Lifespan Nutrition Research Paper

Andrea Meiring Dr. Zemel NUT 302 5 March 2009 Vitamin D and the Health of Postmenopausal Women In recent years, the prevalence of vitamin D deficiency has been a topic of concern for many, especially the aging population whose diseases can be exacerbated by insufficient vitamin D. Vitamin D deficiency is well recognized as a major health problem for adults greater than 50 years of age (1). Research shows that obtaining a proper amount of vitamin D via sunlight or dietary sources is necessary for bone health and prevention of cancers and cardiovascular disease (2). Normal vitamin D status is defined as 25(OH)D (calcidiol) concentrations of 75–125 nmol/L. Sustaining a level below what is considered normal may cause the onset of health problems associated with vitamin D deficiency. Adequate vitamin D should be of special concern to postmenopausal women who as a result of a lower level of estrogen, are at an increased risk for a number of health conditions, such as osteoporosis, heart disease, and breast cancer, all of which sufficient vitamin D offers a protective effect against. Osteoporosis, or porous bone, is a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased risk of fractures of the hip, spine, and wrist. Women have a higher risk of developing osteoporosis because women have less bone tissue and lose bone faster than men because of the changes that happen with menopause. Vitamin D plays a key role in maintaining bone health since it increases the absorption of calcium, the most abundant mineral in bone composition, and the mineralization of the skeletal system. Insufficient vitamin D leads to reduced calcium absorption, 1

elevated blood concentrations of parathyroid hormone, and increased rates of bone resorption, which over time may lead to bone fracture (3). The results of a recent study published in the American Journal of Clinical Nutrition are favorable towards the relationship between proper vitamin D levels and bone strength. Postmenopausal women consuming >= 12.5 µg vitamin D/d from food plus supplements had a 37% lower risk of hip fracture than did women consuming < 3.5 µg/d (3). This same study went on to say that high calcium intake, which is thought by many to prevent bone loss, did not reduce the risk of osteoporotic hip fractures. This evidence expresses how largely calcium absorption is dependent on vitamin D. Therefore, there is a need for monitored vitamin D intake in those most susceptible to osteoporosis, postmenopausal women. The results of a recent cross-sectional, observational study conducted at 61 sites across North America showed that 52% of postmenopausal women receiving therapy for osteoporosis had 25(OH)D, the main circulatory form of vitamin D, levels of less than 30 ng/mL (75 nmol/L) (7). Since hip fractures associated with osteoporosis are the leading cause of nursing home admittance, maintaining a healthy level of vitamin D can prolong the independence and quality of life of older women. According to the American Heart Association, heart disease is the number one killer among postmenopausal women. With this being said, vitamin D in the proper amount has been shown to reduce the risk of heart disease. This may be linked to the fact that vitamin D in the form 1,25(OH)2D is involved in controlling the production of renin, one of the most important hormones for regulating blood pressure (4). In a small blinded study of 18 hypertensive patients randomized to receive repeated exposure to artificial UV-A radiation (which cannot produce vitamin D3) or UV-B radiation (which leads to cutaneous vitamin D3 synthesis) treatment, the UV-B treatment group showed an average 6-mm Hg decrease in 2

both systolic and diastolic blood pressure and a 180% increase in serum 25(OH)D, the major circulating form of vitamin D, levels versus the group exposed to UV-A, who showed no change in serum 25(OH)D levels or blood pressure (5). These results are proof that vitamin D plays a significant role in blood pressure regulation. Keeping blood pressure in a normal range can be very beneficial to the cardiovascular system. If treating vitamin D deficiency shows long-term therapeutic effects in controlling hypertension, then many older adults, including postmenopausal women, will no longer need prescription blood pressure medication and the cost and side effects that come with them. This only accounts for hypertension caused by vitamin d deficiency, not obesity or other factors. Vitamin D should be thought of more as a protective measure against hypertension as opposed to a treatment, especially when the cause does not stem from a deficiency. These results also emphasize the impact of UV-B radiation on increasing serum vitamin D levels. Thus, it is important for postmenopausal women to not only consume vitamin D via diet or supplement, but they also must get adequate sun exposure in a safe amount. The sun is the most abundant source of vitamin D available to humans, more than 90% of the vitamin D requirement for most people comes from casual exposure to sunlight (6). Food sources are limited to fortified foods and dark, oily fish. To obtain the beneficial cardiovascular effects, as well as the other health benefits provided by maintaining a healthy vitamin D level, postmenopausal women must be aware of the sun’s significant role and spend less time indoors when possible. To offer another form of evidence, the Farmingham Heart Study proposed that protection against heart disease lies in the fact that vitamin D receptors have a broad tissue distribution that includes vascular smooth muscle, endothelium, and cardiomyocytes. A growing body of evidence collected from the 1739 3

participants, mean age 59, with no prior cardiovascular disease, suggests that vitamin D deficiency may adversely affect the cardiovascular system (10). Once again this shows the importance of maintaining adequate vitamin D status for protection against possible associated cardiovascular disorders. It has been estimated that tens of thousands of premature deaths occur in the United States annually from a range of cancers due to vitamin D deficiency (8). One cancer that vitamin D is found to prevent and should be of special concern to postmenopausal women is breast cancer. According to the National Cancer institute, the majority of breast cancer cases occur in women older than age 50 (postmenopausal age). Vitamin D has a role in cancer prevention because Vitamin D is one of the most potent hormones for regulating cell growth; 1,25(OH)2D inhibits proliferation and induces differentiation into normally functioning cells (2). To validate this, it has long been observed that people who live at higher latitudes in the United States were noted to have increased risks of breast, colon, and prostate cancers. This was noted as early as 1941 in a study done by Dr. Frank L. Apperly. Higher latitudes lead to less UV-B exposure and thus less cutaneous vitamin D synthesis. To show vitamin D’s effect on breast cancer risk, in one study, women in the highest quartile of serum 1,25(OH)2D had one fifth the risk of breast cancer versus those in the lowest quartile (9). Considering the number of women diagnosed with breast cancer each year, this kind of finding makes one wonder how many women were vitamin D deficient before and upon diagnosis. Research done by Grant led to the proposal that roughly 25% of deaths due to breast cancer among women in northern Europe could be attributed to inadequate vitamin D levels (8). How direct of a role vitamin D deficiency plays in the development of breast cancer is still to be determined, but the kind evidence research is compiling surly expresses a 4

relationship that should not be ignored. The protective effect of sufficient vitamin D against other types of cancer also pertains to postmenopausal women since cancer risks in general rise with age. With the recent awareness of epidemic vitamin D deficiency and cancer related deaths on the rise, it is safe to presume that the two may have a stronger correlation than thought and further studies should be conducted. Therefore postmenopausal women, who are at an elevated risk of developing breast cancer, should monitor their vitamin D status with vigilance. In conclusion, various studies and research show that vitamin D status plays a vital role in the health of postmenopausal women. This is attributed to the findings that vitamin D aids in bone health and in the prevention of breast cancer and cardiovascular disease, all of which afflict postmenopausal women in high numbers. These common health issues are partly due to physiological effects of lowered estrogen but also to the normal aging process. As scientists discover an increasing number of hormonal functions carried out by vitamin D, deficiency awareness is of great priority. It is important that postmenopausal women know the best way to achieve the health benefits vitamin D may offer, is to asses a possible deficiency before it exacerbates any related health problems. The best time to do this would be immediately following menopause or better yet before menopause, so vitamin D deficiency will not go untreated for a prolonged period of time. Adequate vitamin D intake should be a lifelong goal for all, regardless of age, especially since the metabolic activity of bone is a lifelong process. Maintaining good health and nutrition at a young age is one of the best predictors of future health complications during postmenopausal age. Sufficient lifelong vitamin D intake, along with other necessary nutrients is one of many things women can do to decrease the risk of postmenopausal diseases. Physical 5

activity, a healthy diet, and abstinence from smoking are things that must be done in combination with vitamin D intake to guarantee the best quality of life.

6