What are whole grains?

🌾 Whole grains are the entire seeds of a plant, such as wheat, barley, or oats. A seed, also known as a kernel, contains the bran, the germ, and the endosperm. The bran is the outer layer of the seed and supplies fiber, B vitamins, minerals, antioxidants, and other phytochemicals. The germ is the core, or embryo, of the kernel, which has the potential to sprout into a new plant. It houses more B vitamins, vitamin E, minerals, antioxidants, other phytochemicals, and “good” fats. The endosperm is the interior layer and the largest part of the seed. It is composed of carbohydrates, protein, and small amounts of vitamins and minerals.

🥖 Refined grains, like those found in white bread, are missing one or more components of the kernel, and are stripped of a lot of their nutritional value. Although refined grains may be enriched with the nutrients lost in processing, research supports choosing whole grains as often as possible.

Evidence for whole grains directly protecting cognition is limited, but there are plenty of studies indicating the benefits for heart health and diabetes mellitus. Both heart disease and diabetes mellitus may be risk factors for Alzheimer’s disease and other types of dementia, and whole grains may have an indirect preventative effect.

Whole grains contain many B vitamins implicated in brain health. Vitamin B12 and folic acid, for example, are essential for lowering homocysteine levels in the blood. Without these vitamins, homocysteine levels remain elevated and cause brain atrophy, which is linked to dementia. A deficiency of thiamine has long been known to lead to cognitive deficits, such as those in Wernicke–Korsakoff syndrome, which may develop due to long-term alcohol abuse. Riboflavin reduces oxidative stress and inflammation in the central nervous system, preventing damage that may lead to cognitive impairment, and niacin is a necessary component of some coenzymes that the brain requires to function properly.

Vitamin E is present in whole grains and is a potent antioxidant with anti-inflammatory properties. High levels of different tocopherols, the different forms of vitamin E, may decrease the activation of microglia, cells in the central nervous system that are strongly related to Alzheimer’s disease. Iron, a mineral naturally occurring in whole grains, is necessary for proper neurotransmitter signaling, allowing units of the brain called neurons to communicate effectively. Selenium is another mineral in whole grains and a deficiency of it is associated with reduced cognition. Fiber and prebiotics in whole grains help maintain a balance of good gut bacteria. An imbalance of bacteria may produce neuro-inflammation that causes cognitive impairment.