Just as you eat to nourish the rest of your body, you must also nourish your brain. Protein, fat, carbohydrate, vitamins and minerals provide nutrients that keep your brain functioning, prevent deficiencies and promote the activities of substances known as neurotransmitters -- the chemical messengers in the brain. Such nutrients must cross the blood-brain barrier to enter the brain.
Before any nutrient can make it into the brain, it must first be digested. The brain can't use a beef steak in its original form, but it can use the amino acids contained in the meat. The digestive system breaks down all foods into their component parts, which include amino acids, sugars, vitamins, fatty acids and minerals. It is these substances that move into the bloodstream and circulate to the body's cells. The brain, however, has a protective mechanism -- the blood-brain barrier, or BBB for short -- that prevents or limits dangerous substances from reaching the brain cells and affects how nutrients enter the brain.
Glucose is Critical
Glucose is the primary fuel for all the body's cells, including the brain cells. Starches and sugars in carbohydrates -- found in foods such as whole grains, potatoes, vegetables or fresh fruit -- are the primary source of the complex sugars your body digests into the simple sugars it can absorb. Although carbohydrates normally provide most of the glucose your brain and body need, your body can also manufacture glucose from fat and protein through a process called gluconeogenesis. Glucose readily crosses the BBB.
Protein Building Blocks
Proteins are made of different amino acids, each of which has a different function in the body. One of the more important roles for amino acids is the manufacture of neurotransmitters, which affect your moods and the overall function of your nervous system. Getting amino acids across the BBB involves carrier molecules, which provide a transport vehicle for the amino acids. In addition, the carrier molecules must travel specific pathways through the BBB to get into the brain.
Fats and Fatty Acids
Like protein and glucose, your body breaks fats down into their primary components, such as fatty acids. You may already be familiar with such fatty acids as omega-3 and omega-6. Deficiencies in fatty acids such as docosahexaenoic acid may be related to the development of Alzheimer's disease, according to a December 2013 article in "Science Daily." A study reported in the January 2014 "Journal of Internal Medicine" found that when people with Alzheimer's disease received supplements of omega-3 fatty acids, which cross the BBB, the level of fatty acids in their brains increased.
Other nutrients also cross the BBB. Water, for example, may not be something you normally think of as a nutrient, but it is critical for proper body and brain function. Minerals such as potassium and sodium circulate in the bloodstream and cross the BBB. Vitamins also cross the BBB, although some -- such as vitamin B-6 and vitamin B-12 -- need transporter or carrier molecules, according to a June 2009 "BioMed Central" article.
- The Medical Biochemistry Page: Gluconeogenesis - Glucose Synthesis
- Science Daily: Omega-3 Dietary Supplements Pass Blood-Brain Barrier
- The Franklin Institute: Nourish - Proteins
- Neuroscience for Kids: Nutrition and the Brain
- ABC Science: How Does the Blood-Brain Barrier Work?
- Journal of Internal Medicine: Transfer of Omega-3 Fatty Acids Across the Blood–Brain Barrier After Dietary Supplementation With a Docosahexaenoic Acid-Rich Omega-3 Fatty Acid Preparation in Patients With Alzheimer's Disease -- The OmegAD Study
- BioMed Central Neurology: Characteristics of Compounds That Cross the Blood-Brain Barrier
- University of Texas Health Science Center -- Neuroscience Online: Chapter 11: Blood Brain Barrier and Cerebral Metabolism