Meal Frequency and Consistency
Glucose is the primary fuel for brain function. An article from 1930 from Proceedings of the Royal Society of Medicine discussed the relationship between "industrial efficiency" and fatigue. Inadequate energy intake led to a significant "diminution" in the capacity to do work. Simply put, in this article "efficiency would be helped by education... as to best ways to spend the food allowance" to assure adequate caloric intake.
From a 2010 standpoint, there are very easy ways we can apply that learning to today.
- Eat regular meals and snacks, including a balanced breakfast before you start your workday. Not only will this help to keep energy levels constant, but it will also help prevent cravings and overeating later in the day. Smaller, more frequent meals can also allow for easier digestion, and less risk for the Thanksgiving-like "food coma" that may ensue.
- Avoid simple sugars, and instead opt for high-fiber, nutrient-dense carbohydrates that will supply glucose to the working muscles and the brain, but do so in a more sustaining fashion versus a sharp rise and sharp drop. Examples include: whole grains, grain alternatives like quinoa, high-fiber fruits and vegetables, beans and legumes.
Vitamin D
Research has shown us that there are receptors for vitamin D throughout the brain. Ganji, et al. (2010) noted in their large population-based study, that the "likelihood of having depression in persons with vitamin D deficiency is significantly higher compared to those with vitamin D sufficiency." Food Sources
There are limited sources of vitamin D in our diet. We do make vitamin D in our skin with the presence of sunlight; however, in certain areas of the country like the Pacific Northwest, adequate sunlight is nonexistent and many people are subject to vitamin D inadequacy or even deficiency. There are some whole food and fortified food sources of vitamin D, including oily fish like salmon, mackeral and sardines, fish oils like cod liver oil, egg yolks, and fortified foods like milk, cereals, orange juice and yogurt (Holick, 2006).
Dietary Reference Intake for Vitamin D
Very recently, new recommendations were released by the Institute of Medicine for both vitamin D and calcium. The recommended dietary allowance for vitamin D is 600 IU/day for ages 1-70 and 800 IU/day for ages 71 and above. Consequences of inadequate vitamin D can affect the skeletal and neuromuscular systems, and we are learning with continued research that vitamin D may affect many other non-skeletal systems as well.