Natalie Lamb, a member of the British Association of Nutritional Therapists, said SAD is more prevalent than people might think. In speaking with NutraIngredients-USA, Lamb said that one in 15 people can be affected by the disorder. Seasonal affective disorder is estimated to affect 10 million Americans, and another 10% to 20% may have mild SAD symptoms, Lamb said.
Modern life complicates disorder
The disorder, which has sometimes been called the ‘winter blues,’ is associated with lower light levels at high latitudes in wintertime. It is defined as a type of depression which comes and goes in a seasonal pattern. Severity of symptoms can vary but sufferers generally experience persistent low mood, lethargy and a tendency to oversleep, overeat and crave carbohydrates during the winter months (despite feeling happy, active and energetic during the summer).
In the US, where most of the population lives at lower latitudes than in Europe, this disorder used to be associated only with people living in Alaska. But modern leisure choices have complicated that picture, Lamb said, making it more of a lifestyle disorder than it used to be.
For example, a recent survey of British families (whose lifestyles mirror that of US families for the most part) showed that kids today spend half as much time playing out of doors as their parents did. Another recent study conducted in Seattle found that nearly half of preschoolers in a sample representing four million US children did not have even one parent-supervised outdoor play opportunity per day. And a recent US government time-use survey found that watching TV accounts for more than half of leisure time.
“This disorder can be debilitating,” Lamb said. “Suffers experience low mood, lower cognitive function and fatigue. There can be feelings of worthlessness or guilt, and there is less enjoyment of and less participation in habitual activities. Many sufferers will crave stimulants like tea or coffee.”
Lamb, who works with Protexin, the manufacturer of the Bio-Kult line of probiotics, said the low light exposure is linked with low vitamin D levels, which can have cascading effects throughout the system, including changes in the microbiome. That low vitamin D level is not only attributed to less sunlight; Lamb said modern diet choices could play a role, too.
“There is a vitamin D element to the disorder,” Lamb said. “SAD has been linked to low serotonin and vitamin D. We need cholesterol for vitamin D production in the skin, and there is more of a prevalence of low cholesterol in the diet these days.”
It’s the serotonin angle that could provide a marketing avenue for probiotic ingredients, Lamb said. While no dietary supplement marketed in the United States can claim to treat, prevent or cure an illness, which would include SAD, a product could claim a role in supporting a function or structure in the body that could be affected by or associated with a disorder. Serotonin, an important neurotransmitter, has also in recent years been associated with the makeup of the microbiome.
“The general research is showing compelling evidence for a link between the microbiome and brain function. There are lots of individual studies that associate higher serotonin levels with a wide rage of beneficial probiotic strains. It is estimated that 90% of the body’s serotonin is made in the gut. These low levels can be reversed when the gut flora can be rebalanced,” she said.
Lack of seasonal rhythms
Lamb said SAD has probably always been an aspect of human existence while living at high latitudes. With agricultural activities now employing just a tiny fraction of workers, and with the advent of cheap artificial lighting, modern life no longer takes these rhythms into account. This makes having sufficient get-up-and-go year round a challenge for those most susceptible to SAD, Lamb said. Bio-Kult is based on a wide array of probiotic strains, which Lamb said gives the best shot at broad-based serotonin support.
“Traditionally winter is when things slow down and we become more inward focused and reflective. It was a time to plan for the months ahead. In the modern world, though, it’s always business as usual. Bio-Kult, with 14 different strains offering a wide range of benefits, is a product that can be taken year round,” she said.