Did you know that, before pharmaceutical medicine, spending time in and near the ocean was considered a treatment for many ailments? It works for me in the case of skin and respiratory health, but it isn't outdated nonsense in the eyes of science either. Spending time outside has been shown in research to have health benefits!
What is this talking about? One example of this is a 2009 study from the Netherlands. It showed that living within one kilometre of a green space was linked with a lower incidence of 15 diseases, the strongest associations being for anxiety and depression. Asthma, migraines and diabetes were some of the other conditions where going outside had a protective effect. Some of the benefits come from the production of vitamin D when you are exposed to sunlight, which aids absorption of calcium, iron and zinc. It also helps to balance the immune system and strengthen muscles; actually, all tissue types have receptors for vitamin D and therefore need it for healthy functioning. Additionally, some swear by the benefits of exposure to negative ions, which are said to be in higher concentrations in environments such as the beach or countryside. A book by Professor Robert E Thayer cited research showing that negative ion exposure "increased energetic feelings as well as improved reaction time". Natural light is also known to lift people's moods. Compared with exercising inside, physical activity in natural environments is linked with better self-esteem and increased energy. Poor natural light is linked with Seasonal Affective Disorder (SAD), which may be caused by a drop in serotonin and melatonin associated with darkness.
In the Netherlands study, a total of 345,143 people from 195 general practitioners' medical records were involved, making it nothing to sneeze at. Both green space within 3 kilometres and 1 kilometre of a person's residence were analysed in relation to disease prevalence. For those living within 3 kilometres of a significant amount of green space, there was a reduced incidence of anxiety, digestive infections and Medically Unexplained Physical Symptoms (MUPS). Although a "significant" reduction in disease prevalence was only 2-5%, these conditions are very common. The mechanisms behind these benefits may be due to more physical activity (such as in diabetes, musculoskeletal pain and heart disease), better air quality (asthma, COPD and respiratory infections) and the mental health benefits of a natural environment (depression and anxiety).
Robert E Thayer's 1990 book, The Biopsychology of Mood and Arousal, discusses many studies which show a benefit of negative ions and natural light. One study by Cunningham (1979) showed that hours of daily sunshine was positively linked with people's willingness to help out with weather readings. He then found that sunshine and warm weather was correlated with waitresses earning more tips. Negative ions, which he said are concentrated around natural bodies of water, have also been linked to better mood. One 1981 study showed increased tension and irritability around positive ions, and another showed faster reaction times and improved energy around negative ions. Buckalew and Rizzuto (1982) found increases in positive mood and decreases in negative mood with exposure to negative ions. Baron, Russell and Arms (1985) also found that negative ions improved the moods of volunteers. Overall, spending time outside is good for you!