In the news: Can Eating Leafy Greens Lower AMD Risk? Findings From the VITAL Study

Leafy Greens & Eye Health

Leafy green vegetables contain nutrients – lutein, zeaxanthin and vitamin C, for example – that are beneficial to eye health. Now, for the first time, Australian medical researchers report a link between eating vegetable nitrates, abundant in leafy greens and beets, and the risk of developing early age-related macular degeneration (AMD) (1).

The body naturally produces nitric oxide, which plays a number of roles in overall health. One important function of nitric oxide is vasodilation – the relaxation of blood vessels to allow good circulation. Dietary nitrates can be converted to nitric oxide once consumed.

In the present study, researchers used data from over 2,000 participants of the Blue Mountains Eye Study – a large population health study conducted in Australia. Those participants had complete dietary data and information about age-related macular degeneration (AMD), and were re-examined 15 years later.

After taking into account other risk factors that could affect AMD development, the researchers found that those who consumed a moderate amount of vegetable-sourced nitrates each day (100-142 mg) had a 35% lower risk of developing early-stage AMD compared to those who ate less than 69 mg of vegetable nitrates daily.

Eating higher amounts of vegetable-sourced nitrates (greater than 142 mg daily) was not associated with risk reduction, nor did nitrate intake influence the risk of late-stage AMD.

More research must be conducted to see if the association of dietary nitrates and AMD holds up. If the findings are confirmed, dietary nitrates may be another good reason to eat leafy greens (dark leafy greens especially), and beets – vegetables that already established as important for overall health.

Findings from the VITAL Study

The VITAL Study evaluated whether vitamin D (2,000 IU daily) and fish oil (1,000 mg daily) could lower the risk of invasive cancer of any type or major cardiovascular events (a composite of heart attack, stroke, or death from cardiovascular disease) in over 25,800 men and women who were free of cancer and cardiovascular disease at the beginning of the study, and followed for about 5 years (2), (3).

These primary objectives or target endpoints of the study were not met for vitamin D or the omega-3s.

Despite this, separate analyses (called secondary findings) are promising, particularly the lower death from cancer seen for vitamin D compared to placebo. Secondary findings need to be interpreted cautiously, especially because the trial was unable to include some relevant statistical corrections.

However, the vitamin D findings are in line with those from a recent meta-analysis that showed a significant benefit with vitamin D and cancer mortality. Also, another VITAL analysis found that the rate of cancer death was lower with vitamin D vs. placebo when the first 2 years of the study were excluded.

While fish oil didn’t lower all major cardio events as a group (a primary endpoint), a reduction in risk was seen for heart attack, fatal heart attack, and total coronary heart disease when each was looked at separately.

It’s also worth noting that analyses revealed a risk reduction for the primary cardiovascular endpoint with fish oil supplements vs. placebo for those with low fish intake (less than 1½ servings weekly) at the study’s start. No risk reductions were seen for participants with higher fish intake.

In terms of safety, no adverse effects were seen for vitamin D or omega-3 supplementation in VITAL, including no excess bleeding or high blood calcium.

References

1. Gopinath B, et al. Association of dietary nitrate intake with the15-Year incidence of age-related macular degeneration. J Acad Nutr Dietetics. Epub Oct 17, 2018.
2. Manson JE, et al. Marine n-3 fatty acids and prevention of cardiovascular disease and cancer. NEJM. Epub Nov. 10, 2018.
3. Manson JE, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. NEJM. Epub Nov. 10, 2018.