In the news:Flavonoids & Women’s Health: Vitamin D in Diabetic Retinopathy

Certain Flavonoids Might Cut Ovarian Cancer Risk

According to the American Cancer Society, ovarian cancer accounts for only 3% of cancers among women yet causes more deaths than any other cancer of the female reproductive system. Smoking is associated with an increased risk of this cancer, and possibly obesity, but scientists have not been able to clearly identify other lifestyle or dietary risk factors that women can change to reduce ovarian cancer risk.

Flavonoids are nutrients found in many plant based foods and beverages including fruit, vegetables, tea, and wine. There are also many different types or ‘subclasses’ of flavonoids found in the foods we eat.

Earlier studies have hinted at an association between several of these flavonoid subclasses and ovarian cancer risk, but only recently have food databases been developed that provide information on the full range of flavonoids present in the diet.

Taking advantage of this information, researchers from UK and Harvard have examined the association of 6 flavonoid subclasses and their main food sources with the risk of epithelial ovarian cancer. The study (1) involved nearly 180,000 women in the original Nurses Health Study and the Nurses Health Study II. The women were followed for many decades and information on their diet was collected every 4 years.
 
While total intake of all flavonoids was not linked with ovarian cancer risk, women consuming the highest amounts of two subgroups (flavonols and flavanones) had a modestly lower risk of 21-24%. The main sources of these flavonoid subgroups include tea and citrus fruits or juice. In this study, oranges, orange juice and black tea, followed by onions and apples, were the most common sources of these flavonoids.

This finding has to be confirmed by future studies in order to learn whether the foods we choose could have an impact on ovarian cancer risk. But in the meantime, consuming a more plant-based diet that provides flavonoid-rich fruit, veggies and beverages is associated with better health overall.

Low Vitamin D Levels and Diabetic Retinopathy

People with diabetes are at a higher risk for developing diabetic retinopathy because high blood sugar levels can damage blood vessels in the eye’s retina.
 
In some people with diabetic retinopathy, blood vessels may swell and leak fluid leading to macular edema – something that can happen at any stage of diabetic retinopathy. In others, abnormal new blood vessels grow on the surface of the retina. The growth of these blood vessels signals a more advanced stage of the disease (proliferative diabetic retinopathy), which can lead to severe vision loss.

Some studies have reported low levels of vitamin D in diabetics, or that the percentage of patients with vitamin D deficiency increases with severity of diabetic retinopathy.

In the latest investigation, researchers in China divided over 1500 patients with type 2 diabetes into 3 groups: those with no diabetic retinopathy, those with non-sight threatening retinopathy, and patients with sight-threatening retinopathy. Patients with the more advanced stage of sight-threatening diabetic retinopathy had significantly lower blood levels of vitamin D and more vitamin D deficiency (20 ng/ml or less) than the other two groups (2).

After adjusting for other factors that could affect the study results, the researchers concluded that vitamin D deficiency is an independent risk factor for diabetic retinopathy and vision-threatening diabetic retinopathy.

Can maintaining better levels of vitamin D reduce the risk of developing type 2 diabetes? Can correcting deficiencies of this vitamin lower the risk of developing complications like diabetic retinopathy? There are no answers yet, though trials are underway to test these hypotheses.

References

1. Cassidy A, et al. Intake of dietary flavonoids and risk of epithelial ovarian cancer. Am J Clin Nutr [Epub ahead of print] Aug 20, 2014.
2. He R, et al. Vitamin D deficiency increases the risk of retinopathy in Chinese patients with Type 2 diabetes. Diabet Med [Epub ahead of print] Sept 3, 2014.