In the news: Flavonoids May Benefit Cardio- Metabolic, Eye and Cognitive Health

Anthocyanins and Cardio-Metabolic Health

Cardio-metabolic risk refers to your chances of developing diabetes, heart disease or stroke, and includes such risk factors as elevated blood sugar, cholesterol, and blood pressure, and being overweight. Several, but not all, previous clinical investigations suggest a cardio-metabolic role for anthocyanins, the (flavonoid)s that give color to foods like eggplants, red cabbage, blueberries, blackberries, raspberries and concord grapes. Consuming more polyphenols in general (flavonoids are a type of polyphenol) has been tied to lower type 2 diabetes risk (1).

To better understand the effects of anthocyanins on cardio-metabolic risk factors, researchers conducted a review and meta-analysis which included 19 good quality randomized clinical trials investigating anthocyanin supplementation at different doses and over differing periods of time in adults (2).

One factor showing a beneficial response to anthocyanins in this analysis was improvement in a measure of insulin resistance (called HOMA-IR). In addition, a daily dose of more than 300 mg of anthocyanins (roughly, more than ¾ cup blueberries) for at least 3 months had favorable effects on blood levels of total and LDL cholesterol.

The average intake of anthocyanins in the US is a mere 12.5 mg daily. So, bring on the red and purple fruits and veggies to support cardio-metabolic health.

Flavonoids and AMD Risk

In a new study from Australia (3), university investigators followed a group of over 2000 participants of the Blue Mountains Eye Study aged 49 and older. The group’s diet was assessed for flavonoid intake, and the presence of AMD was determined based on retinal photographs. Fifteen years later, the researchers uncovered a protective link between dietary intake of flavonoids and the likelihood of having AMD.

Greater total overall flavonoid intake was associated with a 24% reduced chance of having any AMD. Several classes of flavonoids (flavanones which are abundant in citrus, and flavonols, found in a wide variety of foods such as onions, kale, leeks, broccoli, blueberries, red wine and tea) were particularly linked with lower risk. A 61% reduced risk of late AMD was seen after 15 years in those who consumed one or more servings of oranges daily at the study’s start, vs. non-consumers.

Further studies are needed to confirm these findings. It’s possible, for example, that participants could have changed their diets over the years. However, the findings do make sense since greater intake of fruits and vegetables has previously been shown to reduce AMD risk, and flavonoids have antioxidant and anti-inflammatory activities. It’s also notable that the total flavonoid intake in this study group (median 875 mg/day) is vastly higher than the US intake (median 117 mg/day).

Flavonoids, Aging and the Mind

French researchers carried out a clinical trial (4) to evaluate the effects of a daily polyphenol-rich extract from grape and blueberry (containing 258 mg flavonoids) vs. placebo on memory performance in 215 healthy older subjects 60-70 years-old.

After 6 months, no improvements for the group as a whole was seen in the memory tests conducted. However, in a subgroup with the greatest cognitive decline at the study’s start, there was a significant favorable response to the flavonoids for episodic memory – the ability to mentally recall and verbalize past personal experiences occurring at a particular time and place. Hopefully this study will spur more research interest in flavonoids and memory with age.

References

1. Rienks J, et al. Polyphenol exposure and risk of type 2 diabetes: dose-response meta-analyses and systematic review of prospective cohort studies. Am J Clin Nutr. 108:49-61, 2018.
2. Daneshzad E, et al. Effect of anthocyanin supplementation on cardio-metabolic biomarkers: A systematic review and meta-analysis of randomized controlled trials. Clin Nutr. Epub ahead of print, July 2, 2018.
3. Gopinath B, et al. Dietary flavonoids and the prevalence and 15-y incidence of age-related macular degeneration. Am J Clin Nutr. 108:1–7, 2018.
4. Bensalem J, et al. Polyphenols from grape and blueberry improve episodic memory in healthy elderly with lower level of memory performance: a bicentric double-blind, randomized, placebo-controlled study.J Gerontol. Series A gly166, 2018.