Dietary Supplements: Facts, Myths, and Clarity

By Gena Anderson

It seems like every time we have an ailment, from allergies to aches, a helpful friend is quick to recommend a supplement. Maybe they read about it somewhere, or it helped their neighbor’s best friend, but whatever their reason for the kind suggestion, we’re left wondering if it’s a good idea. The options for supplementation are seemingly endless, and the information available is often conflicting. Given the overwhelming abundance of supplements we could take, we ask the question: What should I take?

Some general considerations about supplementation are helpful. First, the best way to get necessary nutrients is through a varied and colorful diet, and pills are a poor substitute for nutrients your diet lacks.1 Supplements can be beneficial, and sometimes even needed. They also carry certain risks, and are not always worth the money we spend on this booming industry.2 Many factors affect the need for and benefits of supplementation, including age, chronic illnesses, and medical history. Before starting any supplement you should talk to your healthcare provider, who knows your specific needs.

The following are some of the most common vitamins and supplements people use, and some information to help you decide what you might need, and what you might not. 


This vitamin is one of the B vitamins, and it’s necessary for red blood cell and DNA formation as well as neurologic function.7 This is a supplement I recommend for some patients, depending on their specific needs. Deficiency of B12 can occur due to absorption issues and poor dietary intake and a simple blood test can determine if you are deficient. Most of us get enough in our diet, as B12 is found in fish, meat, poultry, eggs, milk products, and many fortified foods.7 Deficiency is associated with anemia, decreased cognitive function, and neurologic disorders. Older adults, those with certain types of anemia or certain gastrointestinal disorders, those who have had bariatric surgery, those who take acid-blocking medications or metformin, and those who follow a vegetarian diet are at higher risk of deficiency.7 There are many claims to the benefits of B12 supplementation, including increased energy and endurance, better cardiovascular health, and improved cognitive function, but evidence has not conclusively supported these claims.7 Supplementing with B12 rarely results in complications or harm, but if you are not deficient it may not offer many benefits. If you think you are at risk for deficiency you should talk to your healthcare provider about checking B12 levels. 

Vitamin C

Vitamin c, is a water-soluble vitamin required to make collagen, some proteins and neurotransmitters, and is better known for its function in immune response and antioxidant capabilities. There is some thought that the antioxidant effects, which limit the damage of free radicals, may prevent cancer or heart disease.3 Scientific evidence is unclear if supplementing is actually helpful in doing so.3 There is evidence that vitamin c supplementation can reduce the duration and severity of viral illnesses, but I don’t find any clear evidence that daily supplementation prevents illness in general. Vitamin c is readily found in citrus fruits, colorful peppers, broccoli, and many other foods, and deficiency is rare in areas with access to adequate food. Supplementation is usually safe, but it can interact with statin drugs and some cancer drugs. It’s definitely a good idea to eat a diet rich in vitamin c, and it might help to supplement when you’re ill or unable to get vitamin c in your diet, but it’s not usually necessary to supplement daily. I sometimes recommend this vitamin to my patients when they have a flu or similar illness, but not often for a daily supplement.

Vitamin D

This fat-soluble vitamin is needed for calcium regulation, neuromuscular and immune function, as well as bone growth and regulation.4  Vitamin d is either made when our bodies absorb sunlight or obtained through dietary sources like fortified milk or some fatty fishes. It is difficult to get enough vitamin d in our diet, and with limited sun exposure compared to generations past deficiency is quite common. Breastfed infants, older adults, people with limited sun exposure, inflammatory bowel diseases, and those with dark skin, or who have undergone bariatric  surgery are all at higher risk of vitamin d deficiency.4 Postmenopausal women are also recommended to take vitamin d. The dose needed depends on your age and other factors, including possibly measuring your level of vitamin d with a blood test. There is a growing body of evidence connecting vitamin d supplementation to many health benefits, including decreased rates of cancer and better management of chronic conditions such as diabetes and multiple sclerosis.4 Though harm from taking too much vitamin d is unlikely, it can occur and includes increased risk of kidney stones as well as damage to kidneys, blood vessels, and the heart.4 For many, daily vitamin d supplementation offers benefits and should be considered with the guidance of a healthcare professional. I sometimes recommend supplementing for premenopausal women, and almost always recommend additional vitamin d for postmenopausal women.6

Vitamin E

This fat-soluble vitamin also has antioxidant properties and is important for immune function as well as certain cellular activities and is readily available in seeds, nuts, leafy greens, and fortified cereals. Vitamin E promotes blood vessel dilation and decreases blood clotting, so there are concerns that supplementation may increase the risk of bleeding or lower blood pressure, especially with older individuals.5 Deficiency is rare, and though supplementation is generally thought to be safe at doses less than 1,000mg per day, there are risks of toxicity and serious side effects such as hemorrhage or medication interactions associated with supplementation, particularly at higher doses.5 Many claims have been made about vitamin e regarding its prevention of heart disease, eye disease, cognitive decline, and cancer, but evidence has been mixed and these claims are not widely validated.5 Talk to your provider before starting a vitamin e supplement, especially if you are taking other medications or over the age of 65. I rarely recommend routine supplementation of vitamin e.


There are so many forms of multivitamins available, with many variations in ingredients, so I’ll touch on these generally. People often take them to prevent diseases, or ensure they are getting adequate nutrients. The research, like the ingredients of these pills, is a mixed bag with some studies documenting benefits such as less incidence of cancer, and others finding increased mortality in those who take multivitamins.8 Currently no professional organization or guidelines recommend a daily multivitamin for the general population, but they are often recommended for individuals who are at risk for nutrient deficiencies because of their diet or medical conditions. Multivitamins do carry risks of getting too much of certain vitamins or minerals, and can interact with medications.8 If you decide to take a multivitamin it may be best to choose one tailored to your age and gender.8 

Omega 3

Found in fatty fish such as salmon, flaxseed, avocados, oils, and other seeds and nuts, these essential fatty acids play a role in our body’s cardiovascular, immune, pulmonary, and endocrine function. Supplements can vary in quality, so it’s good to read the label. Many experts recommend a high amount of krill oil versus other omega 3s. The claimed benefits of taking these supplements are vast, and research is ongoing. There is reasonable evidence that higher intake of omega 3s prevents cardiovascular disease, and they are prescribed to treat high triglycerides. They are usually included in prenatal vitamins to support fetal neurological development. There is some thought that they provide antiinflammatory benefits for certain conditions like rheumatoid arthritis, osteoarthritis, and inflammatory bowel diseases, but this evidence is mixed. Omega 3s have mild blood thinning properties, and can interact with blood thinners or increase the risk of bleeding. There is great support for eating a diet with adequate omega-3s, eating at least eight ounces of fish per week, and there may be benefits to taking a supplement. I regularly recommend omega 3 supplementation to patients based on their individual needs, and often encourage a mediterranean-style diet for heart health, which is high in omega 3s. 


This mineral is readily found in dairy products, kale, broccoli, and fortified grains, and is essential for bone health. It also circulates in a smaller amount in the blood and the blood levels can affect cardiovascular function. Supplements are not as readily absorbed, but when taken with vitamin d, absorption is improved.10 Long-term deficiency in calcium causes bone loss and increases risk for fractures. Since menopause leads to bone loss naturally due to decreased estrogen, it’s important for postmenopausal women to get adequate calcium, along with vitamin d.10 People who get little to no dairy in their diet may also benefit from supplementation.10 Getting too much calcium does carry significant risks, including cardiac arrhythmias, kidney stones, kidney failure, and constipation.10 Generally, dietary intake is the best way to get calcium, and certain individuals, such as postmenopausal women, should consider supplementation.

There’s often a perception that traditional medical providers are pill pushers, and don’t embrace natural remedies such as vitamin supplementation. In reality, I and many of my colleagues embrace and often recommend supplements and lifestyle modifications as part of our treatment plans. Sometimes my patients take a whole battery list of supplements that I am concerned offer little benefits other than supporting the vitamin and supplement industry. You may significantly benefit from certain supplements, and in some cases they may even even be necessary, but I would encourage you to talk to a professional before starting a supplement. Your best friend or favorite blogger don’t know your specific health needs. A simple conversation could work to your benefit, save you time and money, and help you make the best choice.

Be well, friends. Eat well and choose wisely. And, as always, this is not intended as medical advice and should not replace that of your own personal healthcare professional.

  1. American Heart Association (2020). Vitamin Supplements: Hype or Help for Healthy Eating.
  2. Everyday Health (2019). 7 Popular Supplements With Hidden Dangers.
  3. National Institutes of Health (2020). Vitamin C.
  4. National Institutes of Health (2020). Vitamin D.
  5. National Institutes of Health (2020). Vitamin E.
  6. Up to date (2020). Patient education: Calcium and vitamin D for bone health (Beyond the Basics) 
  7. National Institutes of Health (2020). Vitamin B12.
  8. National Institutes of Health (2020). Multivitamin/mineral supplements.
  9. Hjalmarsdottir, Freydis (2018). Healthline. 17 Science-Based Benefits of Omega-3 Fatty Acids. 
  10. National Institutes of Health (2020). Calcium. 

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