In this issue: (1) dark chocolate and eyesight; (2) caffeine in utero and obesity; (3) lutein, zeaxanthin, and cognitive function; and (4) magnesium pairs with vitamin D.

Welcome to the third edition of Thorne’s Research Extracts. This is Thorne’s monthly research update on diet, nutrient, and botanical approaches to good health. Knowing that busy practitioners can’t always focus on the latest research, our medical team of NDs, MDs, PhDs, RDs, and MS (Biol) has summarized the essence of the very most interesting studies.

Will eating dark chocolate improve eyesight?

Contributed by Jacqueline Jacques, ND

Who doesn’t want more good news about chocolate? You may already know that dark chocolate is rich in antioxidants and that the flavanols in chocolate are good for the heart.

Another compound in chocolate, phenylethylamine, can promote a positive mood – and might be part of the reason that eating chocolate makes people happy. This new study indicates that dark chocolate might also benefit eye health. A recent study evaluated vision two hours after eating a serving of either milk chocolate or dark chocolate.

The serving of dark chocolate (72% cacao) resulted in a measurable short-term improvement in “visual acuity and contrast sensitivity,” while the milk chocolate resulted in no change in vision. The researchers suggest this result might be due to an increase in blood flow to the eye and the optic nerve.

Caffeine during pregnancy can increase a child’s early weight trajectory

Contributed by Sheena Smith, MS (Biol)

Data from The Norwegian Mother and Child Cohort Study, which includes more than 50,000 mother-child pairs, was assessed to correlate the mother’s caffeine intake during pregnancy and her child’s early growth trajectory. At week 22, four maternal caffeine intakes were categorized: low (<50 mg/day), average (50-199 mg/day), high (200-299 mg/day), and very high (≥300 mg/day).

Childhood growth data was collected at 11 points between birth and age 8 and assessed for excess growth or overweight/obesity using WHO and International Obesity Task Force standards. With and without adjusting for confounding factors, it was found that any exposure to caffeine in utero increased the risk of excess weight gain during infancy and early childhood.

Higher maternal caffeine intake corresponded linearly to a higher risk of excess growth in infancy. This effect diminished by early childhood, with only the highest levels of prenatal caffeine exposure (200 mg/day is the recommended maximum) correlating to continued excess weight gain at age 8. The study strengthens the recommendation to curtail caffeine intake during pregnancy and emphasizes the 200 mg/day threshold as a meaningful limit. 

Lutein and zeaxanthin: more than just eye health

Contributed by Kathi Head, ND

Lutein and zeaxanthin are known to support ocular health, particularly the macula. What is less well known is the increasing evidence that these two carotenoids also support cognitive health. In this study, serum lutein and zeaxanthin levels were measured in 51 older adults. Visual-spatial processing tests were then conducted during functional magnetic resonance imaging.

The individuals with higher serum lutein and zeaxanthin levels showed less dependency on blood oxygen levels during task performance. The researchers conclude: “L[utein] and Z[eaxanthin] may promote brain health and cognition in older adults by enhancing neurobiological efficiency in a variety of regions that support visual perception and decision-making.

More broadly, the present study bridges the gap between the disciplines of nutrition and neuroscience to advance our understanding of the critical relationship between diet and brain function.”

Magnesium is essential to efficiently metabolize vitamin D

Contributed by Joel Totoro, RD

Although general vitamin D deficiency and insufficiency is now well documented, this paper highlights that vitamin D is inefficiently metabolized without an adequate level of magnesium being present. What makes this finding intriguing is the current state of magnesium intake in the United States. The World Health Organization estimates that three-quarters of U.S. adults do not meet the Recommended Daily Intake of 420 mg of magnesium.

Given the prevalence of the inadequate intakes of these two essential nutrients, and this paper’s finding of the importance of magnesium status on vitamin D metabolism, it is increasingly clear that individuals who supplement vitamin D should consider their magnesium status, and vice versa.