Colorful carbohydrates are wonderful for adding pizzazz to our plates. The purples, reds and blues in vegetables and fruits such as raspberries, blueberries, black grapes and eggplant, have been researched for the benefits of fighting cancer and in cancer prevention. (1) I get questions often on how these colorful carbohydrates may be helpful for people with diabetes or trying to prevent diabetes.

One of the studies below is a report of conclusions from a large group of studies. Research usually starts with small animal and human studies and these are mentioned as well.  We need to follow this research to see where it may lead in recommendations for our health. It is a topic worthy of discussion.


Those Purple Anthocyanins

In botany, the word anthocyanin comes from the Greek flower (anthos) and dark blue (kyanos). (2) In plant biology, anthocyanin’s are the largest group of water soluble pigments, which gives the red, purple and blue colors to fruits and vegetables. They belong to the class of compounds known as flavonoids. (3)

A list of some of the foods that contain anthocyanins includes: apples, blackberries, blueberries, cherries, chokeberries, cranberry, elderberry, gooseberry, black grapes, nectarines, peaches, plums, raspberries, strawberries, black beans, eggplant, cabbage… and a surprise nut, the pistachio. (4)

Study No. 1: Reducing the Risk of Diabetes with Anthocyanins

The American Journal of Clinical Nutrition published an article in 2012 where the researchers followed women in the Nurses’ Health Study and the National Health Service Study and men in the Health Professionals Follow-Up Study. A total of 70,359 individuals did not have diabetes when they started the study. Published results concluded that the risk of acquiring type 2 diabetes was significantly lowered when subjects ate higher intakes of foods containing anthocyanins. The authors of the study particularly noted that eating two or more servings a week of blueberries significantly reduced the incidence of diabetes. Other fruits that had a significant reduction in associated risk were eating five or more servings per week of apples and pears. (5)

Study No. 2: Improving Postprandial Glucose with Berries

(Post-prandial glucose is the amount of glucose present in the blood. In people with diabetes it is usually measured 1-2 hours after the first bite of a meal.)

A small study with 13-20 participants evaluated the glucose response after eating:

- White bread with 150 grams of pureed strawberries, bilberries, loganberries, or chokeberries - or -
- White or rye bread with a mixture of berries consisting of equal amounts of strawberries, bilberries, cranberries, and blackcurrants.

The researchers found the insulin response after eating bread with the pureed berries or the berry mix was significantly reduced compared to eating the bread without the berries.

Strawberries and the berry mix when taken with white bread or rye bread improved the glycemic profile of the breads, i.e., the authors are suggesting that when berries and white bread are consumed together, less insulin is needed for maintenance of normal or slightly improved postprandial glucose metabolism. They also suggest that the insulin response to rye bread can be lowered with berries. (6)

Study No. 3: Purple Carrot Juice

Ask most children the color of a carrot and the reply you most likely will get is orange.  Did you know that actually carrots come in many colors? (You may want to browse other interesting facts such as this at the Carrot Museum.

Purple carrots are another colorful vegetable that contain anthocyanins. In one study, rats were fed a high-carbohydrate, high fat diet which induced the metabolic syndrome (includes: dyslipidemia, impaired glucose tolerance, hypertension, increased abdominal fat deposition and insulin resistance). Purple carrot juice or beta carotene was fed to rats. It was found that the purple carrot juice attenuated or reversed all of the metabolic syndrome changes. The authors concluded that it is likely that anthocyanins were responsible for improving glucose tolerance as well as other health factors. (7)

As we mentioned earlier, studies on foods and health usually begin with animals. The animal studies are exciting because results, if positive, are sometimes then studied in human subjects.  

Study No. 4: Current Study on Purple Vegetables on Cardiovascular Disease Risk Factors (and Type 2 Diabetes Risk)

There is a lot  of interest in purple vegetables. Currently at the University of Guelph in Ontario Canada, a 12-week human study is taking place. Humans will be fed orange or purple carrots or white or purple potatoes. The researchers will be evaluating data analyzing differences in the following between the groups: blood cholesterol, blood pressure, body composition, insulin resistance and circulating biomarkers of cardiovascular disease and type 2 diabetes risk. For more information on this study, click here.

Purple fruits and vegetables have been studied for benefits to our health. The studies continue to discover valuable information concerning disease prevention including diabetes.  Anthocyanins have been associated with helping prevent many diseases including colorectal cancer (8) and heart disease. (9)  The four studies that mentioned above support findings that anthocyanins may be of benefit in preventing type 2 diabetes or helping improve postprandial glucose metabolism. More information is needed on this topic, and as you can see, studies are currently taking place. 

In addition to possibly helping to avoid diseases, foods with anthocyanins provide vitamins and minerals. As foods containing anthocyanins are proven to be beneficial for your overall health, you may want to strongly consider including them in your meal plan. Of course, you should always discuss all relevant information with your health care team. Make sure that if you are a person with diabetes, you count these foods in your carbohydrate allowance. It is always good to get a variety of fruits and vegetables in your diet for optimal health. I am convinced they are beneficial for me and I include them in my diet. In fact, I love eating berries and my purple carrot seeds have been ordered to sow into my vegetable garden for next year!

Article Reference Links:

1, 2, 3, 4, 5, 6, 7, 8, 9

(Note: Link No. 4 will prompt a PDF download)