When was the last time you asked your doctor for a nutrition test, a measurement of the levels of vitamins and minerals in your blood? Vitamins and minerals are micronutrients that you need in tiny amounts. If you don’t have enough of them, you can develop a nutrient deficiency. I’ll talk more about nutrient deficiencies later. 

You might believe you are getting enough vitamins and minerals if you are going by the label on your food. However, did you know the Recommended Daily Value (RDV) on your food and supplement labels is the minimum amount you need to avoid illness?

The Food and Drug Administration (FDA) developed the Recommended Daily Value (RDV) for certain vitamins and minerals during World War II to ensure Americans were getting the minimum amount needed to avoid illness during food rations. Conventional medicine still uses these recommendations to determine if you have a nutrition deficiency. 

In functional medicine, we use the Optimal Daily Intake (ODI) as a guideline for the amount of nutrients your body needs to function at optimal levels. I’m going to tell you the difference between the RDV and ODI, the signs of a nutrient deficiency, and everyone should take a multivitamin that contains optimal levels of essential vitamins and minerals. First, let’s talk about why you need vitamins and minerals. 

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Why Do You Need Vitamins?

Your body needs essential micronutrients (vitamins and minerals) and macronutrients (carbohydrates, protein, and fat) to function. As I mentioned earlier, micronutrients are needed in small amounts, whereas macronutrients are needed in larger amounts.

Vitamins and minerals perform several functions in our bodies. For example, vitamin A supports your immune system and eye health. Vitamin C promotes cell repair and supports your immune system. B vitamins perform a variety of functions from everything to supporting your heart health, to regulating blood glucose levels, to promoting healthy hair, skin and nails. 

Here’s a look at what each vitamin supports in your body: 

Nutrition Test – Vitamins and Their Function – Infographic – Amy Myers MD®Nutrition Test - Vitamins and Their Function - Infographic - Amy Myers MD® https://content.amymyersmd.com/article/nutrition-test/Nutrition Test – Vitamins and Their Function – Infographic – Amy Myers MD®

We get these through our food, however you cannot get optimal amounts of these nutrients from food alone.  For example, today’s conventionally-farmed produce contains 10-25% less zinc, protein, calcium, vitamin C, and other nutrients than it did even 40 years ago because of modern farming practices.1 

Modern cultivation practices focus on speeding growth, increasing size, and improving pest resistance. The increased production from artificial fertilizers decreases concentrations of minerals in plants. This is called the “dilution effect.”2

Furthermore, while modern agriculture has increased the food supply, making more food available for more people, that process has also stripped the nutrients from the soil where our food grows. This is called soil depletion, and every new season of crops grown makes the problem worse. 

Together, the dilution effect and soil depletion have a double whammy on the nutritive value of our food. That’s part of the reason I advocate buying fresh, organic produce whenever possible. Still, even if you eat all organic foods you likely still aren’t getting optimal amounts of vitamins and minerals. 

Why the Recommended Daily Allowance Isn’t Enough

Even if you read labels and believe you’re getting the appropriate nutrients each day, you could be wrong. That’s because the FDA allows a 20% margin of error on the nutrients reported on the nutrition facts panel, which could mean you’re only getting 80% when the label says 100%. Needless to say, it’s an outdated system. 

The FDA guidelines also don’t take into consideration that your body does not store certain vitamins and minerals. B and C vitamins are water-soluble, meaning your body uses what it needs and removes the rest through your urine. 

Consider that the RDV for vitamin C is 65 to 90 milligrams per day. Eating one cup of broccoli will provide you with the recommended amount of vitamin C, according to the RDV. However, your body needs up to 2,000 mg of vitamin C to function optimally.3

That’s why I recommend going by the Optimal Daily Intake when looking at a nutrition test result to determine your vitamin deficiency. 

What is the Optimal Daily Intake?

The Optimal Daily Intake (ODI) is a dietary guideline that is improved to meet optimal nutrition instead of meeting the bare minimum. The idea of Optimal Daily Intake has been around since before the RDV was developed.4 However, it was first established and utilized in the 1990s. Let’s talk about the difference between the ODI and RDI. 

The Difference Between ODI and RDA

The FDA updated the RDV guidelines only once since World War II. However, these guidelines are set at values calculated at just one milligram over the minimum amount you need to avoid illness. This is why, in functional medicine, we use the ODI, which is far more than the RDV and the amount you need for optimal health. 

The ODI was developed to establish the amount of vitamins and minerals your body needs to function optimally. For example, based on the RDV you should get 90 milligrams of vitamin C every day. However, the ODI recommendation for vitamin C is 1,000 mg. Here’s a look at the differences in the amounts recommended by the ODI and the RDV:

Nutrition Test – Are Your Vitamins Optimal – Infographic – Amy Myers MD®Nutrition Test - Are Your Vitamins Optimal - Infographic - Amy Myers MD® https://content.amymyersmd.com/article/nutrition-test/Nutrition Test – Are Your Vitamins Optimal – Infographic – Amy Myers MD®

Now that you understand the differences between optimal amounts and the recommended daily value, let’s discuss how to know if you have a vitamin deficiency. 

How to Know You are Nutrient Deficient

Nutrient insufficiencies are much more common than you’d think. In fact, studies show these insufficiencies affect about 40% of all American adults. Among the most common insufficiencies are:5

The gold standard for testing for nutrient deficiencies is a full panel nutrition blood test, which includes a Complete Blood Count (CBC) and a Total Iron Binding Capacity (TIBC) test. These nutrition tests can be ordered by your doctor, however, you can order home tests. If you want to test your nutrient levels at home, I recommend using a home micronutrient test fromLetsGetChecked. You can choose between the essential vitamin test, which tests the levels of vitamin D, B12, and E, a mineral test, or the full micronutrient test, which tests for the vitamins I mentioned and copper, selenium, zinc, and magnesium. The results are available online so you can share them with your functional medicine doctor. 

Symptoms of a Nutrient Deficiency

Since different nutrient deficiencies have specific symptoms, it can be hard to pinpoint which nutrient you have a deficiency of without a nutrition test. Here are some common symptoms of nutrient deficiencies that could indicate you should do a nutrition test: 

Cracked, Sore Mouth

Sores and cracks in or around the mouth are often caused by a deficiency in one or more nutrients. Mouth sores and ulcers are linked to a deficiency in B vitamins like thiamine (B1), riboflavin (B2),6 or pyridoxine (B6). It can also be a result of an iron deficiency. 

Brittle Hair and Nails

If you notice brittle hair and nails, it could be the result of a biotin deficiency.7 Biotin (also known as vitamin B7) helps the body convert food into energy. A biotin deficiency can also cause muscle cramps, muscle pain, and tingling in the hands and feet. 

Bleeding Gums

Not getting enough vitamin C is one of the main causes of bleeding gums. Your body cannot make its own vitamin C, so it must be obtained through your diet or supplement regimen. Other symptoms of a vitamin C deficiency include bruising, delayed wound healing, and dry skin.8

Poor Vision at Night

We know that vitamin A supports vision health. Not getting enough vitamin A can lead to poor night vision and night blindness. This is because our body needs vitamin A to create rhodopsin, a pigment found in our retina that helps us see in low light or at night.9


Excessive fatigue and exhaustion are common symptoms of a vitamin D deficiency. Many essential foods lack vitamin D. Your body can create its own vitamin D from UV rays from the sun. Besides the sun, you can only get vitamin D through foods like wild-caught salmon and organ meats such as liver. 

Hair Loss

Unfortunately, hair loss comes with age and hormonal changes. An estimated 50% of adults report hair loss by the time they reach age 50. The good news is, a nutrient-rich diet can help slow or prevent hair loss. Vitamin deficiencies in biotin, niacin, and zinc can lead to hair loss. Correcting these deficiencies can prevent or slow down hair loss. 10

Remember that each nutrient deficiency has its own set of symptoms, so it’s always a good idea to have your doctor do a nutrition test to determine if your nutrient levels are optimal. However, your nutrient deficiency could be caused by your diet, autoimmune disease, or genetics. 

Causes of Nutrient Deficiencies 

If your nutrition test determines you have a nutrient deficiency, the good news is that you can correct it by taking a high-quality multivitamin and knowing the root cause of your deficiency. Here are three common causes of a nutrient deficiency: 

A Nutrient-Poor and Inflammatory Diet

If you are eating a poor diet with lots of processed food, refined sugars, and white flours then your meals are completely devoid of nutrients your body needs to balance your mood. Inflammatory foods, such as gluten and dairy, grains and legumes, sugar, eggs, caffeine, nuts, seeds, and nightshades can cause leaky gut, which leads to poor nutrient absorption and health problems.

Leaky Gut

An unhealthy diet, environmental toxins, certain medications, and stress can all lead to leaky gut. In leaky gut, tiny holes in your gut lining allow food particles, bacteria, yeast, and viruses to enter your bloodstream. As a result, your body can’t absorb foods properly, leading to vitamin and mineral deficiencies, inflammation, health problems, and mood imbalances.

Genetic Mutations

One of the best ways to ensure you are getting optimal amounts of the vitamins and minerals your body needs is by taking a high-quality multivitamin. 

Common gene mutations such as MTHFR can reduce your body’s ability to convert nutrients, including B vitamins, folate, and choline to their active form via methylation. VDR mutations can lead to vitamin D deficiency. Mutations that control sulfation can lead to low zinc levels.

Why Everyone Should Take a Multivitamin 

I recommend virtually everyone take a daily multivitamin that contains a combination of micronutrients, including vitamins, minerals, and antioxidants. That’s why The Myers Way® Multivitamin was the first supplement I personally formulated. 

When I custom formulated The Myers Way® Multivitamin, I poured over a decade of research into selecting the nutrient forms that work best with your body. Unlike many other multivitamins on the market today, The Myers Way® Multivitamin has optimal levels of selenium, zinc, and iodine to support thyroid health and contains 100% of the folate you need each day. And of course, I don’t include any of the added sugars or colorings you might find in other multivitamins.

I made sure to include optimal levels of  B Vitamins that far exceed the USDA’s recommended daily value (RDV). I ensured these highly critical vitamins are methylated to ensure they’re in the most bioavailable form to promote cardiovascular and neurological health. This is especially important for those with MTHFR mutations who want to optimize detoxification and methylation. 

Finally, I included bioavailable Vitamin D3 in The Myers Way® Multivitamin which is not only critical to support bone health, it can also promote a healthy immune system. 

Compare the supplement facts label of The Myers Way® Multivitamin with others and you will see for yourself the higher levels of key nutrients designed to support overall general wellness and detoxification. It’s the ideal supplement to start the new year! 

Article Sources

  1. Nutrient Density. Rodel Institute. 2021.
  2. Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence?. Donald R. Davis. American Society for Horticultural Science. 2009.
  3. Is it possible to take too much vitamin C?. Katherine Zeratsky, R.D., L.D.. Mayo Clinic. 2020.
  4. The Vitamin C Content of Apples. Robert E. Hadden. Ulster Medical Journal. 1938.
  5. CDC’s Second Nutrition Report. Centers of Disease Control and Prevention. 2021.
  6. Riboflavin: Fact Sheet. National Institutes of Health. 2021.
  7. Biotin: Fact Sheet. National Institutes of Health. 2021.
  8. Vitamin C Deficiency. Luke Maxfield and Jonathan S. Crane. Stat Perals. 2021.
  9. Vitamin A: Fact Sheet. National Institutes of Health. 2021.
  10. Medical treatments for male and female pattern hair loss. Nicole E Rogers and Marc R Avram. Journal of the American Academy of Dermatology, vol. 59. 2008.