Category Archives: olive oil

Low-Carb Mediterranean Diet Improves Glucose Control and Heart Risk Factors in Overweight Diabetics

In overweight type 2 diabetics, a low-carbohydrate Mediterranean diet improved HDL cholesterol levels and glucose control better than either the standard Mediterranean diet or American Diabetes Association diet, according to Israeli researchers reporting earlier this year.

Background

Prior studies suggest that diets rich in monounsaturated fatty acids (olive oil, for example) elevate HDL cholesterol and reduce LDL cholestrol and triglycerides in type 2 diabetics.

Low-carb diets improve blood sugar levels and reduce excess body weight in type 2 diabetics, leading to the ADA’s allowance in 2008 of a low-carbohydrate diet as an alternative to standard diabetic diets.

Many—probably most—type 2 diabetics have insulin resistance:  the body’s cells that can remove sugar from the bloodstream are not very sensitive to the effect of insulin driving sugar into those cells.  They “resist” insulin’s effect.  Consumption of monounsaturated fatty acids  improves insulin sensitivity.  In other words, insulin is better able to push blood sugar into cells, removing it from the bloodstream.

Previous studies have shown that both low-carb diets and the Mediterranean diet reduce after-meal elevations in blood sugar, which likely lowers levels of triglycerides and LDL cholesterol.

How Was the Study Done?

The goal was to compare effects of three diets in overweight type 2 diabetics in Israel over the course of one year.  Study participants totalled 259.  Average age was 56, average weight 86 kg (189 lb), average hemoglobin A1c 8.3%, and average fasting plasma glucose (sugar) was 10.3 mmol/L (185 mg/dl).  [Many diabetics in the U.S. fit this profile.]  People taking insulin were excluded from the study, as were those with proliferative diabetic retinopathy—no reasons given. 

Participants were randomly assigned to one of three diets, so there were about 85 in each group.  [Over the course of one year, people dropped out of the study for various reasons, leaving each group with about 60 subjects.] 

Here are the diets:

  • 2003 ADA (American Diabetes Association) diet:  50-55% of total caloric intake from carbohydrate (mixed glycemic index carbs), 30%  from fat, 20% from protein
  • Traditional Mediterranean (TM):  50-55% low-glycemic-index carbs, 30% fat—high in monounsaturated fat, 15-20% protein
  • Low-carb Mediterranean (LCM) :  35% low-glycemic-index carbs, 45% fat—high in monounsaturated fat, 15-20% protein

Patients were followed-up by the same dietitian every two weeks for one year.  All were advised to do aerobic exercise for 30-45 minutes at least three days a week.

Olive oil is traditionally the predominant form of fat in the Mediterranean diet and is a particularly rich source of monounsaturated fat.  At no point in this report was olive oil mentioned, nor any other source of monounsaturated fat.  Until I hear otherwise, I will assume that olive oil was the major source of monounsaturated fat in the TM and LCM diets. 

 All diets were designed to provide 20 calories per kilogram of body weight. 

In all three diets, saturated fat provided 7% of total calories.  Monounsaturated fatty acids provided 23% of total calories in the LCM, and  10% in the other two diets.  Polyunsaturated fatty acids provided 15% of calories in the LCM, and 12% in the other two diets.  The ADA diet provided 15 grams of fiber, the TM had 30 g, and the LCM had 45 g.

Adherence to the assigned diet was assessed with a “food frequency questionnaire” administered at six months.

What Did the Researchers Find?

Average reported energy intake was similar in all three groups: 2,222 calories per day.

Monounsaturated fat intake differences were statistically significant: 14.6, 12.8, and 12.6% for the LCM, TM, and ADA diets, respectively.  Polyunsaturated fat intake differences were statistically significant: 12.9, 11.5, and 11.2% for the LCM, TM, and ADA diets, respectively.

Percentage of energy from carbs was highest for the ADA diet (45.4%), intermediate for the TM diet (45.2%), and lowest for the LCM diet (41.9%).

At the end of 12 months, all three groups lost about the same amount of weight (8-9 kg or 18-20 lb), body mass index, and waist circumference.

Hemoglobin A1c fell in all three groups, but was significantly greater for the LCM group than for the ADA diet (6.3% absolute value vs 6.7%).

Triglycerides fell in all three groups, but was significantly greater for the LCM diet compared to the ADA diet.

The LCM group achieved a significant increase (12%) in HDL cholesterol compared to the ADA diet, but not different from the TM group.

LDL cholesterol fell in all three groups, and the LCM group’s drop (25%) was clearly superior to that of the ADA diet (14%) but about the same as the TM diet (21%).

Conclusions of the Investigators

We found that an intensive community-based dietary intervention reduced cardiovascular risk factors in overweight patients with [type 2 diabetes] for all three diets.  The LCM group had improved cardiovascular risk factors compared to either the ADA or the TM groups.

Only the LCM improved HDL levels and was superior to both the ADA and TM in improving glycaemic control.

It would appear that the low carbohydrate Mediterranean diet should be recommended for overweight diabetic patients.

My Comments

There’s no way the average diabetic could replicate this low-carb Mediterranean diet without working closely with a dietitian or nutritionist.

Any superiority of this low-carb Mediterranean diet may have as much to do with the increased monounsaturated fat intake as with the reduced carb consumption.  Monounsaturated fatty acid consumption is thought to improve insulin sensitivity. 

NutritionData’s Nutrient Search Tool can give you a list of foods high in monounsaturated fat.

The Mediterranean diet and low-carb diets independently have been shown to lower after-meal glucose levels, which probably lowers LDL cholesterol and triglycerides.

I’m disappointed the dietitians were not able to achieve a lower level of carbohydrate consumption in the low-carb Mediterranean diet group.  I suspect if they had, improvements in glucose control and lipids would have been even better.  But proof awaits another day.

We saw last year an article in the Annals of Internal Medicine that showed a dramatic reduction in the need for glucose-lowering drugs in type 2 diabetics following a different low-carb Mediterranean diet over four years, compared to a low-fat American Heart Association diet.  These two studies convince me a low-carb Mediterranean diet has real life-preserving and life-enhancing potential. 

Diabetics looking for a low-carb Mediterranean diet today have several options:

If you’re aware of any other low-carb, explicitly Mediterranean-style diets, please share in the Comments section.

Steve Parker, M.D. 

References: 

Elhayany, A., Lustman, A., Abel, R., Attal-Singer, J., and Vinker, S.  A low carbohydrate Mediterranean diet improves cardiovascular risk factors and diabetes control among overweight patients with type 2 dabetes mellitus:  a 1-year prospective randomized intervention studyDiabetes, Obesity and Metabolism, 12 (2010): 204-209.

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

2 Comments

Filed under Carbohydrate, coronary heart disease, Fat in Diet, Glycemic Index and Load, Mediterranean Diet, olive oil

Longevity Components of the Mediterranean Diet

According to Greek researchers, the components of the Mediterranean diet that contribute to longer lifespan are:

  • moderate alcohol consumption
  • low consumption of meat
  • high consumption of vegetables, fruits, nuts, olive oil, and legumes

The following didn’t seem to contribute much, if any:

  • cereals (the grain of a grass such as wheat, corn, oats)
  • dairy products
  • fish and seafood

Investigators at the University of Athens examined the Greek portion of the European Prospective Investigation into Cancer (EPIC) and Nutrition, which included 23,349 men and women free of diabetes, cancer, and coronary heart disease at the outset.  Food habits were documented by questionnaire. 

The focus of this particular study was death rates over an average follow-up of 8.5 years.  Adherence to the traditional Mediterranean diet ranged from minimal to high, as would be expected. 

As with numerous other studies of the Mediterranean diet, higher adherence to the Mediterranean diet was associated with lower chance of death. 

My Comments

The lack of benefit from fish is unexpected.  I have no explanation.  A preponderance of evidence elsewhere suggests fish consumption helps prolong life via lowered rates of heart disease.

Alcohol can be dangerous, of course.  Some people should not partake, ever.     

For people with diabetes who wish to avoid the carbohydrate load in cereals and dairy products, you don’t need to worry much about cutting those out of an otherwise Mediterranean-style diet.

Steve Parker, M.D. 

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

8 Comments

Filed under Alcohol, Dairy Products, Fish, Fruits, Grains, Health Benefits, legumes, Mediterranean Diet, nuts, olive oil, Vegetables

Does Diet Influence Risk of Stroke?

Harvard researchers suggest that our food consumption does indeed influence our risk of suffering a stroke.  This matters since stroke is the third leading cause of death in the U.S.

Scientists looked carefully at 121 different studies—published between 1979 and 2004—on the relationship between dietary factors and stroke.  High blood pressure is a major modifiable risk factor for stroke, so it also was considered.  Dietary factors included fats, minerals, animal protein, cholesterol, fish, whole grains, fiber, carbohydrate quality, fruits and vegetables, antioxidants, B vitamins, and dietary patterns.

I quote their conclusions:

Diets low in sodium and high in potassium lower blood pressure which will likely reduce stroke risk.

Consumption of fruits and vegetables, whole grains, folate, and fatty fish are each likely to reduce stroke risk.

A prudent or traditional Mediterranean dietary pattern, which incorporates these individual dietary components as well as intake of legumes and olive oil, may also prevent stroke.

Evidence is limited or inconsistent regarding optimal levels of dietary magnesium, calcium, antioxidants, total fat, other fat subtypes, cholesterol, carbohydrate quality, or animal protein for stroke prevention.

A diet low in sodium, high in potassium, and rich in fruits, vegetables, whole grains, cereal fiber, and fatty fish will likely reduce the incidence of stroke.

Take Home Points

The article abstract does not address the optimal intake amount of these various foods, vitamins, and minerals.  That’s probably not known with any certainty.

The traditional Mediterranean diet incorporates many of these stroke-preventing foods.  The Advanced Mediterranean Diet helps people lose weight while teaching how to eat Mediterranean-style.

The very low-carb Ketogenic Mediterranean Diet includes these stroke-preventing foods and minerals, except for whole grains and a tendency to be low in potassium.  The KMD is high in total fat and animal protien, and potentially high in cholesterol; this study indicates those issues are nothing to worry about in terms of future strokes.

I’ll use articles such as this to recommend long-term food consumption for followers of any future Diabetic Mediterranean Diet.

Steve Parker, M.D.

Reference:  Ding, E.L, and Mozaffarian, D.  Optimal dietary habits for the prevention of stroke. Seminars in Neurology, 26 (2006): 11-23.

Comments Off on Does Diet Influence Risk of Stroke?

Filed under Fish, Fruits, Grains, Health Benefits, legumes, Mediterranean Diet, olive oil, Stroke, Vegetables

What Are Phytonutrients and What Have They Done For Me Lately?

Nutrition scientists think that plants have small amounts of numerous “bioactive compounds,” sometimes referred to as phytonutrients, that protect us against disease.

Many scientific studies have looked at groups of people over time, noting the various foods they eat as well as the diseases they develop.  These are called epidemiologic, ecological, or observational studies.  One finding is that lower rates of heart disease, vascular disease, and cancer are seen in people consuming plant-based diets.  “Plant-based” isn’t necessarily vegetarian or vegan.  The traditional Mediterranean diet, for example, is considered by many to be plant-based because meat, fish, and poultry are not prominent compared to plants. 

In contemplating what source of carbohydrates a person with diabetes should eat, I’ve been reviewing the scientific literature to see which sources of carbs might provide the biggest bang for the buck in terms of health and longevity benefits.

Here are some quotes from a 2002 review article in the American Journal of Medicine:

Phenolic compounds, including their subcategory, flavonoids, are present in all plants and have been studied extensively in cereals, legumes, nuts, olive oil, vegetables, fruits, tea, and red wine. Many phenolic compounds have antioxidant properties, and some studies have demonstrated favorable effects on [blood clotting] and [growth of tumors]. Although some epidemiologic studies have reported protective associations between flavonoids or other phenolics and cardiovascular disease and cancer, other studies have not found these associations.

Hydroxytyrosol, one of many phenolics in olives and olive oil, is a potent antioxidant.

Resveratrol, found in nuts and red wine, has antioxidant, [anti-blood-clotting], and anti-inflammatory properties, and inhibits [malignant tumor onset and growth].

Lycopene, a potent antioxidant carotenoid in tomatoes and other fruits, is thought to protect against prostate and other cancers, and inhibits tumor cell growth in animals.

Organosulfur compounds in garlic and onions, isothiocyanates in cruciferous vegetables, and monoterpenes in citrus fruits, cherries, and herbs have [anti-cancer] actions in experimental models, as well as [heart-healthy effects].

In summary, numerous bioactive compounds appear to have beneficial health effects. Much scientific research needs to be conducted before we can begin to make science-based dietary recommendations. Despite this, there is sufficient evidence to recommend consuming food sources rich in bioactive compounds. From a practical perspective, this translates to recommending a diet rich in a variety of fruits, vegetables, whole grains, legumes, oils, and nuts.

The article discusses phytoestrogens—plant chemicals that act in us like the female hormone estrogen—but effects are complex and I suspect we know much more now than we did in 2002 .  Soy products are the most well-known source of phytoestrogens.

The traditional Mediterranean diet is rich in all of the foods mentioned above, except for tea.  Even the Ketogenic Mediterranean Diet includes the aforementioned foods except for tea (I need to add tea and coffee), cereals, and cherries.

Steve Parker, M.D.

Reference:  Kris-Etherton, P.M., et al.  Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer.  American Journal of Medicine, 113 (2002. Supplement 9B): 71S-88S.

Comments Off on What Are Phytonutrients and What Have They Done For Me Lately?

Filed under cancer, coronary heart disease, Fruits, Grains, Health Benefits, legumes, Mediterranean Diet, nuts, olive oil