumption, they calculated the sum of 3 items: olive oil used for salad dressings, olive oil added to food or bread, and olive oil used for baking or frying at home

-- age 56, 96% white, 18% of southern European or Mediterranean ancestry, family histories of diabetes 25%/cancer 25%/history of MI 25%, aspirin use 35%, baseline hypercholesterolemia 25%, baseline hypertension 20%, menopausal hormone use in women 29%, current smoker 12%/former smoker 38%, BMI 26, alcohol intake 6 g per day, physical activity 14 MET-h/week in women and 37 in men

-- diet: total calories consumed 1800, red and processed meats one serving/d, fruits and vegetables 5 servings/d, nuts 0.1 serving/d, whole grains one serving/d, soda one serving/d, Alternative Healthy Eating Index 42 (without polyunsaturated fatty acids and alcohol consumption, scores 0-90, higher is better; this index is a more global estimate of healthy eating vs assessing individual dietary components)

-- follow-up 28 years                     

-- statistical analysis included 3 models to adjust the results: model 1 age-adjusted; model 2 also included ethnicity, southern European/Mediterranean ancestry, married, living alone, smoking status, alcohol intake, physical activity, family history hypertension/hypercholesterolemia, aspirin use, postmenopausal hormonal therapy, total energy intake, BMI; model 3 also added red meat consumption, fruits and vegetables, nuts, soda, whole grains, and trans fats

-- categories of olive oil intake: never, >0-1 tsp/d, >0 to 0.5 Tbsp/d, and >0.5 Tbsp/d

 

Results:

-- 36,856 deaths occurred over the 28 years: 22,768 in the NHS study and 14,076 in the HPFS study

-- overall mean consumption of olive oil increased from 1.6 g per day in 1990 to about 4 g per day (about 1 teaspoon) in 2010; intake of other fats remained stable

-- those with higher olive oil consumption tended to be more physically active and more likely to be from southern European or Mediterranean ancestry

 

-- Pooled multivariable adjusted HR in the group with the highest olive oil consumption versus lowest, using adjusted model 3 (see their Table 2 for more detailed info):

    -- total mortality: 19% decrease, aHR 0.81 (0.78-0.84)

    -- cardiovascular mortality: 19% decrease, aHR 0.81 (0.75-0.87)

    -- cancer mortality: 17% decrease, aHR 0.83 (0.78-0.89)

    -- neuro-degenerative disease mortality (eg, dementia-related mortality): 29% decrease, aHR 0.71 (0.64-0.78)

    -- respiratory disease mortality: 18% decrease, aHR 0.82 (0.72-0.93)

-- there was a dose-response curve: significant inverse association for total mortality and cause-specific mortality for each of 5 g/d increase in olive oil intake as a continuous variable

 

-- mathematical analyses based on different oil comparisons, assuming replacement of 10 g per day of other oils with 10 g per day of olive oil:

    -- replacing margarine: 13% lower total mortality risk, HR 0.87 (0.85-0.89)

    -- replacing butter: 14% lower total mortality, HR 0.86 (0.83-0.88)

    -- replacing mayonnaise: 19% lower total mortality risk, HR 0.81 (0.78-0.84)

    -- replacing dairy fat: 13% lower total mortality risk, HR 0.87 (0.84-0.89)

-- these results were similar for cause-specific mortality, eg cardiovascular disease, cancer, neuro-degenerative disease, and respiratory disease mortality

-- however, replacing other vegetable oils with olive oil did not reach statistical significance (ie replacing only animal-based ones mattered)

 

Commentary:

-- olive oil is a main component of the Mediterranean diet and is high in monounsaturated fats as well as polyphenols, all shown to be anti-inflammatory and antioxidant

-- many prior studies have found the benefits of the Mediterranean diet, for example:

    -- http://gmodestmedblogs.blogspot.com/2018/12/mediterranean-diet-dec-cad-and.html, finding that the Mediterranean diet is associated with decreased CAD as well as inflammatory biomarkers, from the Nurses' Health Study; and http://gmodestmedblogs.blogspot.com/2018/06/mediterranean-diet-with-olive-oil-or.html for intervention trial (PREDIMED) finding that consuming extra-virgin olive oil (EVOO) and mixed nuts both decreased major cardiovascular events

    -- http://gmodestmedblogs.blogspot.com/2015/11/breast-cancer-risk-and-mediterranean.html, PREDIMED study finding decreased invasive breast cancer with EVOO and mixed nuts (these PREDIMED trials found marginally higher benefit for EVOO vs mixed nuts)

    --  http://gmodestmedblogs.blogspot.com/2018/11/mediterranean-diet-decreases-knee-oa.html, Mediterranean diet decreases knee OA

    -- http://gmodestmedblogs.blogspot.com/2015/11/mediterranean-diet-and-brain-volume.html, PREDIMED finding higher brain volume with EVOO diet, and this blog has reference to other articles on Mediterranean diet and decreased risk of Alzheimer's

    -- http://gmodestmedblogs.blogspot.com/2014/01/mediterranean-diet-diabetes-prevention.html, PREDIMED study finding that EVOO decreases new-onset diabetes

    --http://gmodestmedblogs.blogspot.com/2017/10/mediterranean-diet-helps-nafld.html, PREDIMED study finding that EVOO helps NAFLD

    -- http://gmodestmedblogs.blogspot.com/2014/05/olive-oil-and-atrial-fibrillation.html, PREDIMED study finding that EVOO decreases new onset atrial fibrillation

-- this current prospective observational study confirmed what has been found in other studies suggesting lower total and cause-specific mortality is associated with higher consumption of olive oil, in a country (US) where olive oil is less integrated into the customary diet

-- as a reference point, in the US approximately 1.1 L of olive oil is consumed per person per year, versus in Greece (the country with the highest olive oil consumption) at 12 L per person per year (the equivalent of about ¼ cup each day). The countries with the next highest olive oil consumption are Spain, Italy, Portugal, Syria, Morocco, and Tunisia.

    -- In the PREDIMED study, they found the mean consumption of olive oil in Spain was 40 g today, versus 10 g per day

-- also, as a perspective, in countries where olive oil consumption is much higher than in the US, the benefits of higher olive oil intake were greater: reductions in overall mortality >25-45% (vs above study in the 15% range)

-- other studies did not find much olive oil protection from cancer mortality, though this current study did have the benefit of a very long-time observation period and lots of cancer deaths, and was therefore more likely to find statistical benefit (though PREDIMED did find olive oil benefit for breast cancer, as noted above)

-- in terms of cognitive impairment, several studies have suggested better cognitive performance, especially with EVOO, which might be related to its anti-inflammatory/antioxidant effects, perhaps related to bioactive polyphenols. And olive oil does decrease inflammatory biomarkers, improves endothelial function, improves insulin sensitivity and glycemic control, and decreases blood pressure (see blogs above)

-- the lack of difference between olive oil and other vegetable oils is a bit surprising. some past studies have suggested that both lower LDL levels, though polyunsaturated fats lower HDL levels and  monounsaturates do not.

Limitations:

-- observational study which controlled for many potential covariates, though there may well be some important unanticipated covariates

    -- for example, more of the people having higher olive oil consumption were of southern European or Mediterranean ancestry, and this group may well have other behaviors that are different from other groups in the US and thereby potentially confounding the statistical analysis ( eg, they were more likely to do physical activity and not smoke, and there may well be other unmeasured healthy behaviors). And, their total mortality was in fact decreased more than in the non-Mediterranean ancestry subgroup after controlling for olive oil consumption: 6% versus 4% risk reduction per 5 g increase in olive oil intake, consistent with there being other non-olive oil factors playing a part)

-- there is always a concern about the role of individual dietary components, given that there may well be important interactions between the different individual components which alter their impact on clinical outcomes. This study did include the AHEI, as a means of looking at the overall food consumption, and actually did find that there was also a somewhat more profound benefit, also after controlling for olive oil consumption

-- these large groups of people in the studies were mostly white healthcare professionals, limiting generalizability to the broader population. They did do sensitivity analyses controlling for socioeconomic status (census tract median family income, home value, percentage with college degree), and that did not influence the results, although this mathematical correction does not take into account many other factors, such as perhaps a different health orientation and lifestyle among health professionals

-- though it is necessary to have long-term follow-up and up-to-date data, over these 28 years there were likely very significant changes in people’s lifestyles, including diet, exercise, weight, stress level/social supports, housing, occupation, environmental exposures, etc., etc. (and, as noted above, overall olive oil consumption did increase over these years.) These types of changes might well have influenced many outcomes, including mortality as assessed above

-- the data input, such as the food frequency questionnaire, depend on self-report over the prior year, which may well have significant bias. In particular, I would guess that health-conscious people (who may well do a variety of healthier behaviors) may overestimate the quantity and frequency of healthier foods over the previous year. And there have been several studies that have made it into the popular press extolling the value of olive oil

-- the causes of death were assessed from a variety of inputs, including death certificates, which are not necessarily so accurate

-- in this population studied, the overall consumption of olive oil was quite low. These results may be quite different (and likely better, as per above) in areas with higher olive oil consumption

-- and, there is this lingering question as to the actual content of olive oil in the United States, with reports of some having minimal or no real olive oil content. In addition, there may well be very different quantities of anti-inflammatory, or antioxidant abilities of the olive oil, depending on the maker and type (eg, EVOO seems better). Again, these might affect the analysis of their outcomes

 

So, this study does support the significant benefit of having a higher dietary olive oil intake. It was notable, however, that the overall difference found was between vegetable-based versus animal-based oils, without a clear difference between olive oil and other plant-based oils (with the caveat that this analysis was in the US with low olive oil consumption, and perhaps there might be a difference between olive and other plant-based oils at higher levels of consumption)

And, do these high doses of olive oil lead to remarkable longevity? the island of Ikaria in Greece is particularly notable where living to 100 is common (one in three living to >90yo) and one person lived to 125yo (see https://neo.life/2021/11/ikaria-the-island-of-mysterious-longevity/ )???? though my guess is that there are multiple issues involved (beautiful island, not much stress, lots of physical activity, lots of social supports, etc). But olive oil may be an important component as well.

geoff

 

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