We are always encouraged to eat fruits and vegetables because they are “Good for Us”. Besides the essential nutrients found in fruits and vegetables, scientists are now looking at health benefits coming from certain flavonoids. Flavonoids are non-nutrient compounds found in fruits, vegetables, herbs, grains, nuts, beverages, and yes, chocolate. They are known as polyphenolic compounds, and currently number over 5000 different compounds¹.

Flavonoids may have both positive and negative effects in a human’s body. Very high intakes of some flavonoids inhibit the break down of food protein in the body, and reduce the absorption of glucose and certain minerals such a non heme iron. In most cases, these effects would be considered negative; however in some cases, these effects may actually be positive. For example, slowing down the rate of glucose absorption would be beneficial to diabetics. Flavonoids can also increase or decrease the effect of certain drugs, which is an important area of research that needs follow-up. Very high levels of flavonoids may have carcinogenic effects; however, this work was done in animals and test tubes. Further studies must be done to look at the dose effects of different flavonoids. Studies must also be done to see how high levels of flavonoids effect growth and body development, particular during gestation¹.

As indicated, much more work is required to fully understand flavonoids. However, a number of studies have started to broaden our understanding of flavonoids.

Epidemiological studies have implied that certain flavonoids have a protective effect against cardiovascular disease (CVD), cancer, and other aging conditions, such as Alzheimer’s^1,2,3. However as of the 2005 review on Flavonoids and Heart Health, clinical evidence was insufficient to support flavonoid’s ability to reduce CVD¹. Research continues in this area. Flavonoids are known to prevent oxidation, lessen allergic reactions, prevent the development of carcinogens, impede the growth of cancer cells, and stimulate the immune system. They also may protect against bacteria and viruses².

A study that looked at the results from over 133 trials found that cocoa or dark chocolate increased endothelial flow mediated dilation, and decreased blood pressure. Flow mediated dilatation is monitored in studies as this parameter correlates well with other CVD risk factors⁴. However, a recent study indicates no effects and disputes the health claims derived from chocolates⁷. This discrepancy in results from two separate studies exemplifies the need for further work to substantiate the effects of flavonoids.

Black tea was found to increase both systolic and diastolic blood pressure. In two further studies that controlled the caffeine content in black tea, diastolic blood pressure was still increased. The study also found that soy protein isolates reduced diastolic blood pressure and LDL cholesterol levels. Green tea was also found to decrease LDL cholesterol levels⁴. Research will need to define if the above effects are caused by the flavonoids found within these foods and drinks.

Flavonoid levels within a food are influenced by the plant variety. The levels are also influenced by the farm practices used; such as the amount of irrigation and fertilization, and the climatic conditions that the plant grows in. The level of maturity when the plant is harvested and how the produce is handled after harvesting also influences the levels of flavonoids found within the food¹.

How foods are processed affects the amount of flavonoids available. For example, the normal manufacturing process for chocolate destroys 25 to 50% of the flavonoid content. Alterations to the heating and alkalization in chocolate processing can help to retain a high level of the flavonoid content⁵. Although chocolate may have health benefits from flavonoids, chocolate also has undesirable effects. Consumption of 50g of dark chocolate equates to 240 Calories and 15g of fat. This consumption amount to 12% of the daily recommended calories coming from one food source (i.e., a normal adult needs to consume approximately 2000 calories a day). Daily fat consumption should only make up 20 to 35% of the caloric intake⁶. Therefore, consuming dark chocolate is not the best idea for proper and balanced nutrition.

Berries are also known to be high in certain flavonoids and Vitamin C. A study in Finland with 72 subjects consuming 2 portions of a berry mixture/day for 8 weeks resulted in a favorable increase in HDL cholesterol levels, slightly decreased blood pressure, and inhibited platelet function⁸. This consumption level equated to 837mg/day of various flavonoids and 61.5mg Vitamin C.

Three flavonoids in red wine are thought to be responsible for the protective effect on heart attacks. Some of these effects may be through flavonoids preserving antioxidant defenses, lowering LDL oxidation, and improving endothelial function. The alcohol in wine is not thought to be a contributing factor, as alcohol free grape juice also has the positive effects¹.