Professor Mary Ward, Northern Ireland Centre for Food & Health, Ulster University, Northern Ireland
Professor Mary Ward is Professor of Nutrition and Dietetics at the Northern Ireland Centre for Food & Health (NICHE), in the School of Biomedical Sciences at Ulster University in Northern Ireland. She is part of the Irish JINGO project which uses the technique of nutrigenomics on a nationwide Irish nutritional phenotype database (1). The detailed information that can be generated by the database enables a close examination of the gene-diet interaction. The JINGO project is enabling the relationship between defined nutritional phenotypes and specific transcriptomic, proteomic and metabolic signatures to be determined, which results in much more accurate dietary and nutritional profiles.
Professors Ward has used a subset of the TUDA study (which investigated nutrition and gene interactions in chronic diseases of ageing in 5200 adults aged >60yrs in Ireland) and part of the Jingo project, to look at the effects of Vitamin D deficiency on immune function in the elderly. Serum 25-hydroxyvitamin D levels and markers of inflammation (serum cytokines IL-6, IL-10, TNF-α and C-reactive protein) were measured in a cohort of 957 Irish adults aged 60 years or more from Northern Ireland (2).
Ireland is at a latitude of 53° North, hence the opportunities for the population to derive their vitamin D3 from sunlight exposure are limited, particularly in the winter months. The main source of vitamin D3 in Ireland is meat and meat products, where the concentrations are low (3). Very few vitamin D fortified foods are available on the Irish market (except for margarine). The result is that dietary intakes of vitamin D3 are very low in Ireland with a recent survey showing a mean daily intake of just 3.9 µg/d, well below most national dietary intake recommendations (4).
Vitamin D3 is important for bone health. It increases the absorption of calcium in the small intestine and indirectly regulates the release of calcium stores in the bones into the circulation. Professor Ward has reviewed the importance of adequate vitamin D3 status in the prevention of the development of osteoporosis(5). She notes that bone density begins to decrease once adults enter their fourth decade, which can be exacerbated by long term vitamin D3 deficiency which in turn results in bone demineralization. Further, she noted that the literature indicated that adverse changes in the immune system of adults aged over 70 years were important factors in the onset of osteoporosis, particularly up-regulation of the pro-inflammatory cytokines IL-1, IL-6 and TNF-α (tumour necrosis factor α).
In the most recent study (2) using the NANS 60+ year cohort, Professor Ward found that the participants with the lowest circulating levels of 25-hydroxyvitamin D were most likely to have the highest levels of the inflammatory cytokines IL-6, IL-10, TNF-α and C-reactive protein. Raised levels of these inflammatory cytokines are associated with increased risk of cardiovascular disease and a range of chronic diseases where inflammation is a key factor, such as rheumatoid arthritis and multiple sclerosis.
The study confirmed the expected seasonal variation in serum 25-hydroxyvitamin D with the highest median concentration in the summer (55.3 nmol/L), compared with 38.6 nmol/L in the spring. The same trend was seen for the cytokine IL-10, but none of the other inflammatory biomarkers. Overall the study demonstrated a significant negative correlation between 25-hydroxyvitamin D levels and IL-6, CRP and the IL-6:IL-10 ratio.
Whilst association is not proof of causation, this study justifies further direct randomized controlled intervention studies with vitamin D3 in the elderly with the aim of lowering the levels of circulating inflammatory cytokines.