June 05, 2024

Harvard scientists find new incredible benefit of following Mediterranean diet

Incredible is the word.  This study has so many holes in it that I found it hard to know where to start pointing them out. 

 So I'll start with the big picture:  Japan has the longest lived national population by far.  So shouldn't we all be living on a diet of rice and fish? That  may suggest that a Mediterranean diet is NOT optimal. Another permissible inference is that both diet and geography do not matter as influences on lifespan

OK: On to the study below.  The journal article is here:

https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2819335

I think the most obvious point is that the hazard ratios were tiny, indicating extrememly marginal effects.  And very weak effects  tend to be unreplicable -- nothing to be relied on for policy purposes.

And as a study based on self-reports it is very questionable. Pychologists have known since the '30s that self reports often misrepresent behaviour:  Mainly because respondents tend to "fake good" on questionnaires.

And it's alarming that no allowance for confounders was reported.  Income is the big confounder.  Poor people regularly have worse healh.  So was it poor people who did less well on the questionnaire.  Were the less long-lived people in the study simply poorer?  We don't know.

And possible psychological confounders are ignored too.  Was it more stable personalities or higher IQ people who stuck more to the diet?  Was it their characteristics that extended life?  We don't know.  High IQ people do in general tend to live longer

So there was a tiny tendency for the diet regulars to live longer  but was it really the diet that mattered?  What if the regulars  lived longer because they were also smarter, richer, more emotionally stable etc?  Was the diet simply a marker for something else? Was the real cause of the longer life something other than the diet?  We do not know and the researchers appear to have done nothing to find out.  

They did put a lot of work into their study so it is quite sad that the safest conclusion we can draw from their work is that  we do not know if diet matters

The Mediterranean diet has been found to reduce the risk of death by all causes by nearly a quarter in women.

A study of more than 25,000 healthy middle-aged American females with an average age of 55 found that following a diet rich in fish, legumes, vegetables, nuts, and whole grains was linked with a 23 percent lower risk of dying by the end of the 25-year study. 

Every woman was quizzed on their adherence to the diet annually, and thos who stuck closely to it over that 25-year period enjoyed a 16 percent lowered risk of death from all causes.  

The Mediterranean diet, which has been crowned the best diet for seven years in a row, has been shown to reduce inflammation in the body, improve the body's regulation in insulin, and manage weight, all of which protect against heart disease, dementia, and diabetes.   

The diet is common in Greece, Italy, and Spain, countries that border the Mediterranean Sea. 

The latest study from Harvard University is among the largest, with 25,315 women involved and perhaps the longest-running, with the women being followed for more than two decades.

At the start of the study, women filled out health questionnaires about their dietary habits, their health, their height and weight to calculate BMI. 

They also had their blood pressure assessed.

Participants filled out health questionnaires every six months during the first year and annually thereafter. 

Researchers assigned scores for adherence to the diet on a scale from zero to nine, with a higher score indicating that the woman stuck to the diet closely.

The scoring was based on the intake of nine dietary components, including a high intake of vegetables (except potatoes), fruits, nuts, whole grains, fish, and monosaturated fats.

If a woman ate less red and processed meats, she got points. If their alcohol consumption fell between five to 15 grams per day, they got an additional point. 

Then, the participants were broken into three categories based on their scores, with low adherence scores ranging from zero to three, intermediate adherence scores being a four or five, and high adherence scores falling between six and nine.

Over about 25 years, researchers counted 3,879 deaths, including 935 from heart disease and 1,531 from cancer.

Women with high adherence scores of six or higher were 23 percent less likely to die from all causes, while those with a score of four or five had a 16 percent lower risk.

The researchers said: ‘Our results suggest that a proportion of the lower risk of mortality may be accounted for by several cardiometabolic risk factors, in particular, biomarkers related to metabolism, inflammation, TRL pathways, insulin resistance, and BMI.

They added: ‘Most of the potential benefit of adherence to the Mediterranean diet and mortality remains unexplained, and future studies should examine other pathways that could potentially mediate the Mediterranean diet–associated lower mortality as well as examine cause-specific mortality.’

Their study was published in the journal JAMA Network Open. 

Few diets are loved by doctors as much as the Mediterranean diet. In addition to reducing one’s risk of heart disease, obesity, and dementia, it has a protective effect against stroke and can extend one’s life.

A 2016 study in the journal Current Opinion in Clinical Nutrition & Metabolic Care reported that people who followed the diet lived about four and half years longer than those who didn’t.

It is meant to be as enjoyable as it is straightforward. It prescribes loading up on veggies and fruits, cutting back on red meat, and incorporating fats, especially extra virgin olive oil, nuts, peanuts, olives, and avocados.

The diet also recommends exercise, the first dietary pyramid to do so. The prescription is based on the lifestyles of people in Mediterranean-bordering countries, specifically Sardinia, Italy, and Ikaria, Greece.

Both are considered Blue Zones – areas of the world where people consistently reach 100 years old. People in Blue Zones plant gardens, go on walks with fellow members of their community, dance with friends, and perform manual labor that anchors them to their surroundings.

https://www.dailymail.co.uk/health/article-13480755/Harvard-scientists-new-incredible-benefit-following-Mediterranean-diet.html

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