The Ever-Popular Mediterranean Diet: Origins and Definition

ORIGINS

It all starts with Ancel Keys.

Keys was the leader of the team who put together the Seven Countries Study, which seemed to demonstrate lower rates of coronary heart disease in countries consuming less saturated fat. [Coronary heart disease is the leading cause of death in Western cultures.] He also found that cardiovascular disease rates rose in tandem with blood cholesterol levels. The two countries particularly illustrative of these connections were Italy and Greece, both Mediterranean countries.

The other countries he analyzed in “Seven Countries” were the United States, Yugoslavia, Japan, Finland, and the Netherlands.

Keys and his wife Margaret, a biochemist, drilled deeper in to the “Mediterranean diet” that was characteristic of Italy, Greece, and other countries on or near the Mediterranean Sea in the 1950s and 1960s. [“Diet” in this context refers to the usual food and drink of a person, not a weight-loss program.] Their efforts culminated in the publication of several best-selling Mediterranean diet books in the 1970s, and Keys’ photo on the cover of Time magazine in 1961.

Thus began the still-popular Mediterranean diet.

Oldways Preservation Trust re-invigorated the Mediterranean diet around 1990, helping the public incorporate Mediterranean diet principals into everyday life. Oldways founder, K. Dun Gifford, passed away in 2011.

DEFINITION

There is no monolithic, immutable, traditional Mediterranean diet. But there are similarities among many of the regional countries that tend to unite them, gastronomically speaking. Greece and southern Italy are particularly influential in this context.

So here are the characteristics of the traditional, healthy Mediterranean diet of the mid-20th century:

•It maximizes natural whole foods and minimizes highly processed ones

•Small amounts of red meat

•Less than four eggs per week

•Low to moderate amounts of poultry and fish

•Daily fresh fruit

•Seasonal locally grown foods with minimal processing

•Concentrated sugars only a few times per week

•Wine in low to moderate amounts, and usually taken at mealtimes

•Milk products (mainly cheese and yogurt) in low to moderate amounts

•Olive oil as the predominant fat

•Abundance of foods from plants: vegetables, fruits, beans, potatoes, nuts, seeds, breads and other whole grain products

•Naturally low in saturated fat, trans fats, and cholesterol

•Naturally high in fiber, phytonutrients, vitamins (e.g., folate), antioxidants, and minerals (especially when compared with concentrated, refined starches and sugars in a modern Western diet)

•Naturally high in monounsaturated and polyunsaturated fats, particularly as a replacement for saturated fats

CONTROVERSIES

Keys has been criticized for “cherry-picking” the data that linked saturated fat consumption with increased heart disease. Subsequent studies indicate a weak link, if any. A list of the pertinent studies de-linking heart disease and saturated fat is at the Advanced Mediterranean Diet Blog.

The Seven Countries Study included only men. It’s practical implications, therefore, may not apply to women.

The traditional Mediterranean diet is increasingly a thing of the past as Mediterranean countries adopt the Western diet characterized by “fast food” and highly processed foods.

FUN FACTS FOR FOOD GEEKS

Ever heard of K rations used by the U.S. military in World War II? Keys invented them. He earned Ph.D.s in biology and physiology. Keys lived to age 100 and was said to be intellectually active through his 97th year.

Steve Parker, M.D.

References:

Keys, Ancel (1970). Coronary heart disease in seven countries. Circulation, 41

Keys, Ancel. Coronary heart disease in seven countries. Circulation, 41, (1970) supplement I: I-1 through I-211.

Keys, Ancel. Seven Countries: A Multivariate Analysis of Death and Coronary Artery Disease. Harvard University Press, 1980.

Oldways website.

Documented Health Benefits of the Mediterranean Diet

The enduring popularity of the Mediterranean diet is attributable to three things:

1.Taste

2.Variety

3.Health benefits

For our purposes today, I use “diet” to refer to the usual food and drink of a person, not a weight-loss program.

 

The scientist most responsible for the popularity of the diet, Ancel Keys, thought the heart-healthy aspects of the diet related to low saturated fat consumption.He also thought the lower blood cholesterol levels in Mediterranean populations (at least Italy and Greece) had something to do with it, too.Dietary saturated fat does tend to raise cholesterol levels.

 

Even if Keys was wrong about saturated fat and cholesterol levels being positively associated with heart disease, numerous studies (involving eight countries on three continents) strongly suggest that the Mediterranean diet is one of the healthiest around.See References below for the most recent studies.

 

Relatively strong evidence supports the Mediterranean diet’s association with:

increased lifespan

lower rates of cardiovascular disease such as heart attacks and strokes

lower rates of cancer (prostate, breast, uterus, colon)

lower rates of dementia

lower incidence of type 2 diabetes

 

 

Weaker supporting evidence links the Mediterranean diet with:

slowed progression of dementia

prevention of cutaneous melanoma

lower severity of type 2 diabetes, as judged by diabetic drug usage and fasting blood sugars

less risk of developing obesity

better blood pressure control in the elderly

improved weight loss and weight control in type 2 diabetics

improved control of asthma

reduced risk of developing diabetes after a heart attack

reduced risk of mild cognitive impairment

prolonged life of Alzheimer disease patients

lower rates and severity of chronic obstructive pulmonary disease

lower risk of gastric (stomach) cancer

less risk of macular degeneration

less Parkinsons disease

increased chance of pregnancy in women undergoing fertility treatment

reduced prevalence of metabolic syndrome (when supplemented with nuts)

lower incidence of asthma and allergy-like symptoms in children of women who followed the Mediterranean diet while pregnant

Did you notice that I used the word “association” in relating the Mediterranean diet to health outcomes?Association, of course, is not causation.

 

The way to prove that a particular diet is healthier is to take 20,000 similar young adults, randomize the individualsin an interventional study to eat one of two test diets for the next 60 years, monitoring them for the development of various diseases and death.Make sure they stay on the assigned test diet.Then you’d have an answer for that population and those two diets.Then you have to compare the winning diet to yet other diets.And a study done in Caucasians would not necessarily apply to Asians, Native Americans, Blacks, or Hispanics.

 

Now you begin to see why scientists tend to rely on observationalrather than interventional diet studies.

 

I became quite interested in nutrition around the turn of the century as my patients asked me for dietary advice to help them lose weight and control or prevent various diseases.At that time, the Atkins diet, Mediterranean diet, and Dr. Dean Ornish’s vegetarian program for heart patients were all prevalent.And you couldn’t pick three programs with more differences!So I had my work cut out for me.

 

After much scientific literature review, I find the Mediterranean diet to be the healthiest for the general population.People with particular medical problems or ethnicities may do better on another diet. People with diabetes or prediabetes are probably better off with a carbohydrate-restricted diet, such as the Low-Carb Mediterranean Diet.

 

Dan Buettner makes a good argument for plant-based diets in his longevity book, The Blue Zones.The Mediterranean diet qualifies as plant-based.

 

Steve Parker, M.D.

 

     Sofi, Francesco, et al. Accruing evidence about benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. American Journal of Clinical Nutrition, ePub ahead of print, September 1, 2010. doi: 10.3945/ajcn.2010.29673

     Buckland, Genevieve, et al. Adherence to a Mediterranean diet and risk of gastric adenocarcinoma within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort study. American Journal of Clinical Nutrition, December 9, 2009, epub ahead of print. doi: 10.3945/ajcn.2009.28209

     Fortes, C., et al. A protective effect of the Mediterraenan diet for cutaneous melanoma. International Journal of Epidmiology, 37 (2008): 1,018-1,029.

Sofi, Francesco, et al. Adherence to Mediterranean diet and health status: Meta-analysis. British Medical Journal, 337; a1344. Published online September 11, 2008. doi:10.1136/bmj.a1344

     Benetou, V., et al. Conformity to traditional Mediterranean diet and cancer incidence: the Greek EPIC cohort. British Journal of Cancer, 99 (2008): 191-195.

Mitrou, Panagiota N., et al. Mediterranean Dietary Pattern and Prediction of All-Cause Mortality in a US Population, Archives of Internal Medicine, 167 (2007): 2461-2468.

     Feart, Catherine, et al. Adherence to a Mediterranean diet, cognitive decline, and risk of dementia. Journal of the American Medical Association, 302 (2009): 638-648.

Scarmeas, Nikolaos, et al. Physical activity, diet, and risk of Alzheimer Disease. Journal of the American Medical Association, 302 (2009): 627-637.

     Scarmeas, Nikolaos, et al. Mediterranean Diet and Mild Cognitive Impairment. Archives of Neurology, 66 (2009): 216-225.

Scarmeas, N., et al. Mediterranean diet and Alzheimer disease mortality. Neurology, 69 (2007):1,084-1,093.

     Fung, Teresa, et al. Mediterranean diet and incidence of and mortality from coronary heart disease and stroke in women. Circulation, 119 (2009): 1,093-1,100.

Mente, Andrew, et al. A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease. Archives of Internal Medicine, 169 (2009): 659-669.

     Salas-Salvado, Jordi, et al. Effect of a Mediterranean Diet Supplemented With Nuts on Metabolic Syndrome Status: One-Year Results of the PREDIMED Randomized Trial. Archives of Internal Medicine, 168 (2008): 2,449-2,458.

     Mozaffarian, Dariush, et al. Incidence of new-onset diabetes and impaired fasting glucose in patients with recent myocardial infarction and the effect of clinical and lifestyle risk factors. Lancet, 370 (2007) 667-675.

     Esposito, Katherine, et al. Effects of a Mediterranean-style diet on the need for antihyperglycemic drug therapy in patients with newly diagnosed type 2 diabetes. Annals of Internal Medicine, 151 (2009): 306-314.

     Shai, Iris, et al. Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet. New England Journal of Medicine, 359 (2008): 229-241.

     Martinez-Gonzalez, M.A., et al. Adherence to Mediterranean diet and risk of developing diabetes: prospective cohort study. British Medical Journal, BMJ,doi:10.1136/bmj.39561.501007.BE (published online May 29, 2008).

     Trichopoulou, Antonia, et al. Anatomy of health effects of the Mediterranean diet: Greek EPIC prospective cohort study. British Medical Journal, 338 (2009): b2337. DOI: 10.1136/bmj.b2337.

     Barros, R., et al. Adherence to the Mediterranean diet and fresh fruit intake are associated with improved asthma control. Allergy, vol. 63 (2008): 917-923.

     Varraso, Raphaelle, et al. Prospective study of dietary patterns and chronic obstructive pulmonary disease among US men. Thorax, vol. 62, (2007): 786-791.

Low-Fat and Low-Carb Diets End Battle in Tie After Two Years, But…

Dieters on low-fat and low-carb diets both lost the same amount of weight after two years, according to a 2011 article in Annals of Internal Medicine. Both groups received intensive behavioral treatment, which may be the key to success for many. Low-carb eating was clearly superior in terms of increased HDL cholesterol, which may help prevent heart disease and stroke.

The study was funded by the National Institutes of Health and was carried out in Denver, St. Louis, and Philadelphia.

How Was It Done?

Healthy adults aged 18-65 were randomly assigned to either a low-fat or low-carbohydrate diet. Average age was45. Average body mass index was 36 (over 25 is overweight; over 30 is obese). Of the 307 participants, two thirds were women. People over 136 kg (299 lb) were excluded from the study—I guess because weight-loss through dieting is rarely successful at higher weights.

The low-carb diet: Essentially the Atkins diet with a prolonged induction phase (12 weeks instead of two). Started with maximum of 20 g carbs daily, as low-carb vegetables. Increase carbs by 5 g per week thereafter as long as weight loss progressed as planned. Fat and protein consumption were unlimited. The primary behavioral goal was to limit carb consumption.

The low-fat diet: Calories were limited to 1200-1500 /day (women) or 1500-1800 (men). [Those levels in general are too low, in my opinion.] Diet was to consist of about 55% of calories from carbs, 30% from fat, 15% from protein. The primary behavioral goal was to limit overall energy (calorie) intake.

Both groups received frequent, intensive in-person group therapy (lead by dietitians and psychologists) periodically over two years, covering such topics as self-monitoring, weight-loss tips, management of weight regain and noncompliance with assigned diet. Regular walking was recommended.

Body composition was measured periodically with dual X-ray absorptiometry.

What Did They Find?

Both groups lost about 11% of initial body weight, but tended to regain so that after two years, both groups average losses were only 7% of initial weight. Weight loss looked a little better at three months in the low-carb group, but it wasn’t statistically significant.

The groups had no differences in bone density or body composition.

No serious cardiovascular illnesses were reported by participants. During the first six months, the low-carb group reported more bad breath, hair loss, dry mouth, and constipation. After six months, constipation in the low-carb group was the only symptom difference between the groups.

During the first six months, the low-fat group had greater decreases in LDL cholesterol (with potentially less risk of heart disease), but the difference did not persist for one or two years.

Increases in HDL cholesterol (potentially heart-healthy) persisted throughout the study for the low-carb group. The increase was 20% above baseline.

About a third of participants in both groups dropped out of the study before the two years were up. [Not unusual.]

My Comments

Contrary to several previous studies that suggested low-carb diets are more successful than low-fat, the study at hand indicates they are equivalent as long as dieters get intensive long-term group behavioral intervention.

Low-carb critics warn that the diet will cause osteoporosis, a dangerous thinning of the bones that predisposes to fractures. This study disproves that.

Contrary to widespread criticism that low-carb eating—with lots of fat and cholestrol— is bad for your heart, this study notes a sustained elevation in HDL cholesterol (“good cholesterol”) on the low-carb diet over two years. This also suggests the low-carbers followed the diet fairly well. The investigators also note that low-carb eating tends to produce light, fluffy LDL cholesterol, which is felt to be less injurious to arteries compared to small, dense LDL cholesterol.

A major strength of the study is that it lasted two years, which is rare for weight-loss diet research.

A major weakness is that the investigators apparently didn’t do anything to document the participants’ degree of compliance with the assigned diet. It’s well known that many people in this setting can follow a diet pretty well for two to four months. After that, adherence typically drops off as people go back to their old habits. The group therapy sessions probably improved compliance, but we don’t know since it wasn’t documented.

How often do we hear “Diets don’t work.” Well, that’s just wrong.

Overall, it’s an impressive study, and done well.

Individuals wishing to lose weight on their own can’t replicate these study conditions because of the in-person behavioral intervention component. There are lots of self-help calorie-restricted balanced diets (e.g., Sonoma Diet, The Zone, Thin For Life, Advanced Mediterranean Diet) and low-carb diets (e.g., the Atkins Diet, the Low-Carb Mediterranean or Ketogenic Mediterranean Diets). On-line support groups—e.g., Low Carb Friends and SparkPeople and 3 Fat Chicks on a Diet—could supply some necessary behavioral intervention strategies and support.

Choosing a weight-loss program is not as easy as many think. (Well, I’ll admit that choosing the wrong one is easy.) I review the pertinent issues in my “Prepare for Weight Loss” page.

Steve Parker, M.D.

Reference: Foster GD, Wyatt HR, Hill JO, Makris AP, Rosenbaum DL, Brill C, Stein RI, Mohammed BS, Miller B, Rader DJ, Zemel B, Wadden TA, Tenhave T, Newcomb CW, & Klein S (2010). Weight and metabolic outcomes after 2 years on a low-carbohydrate versus low-fat diet: a randomized trial. Annals of internal medicine, 153 (3), 147-57 PMID: 20679559

Is a Low-Carb Diet Safe for Obese Adolescents?

I answered this question last year at the Diabetic Mediterranean Diet Blog, based on research from the Department of Pediatrics, University of Colorado.

It’s an important question. Childhood obesity in the U.S. tripled from the early 1980s to 2000, ending with a 17% obesity rate. Overweight and obesity together describe 32% of U.S. children. Some experts believe this generation of kids will be the first in U.S. history to suffer a decline in life expectancy, related to obesity.

Steve Parker, M.D.

Does Diabetes Cause Dementia?

Contrary to popular belief among the experts, type 2 diabetes is not one of the causes of Alzeimer dementia. They may indeed be associated with each other, but that’s not causation.

An oft-repeated theory from Gary Taubes 2007 masterpiece, Good Calories, Bad Calories, is that many of the chronic diseases of modern civilization, including Alzheimer disease, are caused by abnormal blood sugar and insulin metabolism. Especially high insulin levels induced by a diet rich in refined carbohydrates. If that’s the case, you’d expect to see a high prevalence of Alzheimer disease in older type 2 diabetics.

Dr. Emily Deans (psychiatrist) looked at this issue last year at her great Evolutionary Psychiatry blog.

The brains of Alzheimer patients, under a microscope, are characterized by many senile plaques (aka neuritic plaques) and neurofibrillary tangles. That’s the gold standard for diagnosis. Nevertheless, brain biopsies are rarely done to diagnose Alzheimer disease in living patients, and even autopsies after death are rare. The diagnosis usually is clinical, based on ruling out other illnesses, etc.

Nearly all the studies associating diabetes with Alzheimers disease (and other dementias) are observational or epidemiologic. (The exception is the Honolulu-Asia Aging Study.) Establishing an association is helpful in generating theories, but establishing causation is the goal. At least five studies confirm an association.

Neurology in 2011 reported findings of Japanese researchers who examined the brains of 135 people who died between 1998 and 2003. They lived in Hisayama, a town with an incredibly high autopsy rate of 74%. These people before death had undergone an oral glucose tolerance test. Their insulin resistance was calculated on the basis of fasting glucose and fasting insulin (HOMA-IR). None of them showed signs of dementia at the time of study enrollment in 1988.

What Did They Find?

Twenty-one of the 135 subjects developed Alzheimer-type dementia. The investigators don’t say if the diagnosis was based on the brain examination, or just a clinical diagnosis without a brain biopsy or autopsy. How this got beyond the article reviewers is beyond me. [If I’m missing something, let me know in the comments section below.] It must be a clinical diagnosis because if you don’t act demented, it doesn’t matter how many senile plaques and neurofibrillary tangles you have in your brain.

Senile plaques, but not neurofibrillary tangles, were more common in those with higher levels of blood sugar (as measured two hours after the 75 g oral glucose dose), higher fasting insulin, and higher insulin resistance. People with the APOE epsilon-4 gene were at even higher risk for developing senile plaques.

The researchers did not report whether the subjects in this study had been diagnosed during life with diabetes or not. One can only hope those data will be published in another paper. Why make us wait?

Average fasting glucose of all subjects was 106 mg/dl (5.9 mmol/l); average two-hour glucose after the oral glucose load was 149 mg/dl (8.3 mmol/l). By American Association of Clinical Endocrinologists criteria, these are prediabetic levels. Mysteriously, the authors fail to mention or discuss this. [I don’t know if AACE criteria apply to Japanese.] Some of these Japanese subjects probably had diabetes, some had prediabetes, others had normal glucose and insulin metabolism.

As with all good research papers, the authors compare their findings with similar published studies. They found one autopsy study that tended to agree with their findings (Honolulu) and three others that don’t (see references below). In fact, one of the three indicated that diabetes seems to protect against the abnormal brain tissue characteristic of Alzheimer disease.

Botton Line

Type 2 diabetes doesn’t seem to be a cause of Alzheimer disease, if autopsy findings and clinical features are the diagnostic criteria for the disease.

If we assume that type 2 diabetics have higher than normal blood sugar levels and higher insulin levels for several years, then hyperglycemia and hyperinsulinemia don’t cause or contribute to Alzheimer dementia.

Type 2 diabetes is, however, linked with impaired cognitive performance, at least according to many of the scientific articles I read in preparation for this post. So type 2 diabetics aren’t in the clear yet. It’s entirely possible that high blood sugar and /or insulin levels cause or contribute to that. (Any volunteers to do the literature review? Best search term may be “mild cognitive impairment.”)

Type 2 diabetes is associated with Alzheimer disease, but we have no proof that diabetes is a cause of Alzheimers. Nor do we have evidence that high blood sugar and insulin levels cause Alzheimer disease.

Alzheimer disease is a major scourge on our society. I’d love to think that carbohydrate-restricted eating would help keep blood sugar and insulin levels lower and thereby lessen the devastation of the disease. Maybe it does, but I’d like to see more convincing evidence. It’ll be years before we have a definitive answer.

For now, we have evidence that the Mediterranean diet seems to 1) protect againstAlzheimers and other dementias, 2) prevent some cases of type 2 diabetes, and 3) reduce the need for diabetic medications in diabetics.

For more information on practical application of the Mediterranean diet, visit Oldways and the Advanced Mediterranean Diet website.

Steve Parker, M.D.

References:

Matsuzaki T, Sasaki K, Tanizaki Y, Hata J, Fujimi K, Matsui Y, Sekita A, Suzuki SO, Kanba S, Kiyohara Y, & Iwaki T (2010). Insulin resistance is associated with the pathology of Alzheimer disease: the Hisayama study. Neurology, 75 (9), 764-70 PMID: 20739649

Heitner, J., et al. “Diabetics do not have increased Alzheimer-type pathology compared with age-matched control subjects: a retrospective postmortem immunocytochemical and histofluorescent study.” Neurology, 49 (1997): 1306-1311. Autopsy study, No. of subjects not in abstract. They looked for senile plaques and neurofibrillary tangles, etc. The title says it all.

Beeri, M.S., et al. “Type 2 diabetes is NEGATIVELY [emphasis added] associated with Alzheimer’s disease neuropathology.” J. Gerontol A. Biol Sci. Med. Sci. 60 (2005): 471-475. 385 autopsies. The title again says it all.

Arvanitakis, Z., et al. “Diabetes is related to cerebral infarction but NOT [emphasis added] to Alzheimers disease pathology in older persons.” Neurology, 67 (2006): 1960-1965. Autopsy study of 233 Catholic clergy, about 50:50 women:men.

Once Again, Mediterranean Diet Prevents Diabetes

Spanish researchers report that the Mediterranean diet reduced the risk of developing diabetes by 50% in middle-aged and older Spaniards, compared with a low-fat diet.

Over 400 people participated in a trial comparing two Mediterranean diets and a low-fat diet. Over the course of four years, 10 or 11% of the Mediterraneans developed type 2 diabetes, compared to 18% of the low-fatters. One of the Mediterranean diets favored olive oil, the other promoted nut consumption.

We’ve seen previously that the Mediterranean diet prevents diabetes—not all cases, of course—in folks who have had a heart attack. It also reduced the risk of diabetes in younger, generally healthy people in Spain.

So What?

The study at hand is not ground-breaking. It expands the body of evidence that the Mediterranean diet is one of the healthiest around.

Learn how to move your diet in a Mediterranean direction at Oldways or the Advanced Mediterranean Diet website.

Steve Parker, M.D.

Reference: Salas-Salvado, J., Bullo, M., Babio, N., Martinez-Gonzalez, M., Ibarrola-Jurado, N., Basora, J., Estruch, R., Covas, M., Corella, D., Aros, F., Ruiz-Gutierrez, V., Ros, E., & , . (2010). Reduction in the Incidence of Type 2-Diabetes with the Mediterranean Diet: Results of the PREDIMED-Reus Nutrition Intervention Randomized Trial Diabetes Care DOI: 10.2337/dc10-1288

The Whole9 “Five Best Exercises” Series

Thanks to Meredith @HIITMama for bringing this project from Whole9 to my attention:

We brought together 12 fitness experts from a broad range of backgrounds–with bodies of experience ranging from weightlifting to track and field to mixed martial arts, and over two centuries of collective coaching experience–to ask them all the same question:

If you could only perform five exercise movements for the rest of your life, which five would you do? (Assuming your goals are general health, fitness and longevity, and not a specialized sport)*.

The answers may surprise you.

If you want an effective and time-efficient fitness program, I’d review this series carefully.  You may have to research some terms like Turkish get-ups, farmer carries, and dips.  Find examples at YouTube.

Mediterranean Diet Prevents Middle-Age Weight Gain? I Wish…

Several mainstream media sources last year touted the Mediterranean diet as an effective method for prevention of the expected middle-age weight gain. Reuters is one source, for example. Men on the Mediterranean diet gained 2 lb (about a kilogram) less than other men over six years. Mediterranean-dieting women gained weight too, but a whole 0.77 lb (0.35 kg) less than others.

Big whoop.

The media attention was based on a Spanish study of over 10,000 men and women university graduates over the course of six years. Average baseline age was 38. A Mediterranean diet score was calculated based on a food frequency questionnaire given only at the start of the study. Adherence with a Mediterranean-style diet was judged for each individual as either low, medium, or high.

You’d think this research report would tell you how much weight these folks gained on average over six years, and how many pounds less if one followed the Mediterranean diet. Think again. No such luck, which reminds me of one of my favorite aphorisms: “eschew obfuscation.”

I had to do my own calculations based on Table 3. And I still don’t know how much the average person in this cohort gained over six years.

I am a die-hard Mediterranean diet advocate. It’s linked to myriad health benefits. I’d love to believe it prevents middle-age weight gain. But the results of this study are so modest as to be almost nonexistent.

Steve Parker, M.D.

Reference: Beunza, J., Toledo, E., Hu, F., Bes-Rastrollo, M., Serrano-Martinez, M., Sanchez-Villegas, A., Martinez, J., & Martinez-Gonzalez, M. (2010). Adherence to the Mediterranean diet, long-term weight change, and incident overweight or obesity: the Seguimiento Universidad de Navarra (SUN) cohort American Journal of Clinical Nutrition DOI: 10.3945/ajcn.2010.29764

High-Carbohydrate Eating Promotes Heart Disease in Women

Women double their risk of developing coronary heart disease if they have high consumption of carbohydrates, according to research published in the Archives of Internal Medicine.

Men’s hearts, however, didn’t seem to be affected by carb consumption. I mention this crucial sex difference because many experts believe that replacing saturated fat with carbohydrates is a major cause of heart disease. If true, it seems to apply only to women.

(Another nutrition science trend to keep an eye on is the thought that excessive consumption of omega-6 fats contributes to hardening of the arteries, including coronary heart disease. I’m talking about soy oil, safflower oil, corn oil, among others. No doubt, we’re eating a lot more omega-6 now than at the start of the 20th century.)

We’ve known for a while that high-glycemic-index eating was linked to heart disease in women but not men. Glycemic index is a measure of how much effect a carbohydrate-containing food has on blood glucose levels. High-glycemic-index foods raise blood sugar higher and for longer duration in the bloodstream.

High-glycemic-index foods include potatoes and white bread, for example.

The study at hand included over 47,000 Italians who were interrogated via questionnaire as to their food intake, then onset of coronary heart disease—the cause of heart attacks—was measured over the next eight years.

Among the 32,500 women, 158 new cases of coronary heart disease were found.

Researchers doing this sort of study typically compare the people eating the least carbs with those eating the most. The highest quartile of carb consumers and glycemic load had twice the rate of heart disease compared to the lowest quartile.

The Cleave-Yudkin theory of the mid-20th century proposed that excessive amounts of refined carbohydrates cause heart disease and certain other chronic systemic diseases. Gary Taubes has also written extensively about this. The research results at hand support that theory in women, but not in men.

Practical Applications

Do these research results apply to non-Italian women and men? Probably to some, but not all. More research is needed.

Women with a family history coronary heart disease—or other CHD risk factors—might be well-advised to put a limit on total carbs, high-glycemic-index foods, and glycemic load. I’d stay out of that “highest quartile.” Don’t forget: heart disease is the No. 1 killer of women.

See NutritionData’s Glycemic Index page for information you can apply today.

FYI, the Low-Carb Mediterranean Diet and Ketogenic Mediterranean Diet are also low in glycemic index.

Steve Parker, M.D.

Disclaimer: All matters regarding your health require supervision by a personal physician or other appropriate health professional familiar with your current health status. Always consult your personal physician before making any dietary or exercise changes.

Addendum: Alert reader Nadia Hassan brought to my attention that I had originally written that pasta has a high glycemic index. Citing appropriate references, Nadia convinced me that pasta has a low-to-moderate glycemic index, from around 30 to 60. Its GI also is higher if over-cooked. I corrected my original post.

References:

Sieri, Sabina, et al. Dietary glycemic load and index and risk of coronary heart disease in a large Italian cohort. The EPICOR study. Archives of Internal Medicine, 170 (2010): 640-647.

Barclay, Alan, et al. Glycemic index, glycemic load, and chronic disease risk – a meta-analysis of observational studies [of mostly women]. American Journal of Clinical Nutrition, 87 (2008): 627-637.

Chronic Alcohol May Impair Vision in Diabetics

MedPage Today recently reported that long-term consumption of alcohol may impair vision in diabetics. Drinkers performed less well on vision chart tests than non-drinkers. It’s not a diabetic retinopathy issue.

Beer and distilled spirits were riskier than wine.

The MedPage Today article didn’t comment on the potential health benefits of alcohol consumption. You can bet I’ll keep an eye on this.

Steve Parker, M.D.