Would you believe that the majority of the population — up to 90 percent of adults in the U.S. — is believed to have a vitamin D deficiency? Many physicians are starting to take this vitamin deficiency very seriously; in fact, vitamin D is one of the most recommended supplements by physicians today in order to treat and/or prevent vitamin D deficiency symptoms.
Most adults are believed to be at least somewhat deficient in vitamin D, however, people with dark skin, people who live in northern regions of the world where less year-round sun exposure is experienced and those who are overweight have an even greater chance of experiencing vitamin D deficiency symptoms.
According to the National Health and Nutrition Examination Survey, the newest statistics demonstrate that more than 90 percent of people with darker skin pigments (including African-Americans, Hispanics and Asians) living in the United States now suffer from vitamin D insufficiency, while 75 perfect of the white population is deficient. (1)
As the population of overweight and obese adults and children has risen steadily over the past several decades, so has the incidence of vitamin D deficiency symptoms. Sadly, vitamin D deficiency is correlated with increased risks of developing common cancers, autoimmune diseases, hypertension and various infectious diseases, too. (2)
A 2017 study recently revealed that occupation can also play a big role in vitamin D levels. Researchers found that shift-workers, health care workers and indoor workers are at a high risk of developing vitamin D deficiency due to reduced outdoor time and sunlight exposure. (3)
Luckily, there are ways you can naturally increase your vitamin D levels and decrease your risk of developing health conditions like heart disease, cancer, diabetes and other vitamin D deficiency symptoms. Spending time in the sun, without sunscreen, is your surest way to get enough vitamin D, and eating vitamin D-rich foods also helps improve your blood levels. Read on to understand just how much time you need in the sun and what foods will help you to avoid a vitamin D deficiency symptoms.
What Is Vitamin D?
Vitamin D is a fat-soluble vitamin that’s stored in the liver and fatty tissues. This means that increased body fat has the ability to absorb vitamin D and keep it from being used within our body. Vitamin D is somewhat different than other vitamins because our bodies make most of our vitamin D on their own, rather than solely relying on food sources.
The way our bodies make vitamin D is to convert sunshine into chemicals that are used by the body. In particular, when UV-B sunshine rays land on the skin, a substance in the skin called 7-dehydrocholesterol is literally converted into vitamin D3.
7-dehydrocholesterol or the cholesterol in our skin — and very similar to cholesterol itself — converts “previtamin D” and makes it into usable vitamin D3, which is sometimes also called provitamin D. (4) Previtamin D first travels through the kidneys and liver in the bloodstream and then is converted into a biologically active and usable substance called calcitriol.
Vitamin D actually becomes a hormone within the body, particularly a secosteroid hormone. What we know as vitamin D is really a precursor to a steroid hormone. It impacts not only our skeletal structure, but also our blood pressure, immunity, mood, brain function and ability to protect ourselves from cancer. (5)
Vitamin D2 vs. Vitamin D3
There are two types of supplemental vitamin D: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). The precursor to vitamin D is found in both plant and animal products, but animal-derived products of vitamin D3 are thought to be more absorbable and beneficial. Why? Well, manmade vitamin D is made one of two ways: D2 is created by irradiating yeast and other molds (known as vegetarian vitamin D2) or by irradiating animal oils and cholesterol, creating vitamin D3.
The type of vitamin D our bodies naturally make is called cholecalciferol, which is vitamin D3. The body is able to covert some D2 to be used for body functions but prefers and is able to use vitamin D3 much more effectively.
Unfortunately, most vitamin D-fortified foods and dietary supplements mostly contain ergocalcifero, a type of vitamin D2, which is neither as absorbable nor convertible by the body into what it needs.
D3 from animal products (specifically from the cholesterol within these products) is closest to what sunlight naturally produces in humans when the skin works to convert UV light. Vitamin D3 is believed to convert up to 500 times faster than D2 and has been estimated to be four times more effective in humans. (6)
How Our Bodies Get Vitamin D From the Sun to Prevent Vitamin D Deficiency Symptoms
Many people assume that the best way to acquire vitamin D is through drinking milk, eating fish or even taking supplements like cod liver oil. While these do serve as food sources of vitamin D, direct exposure to the sun is actually the best way to absorb this important vitamin.
When you sit in the sun unexposed, without sunscreen, for roughly 10 minutes, you likely absorb about 10,000 units of natural vitamin D. However, keep in mind that this amount differs from person to person, depending on skin tone.
Melanin is a substance that affects how light or dark your skin color is, and the more melanin you have in your body, the darker your skin color will be. Melanin gets released when we are exposed to the ultraviolet rays of sunshine. The more sunshine we receive, the more melanin is released in our skin. It’s believed that up to 90 percent to 95 percent of most people’s vitamin D comes from casual sunlight exposure. The amount of melanin you have in your skin affects the amount of vitamin D you can produce, so the fairer your skin, the more easily you can make vitamin D. (7)
The cholesterol in the skin converts melanin into usable vitamin D to be distributed throughout the body. This is why for many people, a slight to moderate rise in cholesterol levels can be experienced in the winter months when there is less exposure to sunshine, since it’s common to spend much more time indoors.
How Much Sun Is Enough?
Most experts recommend getting about 10 to 15 minutes of direct sunlight daily, without wearing sunscreen, if you are fair to medium toned. If you have dark skin, you will likely need more time in the sun to make enough vitamin D because your skin has more protection against the sun’s effects.
Some experts recommend that darker toned people spend about 40 minutes to one hour in the sun daily if possible. If you live farther from the equator (in the U.S. this would be the mid-states or farther north), then you need more overall time in the sun (closer to one hour a day). If it’s the winter, you need to double the recommended time to allow enough vitamin D production to occur.
Here is a good rule of thumb to know that the sun is creating vitamin D in your skin: You want to look at your shadow and see that it’s shorter than you are. This tells you that the sun is high enough in the sky and strong enough to convert vitamin D in your skin. For example, you may experience this during the hours of 10 a.m. to 3 p.m. but not as much during other times of the day when the sun is lower and therefore less likely to penetrate your skin effectively.
If you are worried about not wearing sunscreen and fear the effect that direct sunlight can have on your skin, try applying sunscreen to your face and hands but not on your limbs (assuming your limbs are exposed). This leaves enough unexposed skin to properly create the vitamin D you need.
What Causes Vitamin D Deficiency Symptoms?
It’s worth repeating that 50 percent to 90 percent of most people’s vitamin D comes from casual sunlight exposure. Your skin makes vitamin D when it comes in contact with the ultraviolet B (UVB) rays from the sun. Therefore one of the biggest reasons that a growing population is experiencing vitamin D deficiency symptoms is because of our modern, primarily indoors lifestyle. This contributes to the two most common causes of vitamin D deficiency symptoms:
1. Lack of Sun
While years ago people spent more time outdoors, walking to do errands and even working outside, today we see a different situation. Most children spend unprecedented hours inside — watching television, playing video games and surfing the internet. Similarly, most adults work indoors, exercise inside gyms and spend their free time inside their homes where they are sheltered from the sun.
With all this time indoors, it’s no wonder we don’t get enough of the “sunshine vitamin” and vitamin D deficiency affects over a billion people worldwide. Traditionally, the human vitamin D system begins in the skin, not from the foods you eat. Although food sources of vitamin D can help raise your levels and prevent a deficiency, the sun is your most effective way to sustain proper vitamin D levels. (8)
Not only are we failing to get enough time outdoors in the sun, but when we do, many of us wear sunscreen nearly the entire time. As the risk for developing skin cancer has also risen in recent years, doctors strongly encourage the use of sunscreen for children and adults, even through the winter months and when sun exposure is generally limited.
Alarmingly, some research shows that when you wear sunblock SPF 8, you reduce your body’s ability to make vitamin D by 90 percent. If you choose a sunblock with a higher SPF of 30 (which is the number normally recommended by doctors), you reduce your body’s ability by up to 99 percent. This results in further deficiencies because even though we spend time outdoors, the sunscreen doesn’t allow our bodies to convert vitamin D from the sun. (9)
Research also shows that certain health conditions, such as abdominal obesity, type 2 diabetes, insulin resistance and hypertension, also increases a person’s risk of vitamin D deficiency.
Vitamin D Deficiency Symptoms
There is a great body of evidence that shows that people with vitamin D deficiency are at an increased risk of developing health complications and conditions like cardiovascular disease, metabolic syndrome, various types of cancer, immune disorders and adverse pregnancy outcomes. According to several scientific studies and reviews, a vitamin D deficiency symptoms can be linked to the following health problems: (10)
- heart disease
- high blood pressure
- autoimmune diseases
- multiple sclerosis
- chronic pain
Researchers suggest that anyone with these health conditions or the following symptoms should be tested for vitamin D deficiency:
- chronic fatigue
- trouble sleeping
- weak or broken bones
- weakened immune system
- inflammation and swelling
The only way to know if you are deficient in vitamin D is to have your doctor perform a test, called a 25-hydroxy vitamin D test. This will tell you if, and how severely, you are deficient. When your doctor performs a blood test and gives you the results for your vitamin D levels, keep these numbers in mind:
- 50+ equals a good level of vitamin D
- 30–50 means you want to supplement with vitamin D, work on spending more time in the sun and add vitamin D foods into your diet
- less than 30 means you are very deficient and definitely want to take immediate action to bring those levels up
Talk with your doctor about supplementing with higher doses of vitamin D if you are severely deficient or have a very low level according to the tests. When your doctor performs a vitamin D test, specify that you would like to have the 25-hydroxoyvitamin D test done, sometimes also called the 25(OH) D test.
Some other types of vitamin D tests can show normal or even elevated levels of vitamin D, which are actually inaccurate and can hide a serious deficiency, so the 25(OH) D test seems to be the most accurate when determining your true vitamin D levels. (11)
Top Vitamin D Sources to Prevent Vitamin D Deficiency Symptoms
While some foods provide vitamin D, exposure to sunlight is still the very best way to get the vitamin D you need in order to prevent vitamin D deficiency symptoms. However, eating foods that are rich in vitamin D also helps you acquire more, so try adding these good-quality, natural sources of vitamin D into your diet regularly: (12)
- Sunlight: Aim to spend 10–20 minutes of unexposed time in the sun daily (between 1,000 and 10,000 IUs). The range is so wide as it depends on the time of year, how far from the equator you live and how much skin is exposed. If you have lighter skin, less time is needed. If you have darker skin or live farther north (in the Northern Hemisphere, like Boston), you need about an hour of sun in the summer to get about 1,000 IUs of vitamin D.
- Carp Fish
- Maitake Mushrooms (exposed to UV light)
- Portobella Mushrooms (exposed to UV light)
- Rainbow Trout
- Cod Liver Oil
- Raw Milk
Vitamin D in Mushrooms
Mushrooms are a very interesting and rare food when it comes to vitamin D. They are one of the only plant sources of vitamin D and actually act similarly to how human skin does, absorbing more vitamin D when exposed to the sun. In some mushrooms that are now available in certain health food stores, the vitamin D content is boosted by exposing these mushrooms to ultraviolet light.
Mushrooms nutrition contains plant sterols that are able to convert UV light to vitamin D. Exposing mushrooms to as little as five minutes of UV light is believed to produce a substantial amount of vitamin D. (13) While mushrooms are typically grown indoors, many growers are beginning to grow them outdoors to take advantage of this, or they place the growing mushrooms under sunlamps.
Rare and sometimes difficult-to-find maitake mushrooms, for example, contain a huge amount of vitamin D, while portobello mushrooms and other mushroom varieties also make good sources, but they are not nearly as high. You can ask the workers at your health food store or the farmers at your local market if their mushrooms were grown indoors or outdoors in order to know if the mushrooms you are purchasing contain higher amounts of vitamin D.
Vitamin D in Pasteurized Milk and Raw Milk
Interestingly, and despite what many people think, regular pasteurized milk does not naturally contain much vitamin D at all. Synthetic vitamin D is added to pasteurized cow’s milk, soy milk and rice milk.
Almost all of the U.S. milk supply is fortified with 400 IU of vitamin D per quart, according to the USDA, but foods made from milk, like cheese and ice cream, are usually not fortified. Synthetic vitamin D added to foods is believed to be much less effective as naturally occurring vitamin D and can also potentially block natural vitamin D’s effects. (14)
Raw milk, on the other hand, is believed to contain a small amount of vitamin D naturally, which is found in its fat and not destroyed during pasteurization. Some sources show that raw milk has about 38 IUs of vitamin D per quart (four cups). However, it’s hard to know for sure how much vitamin D is in raw milk because it differs greatly depending on the specific milk being tested and correlates with the health of the animal that it came from.
On top of this, the USDA does not list the official vitamin D content of raw milk, and many sources claim different amounts of vitamin D to be present within raw milk. Keep this in mind if you consume raw milk to increase your vitamin D levels.
The reason raw milk is thought to be a better source of vitamin D than pasteurized milk is because unpasteurized, raw milk is usually superior in almost every vitamin and mineral overall. Raw milk normally comes from cows that are free to graze outside and to eat their natural diet of grass, as opposed to being force-fed grains and living indoors. Because the animal is healthier, so is its milk.
A lot of the nutrients that are in regular milk are also destroyed during the high-heat pasteurization process. Therefore it seems logical that higher quality raw milk would have more vitamin D to begin with and also retain more of it since it does not go through this nutrient-destroying high-heat pasteurization process.
Top 7 Health Benefits of Vitamin D
1. Contributes to Bone Health
Vitamin D plays a role in calcium absorption into the bones. Calcitriol (converted vitamin D) works with the parathyroid hormone to maintain calcium levels. Additionally, vitamin D has an effect on other important vitamins and minerals that contribute to both health, including vitamin K and phosphorus. Vitamin D is partially responsible for maintaining phosphorous levels in the blood, and since vitamin D affects calcium’s ability to bind to proteins, it’s believed that it’s also linked to vitamin K.
A deficiency in vitamin D can result in the softening of your bones, which is called osteomalacia, or a bone abnormality called rickets. Additionally, a deficiency increases your risk for developing osteoporosis and experiencing fractures or broken bones.
Studies have shown that vitamin D in doses of 800–5000 IU per day can improve musculoskeletal health by naturally slowing aging of the skeletal structure and reducing the rate of fractures and falls in older adults that are over 65. (15) Older adults with adequate vitamin D levels are more likely to be active, have improved muscle strength, and are less prone to falls and injuries.
When vitamin D levels are low, the parathyroid becomes overactive. This is known as hyperparathyroidism and results in drops in phosphorous. Phosphorus, in addition to calcium and other compounds, is needed in order to properly mineralize bone density.
2. Helps Manage Blood Sugar Levels and Can Prevent Diabetes
Diabetes symptoms result from a lack of insulin or inadequate insulin secretion following increases in insulin resistance. According to research conducted at the London School of Medicine and Dentistry, calcium is necessary for insulin secretion, and vitamin D promotes calcium absorption and utilization, therefore contributing to the regulation of insulin secretion. (16)
According to a 2015 study published in Current Diabetes Reviews, vitamin D replacement has beneficial effects on all aspects of type 2 diabetes, including the incidence, control and complications of the disease. There is also mounting evidence linking low vitamin D levels to diabetes. (17)
3. Protects Against Cancer
Vitamin D deficiency symptoms have been correlated with increased risks for cancer development, especially breast, colon and prostate cancers. According to research published in Frontiers in Endocrinology, vitamin D plays a role in factors that influence tumor growth, cell differentiation and apoptosis. Researchers have found that increased sunlight exposure and circulating levels of vitamin D are associated with the reduced occurrence and mortality in many types of cancer. (18)
Research shows that vitamin D can affect the risk of breast, colon and ovarian cancers possibly due to its role in the cell life cycle or its ability to block excess estrogen. According to research published in the American Journal of Clinical Nutrition, improving vitamin D and calcium nutritional status substantially reduces the risk of cancer in postmenopausal women. (19)
4. Combats Heart Disease
A growing number of research points to the fact that vitamin D deficiency is linked to increased risks for cardiovascular disease since it’s involved in regulating blood pressure, cholesterol levels and inflammation.
Animal studies have shown that the disruption of vitamin D signaling promotes hypertension, atherosclerosis and cardiac hypertrophy. We know that humans who are deficient are more likely to die from coronary heart disease and other heart-related symptoms, according to research from the Vanderbilt University Medical Center. (20)
5. Enhances the Immune System
Vitamin D helps with healthy cell replication and may play a role in protecting against the development of autoimmune conditions in addition to less serious common colds and the flu.
Our immune cells contain receptors for vitamin D, and it’s been shown that vitamin D seems to prevent prolonged or excessive inflammatory responses. Inflammation is often at the root of many modern, chronic diseases and autoimmune disorders: multiple sclerosis, rheumatoid arthritis, irritable bowel syndrome and other digestive disorders, high blood pressure, and more. (21)
6. Facilitates Hormone Regulation and Helps Improve Mood
Because it acts like a hormone within our bodies and affects brain function, vitamin D deficiency has been linked to an increased risk for mood disorders, including depression, seasonal affective disorder, and severe mood problems experienced during PMS, insomnia and anxiety. (22)
Low levels of vitamin D can also interfere with proper testosterone and estrogen production, leading to imbalances that can result in many unwanted symptoms.
7. Helps with Concentration, Learning and Memory
Several studies have shown that vitamin D also affects our ability to make decisions, concentrate and retain information. Some studies have shown that people with lower levels of vitamin D perform poorly on standardized exams, may have poor decision making skills, and have difficulty with tasks that require focus and attention. (23)
Recommended Daily Intake of Vitamin D to Prevent Vitamin D Deficiency Symptoms
Because vitamin D deficiency symptoms are a growing concern worldwide, especially in Western developed nations, authorities recently increased the recommended daily intake of vitamin D to double the previous amount for newborns, kids and adolescents.
The RDA for vitamin D according to the USDA is 600 IU per day for adults. I personally recommend getting 5,000 IU per day, especially since there is little risk in over-supplementing with vitamin D but many benefits to gain from having adequate levels. However, keep in mind that this is a general recommendation, and there is no way to know the exact amount that’s best for you without a blood test. You may need a higher or lower amount and should speak to your doctor. This way you can purchase a good-quality, food-based vitamin in the proper dose you need right away.
Some studies have shown that in patients with documented vitamin D deficiency, a very high, cumulative dose of at least 600,000 IU administered over several weeks appears to be necessary to replenish stores within the body. This goes to show that having a blood test to detect your exact vitamin D levels can be beneficial in telling you exactly how to replenish your body levels properly. Ideally, you want to supplement with a high-quality, whole food-based multivitamin or vitamin D supplement until your blood level of vitamin D is between 50–60 nanogram per milliliter.
My Recommendation for Children:
- Below 5: 35 units per pound/day
- Ages 5–10: 2,500 units/day
My Recommendation for Adults (including pregnant women):
- 5,000 units/day
However to be clear, below is the USDA’s official recommendation of vitamin D: (25)
- 1–3 years: 600 IU (15 mcg/day)
- 4–8 years: 600 IU (15 mcg/day)
Older Children and Adults:
- 9–70 years: 600 IU (15 mcg/day)
- Adults over 70 years: 800 IU (20 mcg/day)
- Pregnant and breastfeeding: 600 IU (15 mcg/day)
Certain supplements do provide the preferred type of vitamin D3. You want to look for a supplement that provides the actual food source of the vitamin, along with all of the other enzymes and compounds that naturally help utilize it. This makes it more effective than the isolated vitamin alone.
Vitamin D Interactions and Concerns
Luckily your skin is able to regulate vitamin D conversion according to heat and other factors. It can store previtamin D for future use and destroy amounts above and beyond what is safe. So deficiency is usually a much bigger concern than consuming too much vitamin D (vitamin D toxicity is very rare and consists of a buildup of calcium in the blood, called hypercalcemia).
Because vitamin D is a fat-soluble vitamin, it ideally needs to be consumed with fat in order to have optimal absorption. If you are going to eat a food source of vitamin D, it’s best to combine it with some more of essential fat source too, like ghee, coconut oil, nuts, seeds or fish.
Vitamin A and vitamin D have an important relationship. Some studies have recently suggested that there is a possibility for vitamin D deficiencies to become worse when a person takes a high supplemental intake of vitamin A. These studies reveal that when blood levels of vitamin D fall below 50 on a vitamin D blood test (which means the person is nearing deficiency), higher supplemental intake of vitamin A can worsen the problem. (26)
The good news is that when vitamin A and D levels are both sufficient, research has shown that they work together to help your body metabolize the vitamins and use them to their best ability. Supplementing with very high doses of vitamin A is not recommended, so if you have a known vitamin D deficiency or experience vitamin D deficiency symptoms, it can lead to certain problems.
Final Thoughts on Vitamin D Deficiency Symptoms
- Up to 90 percent of adults in the U.S. may suffer from vitamin D deficiency and vitamin D deficiency symptoms, which can lead to major health issues, such as cardiovascular disease, diabetes, autoimmune disease and cancer.
- Two major causes of vitamin D deficiency symptoms are a lack of sun exposure and the use of sunscreen. When you sit in the sun unexposed, without sunscreen, for roughly 10 minutes, you likely absorb about 10,000 units of natural vitamin D. This is the most effective way to increase your vitamin D levels to prevent vitamin D deficiency symptoms.
- There are also food sources of vitamin D, including fish, mushrooms exposed to UV rays, eggs and raw milk. Eating these foods can help increase your vitamin D levels, but sun exposure is the best way to avoid a vitamin D deficiency symptoms.
- The most common signs of a vitamin D deficiency include weakness, chronic fatigue, depression, anxiety, trouble sleeping, weak bones and weak immune system, and vitamin D deficiency symptoms can include other health conditions, such as diabetes, heart disease and more.
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