By Mario Kratz, PhD
Published March 22, 2022
I claim that what we eat, both the quantity and the quality of our food, is one of the key factors that determine whether we are vibrantly healthy and fit, or miserably sick and frail. This post is the first in a mini-series of three in which I will take you on a tour of some of the evidence that demonstrates the tremendous impact of nutrition on our health.
In this first post today, we’ll be looking at an issue that – in my opinion – should be taking much more of a center stage in the discussion of nutrition and health: micronutrient deficiencies!
I’d like to start with a discussion of micronutrient deficiencies because these are the most obvious health issues that are directly affected by what we eat. As you probably know, we need a fairly large number of different vitamins, minerals, and trace elements because our bodies cannot produce them.
If our diet is chronically low in any one of these essential micronutrients, we develop a deficiency. I will cover four micronutrient deficiencies as examples in this blog post. All of these are so common that you, no matter who you are and where you live, may be affected by one or the other in your lifetime. Now, I don’t want to scare anyone, because the good news is that all of these are entirely preventable.
Calcium Deficiency and Osteoporosis
The first disease that is strongly linked to micronutrient deficiencies is a great example of this: I’d like to talk about osteoporosis, a condition afflicting mostly older women. Osteoporosis is characterized by weak and brittle bones due to low bone mineral density. Even if you don’t consider yourself an older woman, I encourage you to keep reading because our risk of osteoporosis is related to our diet and lifestyle habits throughout our entire life. Specifically, bone formation occurs early in life, and our bone mineral density reaches a peak around our 30s birthday. And low bone mass is not just a problem that can occur in the elderly. In our research studies, we regularly conducted so-called DEXA-scans to assess the body composition and fat mass of our research participants. DEXA-scans happen to also be the gold-standard measurement of bone mineral density, and so we also routinely obtained data on bone mineral density, kind of as a side product of our measurement of body fat mass. I have seen several unsuspecting young research participants in their 20s who we found to have osteopenia, i.e., a low bone mineral density that is a major risk factor for osteoporosis. These individuals were lucky in that they were able to change their diet and exercise habits early enough to increase their bone mineral density; without any change, many of them would be expected to develop osteoporosis by the time they are 50 or 60.
The way the body builds bone is actually super fascinating, and I’d like to explain this briefly, because it illustrates why the quality of our diet is so important when it comes to healthy bones. When you look at a bone, it appears solid, hard, and strong. But if you looked at it through an electron microscope, what you’d see is more similar to this picture below.
Now, this is a specific, spongy type of bone, but even in general, bone does have somewhat of an open, honeycomb-like structure. The way the body builds bone is to lay down protein fibers that are a type of collagen. You can see these collagen fibers very nicely at the bottom of the picture above. These fibers form bundles, but by themselves, they are fairly soft. They only become hard once minerals such as calcium and phosphorus attach to them.
What is fascinating about bone is that there are specialized cells called osteoclasts that are wandering around the bone that constantly break down bone tissue, and others called osteoblasts that lay down new bone tissue. And that new bone tissue is laid down such that the bone becomes strong in the exact direction that force is applied upon it. So basically, the bone senses in which direction it needs to be strong, and then these cells lay down new bone tissue to provide strength along that axis. Similar to a construction worker placing a beam to support a ceiling. At the same time, because bones are porous, they remain quite lightweight.
This entire process is highly regulated, and many hormones play a role. Given that the bone senses force applied to it, exercise is also a major factor. If you jump around, run, or lift weights, that puts stress on the bones that forces them to grow stronger. But the process of growing strong bones also requires numerous essential micronutrients. These include vitamin D and vitamin K, but particularly minerals such as calcium.
You see, without enough calcium, a bone loses its key functional characteristic, strength. Without minerals, what remains would mostly be a fibrous kind of protein. It would be as stable and strong as a piece of meat with lots of holes in it. Not the stuff you want for bones …
So, this hopefully makes it clear why we need to get enough calcium and all of the other essential micronutrients in our diets to help our bodies make strong bones. And we need to do so regularly because our bones are constantly being remodeled.
Now, the treacherous issue with bone health is that in the short term, particularly when you are young, having low bone mineral density, low calcium intake or a poor vitamin D status would not be obvious because you’d likely not have any symptoms. While it can happen, it’s rare for young people to have osteoporotic bone.
The picture above shows a graph of the bone mineral density of a 30-year old woman, measured by a DEXA-scan. Let’s take a look at the information in this graph. The x-axis shows the age of the patient in years, and the y-axis the bone mineral density (abbreviated here with BMD).
We see an obvious categorization by bone mineral density, with the green area on top showing healthy bone mineral density, and the yellow indicating low bone mineral density. That’s the condition known as osteopenia I mentioned above. The red area indicates very low bone mineral density, i.e., osteoporosis. What this really means is that there are so few minerals, mostly calcium, attached to these collagenous fibers in our bone that the bones are weak, brittle, and prone to breaking.
Another thing we see here are these three lines that are sloping down with age: the middle line shows the average bone mineral density throughout the adult lifespan of a woman. The lines above and below indicate one standard deviation above and below the mean. So most women’s bone mass will be somewhere in this range throughout their life. Bone mineral density usually reaches a peak around 30 years of age. Then, starting in the mid-40s to early 50s, bone mineral density tends to decline. That decline is more pronounced in women due to hormonal changes associated with menopause, but it does also occur in men. What is scary here is that many women will experience osteoporosis once they cross into their 60s and 70s even if they are within what we may consider the ‘normal range’.
So, the patient who was scanned here had very high bone mineral density at age 30, indicated by the square. And that is exactly where we’d ideally want to be prior to beginning menopause. Because if now due to aging and hormonal changes, her bone mineral density declines over time, she has a good chance of avoiding osteoporosis even into her 80s, 90s, or beyond, as long as she meets her requirements for calcium, vitamin D, and other micronutrients, and stays active. Obviously, there are always unknown factors that could still lower her bone mineral density, such as a disease, an injury that affects her ability to move, or certain types of medication, but by having high bone mineral density early in life, and developing good dietary and exercise habits, you are stacking the odds in your favor that your bone mineral density will not become too low when this typical decline happens later in life.
Sadly, many people are not getting enough of all of the micronutrients in their diet that we need for such strong bones. Let’s look at calcium intakes. The RDA, or recommended dietary allowance, for calcium is 1,000 mg/d for middle-aged men and women. The RDA is actually higher than 1,000 mg per day for some groups, such as teenagers or men and women over the age of 70. The RDA is the amount recommended here in the United States for different groups of people based on their age and gender, and for women also dependent on whether they are pregnant or breastfeeding. For every micronutrient, a committee of experts picks one criterion on the basis of which the RDA should be determined. For calcium, the RDA is set to ensure that the majority of the population has a calcium intake that is sufficient for optimal bone mineralization. To clarify, that doesn’t mean that everyone needs 1,000 mg per day; some people may have optimal bone mineralization at 800 or 900 mg/day. The problem is that you personally cannot know how much you exactly need without undergoing a bunch of sophisticated tests, and so to make sure your bones are getting enough calcium, you should make sure that you regularly meet the RDA.
How does that recommended amount compare to actual intakes?
In a paper published in 2017, data on calcium intakes in different countries that were measured between 2000 and 2012 were visualized in the map below. The dark green color shows those countries where average intakes are greater than 1,000 mg per day, so those are the countries in which the average intake meets the recommended amount for adults, or at least close to it. For most countries for which we have data, average intakes are lower, in many cases a lot lower.
Look at the yellow countries here: Canada, Spain, Italy, Chile, and Russia with average calcium intakes of 700-800 mg/d. Brazil and Japan in orange are at 500-600 mg/d, Argentina, South Africa, and India in burgundy red have average intakes between 400 and 500 mg/d, and China and Indonesia in red consume, on average, less than 400 mg/d. All of these are extremely low intakes and quite concerning.
Now, we need to consider that these data are based on self-reported dietary intakes, which tend to be subject to underreporting. My best estimate is that actual intakes may be a bit higher, maybe by up to 20% or 30% higher. Even if we consider that though, it’s clear that calcium intakes are way too low in a very large percentage of the world population.
So, it may not come as a surprise then to learn that osteoporosis is a major health problem all over the world. Even in the United States, where the average calcium intake is close to the RDA, approximately 10 million people had osteoporosis in 2010, and another 43 million had low bone mass, so osteopenia, predisposing them to osteoporosis later in life. And this number is expected to grow further, based on these estimates below that were published in 2014.
The situation is even worse elsewhere in the world.
In China, where average calcium intakes are less than 400 mg/d, more than 50% of women older than 70 have osteoporosis, and that number increases to 68% in those older than 80. And even among men, the situation is not rosy.
This massive osteoporosis prevalence is associated with a substantial burden of fractures in those that are older than 40. Data below are showing vertebral fractures, and that’s a dramatic picture, particularly in those that are older than 60. Look at the over 80-year-olds, with almost 40% of that population having at least one vertebral fracture, in both women and men.
Globally, the prevalence of osteoporosis among adults is around 18%. And that’s among all adults, not just among the elderly. That number is 23% in women and 12 % in men.
Even before I researched the data for this post, I knew that this was a massive public health issue, but I am still shocked about the extent of the problem. Osteoporosis fractures can have a huge impact on the quality of life of affected people, and this is not an issue to be taken lightly.
So, please, take good care of your bones!
Even though osteoporosis is not always, or not entirely due to micronutrient deficiencies, I hope I have convinced you that this is clearly a major health issue all around the world that is largely related to the quality of our diet and lifestyle, and in most cases preventable.
Vitamin A Deficiency and Vision Loss
OK, let’s take a look at another health issue that is linked to a micronutrient deficiency: vision loss. Vision loss can have many causes, but the biggest one globally is vitamin A deficiency. Now, vitamin A deficiency is not primarily a problem in the United States or other developed countries, which is partly thanks to food fortification with vitamin A. The grey line at the bottom here in the graph below represents high-income countries including the United States, Canada, Western Europe, Australia, and New Zealand.
Vitamin A deficiency affects about 10% of people in those countries, which – if you ask me – is already too high a number. However, vitamin A deficiency is a much more substantial issue in most of the rest of the world. For example, the percentage of people who are vitamin A deficient in sub-Saharan Africa in red, South Asia in dark blue, and Southeast Asia in light blue was between 60% and 80% in 2011, when this last datapoint was measured.
Given that vitamin A plays a critical role in the functioning of our eyes, this comes with a substantial burden of vision loss due to vitamin A deficiency. Globally, the prevalence of vitamin A deficiency-induced vision loss is around 75 cases per 100,000 people. That by itself is already quite bad. But that number is substantially higher in South Asia and Central Sub-Saharan Africa, which you’ll see at the bottom of the graph below. Again, the two lines here show data separately for males and females.
The American Academy of Opthalmology estimates that every year, about 500,000 children experience vision loss, and 1 Million die as a result of vitamin A deficiency. These are truly sobering numbers.
Iodine Deficiency and Thyroid Disease
The next very common micronutrient deficiency that I’d like to address is iodine deficiency, which is a major cause of hypothyroidism, meaning low thyroid function. Hypothyroidism is most often due to a deficiency in the essential trace element iodine. Take a look at this table below, showing that more than a third of the general global population, and also more than a third of school-age children, was estimated to be iodine-deficient in 2003. The numbers are particularly alarming in Europe, the Eastern Mediterranean region, Africa and Southeast Asia. But even in the Americas, where the prevalence is lowest, about 10% are iodine deficient.
When this paper was published, it was estimated that about 2 Billion people worldwide were suffering from iodine deficiency, and according to a 2017 paper, this number hasn’t changed substantially since. Iodine deficiency is nothing to take lightly because it can lead to a condition called hypothyroidism, meaning thyroid hormone levels that are too low, and an enlargement of the thyroid called a goiter. That is because just like calcium is a building block of bone, iodine is a building block of thyroid hormone. And without the right amounts of iodine in our diets, the thyroid gland simply cannot make enough thyroid hormone.
That can lead to major health issues because thyroid hormone regulates many aspects of our metabolism, acting on most cells in our body. For example, remember I said above when we discussed about osteoporosis that bone growth and bone remodeling underlie hormonal regulation. One of these hormones is thyroid hormone. Thyroid hormone also regulates the growth of nerve cells, the production of heat, and the conversion of food to energy in our bodies. Having low thyroid hormone levels will make you constantly feel tired, lethargic, and cold, and also prone to gaining weight. Also, if a pregnant woman is iodine deficient, it can dramatically affect the cognitive development of her unborn child, in the worst case leading to intellectual disability. So, again, not good, and frustrating because it’s a problem that could easily be prevented on the population level by the widespread use of iodized salt.
Iron Deficiency and Anemia
And lastly, another disease that is extremely common around the world that often is caused by a lack of specific micronutrients is anemia. Anemia is a condition characterized by insufficient healthy red blood cells. Because red blood cells transport oxygen around the body, not having enough healthy red blood cells means that the blood is unable to transport all the oxygen the cells need. As a result, the patient feels tired and lethargic, dizzy, and lightheaded. That may not sound like such a big deal, but in advanced stages, the patient is not able to function normally at all, and in extreme cases, the condition can even be fatal.
Take a look at the map below here that shows the prevalence of anemia in the world. In most of the wealthy Western countries, such as the United States, Western European countries, Canada, or Australia, between 3 and 10% of the population was anemic at the time of this study, which was 2019. That is a substantial burden already. However, look at Russia or Brazil, where the prevalence is between 10% and 25%, or South Asia and central Africa with rates up to 50%.
Because of the regular loss of blood in menstruating girls and women prior to menopause, the prevalence tends to be about twice as high in women between the ages of 15 and about 45 (shown below in red) compared to men (blue). The figure below shows the prevalence on the right side and absolute numbers on the left side. Just look at these numbers. What we are talking about are tens of millions of affected people in each of these groups by age and gender. So, for example, about 80 Million young women aged 15 to 19 suffer from anemia worldwide, another 80 million young women between 20 and 24 years of age, and so on. Staggering!
Now, anemia can be caused by a lot of different medical issues, such as infection or chronic kidney disease, but globally, at least 50% of all cases are due to dietary iron deficiency, shown in the figure below in orange. There are additional dietary factors that can cause anemia, including vitamin A deficiency or a deficiency in folic acid or vitamin B12, so it’s clear that this is a major diet-related health problem affecting hundreds of millions of people around the world.
Conclusion: Eat Nutrient-Dense Foods to Prevent Micronutrient Deficiency Diseases
This is by no means a complete list of common micronutrient deficiencies, but I hope that the discussion of these few examples has made it clear that micronutrient deficiencies are still a major public health problem all around the world.
And let’s revisit the question we asked above. “What kind of evidence do we have that shows that what we eat really matters for our health?”
I’d say we have the first answer: good, nutrient-rich foods will provide us with all of the essential vitamins, minerals, and trace elements our bodies need, giving us a chance to have everything run smoothly, feeling fit and healthy. Above all, regularly meeting our micronutrient needs will help us prevent a wide range of more or less devastating micronutrient deficiency diseases.
What I am hoping you will take away from this article is that nutrient-dense food is the foundation of good health, and that should be the case no matter which other diet philosophies you adhere to. Whether you are vegan or follow a normal mixed diet or a ketogenic diet, your body needs sufficient amounts of all of the essential micronutrients.
I have plans for a couple of blog posts and videos about the nutrient density of foods, and how to make sure we are regularly getting enough of all of the essential micronutrients. These should post in 3, 4 weeks.
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- National Academies of Sciences, Engineering, and Medicine. 2020. Harmonizing the process for establishing nutrient reference values: a tool kit. Washington, DC: The National Academies Press.
- National Academies of Sciences, Engineering, and Medicine. 2017. Guiding principles for developing dietary reference intakes based on chronic disease. Washington, DC: The National Academies Press.
- National Institutes of Health, Office of Dietary Supplements. Fact Sheet for Professionals: Calcium. Accessed on March 22, 2022.
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- American Academy of Ophtalmology. Vitamin A Deficiency – Sub-Saharan Africa. Accessed on February 10, 2022.
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- Safiri et al.; Burden of anemia and its underlying causes in 204 countries and territories, 1990-2019: results from the Global Burden of Disease Study 2019. J. Hematol. Oncol. 2021; 14: 185.