Since we were already talking about it in the last article, let’s go ahead and continue with chloride or Cl–. Besides helping regulate membrane voltage along with sodium and potassium (which may still sound like a crazy concept), chloride is absolutely essential in the acid-base buffer system of the human body. There are various regions in the gastrointestinal tract that require a very specific pH (measure of hydronium ion concentration to test for acidic or basic conditions) such as the acid of our stomachs which maintains a pH of about 1 to 3 for the corrosion and breaking down of food, and the alkaline (basic) liquefied emulsion of food and bile from the gall bladder in the upper small intestine which needs a pH of about 8 in order for the enzymes of the pancreas to remain active in digesting fat. For the “totally confused already” crowd:
Human blood hovers around a slightly alkaline pH of 7.4 (as a frame of reference, pure water is at a neutral pH of 7) and any fluctuations of above 7.45 (alkalosis) or below 7.35 (acidosis) can bring about severe consequences such as the denaturation of enzymes (think of pan frying the whites of eggs), respiratory distress, coma, and death. Maintenance of the above pH values is just one of several processes the body undergoes to maintain a state of homeostasis or a healthy equilibrium that ensures the survival of the individual. Why chloride is relevant in this regard is because it is part of the molecule hydrochloric acid or HCl which is the major constituent in stomach acid and the reason the pH is as low as it is (matter of fact it is so acidic that if the lining of the stomach was compromised by a puncture wound or peptic ulcer, the gastric juices would internally corrode various tissues of the body). The Adequate Intake (AI) for chloride is 2,300 milligrams (mg) and this is easily met considering that it is attached to salt in NaCl and salt substitute in KCl. There is no Upper Tolerable Intake Level (UL) for chloride by itself but no more than 3,600 mg daily is recommended when it comes in the form of table salt (to keep sodium at bay really).
Now we come back to the mineral that is calcium which exists as Ca2+ in its electrolyte form. Before we talk about its more commonly known role in skeletal health, let’s continue to address its function first as an electrolyte in muscular contraction. At this point, it needs to be understood that cells communicate with one another and not only through chemical mediated pathways that involve hormones but by sensing changes in electrical charge and also nerve transmission involving the brain. As an aside, the heart is one of the more interesting organs in the fact that it operates (contracts and relaxes) on an electrical current independent of the rest of the body. Now calcium (like sodium and chloride) can be found in ample amounts in the blood and these cations interact with muscle cells to facilitate contraction and relaxation. First, the brain signals to the muscle cells that contraction is needed (due to exercise or fear) and so an influx of calcium ions flows out from a region in the muscle cell called the sarcoplasmic reticulum through a so-called calcium gate to what are called the myofilaments (the contractile tissue). This can be considered a chain reaction because all of the other muscle cells do this synchronously in the muscle tissue being stimulated by the nerve impulse. Once the impulse from the brain ceases, the calcium ions flow out of the area of the myofilaments (through the calcium gate) and back into the sarcoplasmic reticulum. Take a peek:
So now (before all of the muscles in our faces contract due to frustration) let us move forward into a subject not as foreign to us…Bone consists of what is called bone matrix made up of the inorganic (molecules absent of carbon atoms) substance hydroxyapatite (Ca10(PO4)6(OH)2) and organic (molecules containing carbon) Type 1 collagen. The “P” in the above molecule is for phosphorous which is definitely important in regards to bone health but since it is calcium’s time to shine we will save our discussion about phosphorous for later. Calcium is the most abundant mineral in the body and 99% of the calcium absorbed from diet is stored in the bones and teeth. This micronutrient is now so well known for its role in the strength and durability of our skeletal system that calcium fortification (in the form of calcium citrate) has become a great selling point for many juices and grains products. What some members of the general population may not be aware of, however, is the importance of our friend vitamin D (the sunshine vitamin) in assisting with the absorption of dietary calcium (products that are calcium fortified are usually but not always enriched with vitamin D).
The novel problem that we face today is that as concerns over sun exposure and skin cancer continue to rise (and legitimately so) and as our culture remains accustomed to including carbonated beverages high in phosphoric acid (leeches calcium out of the bones and corrodes teeth enamel) as part of the staple diet, conditions such as rickets among children and osteoporosis among adults are becoming prevalent in industrialized nations where dietary calcium is plentiful (too much animal protein combined with a diet lacking in fruits and vegetables also contributes). It is especially important to get adequate calcium and vitamin D in our diets during our younger years because our bodies, although they don’t grow taller past age 20-21, continue to thicken and strengthen bone until we are 30 years old. At this age we have reached our peak for maximum bone density and the body is able to hold this peak until about 35 years old when the breaking down of bone (by osteoclast cells) starts to outpace rebuilding and remodeling (by osteoblast cells). Exercise with an emphasis on those activities which are weight bearing will slow down the process of age related bone loss but it is still an inevitability. Women tend to be at higher risk for osteoporosis especially at post menopausal age and 50% of all American women will experience an osteoporotic fracture by the age 65. The following picture is definitely not pretty:
Rather than focus on the “doom and gloom” we should plan ahead in order to prevent such problems. First, it would wise to review the vitamin D post for food sources and recommendations. Next, we should ask ourselves, “Am I doing weight bearing activity as a part of my weekly physical regimen?” Lastly, we need to ensure that we are consuming the Recommended Dietary Allowance (RDA) for calcium which is 1,000 mg daily for individuals aged 19 to 50 years and 1,200 mg for those aged 51 years or more and from the following foods: 8 ounces (oz) plain yogurt (415 mg), 1.5 oz mozzarella cheese (333 mg), 3 oz canned sardines with bone (325 mg), 8 oz cow’s milk (299 mg), 8 oz fortified soy milk (299 mg), 6 oz fortified orange juice (261 mg), 1/2 cup fortified tofu (253 mg), 3 oz canned salmon with bone (181 mg), 1/2 cup cooked kale (100 mg) and 1/2 cup cooked turnip greens (99 mg). Too much calcium in the diet can cause calcium deposits on the bone, kidney stones and can impair the absorption of dietary iron and so the Upper Tolerable Intake Level (UL) is 2,500 mg daily for individuals aged 19 to 50 years and 2,000 mg for those aged 51 years or more.
http://en.wikipedia.org/wiki/Electrolyte; http://en.wikipedia.org/wiki/Water-electrolyte_imbalance; http://en.wikipedia.org/wiki/Chloride; http://en.wikipedia.org/wiki/PH; http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0004334/; http://www.ncbi.nlm.nih.gov/pubmed/10421978; http://www.chemistry.wustl.edu/~edudev/LabTutorials/Buffer/Buffer.html; http://lpi.oregonstate.edu/infocenter/minerals/sodium/; http://lpi.oregonstate.edu/infocenter/minerals/potassium/; http://lpi.oregonstate.edu/infocenter/minerals/calcium/; http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional/; http://www.livestrong.com/article/555341-calcium-for-coccyx-pain/; www.ncbi.nlm.nih.gov/pubmed/18937749; http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1851862/