How many bones are in the human skeleton? How come it’s on the inside? What does it do? Does anybody really care? Sometimes.
The human skeleton offers shape and protection to the body. It supplies a place for organs to attach or to be supported. It comprises 206 bones, the largest of which is the thigh (femur). It makes up about 15% of your body weight, part of which is water. This fifteen percent refers to ideal body weight, not to a 400-pound behemoth who is less than six feet tall. Infants have more than 206. The skull starts out with more than twenty bones, some of which fuse together during development. Besides helping you to move, bones make red and white blood cells in their marrow, and act as a storage house for minerals. It takes about twenty years to develop completely.
Bone is actually a type of connective tissue, obviously denser than cartilage, which is the flexible stuff at the flap of your ear (tragus) and the tip of your nose. Cartilage also makes the discs that separate your vertebrae from each other and the femur from the tibia at the knee. Bone tissue is heavily mineralized by a form of calcium called hydroxyapatite. Calcium is the mineral found in the greatest amount in the body, about ninety-nine percent of which is in bone. Phosphorus works with calcium to maintain bone health by combining to make hydroxyapatite. This aggregation helps bone to remodel—to break down and then to redeposit. Trace amounts of other minerals, including magnesium, boron, copper and zinc, stimulate bone growth. But there’s one element of bone health that is overlooked because it’s thought of as nothing more than an anti-oxidant—vitamin C, aka ascorbic acid.
In a study of prepubescent females done in Philadelphia, it was learned that specific bone parameters were positively affected by vitamin C, especially in combination with zinc. For every milligram a day of vitamin C intake, there was an increase in trabecular bone area (Laudermilk, 2012). That’s the porous part of a bone found in the center and at the end of a long bone, like the femur. It’s important to the manufacture of blood cells inside the red marrow. Because it’s porous, trabecular bone is not as strong as the harder cortical outer layer. As hormones change with development, bone requirements also change. This is why it’s necessary to lay down as much bone as possible in one’s early years. By the time a girl reaches thirty, she will have laid down all the bone she ever will, which is probably why a DXA scan compares/contrasts a patient’s bone density to that of a thirty-year-old. You can read about this at the NIH Osteoporosis and Related Bone Diseases National Resource Center website,
If vitamin C intake promotes bone, then deficiency must degrade it. Too little vitamin C causes scurvy, the condition that once affected seamen who were deprived of fresh fruits and vegetables for prolonged periods. That doesn’t happen anymore; at least it shouldn’t. The sailors’ joints and muscles would hurt, they bruised easily, their gums would bleed, and their teeth would sometimes fall out. Since vitamin C is responsible for the formation of connective tissue, these occurrences seem relevant. Spontaneous fractures caused by low bone mineral density, and considered to be induced by a failure of collagen synthesis, also characterize scurvy (Park, 2012). Deficiency of vitamin C is implicated in scurvy by the inhibition of osteoblast activity. You remember osteoblasts. They’re the cells responsible for making new bone material.
Most animals do not require external sources of vitamin C because they can get it from glucose through their enzyme systems. Humans and other primates, guinea pigs, and fruit bats lack this ability, so they have to get it from their diets. Since fast foods have replaced fruits and vegetables, many of us may be vitamin C deficient in the absence of supplementation. Lettuces, onions, apples and bananas don’t help. Citrus fruits, cruciferous vegetables and strawberries do. Besides diet, other lifestyle factors influence vitamin C status, especially smoking, a habit that seriously affects the neck of the femur (Sahni, 2008) unless ascorbic acid intake is considerably greater than the RDA. The dietary recommendation for vitamin C is that amount needed to prevent a condition caused by its lack, in this case, scurvy and its aftermath. Sixty milligrams a day is hardly enough to meet a human’s physiological and metabolic needs. The 400-pound gorilla at the zoo gets 4000 milligrams a day. Shouldn’t a 200-pound human get 2000, then?
Speaking of the femur…This is where the hip joint is, at the top of the thigh bone. In a seventeen-year follow-up study conducted by Tufts University, those elderly (70-80 yrs.) in the highest third of vitamin C intake had significantly fewer hip and non-vertebral fractures than those in the bottom third, suggesting a protective effect of vitamin C on bone health (Sahni, 2009). It’s important to note that oral contraceptives may adversely affect vitamin C accumulation. Women who fail to supplement while taking hormones as oral contraceptives have lower plasma levels of vitamin C than those who do supplement (Kuo, 2002). This, however, would seem to be the case regardless of contraceptive use. Concerning sex steroids, both estrogen and testosterone are important for developing peak bone mass (Riggs, 2002). In the case of hypogonadism, where sex glands produce little or no hormones, vitamin C stimulates bone formation (Zhu, 2012), allowing bone recovery in light of hormone deficit. This finding is particularly important to those at risk for osteoporosis, as may be such in developing countries, among the food insecure, and in men who have had certain treatments for prostate disease, including one called gonadotropin-releasing hormone, abbreviated GnRH (Mittan, 2002).
Despite having lost the ability to synthesize vitamin C, humans can take supplements or increase dietary intake to avert the onset of osteoporosis, realizing that ascorbic acid can block osteoclast proliferation and bone loss while promoting osteoblast activity and bone remodeling.
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