When someone is eating a healthy diet, high in fresh fruits, vegetables, greens, legumes, whole grains, nuts and seeds, and low in harmful substances – do they still need to take multivitamins?

I always stress the importance of a whole foods plant-based diet and urge everyone to get their nutrients directly from the source: plants. Just as people are trying to find an easy solution for wellness through pharmaceuticals, many are also replacing proper eating with vitamin and mineral supplements.

But does eating a healthful diet based on whole plant foods offer sufficient protection against chronic disease and excessive weight gain?

According to many experts, there are some nutrients that are lacking even in an ideal diet, and deficiencies can undermine your health. Also, we cannot be really sure that we are getting the precise optimal amounts of vitamins and minerals every day from our diet – especially since absorption efficiency and utilization of nutrients varies from person to person.

So, a high quality supplement can fill these gaps, ensuring that we get adequate amounts of essential micronutrients.

If I drink green smoothies and eat a healthy diet, do I still need a multivitamin?

The best way to find out whether or not you have any nutritional deficiency is by getting tested.

The following vitamins and minerals are often lacking even in a healthy diet and need to be supplemented:

  • Vitamin B12
  • Vitamin D
  • Vitamin K2
  • Iodine
  • Zinc

Vitamin B12

Vitamin B12 is required for important biological functions like red blood cell production, nervous system function, and DNA synthesis. Deficiency in B12 can cause a variety of health problems including elevated homocysteine (a cardiovascular risk factor), anemia, depression, confusion, fatigue, digestive issues, and nerve damage.  Insufficient B12 levels are also associated with increased risk of Alzheimer’s disease.

Vitamin B12 is unique in that it is made only by microorganisms. Because our produce is washed and often transported far before we eat it (soil contains B12-producing microorganisms), most of us are unable to get sufficient B12 from plant foods alone. Some foods (seaweed, mushrooms, tempeh, miso, tamari, and spirulina) have been marketed as good sources of B12, but this was based largely on faulty testing methods. Though they may contain some amounts of B12, many experts contend that these levels are not consistent enough for people to rely on these foods as the sole source of B12 in their diet.

B12 deficiency is common, especially in vegans who don’t supplement and in the elderly – our ability to absorb B12 decreases with age, and about 20% of adults over the age of 60 are either insufficient or deficient in vitamin B12. Supplementation with vitamin B12 is likely important for most people, and absolutely required for most vegans to achieve sufficient B12 levels.

Vitamin D

The best source of vitamin D is the sun, but many people spend most of their time indoors or wear sunscreen, which blocks the absorption of vitamin D. People living in northern climates – or in states with long, cloudy winters – miss out on this “sunshine vitamin.” Also, although most light-skinned people can make enough vitamin D exposing the face and arms each day with five to fifteen minutes of warm sunshine, people with darker skin need at least a half-hour.

Insufficient vitamin D levels are very common. Low levels of vitamin D levels are associated with several cancers, diabetes, cardiovascular disease, depression, and autoimmune diseases.  Supplementing is often the best choice for achieving adequate vitamin D levels. Supplementing with at least 1000 IU or even 2000 IU – if you are deficient – you may want to get a blood test to confirm adequate levels.

Vitamin K2

There are two forms of vitamin K, K1 and K2. Vitamin K2 seems to be more important to supplement – vitamin K1 is abundant in leafy green vegetables; vitamin K2 is produced by microorganisms and is low in plant foods. Vitamin K2 supplementation has been shown to reduce the risk of fracture, reduce bone loss, and increase bone mineral density in women with osteoporosis.  In several studies, vitamin K2 intake was associated with reduced risk of heart disease or coronary artery calcification (an indicator of increased cardiovascular risk). The human body can synthesize some K2 from K1, and intestinal bacteria can produce some usable K2, but these are very small amounts. Therefore, it is likely important to supplement with K2.


Iodine is required by the body to make thyroid hormones. Most plant foods are low in iodine due to soil depletion. Kelp, a sea vegetable, is a good source of iodine, but is not commonly eaten on a regular basis and may actually provide excessive amounts of iodine. The chief source of iodine in the typical American diet is iodized salt. Since salt should be avoided for good health, it is important to supplement with iodine to maintain adequacy.


Zinc is essential for immune function, growth, and reproduction, and supports hundreds of chemical reactions. Zinc is abundant whole plant foods, but is not readily absorbed. Beans, whole grains, nuts, and seeds contain zinc, but also contain substances that inhibit zinc absorption. Zinc is especially important for men, because it is concentrated in the prostate and promotes death of cancer cells, possibly by suppressing the activity of inflammatory molecules. Long-term zinc supplementation is associated with reduced risk of advanced prostate cancer.


Calcium is a vital nutrient for bone health, muscle contraction, nerve transmission, blood clotting and much more. Calcium requirements vary by age. For adults it’s about 1000 mg.  Getting enough calcium should not be a problem for anyone eating a healthy diet, rich in leafy greens, beans, nuts, as well as calcium fortified foods.  Although dairy is usually considered the best source of this nutrient, there are many problems with this food group. Read more about calcium rich foods.


There are some variations for babies, toddlers, and seniors, but the daily recommendation for the U.S. and Canada is 8 milligrams for adult men; 18 milligrams for adult menstruating women, and 27 milligrams for pregnant women; 9 for lactating women (since they’re not menstruating); and 8 for postmenopausal women over 50. None of these groups should exceed 45 milligrams a day, as too much iron can cause an overload.

I get a significant amount of my iron from leafy greens such as parsley, kale and dandelion as well as through other sources in my diet throughout the day. I don’t rely solely on green smoothies for iron, however. Other iron-rich foods include iron-fortified cereals, beans, whole grains (oatmeal, quinoa), seeds (pumpkin) and dried fruits (apricots). 

Generally, iron supplements should be avoided (see below). The appropriate times to supplement with iron, are when there is a deficiency or an increased biological need, such as in pregnancy.

Multivitamins must be chosen wisely

Though supplements may be essential when there is a true deficiency or need, they can be unnecessary or even detrimental when we use them as a substitute for a healthful diet. While most people can certainly benefit from a multivitamin, it is important to choose the right one. Some common ingredients in multivitamins may be harmful in isolated supplement form.

The following ingredients should be avoided:

  • Vitamin A
  • Beta-carotene
  • Vitamin E
  • Selenium
  • Copper
  • Folic acid

The synthetic folic acid in supplements is not the same as natural folate, found in high concentrations in green vegetables. If you are drinking green smoothies and/or eating your leafy green vegetables, you should be getting enough of this nutrient. Taking supplemental folic acid may increase the risk of breast, prostate, and colorectal cancers.  Vitamin A and beta-carotene in supplement form have also been shown to increase the risk of cancers, possibly by interfering with the absorption of other carotenoids, and supplemental vitamin A, beta-carotene, or vitamin E are all associated with increased risk of death. These shocking scientific findings mean that most conventional multivitamins act as a double-edged sword, containing both helpful and harmful elements.

Excess iron may build up and become toxic. The most common culprits of iron and copper excess are red meat and multivitamins. The human body evolved to store excess iron and copper to fuel these reactions in case of extreme conditions like bleeding or famine. However, their accumulation over time may be detrimental because both metals are involved in generating oxidative stress, a byproduct of energy production, which contributes to chronic diseases — specifically cardiovascular disease and brain disorders like Alzheimer’s disease.





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