Research has confirmed the link between depression and a lack of vitamin D, and it is vital to eat foods that contain it, finds Margaret Jennings
FEELING the winter blues? It may not be just those long dreary grey days that are dragging you down, but the lack of actual sunlight too, or more importantly the ‘sunshine vitamin’ D.
A recent study by Trinity College Dublin showed for the first time in Ireland, that a deficiency in vitamin D was associated with a substantially increased risk of depression among older people here.
While small studies have previously found links between vitamin D and depression, few have followed up with the same affected people, in this case over four years, or other researchers in this field may not have taken into account additional factors that can also affect depression, such as depressive symptoms, chronic disease burden, physical activity, and cardiovascular disease.
Taking all this into consideration, the Tilda study found that the risk of depression grows by 75% in someone who does not have enough vitamin D over a four-year follow-up period.
These findings, published in The Journal of Post-Acute and Long-Term Care Medicine are important, as the Tilda team had previously reported that one in eight older adults are deficient in vitamin D.
And while depressive symptoms as we age may also be influenced by lots of other factors, the authors do point out that our vitamin D levels are relatively easy and inexpensive to modify through supplementation or fortification.
However, In Ireland, fortification of food products with vitamin D is voluntary and few manufacturers do so and this is compounded by the lack of any vitamin D guidelines from the Government.
In a small study carried out here last October, it’s interesting to note that 29% of participants aged over 55 said they relied on sunlight for their daily vitamin D requirements, while 26% said they used vitamin supplements, and 21% vitamin-rich foods.
This research was carried out to coincide with the launch of a fortified food —– a new range of white mushrooms from The Mighty Mushroom Co, called Immune closed cup mushrooms. These mushrooms are grown in selenium-rich soil and exposed to additional light, thereby naturally producing vitamin D.
Dietitian Sarah Keogh of Eatwell in Dublin, who worked with the Mushroom to Improve campaign linked to this launch, stresses the importance of older people becoming more educated about eating fortified food to meet our immunity needs throughout the winter.
“Our research found that 52% of 55+ adults worry about their health and immune system more in winter,” she says. “Yet the majority of them relied on sunlight for getting vitamin D.”
A 100g portion of the Immune closed cup mushrooms, available in Dunnes Stores outlets, provides over half, 54%, recommended dietary allowance of vitamin D, contributing to a healthy functioning immune system, she tells Feelgood.
“The sun that hits Ireland from October to March is too weak for us to make any vitamin D even on sunny days. As a result, we need to eat foods that are a good source of vitamin D to make up for this lack of sunlight. But the 2011 National Adult Nutrition Survey found that over half of people aged over 65 here, do not eat enough vitamin D.”
Foods that naturally have good amounts of vitamin D which we should include in our diet are oil-rich fish like salmon, mackerel and sardines, as well as a small amount in eggs, says the dietician.
The importance of highlighting and exploring the risks associated with reduced vitamin D intake among the population could well be traced to research carried out at UCC in 2005.
Back then, Mairead Kiely, who is now professor of Human Nutrition at UCC, and her colleague Kevin Cashman, now UCC professor of Food and Health, carried out evidence-based research within the Cork Centre for Vitamin D and Nutrition Research group.
They challenged the existing academic dogma that suggested we do store enough vitamin D in our bodies from sun exposure in the summer, to carry us through our long winter months. Their randomised controlled studies and interventions found this was not the case and that in fact, we actually need 10 micrograms a day — recommendations that have now been adopted at a global level.
Meanwhile, the authors of the TCD study suggest the link with increased depression among study participants could be due to the potential direct effect of vitamin D on the brain.
Given the structural and functional brain changes seen in late-life depression, vitamin D may have a protective effect in attenuating these changes, they say. All older people should be boosting their immune system which affects all aspects of our health, says Ms Keogh.
“Although vitamin D is a key nutrient we really do need a little of everything when it comes to nutrition for our immune systems, so a healthy, balanced diet is essential.”