A Functional Medicine Guide To Supplements


I have a love-hate relationship with the internet. On one hand, it’s a fantastic way to get great information right at your fingertips (like this article!) On the other hand, it is full of conflicting information – especially about health, and even more specifically about vitamins and supplements. If the internet is your source for information about what supplements you should and should not take, it can get pretty confusing and many of my patients tell me they don’t know where to start. Part of the problem is that there are thousands of supplements on the market – probably hundreds of thousands, maybe even millions. You’ve got your basic types, multivitamins and multiminerals, omega fats, single vitamins like vitamin D, different antioxidants of all types, and a lot of other ones that you may not recognize at all.

As a functional medicine practitioner, I have my informed opinions about the wide range of well-intentioned supplements that I consider to be unnecessary. Oftentimes, any individual really only needs a small handful of targeted vitamins and supplements that will actually be beneficial. Let’s cut through the confusion to determine what supplements you should take, and how to incorporate them into your existing routine.

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Essential Supplements - What Supplements You Should Take

Vitamin D

No other vitamin can hold a candle to vitamin D when it comes to importance and influence on health. Since vitamin D is fat-soluble, it acts more like a hormone than a vitamin by regulating hundreds of uber-important pathways in your body. Besides your thyroid hormones, this vitamin is the only other thing every single cell of your body needs in order to function properly. Also known as the sunshine vitamin, vitamin D is synthesized by your body when your bare skin is exposed to sunlight. It is impossible to get enough vitamin D from food alone, and unless you live in a very sunny place (like near the equator) and are outside frequently without sunscreen, you are probably deficient. This is therefore one of the most important supplements you should take.

Dosage: If you have had your vitamin D tested by your doctor, you will find that the standard reference range for vitamin D levels falls between 50 and 60 ng/mL. In functional medicine, we aim for an optimal range between 60 and 80 ng/mL. Depending on where your starting levels are, you should be taking anywhere between 2,000 and 6,000 IU of vitamin D per day. Make sure to test your vitamin D levels to find out your starting point, and retest to gauge how your vitamin D level optimization is going. This is a common and easy test and your doctor will likely be fine with it if you ask.

How to incorporate: Since vitamin D is fat-soluble, take advantage of vitamin synergy by combining your supplement with other fat-soluble vitamins, such as A and K2. This will help make it more bioavailable and balanced. It’s also a great idea to take them with fatty foods like avocado, olive oil, wild-caught fish, and coconut to increase their bioavailability. If you put fats in your daily smoothie (and you should!), this is a good time to pop that vitamin D as well.


Magnesium is a crucial mineral needed for over 300 essential biochemical reactions in your body, including the regulation of neurotransmitters. Up to 80 percent of the population is deficient in this nutrient, and that deficiency can show up as problems with sleep, anxiety, migraines, and brain fog. Most deficiencies come from a poor diet or gut problems that interfere with magnesium absorption.

There are many different forms of magnesium, so let’s break down the best. Magnesium oxide is the most commonly found in supplement form, but it is not nearly as easily absorbed as other forms. Magnesium citrate is a good option, especially if you tend to get constipated. Magnesium glycinate is excellent for its calming effects, and magnesium threonate has shown promise for its neurological support. Magnesium oil is another great way to boost this vital nutrient. You rub it on your skin instead of ingesting it.

Dosage: 350 mg per day.

How to incorporate: Taking magnesium right before bed is often best as it promotes better sleep by relaxing muscles and helping boost levels of the calming neurotransmitter, GABA, in your brain.

For more information on magnesium as a supplement, read this article.


As Hippocrates said, “All disease begins in the gut.” Science is finally catching up, with research showing that the gut is the foundation for almost all aspects of your health – regardless of whether you are having digestive symptoms or not. Your gut microbiome contains trillions of bacteria, many of which are beneficial to human health, and some which can cause health problems. When the bad guys start to outnumber the good guys, it can affect everything from your weight to your hormones. While it is important to include probiotic-rich foods into your diet (give kefir, sauerkraut, kimchi, and kombucha a try). If you struggle with permeability in your gut, a probiotic supplement may be the best supplement to take.

Dosage: At least 10 billion CFU per day.

How to incorporate: Feed the probiotics you are trying to grow with prebiotic foods rich in fiber, especially garlic, asparagus, and onions. These foods help facilitate the growth of good gut bacteria. When choosing a probiotic, make sure to take on that includes strains of Lactobacillus and Bifidobacterium. These two specific strains have been shown (1) to reduce inflammation. I am also a fan of soil-based probiotics (SBO) to further support rich bacterial diversity.

Omega-3 fish oil

Your brain itself is comprised of about 60 percent fat, so depriving your body of fat can contribute to all kinds of unpleasant brain symptoms, from brain fog and fatigue to depression and anxiety. In other words, healthy fat is essential for optimal brain health. If you’re not getting enough healthy fats, specifically from wild-caught seafood, you might want to consider an omega-3 fish oil supplement. Omega fats can be found in plant sources such as flax, but it’s not easily used by our bodies because it must be converted into DHA or EPA, which is an inefficient process. Because of this, I suggest getting your omega fats from krill oil, or fish oil from salmon, cod liver, or sardines. This is a supplement you should take if fish isn’t a part of your regular diet.

Dosage: 2250 mg EPA / 750 mg DHA per day.

How to incorporate: If you’re eating more omega-6 fatty acids (like those found in many types of vegetable oils, you may be suffering from increased inflammation. Fish oil may noticeably reduce these inflammatory effects.


Think of this blue-green algae as your superfood of the sea. Spirulina is a great source of iron, phytonutrients, and iodine, all commonly lacking in the modern Western diet.

Dosage: 3 grams per day.

How to incorporate: Spirulina is most commonly available in powder form, which makes it perfect to just stir into your tea or add to your daily smoothie!


Inflammation is at the center of every chronic health problem today and turmeric is a spice that contains one of the most powerful natural anti-inflammatory tools we know of. Whether you use the spice itself, or its active component (curcumin) in supplement form, this is a supplement you should take if you are on the anti-inflammatory war path.

Dosage: For those looking for inflammation maintenance, 2 grams per day is a good start, but as much as 10 grams per day may be needed (2) to drive down higher levels of inflammation.

How to incorporate: Unless you know you have a problem with inflammation, don’t worry about using turmeric every single day. For most people, using turmeric in cooking a few times a week is enough to enjoy the benefits. Always add black pepper, which contains piperine, because it increases the bioavailability of curcumin by 2,000 percent. If you are struggling with chronic inflammation, take a turmeric supplement every day, and find a supplement that also includes piperine.

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Vitamin C

This immune-boosting, common-cold-busting vitamin can reduce (3) symptoms of the cold by up to 30 percent. Most people get enough from food (65 to 90 mg per day), since a lot of foods contain it. Don’t worry about this supplement unless you feel the sniffles coming on.

Dosage: 1,000 to 4,000 mg per day to boost your immune system and promote healthy skin.

How to incorporate: Combining with zinc can increase vitamin C’s immune-boosting properties. Look for powdered supplements that you can mix with water to take with you for when you start to feel a little less than 100 percent.


Your body has no way to store this important mineral, so it is important to make sure you’re getting this through your diet or supplementation. Zinc’s main role is to help your body increase white blood cells and fight off infection, and it also assists with the release of antibodies. Deficiency has been linked (4) to increased instances of sickness, so it is no wonder you often find zinc as a common ingredient in the cold and flu aisle of your pharmacy. As I mentioned above, supplements that combine the power of vitamin C and zinc are the best supplements to take.

Dosage: 15 to 30 mg per day. Pregnant women should aim for 12 mg per day since it’s essential (5) for normal fetal development.

How to incorporate: If you’re eating a healthy well-rounded diet, you should be getting in the proper amount of zinc per day without needing a supplement. But if getting over a cold quickly is your goal, supplementing at least 75 mg per day can reduce (6) cold duration and symptoms so you can get back to your life.

Methylated B complex

B vitamins are the fuel behind methylation, a biochemical process that happens more than 1 billion times every single second inside your body. It helps keep you alive and healthy by assisting your body’s ability to properly detox. There are so many different types of B vitamins, so it’s important to get a well-rounded amount of each.

Dosage: 400 to 800 mcg methylfolate (B9), 1,000 mcg methylcobalamin (B12) per day.

How to incorporate: The best B-vitamin supplement would be a B-complex vitamin containing methylated B vitamins, especially if you have methylation impairments like the MTHFR gene mutation. Look for activated B vitamins like B9 L-Methylfolate (L-5-MTHF), B6 Pyridoxyl-5-Phosphate (P5P), and B12 versions (such as Adenosyl B12, Cyano B12, Hydroxycobalamin B12, or Methyl 12).

Vitamin A

Vitamin A is essential for a strong immune system and vitamin A deficiency has been linked (7) to autoimmune diseases, which are on the rise in a major way. Some researchers believe this has to do with our dendritic cells; our alarm cells of the immune system that can send out a “red alert” to stimulate immunity, or a “calm down” message that tones down excessive immune reactions that can damage the body. The “calm down” message makes use of vitamin A.

Plant beta-carotenes, a precursor to vitamin A, are found in sweet potatoes and carrots but the conversion rate to the usable retinol is very weak. In fact, research suggests (8) that just 3 percent of beta-carotene gets converted in a healthy adult. Because of this, look for vitamin A sources from either whole-food sources like fish liver oil or retinyl palmitate.

Dosage: 2,000 to 10,000 IU per day.

Vitamin K2

Vitamin K2 is one of the most common nutrient deficiencies in the Western diet, but it is essential for controlling inflammation. One study (9) in the Journal of Neuroimmunology found that vitamin K2 was effective at inhibiting the pro-inflammatory iNOS in the spinal cord and the brain immune system in rats that had multiple sclerosis symptoms. There are several types of K2, but I suggest looking for the MK-4 version. MK-4 regulates gene expression in specific ways that no other form of vitamin K does. MK-4 plays an exclusive role in cancer protection and sexual health.

Dosage: 100 to 200 mcg per day.

How to incorporate: Taking these fat-soluble vitamins together with vitamin D will help keep your levels from going too high as well as making vitamin D more bioavailable to your body! Take them with a fat-containing meal such as avocado, salmon, or just a bit of butter or coconut oil added to whatever you’re cooking.


This protein helps form our connective tissue, including tendons, skin, cartilage, bones, blood vessels, ligaments, and more. It also helps regulate metabolism and our body’s own collagen production. Made up of three amino acids (glycine, proline, and hyroxyproline), each produced in our body but not at sufficient levels, most people can benefit from a collagen supplement. For example, we require around 15 grams of glycine per day, but most of us only get 3 grams per day from our modern diet.

Dosage: 8 grams per day.

How to incorporate: Powdered collagen peptides are fantastic because these are easy to add to smoothies or any other liquid, making them one of the best supplements to take. Look for brands that derive their collagen from grass-fed and pasture-raised protein sources or use marine collagen, for the purest, toxin-free form.

Everything You Need To Know About IV Supplementation

In the United States,  almost 95 percent  (14) of the population is not getting enough vitamin D, making this deficiency number one in the country. It is a high number and is more astounding when you learn that vitamin D is the only single vitamin that is needed by every cell in your body to function properly. Vitamins like magnesium, vitamin A, and vitamin E are also hard to get an adequate amount of through just food. At my functional medicine clinic, I see that being deficient in these vitamins and minerals has an effect on major systems in the body like detoxification processes, immune health, and hormone production.

When most people are woefully deficient in what their body needs, it isn’t enough to just eat well, making intravenous drips appear to be an answer to prayer! IV supplements are rapidly becoming an answer for our fast-paced culture of individuals looking for the most efficient fix. As simple as ordering your go-to take-out meal, you can now order customized IV drips delivered to your doorstep or workplace with an included nurse. What once started as a hangover cure has grown in popularity as celebrities and the rest of the wellness world catches on.

IV drips are typically a much higher dose than in supplements or food alone. They can be customized to your body’s needs, and take only about 20 to 30 minutes to administer. A single IV drip starts at around $100 for one nutrient, and the price continues to rise with each nutrient added.  Even if you can afford the higher cost, as with anything, there are arguments for and against using this type of supplementation. Before you fill your cart with your first IV drip order, let’s look at how this option stacks up for your health:

The Pros Of IV Supplements:

  1. They are the most bioavailable type of supplement

Absorption of supplements and food happen in the gut through a properly functioning digestive system which releases them into the bloodstream. If you have leaky gut syndrome or other gut problems, an IV drip can be more efficient at this process as these nutrients are absorbed into the bloodstream directly, bypassing the gut. This makes the IV a good choice for some with gut problems, or in certain situations in which a rapid dose of nutrients is needed.

  1. They are completely customizable

Convenient and customized, you can blend your IV drip specifically to your body’s needs.  Administering all of your supplements in one dose is another convenience that many appreciate.

  1. They can help keep you hydrated

Since the nutrients in an IV drip are contained in a liquid salt solution, you’ll not only get the vitamins you need, you’ll also be instantly hydrated and will boost your electrolyte levels.

  1. They can offer a quick boost

IV supplements are a targeted answer to many short term health issues. If you have an important event in your future but wake up feeling less than great; you can just add a higher dose of a supplement like vitamin C to ward off your wellness woe, just like at your favorite smoothie spot!

  1. They can slow the aging process

Popular among youth seeking celebrities, adding glutathione to an IV drip can keep skin looking radiant and young. Glutathione acts as an antioxidant in the body to fight off free radicals that add to wrinkles and other signs of aging. Due to greater bioavailability, the effects of glutathione are more powerful when added to a drip than taken orally.

The downside of IV supplements:

  1. They can be dangerous

While all of the nutrients contained in a drip are healthy, they can become detrimental if given at a higher than necessary dosage. Each individual has their own unique biochemistry. Even with the same diagnosis as another person, your body’s nutritional needs and treatment plan are specific to you. IV supplements can quickly become dangerous if you don’t know exactly what you need. Be sure to partner with your doctor and run labs before opting for an IV drip to know exactly what your nutrient deficiencies are, and what your ideal dose should be.

  1. They are not a long-term solution

IV supplements are great in a pinch, but if your lifestyle and eating habits are poor they are not a long term solution. Things like gut dysfunctions, for example, can make it difficult to fully absorb nutrients from food even if you are eating whole, nutrient-dense food. If you fix the systemic function issues within the body, you will increase your likelihood of absorbing nutrients from whole and healthy foods which can make an IV drip simply unnecessary.

  1. They are not all created equal

To protect your health and avoid any dubious additives, make sure that your IV comes from a reputable distributor. Check for potency of ingredients, and be sure that the contents of the drip are made in an FDA-approved facility.

  1. They can cause immediate reactions

Inflammation, bruising, and infection are all immediate risks involved with IVs of any kind. If you are sensitive as a rule, or you get a drip from a less-than-reputable facility, you are putting yourself for a higher risk for these reactions.

  1. They may not actually help at all

Interestingly enough, the noticeable improvement in health many feel after an IV drip may not be due to the IV at all. Simply put, you’ll feel better because you believed that you would. This is attributed to the placebo effect. One study (15) looked at this by giving half a group of fibromyalgia patients a solution with vitamins and half without. The study found that both groups showed improvement.

Our final verdict? While a fantastic option for those needing an immediate boost, or with a medical condition requiring immediate nutrients- the pros seem to be outweighed by the cons. IV drips shouldn’t be ruled out completely, but they will never outperform long term, sustainable steps to health like whole, nutrient dense food and lifestyle changes.

As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people around the globe. 

Photo: unsplsh.com

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Dr. Will Cole, DNM, IFMCP, DC is a leading functional medicine expert who consults people around the globe, starting one of the first functional medicine telehealth centers in the world. Named one of the top 50 functional and integrative doctors in the nation, Dr. Will Cole provides a functional medicine approach for thyroid issues, autoimmune conditions, hormonal imbalances, digestive disorders, and brain problems. He is the host of the popular The Art Of Being Well podcast and the New York Times bestselling author of Intuitive Fasting, Ketotarian, The Inflammation Spectrum and the brand new book Gut Feelings: Healing the Shame-Fueled Relationship Between What You Eat and How You Feel.

Gut Feelings Dr. Will Cole 6

Gut Feelings

Healing The Shame-Fueled Relationship
Between What You Eat And How You Feel