In the News: Healthy Flavonoids, Vitamin D & AMD Risk

Flavonoids are a “Hot” Research Topic

Flavonoids, also referred to as bioflavonoids, are polyphenol antioxidants found naturally in plants. Flavonoids are nutrients found in fruits, vegetables, herbs, wine, cocoa and teas. There are many different families of flavonoids, and various families are thought to have protective effects against chronic diseases. We consume an estimated 190 mg of flavonoids daily, and researchers are trying to better understand their contribution to health and to determine optimal intakes. The results of two new studies, which focus on citrus flavonoids, illustrate the potential benefits of flavonoids and suggest that higher intakes are warranted.

Citrus Flavonoids Lower Blood Pressure

Researchers studied the effects of orange juice (OJ) and its major flavonoid, hesperidin, on blood pressure and blood vessel function in overweight but otherwise healthy men (1). About 1/3 of the men had elevated blood pressure, but were taking no anti-hypertensive medications.

During 3 successive 4 week periods, the men drank either 17 oz of orange juice daily, a control drink with 300 mg hesperidin capsules (the same amount as the orange juice contained), or a control drink along with a placebo capsule.

At the end of both the OJ and hesperidin test periods, diastolic pressure was significantly lower than after the placebo period. Diastolic pressure (the second number in blood pressure readings) measures the pressure in blood vessels between heart beats, when the heart is resting. Even a decrease of just 3-4 points in diastolic pressure could translate into a 20% reduction in the incidence of coronary heart disease.

The researchers also tested a variety of measures of blood vessel activity, including the ability of vessels to dilate. Both OJ and hesperidin showed positive effects compared to placebo.

More Flavonoids, Less Inflammation

In another study (2), researchers examined flavonoid intake and blood markers of inflammation in a large group of women. The investigators found that women eating the highest amount of total flavonoids had the lowest blood levels of one marker (IL-8). Among foods, higher intakes of grapefruit were linked to lower levels of two more markers (CRP and TNF-R2). Finally, citrus flavonoids in particular were associated with lower levels of another inflammatory marker (IL-18).

Why is this finding important? Well, most people are aware of acute inflammation – the redness, swelling and pain encountered with injury. However, it’s long-term unresolved inflammation that is believed to underlie many chronic diseases, including ocular conditions such as age-related macular degeneration (AMD), dry eye and glaucoma.

Vitamin D May Protect Against AMD in Women

Higher blood levels of vitamin D are associated with a lower risk of developing AMD, according to new research (3). Looking at vitamin D and AMD status in over 3,000 postmenopausal women, investigators found that higher blood levels of this “sunshine vitamin” decreased the risk of early AMD in women under 75. For those over 75, the association was borderline.

In terms of vitamin D intake from supplements and foods, those consuming the highest amount (on average about 600 IU) daily, had a 59% lower risk of AMD compared to those getting the least (about 300 IU on average).

This is the second study to report a relationship between vitamin D and AMD. The vitamin has anti-inflammatory actions, and inflammation plays a role in AMD development. Specifically, the vitamin may interfere with the destructive inflammation that happens in the early stages of the disease at the interface of the retina’s blood supply (choroid) and the pigment-containing cells of the retina.

References

1. Morand C, et al. Hesperidin contributes to the vascular protective effects of orange juice: a randomized crossover study in healthy volunteers. Am J Clin Nutr 93:73–80, 2011.
2. Landburg R, et al. Selected dietary flavonoids are associated with markers of inflammation and endothelial dysfunction in U.S. women. J Nutr. 141:618-25. Epub Feb 16, 2011.
3. Millen AE, et al. Vitamin D status and early age-related macular degeneration in postmenopausal women. Arch Ophthalmol 129:481-89, 2011.