This post was written by Wendy Chung, dietetic intern, and reviewed/edited by Edith Yang, RD, CSR, CLT, FAND
Hello, my name is Wendy Chung, and I am a current dietetic intern getting guidance from Edith Yang, dietitian and founder of Healthy Mission Dietitian. There’s nothing more that I like than writing and researching about health and nutrition — not to mention all about bone health! In this blog post, my goal is to help you understand that bones are inarguably one of the most important components of the human body. If you’d like to see more of my past work and research, connect with me through my LinkedIn page.
Without bones, we would be shapeless. However, bones do way more than give us shape. Bones perform other functions that are necessary for our health. Read more to understand the structure and functions of the bone itself, how bones evolve during our lifetime, how to preserve bone health and prevent bone disorders, and what foods are best for bone health.
Bone Health: Bone Composition and Functions
What do our bones consist of? What do they exactly do?
To understand the complete structure of bones, let’s break it down into two separate categories — macro and micro. Macro consists of the general anatomy of the bone which includes the external dense and smooth layer called the compact bone, and the internal honey-combed layer known as spongy bone. Micro consists of the cells of the bone tissue. There are five important cells that compose bone tissue: osteogenic cells, osteoblasts, osteocytes, bone lining cells, and osteoclasts. The table below compares their functions.
|Osteogenic||They are mitotically active, meaning that when stimulated they can transform into an osteoblast or bone lining cell|
|Osteoblast||They are responsible for bone growth|
|Osteocyte||They monitor and maintain the mineralized bone matrix|
|Bone lining||They are very similar to the osteocyte in helping maintain the bone matrix|
|Osteoclast||They resorb or “break down” the bone matrix|
Now that we have broken down the overall structure of the bone, we can then better understand the chemical composition of the bone. The chemical composition of the bone is also categorized into two substances — organic and inorganic. Organic substances include all the cells of the bone tissue (i.e., osteogenic, osteoblasts, osteocytes, bone lining cells, and osteoclasts), and the inorganic substances are mineral salts which are tiny, tightly-packed needle-like crystals of calcium phosphates. The mineral salts are what make the bones durable and hard. This allows it to withstand compression and tension.
Besides the bones supporting the basic framework of the body, there are several other important functions that bones perform. Bones protect the organs of the body (i.e., the skull protects the brain), and they also act as “leverages” by being attached to the skeletal muscles to move the body and its parts. Bones are also considered as storage for minerals, growth factors, and fat. They store minerals such as calcium and phosphate that are then released into the bloodstream and store fat, as a source of energy for the body. They are also responsible for blood cell formation in the red marrow cavities, and for hormone production.
How do our bones evolve over time during each age stage of our lives?
As our physical appearances change over time, so do our internal organs and tissues. As mentioned, bones are responsible for the support they provide to the entire structure of the body. They also help balance both calcium and phosphate in the body. About 5-7% of bone mass is recycled on a weekly basis and approximately half a gram of calcium enters and exits the adult skeleton regularly. The compact bone is replaced every ten years, while the spongy bone is replaced every 3-4 years. Let’s dive into each life stage and its relation to bone evolution.
During our infancy and childhood, the long bones (arms, legs, wrist, and ankle) stretch and widen out completely by interstitial and oppositional growth. Once adolescence is reached, most of the long bones stop growing. As adolescence ends, the chondroblasts (cells that help form the cartilage) of the growth plates divide less often, and the plates become thinner until replaced by bone tissue. In adulthood, bone remodeling tends to happen — this is when bone deposition (new bone is formed) and bone resorption (bones are broken down) take over. Remember those osteoblasts and osteoclasts? They play a huge role in bone remodeling by building and breaking down new and old bone materials. This is very important in maintaining the balance of calcium and phosphorus in the body and protecting the entire structure of the skeleton.
Bone Health: Bone Preservation
What can we do NOW to preserve our bone health? What about the older population and those with chronic illnesses?
You can see how essential bones are to the body, and what they do to make sure that your body is running efficiently at all times. In order to protect our bones, it’s also very important to understand the power of maintaining a well-balanced diet and regular physical activity. As we age, our bones do their very best to continuously remodel themselves by depositing and resorbing bone material. However, the geriatric community or the elderly, and anyone that may deal with chronic illnesses such as prostate cancer or kidney disease may be vulnerable to bone disorders (i.e., osteoporosis or osteomalacia). Bone mineral disease is a common issue in people who have chronic kidney disease, and it can have an effect on almost all people who are on dialysis. Osteoporosis, in particular, occurs often among post-menopausal women. As mentioned, bones are responsible for hormone production, and usually, the sex hormones such as estrogen in women decrease with age. But there are other factors that increase the risk of osteoporosis, and those include:
- A diet low in calcium and protein
- Insufficient weight-bearing exercises
- Irregular vitamin D receptors
- Hormone-related illnesses such as hyperthyroidism and diabetes
So, what can we do as of NOW to take care of our bone health? First and foremost, eating enough calcium and vitamin D while your bones are either building or maintaining bone density. Second, limiting carbonated and alcoholic drinks since it drains minerals from the bones and lessens bone density. Last but not least, doing plenty of weight-bearing exercises (i.e., walking, sports, swimming, jogging, etc) increases bone mass. As always, please consult with your physician or registered dietitian if there are certain dietary or physical limitations you must stick to.
Nutrition for Bone Health
What are the recommended daily allowances (RDAs) for calcium and vitamin D? What are the best food sources for calcium and Vitamin D?
In particular, calcium and vitamin D play a crucial role in bone health. Calcium has been reported in research studies about its protective qualities against chronic inflammatory diseases and overall mortality. In a study done by Yoo et el., they concluded that young Korean adults 19 years or older with a low calcium intake of 500 mg per day were significantly associated with a higher risk of mortality. Vitamin D is a fat-soluble vitamin that improves calcium absorption and bone growth. Similarly, a study by Fagnant et el., reported that healthy military recruits aged 17 years or older that often skipped breakfast (typically including eggs, fortified dairy, orange juice, and cereal) were related to having higher chances of vitamin D deficiency.
Eating well-balanced meals from other food groups is just as important. A 2018 study by Fung, Meyer, and others, found that women over the age of 50, in particular, that had a higher intake of fresh fruit and vegetable, nuts, legumes, whole grains, polyunsaturated fats, and omega-3 fatty acids had a lower risk of hip fractures. The table below shows the recommended daily allowances (RDA) for calcium and vitamin D levels in different age groups:
|Age range||Calcium (mg) range||Vitamin D (IU) range|
|14-18 years||1,300 – 3,000||600 – 4,000|
|19-50 years||1,000 – 2,500||600 – 4,000|
|51-70 years male||1,000 – 2,000||600 – 4,000|
|51-70 years female||1,200 – 2,000||600 – 4,000|
|70 years +||1,200 – 2,000||800 – 4,000|
Foods that are high in calcium include yogurt, cheese, milk, soymilk, kefir, dark leafy vegetables such as kale, collard greens, and spinach, soybeans, salmon, and sardines. Foods that are high in vitamin D include egg yolks, fatty fish (i.e., mackerel), cheese, mushrooms, fortified foods such as orange juice, cereals, soymilk, and other dairy products. Also, do not forget about getting around 10-30 minutes of sunlight at least twice a week! A few simple and great recipes to prepare at home are:
- A healthy yogurt bowl with fresh fruit and granola
- Broiled or baked salmon with tomatoes and sauteed spinach
- A smoothie with fresh fruit with either fortified orange juice, soymilk, or milk
As we age, it seems like certain parts of our bodies do not operate the way they used to, but that does not mean that we should restrict ourselves entirely when it comes to nutrition and health. All we need is to be mindful of how we are taking care of our bones with the health choices we make every day. If you’re interested in consulting with a registered dietitian regarding geriatric health or simply want to know more about maintaining healthy bone density, book a 1:1 session at Healthy Mission Dietitian! Comment below in what ways you’d like to preserve bone health, or feel free to ask any questions. Remember, your health is worth it!
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Dawson-Hughes, B., MD, Harris, S. S., DSc, Lichtenstein, A. H., DSc, Dolnikowski, G., PhD, Palermo, N. J., & Rasmussen, Helen, PhD, RD. (2015). Dietary fat increases vitamin D-3 absorption. Journal of the Academy of Nutrition and Dietetics, 115(2), 225-230. https://10.1016/j.jand.2014.09.014
Dr. Samanthi. (2019, April 24). Difference between bone deposition and resorption. Compare the Difference Between Similar Terms. Retrieved September 7, 2022, from https://www.differencebetween.com/difference-between-bone-deposition-and-resorption/#Summary
Fagnant, H. S., Lutz, L. J., Nakayama, A. T., Gaffney-Stomberg, E., McClung, J. P., & Karl, J. P. (2022). Breakfast skipping is associated with vitamin D deficiency among young adults entering initial military training. Journal of the Academy of Nutrition and Dietetics, 122(6), 1114-1128.e1. https://10.1016/j.jand.2021.09.016
Fung, T. T., Meyer, H. E., Willett, W. C., & Feskanich, D. (2018). Association between diet quality scores and risk of hip fracture in postmenopausal women and men aged 50 years and older. Elsevier BV. https://10.1016/j.jand.2017.11.022
Marieb, E. N., & Hoehn, K. (2022). Chapter 6: Bones and Skeletal Tissues. In Human Anatomy & Physiology (10th ed., pp. 173–194). essay, Pearson.
Yoo, J. Y., Cho, H. J., & Lee, J. E. (2022). Lower dietary calcium intake is associated with a higher risk of mortality in korean adults. Journal of the Academy of Nutrition and Dietetics, https://10.1016/j.jand.2022.02.012