We all know that greens are good for us, but could another coloured vegetable provide further health benefits? This week’s Nutrition News covers the latest studies illustrating how the food we eat has a huge impact on our health.

The anti-diabetic properties of purple vegetables

Maintaining blood sugar levels through nutrition is a form of diabetes support that can have life changing effects for those affected.

This recent article by Medical News Today reviews a number of studies that have been carried out to better understand the anti-diabetic properties of anthocyanins, which are the type of polyphenols that are responsible for giving red-orange to blue-violet colours in plants including studies in the United States and Finland that have shown that consumption of anthocyanin-rich foods, particularly berries, reduces the risk of type 2 diabetes. The article also covers a new review article published in the Journal of Agricultural and Food Chemistry, which summarises the effects of anthocyanins on gut microbiome, energy metabolism and inflammation. It is thought that this is due to acylated anthocyanins having a probiotic-like property and lower bioavailability, which are likely to have different biological effects from nonacylated anthocyanins on diabetes.

Acylated anthocyanins have a chemical group called an “acyl group,” which nonacylated anthocyanins lack. Compared to nonacylated anthocyanins, acylated anthocyanins are more stable and more resistant to digestion, which means they are not digested and absorbed in the stomach, and upper intestine and they pass through to the colon, where they are degraded extensively by gut microorganisms. Examples of nonacylated anthocyanins containing foods include elderberry, blackberry, and blackcurrant, while acylated anthocyanins can be found in red radish, purple corn, black carrot, red cabbage, and purple sweet potato.

Speaking of the findings, Dr. Taylor C. Wallace, adjunct professor in the Department of Nutrition and Food Studies at George Mason University and principal and CEO at the Think Healthy Group said, “[Acylated anthocyanin-rich] purple potatoes also contain a lot of resistant starch and other compounds that may contribute to their anti-diabetic effects. [Nonacylated anthocyanin-rich] berries contain a significant amount of natural sugar that may negate some of the anthocyanin’s anti-diabetic effects.”

The effects of intermittent fasting on the immune system

While intermittent fasting has been found to have many health benefits, including reducing the risk of age-related illnesses, a new study, as reported in this Medical News Today intermittent fasting article, suggests it may also have a potential downside.

Researchers from the Cardiovascular Research Institute at the Icahn School of Medicine at Mount Sinai in New York found that, after four hours of fasting, there was a 90% decrease in the number of monocytes – a type of immune cell – in the bloodstream of subjects that fasted. This suggests that intermittent fasting could have a detrimental impact on the immune system.

In the study, the cells, which normally patrol the body for pathogens and play a role in inflammation and tissue repair, were shown to return to the bone marrow during periods of fasting. The researchers noted, however, that upon feeding, there was a surge of monocytes flooding back into the bloodstream which could be problematic.

The subjects that fasted for 24 hours, and then ate for four hours, also had a reduced ability to fight off an infection. The researchers also found that fasting led to changes in the brain, triggering the release of the stress hormone corticosterone, which in turn recalled the immune cells to the bone marrow.

While there is much evidence that intermittent fasting has benefits, the researchers suggest the key to balancing the risks and benefits may be more measured forms of fasting and controlled re-feeding.

Study suggests vitamin D could support brain health

A new study published in the journal Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring, reported by Science Daily, has revealed that vitamin D supplementation is linked to a lower risk of dementia.

Researchers from the University of Calgary's Hotchkiss Brain Institute in Canada and the University of Exeter in the UK examined the association between vitamin D supplementation and dementia in more than 12,380 participants of the US National Alzheimer's Coordinating Center. Of the group, 4,637 took vitamin D supplements. The team found that taking vitamin D was associated with living dementia-free for longer and that there were 40% fewer dementia diagnoses in the group who took supplements. Across the entire sample, 2,696 participants developed dementia over ten years; amongst them, 2,017 had no exposure to vitamin D throughout all visits prior to dementia diagnosis, and 679 had baseline exposure.

The study suggests that vitamin D supplementation is beneficial to cognitive health. Previous research has found that low levels of vitamin D are linked to higher dementia risk. Vitamin D is involved in the clearance of amyloid in the brain, the accumulation of which is one of the hallmarks of Alzheimer's disease. Studies have also found that vitamin D may provide help to protect the brain against the build-up of tau, another protein involved in the development of dementia.

The researchers found that vitamin D was effective in all groups but had significantly greater effects in females, those with normal cognition compared to those with mild cognitive impairment, and those who did not carry the APOEe4 gene, which is known to present a higher risk for Alzheimer's dementia. The authors suggest that people who carry the APOEe4 gene absorb vitamin D better from their intestines, which might reduce the vitamin D supplementation effect. However, no blood levels were drawn to test this hypothesis.

The ongoing VitaMIND study at the University of Exeter is exploring the issue further by randomly assigning participants to either take vitamin D or a placebo and examining changes in memory and thinking tests over time. So, while the research is promising, no clear conclusions have yet been reached and it may be some time before we fully understand the link between vitamin D and brain health.

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Alison Astill-Smith author Alison is Director and Founder of Metabolics who writes about Metabolics updates, events and natural healthcare. Her experience and passion for natural supplements and healthcare comes from her years of experience as a practising osteopath, having founded Metabolics in her search for high quality, natural products in her own work. Alison has been a qualified and practising Osteopath since 1981 and regularly gives seminars on a range of healthcare subjects to the wider practitioner community helping share her knowledge and experience.