New studies are published in the sphere on nutrition every day and uncover some of the most surprising correlations between seemingly everyday foods and our health. This week’s Nutrition News includes analysis of studies centering on cognitive health and its link with strawberries as well as how maternal vitamin D levels affect their offspring’s respiratory health.

Find out more by reading the article in full here.

Strawberries may reduce dementia risk

Alzheimer's disease (AD) presents a growing concern in the realms of cognitive health as it is predicted to reach epidemic levels in the near future. This neurodegenerative condition shares a concerning link with metabolic disturbances such as insulin resistance, obesity, and related health issues. Given its prevalence, research is mounting in this field, especially in areas that are showing promise for mitigating against cognitive decline and dementia risk.

AD pathology develops over many years before evident symptoms emerge, offering a window for intervention. Intriguingly, this preclinical phase coincides with midlife, where metabolic issues surface. Metabolic health in the US population is notably low, with nearly half of middle-aged adults experiencing insulin resistance.

Research, as reported in the article “A cup of strawberries a day may help keep dementia away” by NutraIngredients indicates that metabolic issues, notably insulin resistance and obesity, play a role in early neurodegenerative changes, accelerating the onset of conditions such as dementia. They trigger beta-amyloid deposition and tau hyperphosphorylation, characteristic Alzheimer’s disease features.

Metabolic disturbance and obesity foster chronic inflammation, impacting various organs, including the brain. This neuroinflammation significantly contributes to brain dysfunction and progressive neuropathology. Berry fruits, especially with anthocyanins present in strawberries and blueberries, shows promise for their anti-inflammatory properties and correcting metabolic dysfunction, potentially improving neuronal signalling.

Studies involving obese, insulin-resistant adults demonstrate that daily strawberry intake effectively lowers fasting insulin and insulin resistance markers. These effects are attributed to anthocyanins, which reduce levels of branch chain amino acids linked to decreased type 2 diabetes risk.

In addition to its metabolic benefits, strawberry consumption showcases preliminary evidence of supporting neurocognitive function. Studies reveal supported cognitive performance, including spatial navigation and recognition memory, in older adults supplemented with strawberry powder for 90 days.

A recent controlled pilot trial, focusing on middle-aged individuals at risk of cognitive decline, showed promising results. Overweight participants treated with whole-fruit strawberry powder for 12 weeks exhibited reduced memory interference during learning tasks and reported lower levels of depressive symptoms, suggesting improved executive control and emotional coping capabilities and further supporting the importance of weight management for optimum health.

While these findings are encouraging, the study highlights the need for further investigation with varying dosages, larger sample sizes, and longer intervention periods to comprehensively explore the health and neurocognitive benefits associated with strawberry consumption.

Study shows iron deficiency increases chances of depression in women

Iron deficiency remains a prevalent global issue, particularly impacting women of reproductive age and children across various countries. In the United States, about 10% of non-pregnant women within this age range grapple with ID, while females aged 25 to 44 face a significant lifetime risk of major depressive disorder, with potential contributions from nutrient deficiencies such as iron deficiency, according to the article “Iron deficiency may make women more prone to depression: Study”.

Research suggests a link between iron deficicent and adverse psychosocial outcomes, such as depression, due to iron's role in neurotransmitter chemistry. Observational studies have established this connection, yet evidence from randomised controlled trials (RCTs) remains limited and inconclusive due to small sample sizes and insufficient control for environmental factors. Recent assessments of depression measurement tools, such as the Patient Health Questionnaire (PHQ-9), have enhanced their accuracy in detecting depressive symptoms across diverse demographics.

To gain clarity on the relationship between iron status and depression, especially across income levels, a study was conducted using the nationally representative NHANES data among non-pregnant women of reproductive age. The findings revealed that women with iron deficiency had higher odds and scores for depressive symptoms, especially those from low-income backgrounds.

This study is pioneering in examining the association between iron status and depressive symptoms, categorising them by specific aspects (cognitive/affective vs. somatic). It identified a significant impact of iron deficiency on somatic symptoms of depression, encompassing sleep disturbances, fatigue, and appetite changes. Prior evidence has hinted at associations between poor iron status and these symptoms, indicating a potential pathway for intervention through iron supplementation and dietary recommendations.

The study's strength lies in its use of a large, representative sample and appropriate statistical techniques, uncovering subtle nuances in the iron-depression relationship. However, the findings are limited by the cross-sectional nature of NHANES, preventing the establishment of causal relationships.

In essence, this study emphasises the importance of addressing iron deficiency, particularly in relation to women’s health, as a potential strategy to mitigate depressive symptoms. Future research, especially randomised trials controlling for various factors, could offer insights into the effectiveness of iron supplementation in alleviating deficiencies and reducing depressive symptoms in this population.

Prenatal vitamin D may reduce the likelihood of childhood asthma

A comprehensive analysis, reported in the article “Prenatal vitamin D may reduce child’s asthma risk: Harvard study” spanning 15 years from the Vitamin D Antenatal Asthma Reduction Trial (VDAART) revealed that administering vitamin D during pregnancy notably reduced the occurrence of childhood asthma and wheezing compared to standard prenatal multivitamin supplements.

Brigham and Women's Hospital investigators, affiliated with the Mass General Brigham healthcare system, presented a compelling link between maternal vitamin D levels and the risk of childhood wheezing and asthma. Their review strongly advocates for the consideration of vitamin D3 supplementation—specifically, a daily intake of at least 4400 IU throughout pregnancy, commencing at conception—for all expectant mothers.

Vitamin D, obtained through sunlight exposure, diet, or supplements, is commonly recognised for its pivotal role in bone health, yet it also influences autoimmune health and other health conditions. This analysis ties vitamin D deficiency to childhood asthma and wheezing, supporting children’s health. Statistics reveal that about 40% of children experience daily wheezing by age three, with a 20% diagnosis rate for asthma by age six.

While observational studies suggested a protective link between higher maternal vitamin D levels and childhood asthma, clinical trials like VDAART did not exhibit conclusive evidence when comparing supplemented groups with non-supplemented ones.

Re-analysing VDAART findings, accounting for baseline vitamin D levels, unveiled a substantial 50% reduction in asthma and wheezing, aligning with observational study outcomes. These reanalyses were published in renowned journals like JAMA (2016) and NEJM (2020), underscoring the significance of adjusting for baseline vitamin D levels.

Weiss's group underscored the need for follow-up studies, suggesting that clinical trials, commencing early in pregnancy with 6000 IU vitamin D supplementation, and inclusive of diverse ethnic groups, could enhance comprehension of vitamin D's impact on pregnancy outcomes and childhood asthma as well as inform fertility and conception support recommendations. This latest review article encapsulates these insights and emphasises the importance of comprehensive planning for future studies in this domain.

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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.