Serum Vitamin D Predicts Cognitive Performance in Adults

Much of the research on the relationship between vitamin D and cognitive function has been conducted on older people or individuals who have a diagnosis of Alzheimer’s Disease or other dementia. This is because older people are less able to synthesise vitamin D in their skin and because dementia is typically a disease of aging. A study published in August 2015 looked at the relationship between vitamin D status and cognitive function in two cohorts of healthy individuals; those aged 30-60 and 60+. Research on disease-free groups is important because it allows us to look at the potential effect that nutritional deficiency has on the general population and on sub-clinical (no diagnosis) functioning. That is to say that we can learn more about how dietary insufficiencies might be affecting the general population long before disease onset. This information allows us more opportunity to intervene with treatment.

In this study of vitamin D in the blood were strongly associated with the degree of cognitive impairment on tests of visual spatial memory (recalling and recreating a complex shape) and processing speed. In this study lower levels of vitamin D were associated with poorer performance on these tests even in people aged 30.  This study complements a growing body of research that is demonstrating a relationship between vitamin D status and brain function (including influence on mood and anxiety disorders).

There is also growing concern worldwide about the ‘pandemic’ of vitamin D deficiency and the many health concerns it is associated with such as osteoporosis, fractures, and increased risk of some cancers and autoimmune diseases. It is estimated that at least 50% of people are vitamin D deficient and the situation is worse for those of with dark skin as the melanin pigment blocks the action of vitamin D synthesis in the skin. Food sources of vitamin D include oily fish (salmon, sardines and mackerel), eggs and fortified cereals, though few people are eating sufficient amounts of these foods to keep their levels topped up, and vegetarians and vegans need to be very thoughtful about their food/supplement choices to ensure adequate levels.

Reference

Darwish, H., Zeinoun, P., Ghusn, H., Khoury, B., Tamim, H., and Khoury, S. J. (2015). Serum 25-hydroxy vitamin D predicts cognitive performance in adults. Neuropsychiatric Disease and Treatment, 11, 2217–2223.

Healthy Diets Reduce Risk of Depression

A large (15,000 participants) Spanish study has shown that diets high in nutrients are linked to a reduced risk of depression. This study has generated a lot of interest not only because of the large cohort size, which makes the results more generalisable, but because it is thought to be the first to follow healthy individuals and track, over 10 years, those who went on to develop illness and disease.

The researchers looked at three diets:

• Mediterranean Diet – characterised by the consumption of vegetables, legumes, fruits and nuts, cereals, fish and seafood; low intake of meat and dairy products, and moderate alcohol intake.

• Vegetarian Dietary Pattern – a kind of ‘flexitarian’ diet that promotes eating plant foods (including potatoes) most of the time but allowing for a little meat

• Healthy Eating Index- promotes eating larger amounts of vegetables, fruits, whole-grain bread, nuts, beans and pulses, omega 3s and unsaturated fats, and smaller amounts of sugar-sweetened beverages and fruit juice, red/processed meat, trans fats, and alcohol.

As part of the study the researchers also looked at activity levels, BMI, health history and vitamin supplementation, and the analysis was controlled for a number of variables including age, sex and smoking status.

For the statistical analysis the levels of adherence were split in to five groups (quintiles). So on a scale of 1-5, those in group 1 ate the least healthy diets while those in group 5 were paragons of healthy eating. The results showed that those in groups 2-5 had a 25-30% reduced risk of developing depression than those in group 1. Interestingly, there was a plateau in this effect once the respondents had moderately good diets. The researchers believed this to be due to a threshold effect; once you are consuming adequate amounts of a nutrient there is no additional benefit of consuming larger quantities of it.

The researches did not highlight any individual food or nutrient as being particularly important or protective. In fact they pointed out in their discussion the inconclusive results from other studies that looked at the relationship between individual nutrients (vitamins, minerals or fats) and depression. However, this and other studies have demonstrated the strong relationship between the quality of the overall diet and risk of depression. It is likely that it is the interaction of different compounds from various foods that offers most protection not just to depression but to overall health. 

Reference

Sánchez-Villegas, A., Henríquez-Sánchez, P., Ruiz-Canela, M., Lahortiga, F., Molero, P., Toledo, E., & Martínez-González, M. (2015). A longitudinal analysis of diet quality scores and the risk of incident depression in the SUN Project. BMC Medicine, 13, 197-197.

Probiotic Alleviates Stress and Anxiety

We have known for some years now that there is a comorbidity between psychological problems such as depression and anxiety and gastrointestinal disorders. That is to say people who present with these psychological problems often have a gut issue at the same time and vice versa. Recent research that has started to explain some of the processes underlying this relationship and the term given to this connection is the ‘gut-brain axis’. The community of bacteria in the gut is central to the gut-brain axis with the bacteria playing an essential role in nutrient absorption and production, inflammation and immunity amongst many others.

Much of the research into the gut-brain axis is of potential treatments: the researchers are looking to relieve a particular disorder and so the results can often only accurately be applied to groups who suffer from that disorder. However, a recently presented study looked at the effects of probiotic (beneficial bacteria) supplementation on healthy people.

Researchers from Ireland put 22 male participants through a battery of tests to assess their cognitive performance, perceived stress and stress hormone levels before and after a four-week course of a daily supplement of the bacteria Bifidobacteria longum. At the end of the study the participants reported feeling less anxious and stressed, had significantly improved cognition scores and were producing lower levels of stress hormones.