Nutrition and Osteoporosis in Postmenopausal Women: Mitigating Risk Factors through Dietary Intervention
-Written by Krishna Priya
Menopause occurs naturally when the ovaries stop functioning and undergo a process of cell death called apoptosis. The onset of menopause is characterised by decreased production of estradiol, and increase in the levels of follicle-stimulating hormone (FSH).
Osteoporosis is a multifactorial systemic skeletal disease. It is defined by reduced bone mineral density (BMD) and deterioration of bone tissue architecture resulting in bone fragility.
The level of hormones, particularly oestrogen, controls the accretion of bone mass. Accumulation of peak bone mass may also be influenced by other factors, such as nutrition, smoking, and exercise. It is estimated that about 50% of postmenopausal women develop osteoporosis at some point in their lives. Among these women, around 25% develop deformity in their vertebrae, while approximately 15% may experience a hip fracture.
This article primarily focuses on how nutrition plays a crucial role in mitigating the risk factors associated with osteoporosis in postmenopausal women.
As per the National Institutes of Health Consensus Development Panel on Osteoporosis, it is defined as “a skeletal disorder characterised by compromised bone strength predisposing to an increased risk of fracture” Osteoporosis is categorised into primary and secondary forms.
Primary osteoporosis is subdivided into type I, or postmenopausal osteoporosis, and type II, or senile osteoporosis. Secondary osteoporosis has recognized causes, including malabsorption, some drugs like glucocorticoids, and particular conditions like hyperparathyroidism.
Causes of osteoporosis: Females exhibit a higher susceptibility to osteoporosis compared to males. Besides sex, other factors that contribute include increasing age, postmenopausal status, premature ovarian failure, low BMI, rheumatoid arthritis, low BMD, vitamin D deficiency, inadequate calcium intake, smoking, alcohol abuse, and overuse of certain medications, such as glucocorticoids, anticoagulants, cancer chemotherapeutic drugs, and gonadotropin-releasing hormone agonists.
OSTEOCLAST AND OSTEOBLAST
The maintenance of proper skeletal structure and function relies on the continuous process of bone remodelling, involving a variety of cells. Different types of cells and multiple factors are involved in this process. Key cells participating are osteoblasts and osteoclasts. Osteoclasts are responsible for resorption of old bone tissue and osteoblasts are responsible for new bone formation. They communicate with each other via various mechanisms, including direct cell-cell contact, cytokine or cell-bone matrix.
OSTEOPOROSIS AND MENOPAUSE
Oestrogen affects bone through several mechanisms. A few examples include: 1) reducing bone resorption by lowering the sensitivity of bone mass to PTH (parathyroid hormone), 2) expediting calcium absorption by the intestine, 3) directly affects the bone due to the presence of oestrogen receptors.
At menopause, the lack of oestrogen impairs the normal bone turnover cycle. This is explained by the presence of oestrogen receptors in osteoclasts and osteoclast progenitor cells. There is a net loss of bone due to the increase in osteoclastic resorption and decrease in osteoblastic activity. Reduced availability of oestrogen affects both osteoclastogenesis and osteoclast activity.
RISK FACTORS IN POSTMENOPAUSAL WOMEN
The primary risk factors include low bone marrow concentrate (BMC) either in the lumbar spine or in the hip, and a history of prior fractures. Furthermore, the likelihood of developing osteoporosis increases with rising age, smoking, height loss, inadequate calcium intake and low BMI.
Around two billion people have micronutrient-deficient diets. This, along with increasing life expectancies, causes health issues, such as osteoporosis, which affects the later stages of life.
In order to maintain the integrity of bones and skeletal muscles, one needs protein, calcium, potassium, magnesium, and vitamin D.
In a metabolic study, 16 women of ages between 20 and 30 were assigned to consume whole foods that contained the same amount of phosphorus. The findings indicated that consumption of cheese caused a significant decrease in serum parathyroid hormone levels and bone resorption.
To prevent osteoporosis, adopting a whole food approach including nutrient-rich sources such as eggs, fish, and meat may be a more effective strategy.
Calcium is a vital element and plays a critical role in several cell functions in the human body. It is an integral component of bone structure and is necessary for bone mineral deposition.
Intake of foods rich in calcium is necessary to meet the daily dietary requirement. Dairy products are considered one of the best sources due to their high calcium content, and absorption rate. Other sources include mineral waters that are enriched with calcium.
Several varieties of calcium supplements are available to ensure adequate intake of calcium, with calcium carbonate and calcium citrate being the most widely used ones.
A daily calcium intake of 1000 mg is recommended for premenopausal women and men, while postmenopausal women should increase their intake to 1200 mg.
Vitamin D has 2 main roles: regulating the intestinal absorption of calcium, and stimulating bone resorption, which helps maintain calcium levels in the bloodstream.
Vitamin D can be obtained from various sources. They include sunlight, diet, and supplements. Dietary sources are absorbed into the lymphatic system by chylomicrons. After entering the circulation, it binds with vitamin D binding protein (DBP) and is then taken to the liver and kidneys. Here, they are converted to the active form of vitamin D.
Foods rich in vitamin D include fish, egg yolks, and cod liver oil. Other vitamin D rich foods include milk, orange juice, and some cereals. However, supplements of vitamin D may be required to ensure sufficient intake.
A daily intake of at least 600 IU of vitamin D is recommended for adults, but doses of 1000 to 2000 IU are also considered safe. Postmenopausal women are, however, advised to take a minimum of 800 IU daily according to current recommendation.
Studies have demonstrated that dietary protein can enhance intestinal absorption of calcium, reduce bone resorption, and IGF-1 production, a vital factor in maintaining bone health.
Bone loss can occur as a result of losing weight. However, incorporating dairy products, protein-rich foods, and calcium into one’s diet notably increases the markers for bone formation, such as osteocalcin and procollagen 1 amino-terminal propeptide. Additionally, it elevates 25-hydroxy vitamin D levels and decreases parathyroid hormone levels.
When magnesium levels are insufficient, bone health may be impacted in multiple ways. For instance, magnesium deficiency can directly diminish bone rigidity, boost osteoclast activity, and reduce osteoblasts. Moreover, it can indirectly disrupt parathyroid hormone and vitamin D, promote inflammation and oxidative stress, and consequently cause bone loss. Magnesium is also a crucial cofactor in the synthesis and activation of vitamin D. The United States Food and Nutrition Board has established recommended intake levels for magnesium. For men, the reference value ranges from 400 to 430 mg/day, while for women, it varies from 310 to 320 mg/day. During menopause, 320 mg of magnesium from either dietary sources or supplements can be beneficial.
Potassium in the diet lowers the acid levels in the body, subsequently mitigating calcium depletion from bones. In addition to its function in maintaining the body’s alkaline state, potassium can also aid in increasing calcium accumulation in the kidneys.
In conclusion, osteoporosis is a complex skeletal disease that is characterised by compromised bone strength and increased risk of fractures. It is caused by several factors, including inadequate nutrition, hormonal imbalances, and certain medications.
Menopause is a significant risk factor for osteoporosis due to the decrease in oestrogen levels, which impairs the normal bone turnover cycle. Adequate calcium and vitamin D intake and adoption of a whole food approach may be effective strategies to prevent osteoporosis. It is essential to consult a healthcare provider or a registered dietitian for tailored nutrition advice.
About The Author
Krishna Priya is a first-year medical student with aspirations to become a physician in the future. She is passionate about promoting preventive health measures and raising awareness about osteoporosis in postmenopausal women. Her article on the role of nutrition in preventing osteoporosis reflects her dedication to educating the public on healthcare matters.
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