In the news: Poor B1 status with low-carb diets; Retinal Benefits of Dark Chocolate?

Daily Multi-Vitamin for Low Carb Consumers

Low carbohydrate diets (LCD) and ketogenic diets (KD) have become popular for weight loss and for managing type 2 diabetes.

LCDs are generally defined as consuming less than 26% of a day’s total energy intake as carbohydrates (or less than 130 g/day). For ketogenic dieters, carbohydrates generally provide less than 10% of total energy intake (or less than 20-50 g daily).

Not much is known about the micro-nutrient intakes and status of LCD-followers. Of special concern is the status of vitamin B1 or thiamine, as this vitamin is mainly obtained from high carb foods made with whole grain or fortified flour, with smaller amounts coming from meat and fish.

Vitamin B1 is an important cofactor for a wide variety of enzymes engaged in metabolic processes. Low status of thiamine has recently been associated with increased risk of late AMD (see EduFacts Vol. 28; www.sbh.com).

At least one observational study has reported that half of LCD followers had B1 and magnesium intakes below recommendations.

In a new study(1), researchers assessed the intake of selected vitamins and minerals in LCD followers and controls using food frequency questionnaires. Red blood cell thiamine diphosphate (TDP) was used to measure B1 status, and plasma magnesium, zinc, copper and selenium were measured.

The study found that 43% of LCD participants failed to meet the reference nutrient intake for thiamine (vs. 14% of controls, p=0.002). When thiamine from supplements was included, intake differences were not apparent between groups although B1 status (red blood cell TDP) was still lower in LCD followers than controls (p=0.001). No differences in intake or plasma levels were seen for the other nutrients.

The authors conclude that individuals embarking upon LCDs should have dietary guidance and diet supplementation.

Flavanol-rich Chocolate Impacts Retinal Vessels

Cocoa polyphenols (especially flavanols) have been shown to have antioxidant, anti-inflammatory and vasodilatory effects. Flavanols have been shown to induce the release of the vasodilator nitric oxide.

So far, studies published on the effects of dark chocolate on vision have reported different results: some have reported improvements in contrast sensitivity or short-term acuity, while others have not. Most of these studies, however, have not employed newer imaging and functional methods.

To further evaluate the potential effect of dark chocolate on the functionality and anatomy of retinal vessels in healthy individuals, researchers measured parameters of visual acuity, dynamic vessel analyzer (DVA) and optimal coherence tomography angiography (OCT-A)(2).

Participants were randomized to receive either 20 g of dark chocolate (400 mg of flavanols) or 7.5 g of milk chocolate (lower cocoa and flavanols) then crossed over one week later to receive the opposite chocolate intervention. Measurements were made before consuming the chocolate, and 2 hours later.

Using OCT-A, no differences were seen in terms of diffusion density changes after dark and milk chocolate intake. Using DVA, a significant increase in arterial dilation was noted after the dark chocolate, but not the milk chocolate intake.

According to the authors, the beneficial, functional short-term effects of a relatively small amount of dark chocolate (about ¾ of an ounce) in retinal vessels warrants further study to see whether flavanol-rich chocolate consumption may possibly have a role in the prevention of retinal diseases.

References

1. Churuangsuk C, et al. Low thiamine status in adults following low carbohydrate / ketogenic diets: a cross- sectional comparative study of micronutrient intake and status. Eur J Nutr. 63:2667-79, 2024,
2. Sacconi R, et al. Benefits of dark chocolate intake on retial vessels functionality: a randomized, blind, crossover clinical trial. Sci Rep. 14:20203, 2024.