In the news: Avocados for the Mind & Vision; Flavonoids & Healthy Body Composition

More Avocados For Good Vision & Cognition

The September issue of Staying Healthy focused on research exploring whether lutein and zeaxanthin may support brain function in older people and children. Avocados were also mentioned as a good dietary source of these carotenoids.

The body selectively concentrates lutein from the foods we consume into the eye’s macula and into brain tissue. Studies have shown that lutein levels in the macula (measured via macular pigment density or MPD) reflect lutein levels in the brain. So MPD is considered a biomarker for brain concentrations of lutein.

As follow-up, a new study from Tufts University reports that daily consumption of avocados increases MPD, and that those increases appear to be related to better cognitive performance (1).

In the trial, older participants were randomly assigned to a group eating one avocado daily or to a group consuming one cup of chickpeas or one potato (neither of which contain lutein) each day. MPD was measured and cognitive testing was conducted at the study’s start, and at three and six months.

Only the avocado group had a significant increase in MPD at the end of the study. That group also fared better on tests of sustained attention. The increases in MPD seen in the avocado group were related to improved scores on tests of working memory and efficiency in approaching a problem.

Both groups, however, saw improvements in tests for memory and spatial working memory. The researchers suggest this finding might be a result of increasing familiarity with these tests over the course of the study.

The avocados provided only ½ milligram of lutein daily- far less than the amounts of lutein typically supplemented in other studies. Yet the avocados appeared to be quite efficient in increasing lutein levels in blood and in the macula.

The study authors suggest that this efficiency could be due to the monounsaturated fats in avocados. Mono-unsaturated fat from avocados has been reported toincrease HDL cholesterol- important because lutein is transported in the body by HDL molecules. In the present study, avocado intake resulted in higher blood levels of lutein that were significantly related to increases in HDL.

Avocados complement other rich sources of lutein like green leafy vegetables (e.g. spinach and kale) and egg yolks. The avocado, a fruit, provides substantial amounts of vitamins, minerals and other nutrients with relatively few calories.

Flavonoids Linked to Body Fat Accumulation

Increasing evidence suggests that eating flavonoids from plant-based foods such as fruits, vegetables, tea, wine, and chocolate, may be beneficial for weight maintenance. Now for the first time, researchers report that flavonoid-rich foods may affect body fat and where it’s distributed in the body (2).

The study was conducted in the UK and included over 2700 healthy identical twins, all women. Any differences between identical twins are due to factors other than genetics.

In brief, higher consistent intake of a number of flavonoids, including anthocyanins (e.g. blueberries,
grapes, and wine), flavan-3-ols (e.g. apples, tea and wine), flavonols (e.g. onions, tea, and pears), and proanthocyanidins (e.g. apples, cocoa), were associated with lower body fat, and not due to shared genetic and common environmental factors including physical activity and intake of sugar-laden beverages.

It was striking that twins with the highest intake of many of these flavonoids had less fat accumulation in the lower torso around the stomach and abdomen than their co-twins. Fat in this area is particularly unhealthy as it’s associated with insulin resistance, the metabolic syndrome and higher risk of cardiovascular disease.

References

1. Scott AM, et al. Avocado consumption increases macular pigment density in older adults: A randomized, controlled trial. Nutrients; 9(9):919, 2017.
2. Jennings A, et al. Higher dietary flavonoid intakes are associated with lower objectively measured body composition in women: evidence from discordant mono- zygotic twins. Am J Clin Nutr; 105:626-34, 2017.