How to Know Which Supplements You Need

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(This month FoodTrients writer and nutritionist Ginger Hultin continues her four-part series on vitamins and supplements. Part 3 explores vitamin deficiencies and what you can do.)

Despite what the supplement industry may have you believe; in a balanced whole food-based diet you will get most of the vitamins and minerals your body needs. You’ll also get other health boosting ingredients such as phytochemicals, fiber, and antioxidants. However, there are times that supplementation can be beneficial but how to tell what you need can be confusing and complex. Overt signs of deficiency can be hard to assess without lab testing and support from a medical professional like a doctor or registered dietitian nutritionist. It is also important to be knowledgeable about how much of which supplement to take if you choose to take them, and any possible interactions with mediations or other supplements. Let’s discuss when you may need to supplement, how to know, and how to dose them if you do take them.

Common Nutrient Deficiencies
In the United States there are common deficiencies within our population. For example, we tend to have lower intakes of magnesium and potassium from natural dietary sources. People in more northern latitudes have increased risk of deficient vitamin D levels due to less consumption of foods rich in these nutrients and lack of sun exposure, which is used by the body to create vitamin D. Further north, the angle of the sun between November and March blocks nearly all UVB rays, the kind that can synthesize vitamin D.

This chart highlights some common nutrients of concern, the recommended intake for adults, and where you can find it in foods to ensure you’re getting enough.

chart 2

Diet-Specific Deficiencies
Deficiencies can also occur in restrictive diets such as low carb (South Beach, Atkins, Ketogenic, etc.), vegan diets, or other patterns that restrict certain food groups. Any time that you remove a food (even gluten free or dairy free diets!), you risk removing certain key nutrients. Here’s an overview of what to consider with common dietary restrictions:

Natural sources of vitamin d and calcium

Low Carb Diets
Deficiencies could include potassium, magnesium, phosphorus, calcium, and many of the B vitamins. These nutrients are commonly found in carbohydrate-rich foods such as whole grains and starchy vegetables. Additionally, many of these nutrients including calcium and magnesium, are underrepresented in daily multi-vitamins due to the physical size of the molecules. That could mean taking additional supplementation that a general multivitamin can’t meet.

Vegan Diets
Though vegan diets have proven to be health-promoting, cutting out animal products can lead to low levels or deficiencies including B12, vitamin D, omega 3 fatty acids, iron, zinc, calcium, and iodine. Supplementation is definitely needed for B12 but be sure to consider other nutrients, especially if you don’t consume adequate calories or have other restrictions within the dietary pattern (no gluten, no soy, grain-free, etc.)

Sick man taking medication after drinking hot tea

How to Find Nutrient Deficiencies

Testing – Blood tests are the most common way to assess vitamin and mineral levels. Some companies are offering at-home blood or saliva tests, though it is best to work with a doctor or naturopath if deficiencies are suspected to get their professional input on types and amounts of supplements, and to monitor levels during supplementation.

Physical Symptoms – Some people may have symptoms of deficiency such as fatigue, skin problems, brain fog, thinning hair or nails, or digestive issues. However, it can be difficult to attribute these symptoms to a certain deficiency unless testing is done to confirm.

Additional Considerations

Genetic mutations – Genetic issues can cause increased needs for certain nutrients. One example is a mutation in the MTHFR gene which impacts vitamin B12 and folate metabolism and may require supplementation. Speak to your doctor to see if testing could be beneficial based on your unique needs and medical history.

Toxicity – Taking too much of a certain nutrient can cause toxicity or can impact absorption of other nutrients. Even vitamins can be problematic. For example, vitamin C or magnesium in high doses causes diarrhea, and fat soluble vitamins such as A, D, E, and K can become toxic when levels are too high.

Dietary Reference Intakes (DRI)
These references are issued by the Food and Nutrition Board of the Institute of Medicine which is part of the National Academy of Sciences. This board reviews current research to assess the adequate nutritional intake for most people. Here is a breakdown of how you may see this on labels so you can better understand the language on products:

chart 3

Supplements can be a great addition to a healthy diet when they’re indicated to support your needs. Working with a licensed and credentialed health professional who is familiar with supplements is helpful to find any areas that need to be supplemented, which form will be most beneficial, and how much is needed. Often the best way to increase nutrient intake is through foods as this is generally the best way to optimize the body’s ability to absorb and use nutrients. Foods rich in vitamins and minerals often have other benefits as well, which can be an extra boost to our health. A registered dietitian nutritionist (RDN) is a great resource if you want help with this.

Marra MV, Bailey RL. Position of the Academy of Nutrition and Dietetics: micronutrient supplementation. Journal of the Academy of Nutrition and Dietetics. 2018 Nov 1;118(11):2162-73.
U.S. Department of Health and Human Services. (n.d.). Office of dietary supplements – nutrient recommendations : Dietary reference intakes (DRI). NIH Office of Dietary Supplements. Retrieved April 20, 2022, from,%25%2D98%25)%20healthy%20people.

About Ginger Hultin, MS RDN CSO

Ginger Hultin, MS, RD, CSO, LDN, is a health writer and owner of Champagne Nutrition specializing in integrative health and whole food-based nutrition. She serves as Immediate Past President for the Chicago Academy of Nutrition and Dietetics, Chair-Elect of the Vegetarian Nutrition Dietetic Practice Group and is a Media Representative for the Illinois Academy. Read Ginger's blog, Champagne Nutrition, and follow her on Facebook, Twitter, Instagram and Pinterest. Ginger Hultin MS RD CSO LDN | @GingerHultinRD Chair-Elect, Vegetarian Nutrition Dietetic Practice Group  
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