Category Archives: Fruits

Another Sacred Cow Slaughtered: Fruits and Vegetables DON’T Prevent Cancer

We’ve been told by the authorities repetitively that eating plenty of fruits and vegetables will lower our risk of cancer.  However, a recent study in the American Journal of Clinical Nutrition says that ain’t so.

Fire up the grill—we’re havin’ steak tonight!

Researchers looked at data from over 450,000 participants (men and women over 50) in the National Institutes of Health—AARP Diet and Health Study.  Diet data was collected by self-administered questionnaire.  State-level cancer registries identified the cancers that developed during the average follow-up of seven years.

Their conclusions and selected comments:

Intake of fruit and vegetables was generally unrelated to total cancer incidence in this cohort.

However, on the basis of animal studies, human case control and cohort studies, and randomized controlled trials, there is likely no harm associated with the consumption of fruit and vegetables and their consumption may prevent cardiovascular disease.

Indeed, analyses in this cohort and in others that have investigated dietary patterns rich in fruit and vegetables have found reduced risks of colorectal cancer [three references cited] and mortality, including death from cardiovascular disease and all cancers [one reference was cited supporting reduced deaths from CVD and all cancers—a Mediterranean diet study].

As in all good science reports, the researchers compare and contrast their findings with similar published research.  They note that theirs is one of only four large cohort studies that have examined this issue.  Two of the other three (see references below) also found no association between total cancers and fruit and vegetable consumption.  The one that did find a beneficial linkage was the smallest of the four, so not as compelling.

Before this research was published, some experts suggested that adequate fruit and vegetable intake could prevent between 5 and 12% of cancers.

Eat your fruits and vegetables because they taste good, provide myriad nutrients, and may have some other healthful properties.  But not to lower overall cancer risk.  

Steve Parker, M.D.

References:

George, Stephanie, et al.   Fruit and vegetable intake and risk of cancer: a prospective cohort studyAmerican Journal of Clinical Nutrition, 89 (2009): 347-353. 

Hung, H.C., et al.  Fruit and vegetable intake and risk of major chronic disease.  Journal of the National Cancer Institute, 96 (2004): 1,577-1,584.

Takachi, R., et al.  Fruit and vegetable intake and risk of total cancer and cardiovascular disease [in Japan].  American Journal of Epidemiology, 167 (2008): 59-70.

Benetou, V., et al.  Vegetables and fruit in relation to cancer risk: evidence from the Greek EPIC Cohort Study.  Cancer Epidemiology, Biomarkers, and Prevention, 17 (2008): 387-392.

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Filed under cancer, Fruits, Mediterranean Diet, Vegetables

Eat the Right Carbs to Alleviate Diabetes and Heart Disease

Harvard’s Dr. Frank Hu in 2007 called for a paradigm shift in dietary prevention of heart disease, de-emphasizing the original diet-heart hypothesis and noting instead that “. . . reducing dietary GL [glycemic load] should be made a top public health priority.”  Jim Mann at the University of Otago (Dunedin, New Zealand) authored a 2007 review of carbohydrates and effects on heart disease and diabetes.  Here are highlights from the article summary in the European Journal of Clinical Nutrition:

The nature of carbohydrate is of considerable importance when recommending diets intended to reduce the risk of type II diabetes and cardiovascular disease and in the treatment of patients who already have established diseases. Intact fruits, vegetables, legumes and whole grains are the most appropriate sources of carbohydrate. Most are rich in [fiber] and other potentially cardioprotective components.  Many of these foods, especially those that are high in dietary fibre, will reduce total and low-density lipoprotein cholesterol and help to improve glycaemic control in those with diabetes.

Frequent consumption of low glycaemic index foods has been reported to confer similar benefits, but it is not clear whether such benefits are independent of the dietary fibre content of these foods or the fact that low glycaemic index foods tend to have intact plant cell walls.

A wide range of carbohydrate intake is acceptable, provided the nature of carbohydrate is appropriate. Failure to emphasize the need for carbohydrate to be derived principally from whole grain cereals, fruits, vegetables and legumes may result in increased lipoprotein-mediated risk of cardiovascular disease, especially in overweight and obese individuals who are insulin resistant.

Why does this matter to me and readers of this blog?  Dietary carbohydrates are a major determinant of blood sugar levels, tending to elevate them.  Chronically high blood sugar levels are associated with increased complication rates from diabetes.  People with diabetes are prone to develop heart disease, namely coronary artery disease, which causes heart attacks, weakness of the heart muscle, and premature death. 

Steve Parker, M.D.

References: 

Mann, J.  Dietary carbohydrate: relationship to cardiovascular disease and disorders of carbohydrate metabolismEuropean Journal of Clinical Nutrition, 61 (2007): Supplement 1: S100-11.

Hu, Frank.  Diet and cardiovascular disease prevention: The need for a paradigm shift.  Journal of the American College of Cardiology, 50 (2007): 22-24.

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Filed under Carbohydrate, coronary heart disease, Fiber, Fruits, Glycemic Index and Load, Grains, legumes, 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.

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

Diabetes + Overweight and Obesity = Diabesity

Mark Hyman, M.D., blogged about diabesity at the Huffington Post December 24, 2009.  He defines diabesity as a problem with glucose regulation associated with overweight and obesity.  The glucose physiology problem ranges from metabolic syndrome to prediabetes to full-blown type 2 diabetes.

“Diabesity” has been in circulation for a few years, but hasn’t caught on yet. 

What interested me about his blog post was that he advocates the Mediterranean diet as both therapeutic and prophylactic.  To quote Dr. Hyman:

The optimal diet to prevent and treat diabesity includes:

  • Fruits
  • Vegetables
  • Nuts
  • Seeds
  • Beans
  • Whole grains
  • Healthy fats such as olive oil, nuts, avocados, and omega-3 fats
  • Modest amounts of lean animal protein including small wild fish such as salmon or sardines

This is commonly known as a Mediterranean diet.  It is a diet of whole, real, fresh food. It is a diet of food you have to prepare and cook from the raw materials of nature.  And it has broad-ranging benefits for your health.

Food for thought, no doubt. 

Steve Parker, M.D.

Reference:  Hyman, Mark.  The diabesity epidemic part III:  Treating the real causes instead of the symptoms.  The Huffington Post, December 24, 2009

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Filed under Causes of Diabetes, Fish, Fruits, Grains, legumes, nuts, Overweight and Obesity, Prevention of T2 Diabetes

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.

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

Legumes and Whole Grains: Any Role in Diabetes?

Expert nutrition panels consistently recommend whole grains and legumes for people with diabetes.  Why?  And do these foods affect development of diabetes?  I found a pertinent scientific review article on the subject from 2004 in the European Journal of Clinical Nutrition.  Here are some pertinent quotes from the summary:

Epidemiological studies strongly support the suggestion that high intakes of whole grain foods protect against the development of type II diabetes mellitus (T2DM). People who consume approximately 3 servings per day of whole grain foods are less likely to develop T2DM than low consumers (<3 servings per week) with a risk reduction in the order of 20-30%.

The role of legumes in the prevention of diabetes is less clear, possibly because of the relatively low intake of leguminous foods in the populations studied. However, legumes share several qualities with whole grains of potential benefit to glycaemic control including slow release carbohydrate and a high fibre content. A substantial increase in dietary intake of legumes as replacement food for more rapidly digested carbohydrate might therefore be expected to improve glycaemic control and thus reduce incident diabetes. This is consistent with the results of dietary intervention studies that have found improvements in glycaemic control after increasing the dietary intake of whole grain foods, legumes, vegetables and fruit.

. . . it is cereal fibre that is largely insoluble [rather than soluble fiber] that is associated with a reduced risk of developing T2DM.

Thus, there is strong evidence to suggest that eating a variety of whole grain foods and legumes is beneficial in the prevention and management of diabetes. This is compatible with advice from around the world that recommends consumption of a wide range of carbohydrate foods from cereals, vegetables, legumes and fruits both for the general population and for people with diabetes.

Gluten Intolerance

A major protein in wheat is gluten.  The last few years have seen the popular emergence of gluten-free this and gluten-free that.  The idea is that gluten causes a variety of gastrointestinal, immunologic, and other problems, so wheat products should be avoided.  Certainly they should be avoided in people with celiac disease, a well-established medical condition.  I follow a few paleo blogs and know that grains and legumes are not part of that way of eating: the paleos say we are not evolved optimally to process them.    

If legumes or wheat or other grains cause problems for you, don’t eat them.  They have no essential nutrients that you can’t get elsewhere. 

Glycemic Index

In my quest to develop a healthy Diabetic Mediterranean Diet, I’m finding that grains—compared to nearly all other carbohydrate-containing food groups—tend to have a higher glycemic index (GI).   A low GI is 55 or less.  High GI is 70 or greater.  Grains in general raise blood sugar levels higher than many other sources of carbohydrates.  But this is highly variable and depends partially on preparation of the grain.  Whole grain products have a lower GI than highly processed counterparts.  For instance, white bread has a GI of 70; whole wheat bread 67.  Regular spaghetti is 38.  Table sugar’s GI must be sky high, right?  No, its just 61.  A baked potato is a whopping 85.   

Beans have a GI around 30 or 40.  And they pack a lot more fiber per serving.  For a diabetic struggling to keep blood sugars under control, which is a better choice: grains or legumes?  I’m leaning towards legumes and other components of a low-glycemic-index diet.   

Steve Parker, M.D.

PS:  [Before you correct my GI numbers, please note I’m  aware that various GI lists don’t agree with each other.]

Reference:  Venn, B.J. and Mann, J.I. Cereal grains, legumes and diabetes.  European Journal of Clinical Nutrition, 58 (2004): 1,443-1,461.

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Filed under Fiber, Fruits, Grains, legumes, Prevention of T2 Diabetes, Vegetables

Do Fruits and Vegetables Really Help Prevent Disease?

How many times have you heard how important it is to eat fruits  and vegetables?  Now, is it five or nine servings a day?  Why are fruits and veggies always lumped together?  What does a watermelon have in common with spinach?

The author of a 2004 article in the Journal of Postgraduate Medicine answered some of these questions.  Here are a few quotes from from the summary:

The intake of 400-600 g/d of fruits and vegetables is associated with reduced incidence of many common forms of cancer, and diets rich in plant foods are also associated with a reduced risk of heart disease and many chronic diseases of ageing.

These foods contain phytochemicals that have anti-cancer and anti-inflammatory properties which confer many health benefits. Many phytochemicals are colourful, and recommending a wide array of colourful fruits and vegetables is an easy way to communicate increased diversity of intake to the consumer. For example, red foods contain lycopene, the pigment in tomatoes, which is localized in the prostate gland and may be involved in maintaining prostate health, and which has also been linked with a decreased risk of cardiovascular disease. Green foods, including broccoli, Brussels sprouts and kale, contain glucosinolates which have also been associated with a decreased risk of cancer. Garlic and other white-green foods in the onion family contain allyl sulphides which may inhibit cancer cell growth. Other bioactive substances in green tea and soybeans have health benefits as well.

Consumers are advised to ingest one serving of each of the seven colour groups daily, putting this recommendation within the United States National Cancer Institute and American Institute for Cancer Research guidelines of five to nine servings per day. Grouping plant foods by colour provides simplification, but it is also important as a method to help consumers make wise food choices and promote health.

Asking U.S. consumers to eat one serving from each of seven fruit and vegetable color groups daily is a bit much.  I don’t see that happening.  But the suggestion is a start.  Darya Pino (Summer Tomato blog) probably does it every day, but I don’t know any others.  My simplified message: Eat a variety of colorful fruits and veggies daily.

Note that the very low-carb Ketogenic Mediterranean Diet provides 400 grams of vegetables and fruits daily, and I count seven colors (assuming you allow me to include black olives).  On the KMD document I list avocado, cucumber, and tomato under “vegetables,” but they are indeed fruits.  Heck, I guess olives are fruit, too.

“So, what’s your point, Parker,” you might well ask.  I don’t expect anyone to follow the Ketogenic Mediterranean Diet for life.  When it’s time to move on to a “Diabetic Mediterranean Diet,” I’m considering adding more options: traditional fruits and some colorful vegetables like purple beets, yellow corn, and orange carrots and sweet potatoes.

I still don’t know why “fruits and vegetables” are joined at the hip.  Legumes, grains, and dairy products all rate their very own category.  It’s just not fair.

Steve Parker, M.D.

Reference:  Heber, D.  Vegetables, fruits and phytoestrogens in the prevention of diseases.  Journal of  Postgraduate Medicine, 50 (2004): 145-9.

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Filed under Fruits, Health Benefits, Vegetables

Top 10 Diabetes Superfoods

The American Diabetes Association has published a list of  Top 10 Diabetes Superfoods.  They share a low glycemic index and provide key nutrients, according to the ADA.  Click the link for details.  Here they are in no particular order:

  • beans
  • dark green leafy vegetables
  • citrus fruit
  • sweet potatoes
  • berries
  • tomatoes
  • fish high in omega-3 fatty acids
  • whole grains
  • nuts
  • fat-free milk and yogurt

Regular readers here know I have no problem generally with regular or high-fat versions of dairy products.  An exception would be for people trying to lose weight while still eating lots of carbohydrates; the low- and no-fat versions could have lower calorie counts, which might help with weight management.

But compare non-fat and whole milk versions of yogurt in the USDA nutrient database.  One cup of non-fat fruit variety yogurt has 233 calories, compared to 149 calories in plain whole milk yogurt.  The “non-fat” version  reduced the fat from 8 to 2.6 g (not zero g) and replaced it with sugars (47 g versus 11 g). 

Unfortunately, your typical supermarket yogurts are low-fat yet loaded with sugar or high fructose corn syrup that impede weight loss.

Nevertheless, this superfoods list may give us some guidance in design of a Diabetic Mediterranean Diet.  Except for “fat-free,” everything else on the list is a component of the traditional healthy Mediterranean diet.  “Fat-free” is a modern invention and not necessarily an improvement.

Steve Parker, M.D.

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Filed under Dairy Products, Fish, Fruits, Glycemic Index and Load, Grains, Health Benefits, legumes, Mediterranean Diet, nuts, Vegetables