Goal: Correct Supplementation is just as important as supplementing at all. This article addresses common deficiencies and why you should supplement there.


Supplement Wisely

In a perfect world, none of us would ever need to take supplements. We’d be able to meet all of our nutritional needs through food, our sleep would be deep and restful, we’d get plenty of exercise, we’d live in a pristine environment without chemicals and toxins, we’d have minimal amounts of stress, we’d live in a tight-knit community with close, meaningful relationships and we’d have plenty of time for leisure and fun. We would have been born naturally to a mother that was equally healthy, been breastfed exclusively for 2 years, ate a “real food” diet throughout our entire childhood and never taken antibiotics.

Raise your hand if this describes your life. If you’ve got your hand in the air, you can probably stop reading this and skip to Step 9.

But if you’re like the rest of us, this doesn’t describe your life. You don’t sleep as much as you’d like. You’re stressed out. You work at a desk and even though you go to the gym a few times a week, you know sitting all day isn’t healthy. You live in the city and you’re exposed to chemicals and toxins every day. Your mom had autoimmune disease and it looks like she passed those genes down to you. Or maybe you were born via c-section and/or not breastfed, or you took antibiotics for acne as a teenager, and now your gut is screwed up. Unfortunately, this is not unusual. It’s the rule, rather than the exception.

A clean diet is the best possible starting place, but it’s not always enough to solve chronic health problems. This is where supplementation can be extremely valuable.

There are two kinds of supplementation: maintenance and therapeutic. Maintenance supplementation involves supplementing with basic micronutrients that may be difficult to obtain enough of even in the context of a healthy diet. Examples might include vitamin D, vitamin A, EPA and DHA, protein powder, and probiotics.

Therapeutic supplementation is designed to accomplish a specific goal, such as treating a particular health condition or addressing a specific symptom, like insomnia.

Therapeutic supplementation is beyond the scope of this eBook because it largely depends upon your individual circumstances: your health status and the problems you’re trying to address.

Instead, let’s discuss maintenance supplementation because although the maintenance supplements that are appropriate for you will also vary based on your circumstances, there are some common guidelines I can share that will help you to choose.

Which nutrients should you consider supplementing with?

Vitamin A (retinol)

Vitamin A is important catalyst for a variety of biochemical processes in the body. It’s required for assimilation of protein, minerals and water-soluble vitamins, and it also acts as antioxidant, protecting the body against free-radical damage and diseases like cancer. Vitamin A plays a crucial role in reproduction, promoting full-term pregnancy and the proper development of the face (eyes, nose, dental arches & lips).

The RDA for vitamin A (2,600 IU) is woefully inadequate, and even then, over 25% of Americans consume less than half of the recommended amount. Native populations such as the traditional Inuit—which were free of modern, degenerative disease—got much more vitamin A than the average American. The Greenland Inuit of 1953, prior to much contact with the Western world, got about 35,000 IU of vitamin A per day.

Vitamin A (retinol) is only found in significant amounts in organ meats, which explains why many Americans don’t get enough. If you follow my recommendations in Step 2: Nourish Your Body, and you do eat organ meats (especially liver), you’re probably getting enough vitamin A and thus don’t need to supplement. However, if you’re like most Americans and you’ve never eaten liver in your life (and don’t plan to start), you may benefit from supplementing with A.

There’s been a lot of discussion in the media about the toxicity of vitamin A. Some researchers and doctors now recommend avoiding cod liver oil because of this concern. Even Dr. Mercola has jumped on the “vitamin A is toxic” bandwagon. But is this true?

It is true that vitamin A is potentially toxic. Some evidence suggests that excess vitamin A increases the risk of osteoporosis. For example, one study showed both low and high serum vitamin A carried double the risk of fractures as did optimal levels.

But if we dig deeper we find that excess vitamin A only causes problems against a backdrop of vitamin D deficiency. In his excellent article Vitamin A on Trial: Does Vitamin A Cause Osteoporosis?, researcher Chris Masterjohn summarizes evidence demonstrating that vitamin D decreases the toxicity of and increases the dietary requirement for vitamin A. Studies show that supplementing with vitamin D radically increases the toxicity threshold of vitamin A. In a hypothetical 160 lb. person, vitamin D supplementation increases the toxicity threshold of vitamin A to more than 200,000 IU/ d. You’d have to eat 22 ounces of beef liver or take 5 TBS of high vitamin CLO each day to get this amount. Not likely!

To meet vitamin A needs (assuming you’re not up for eating organ meats), I recommend taking high vitamin cod liver oil (CLO) to provide a dose of 10-15,000 IU per day. Cod liver oil is really more of a food than a supplement, but since it’s not a normal part of people’s diet we’ll consider it as a supplement. CLO is an ideal vitamin A source because it also contains vitamin D, which as we just learned, protects against the toxicity of A.

But not all cod liver oil is created alike. It’s important to choose a brand that contains the naturally occurring vitamins, rather than synthetic vitamins added after the fact. How the cod liver oil is processed is also important; it contains fragile fatty acids that are susceptible to damage by heat, so it’s best to choose a brand that uses fermentation or another cold-processing method. I’ll tell you which specific product I recommend to my patients at the end of this section.

Vitamin D

Much has been written about the need for and benefits of vitamin D supplementation over the past several years—and with good reason. It’s critical for health and up to 50% of Americans are deficient.

We can get vitamin D from two sources: food and sunshine. Seafood is the only significant source of vitamin D, but you’d still have to eat a lot of it to get enough. 8-9 ounces of herring provides about 2,000 IU of vitamin D, which is the minimum daily requirement for most people to maintain adequate blood levels.

Sunlight converts a precursor called 7-dehydro-cholesterol in our skin to vitamin D3. This D3, along with the D3 we get from food, gets converted by the liver into 25- hyrdroxy-vitamin D (25D), which is what typically gets measured when you have a vitamin D test. The optimal 25D level is somewhere between 30 and 50 ng/mL. Contrary to what some researchers and doctors have recommended, there’s no evidence that raising blood levels of 25D above 50 ng/mL is beneficial, and there’s some evidence that it may cause harm. Studies show that bone mineral density peaks at 45 ng/mL and then falls again as 25D levels rise above 45. Other studies have shown that the risk of kidney stones and CVD increase with high 25D levels due to the elevated serum calcium levels that accompany excess vitamin D.

However, we also know that vitamin A and vitamin K2 protect against vitamin D toxicity, and vice versa. As I explained in the vitamin A section, fat soluble vitamins exist in a synergistic relationship. It’s possible that the people in the studies above that experienced problems with excess 25D levels were deficient in vitamin A or K2, or both. This is why it’s so important to supplement with all of the fat-soluble vitamins together.

What about sunlight? Well, in summer mid-day sun with pale skin, 30 minutes of direct sunlight will produce 10–20,000 IU of vitamin D. But this is a best-case scenario. With darker skin, or different times of year, or buildings that block the sunlight, or increased time spent indoors, we won’t be producing that much. It’s also true that aging, overweight, and inflammation reduce our conversion of sunlight to vitamin D. This is why sunlight alone isn’t normally a sufficient source of vitamin D.

With this in mind, most people should supplement with Vitamin D. The amount needed to maintain blood levels of 30-50 ng/mL varies depending on some of the factors I’ve listed above, but in my clinical experience it’s usually somewhere between 2,000–5,000 IU in the winter and anywhere from no supplementation to 2,000 IU in the summer. However, this will vary depending on your skin tone and where you live. That’s why it’s important to test your 25D levels first, then begin supplementation, and then re-test a few months later to determine the correct maintenance dose.

As with vitamin A, the best source of vitamin D is high-vitamin cod liver oil. It contains not only vitamins A & D, but also natural vitamin E and other quinones.


There are few compounds in the body more important to overall health than magnesium. Over 300 enzymes need it, including every enzyme associated with ATP, and enzymes required to synthesize DNA, RNA, and proteins. Magnesium also plays an important role in bone and cell membranes, as it helps to transport ions across the membrane surface.

Studies show that most Americans don’t get enough. The median intake across all racial groups is far below the RDA, which is 420 mg/d for men and 320-400 mg/d for women. Although half of Americans take a multivitamin daily, most don’t contain enough magnesium to make up for the shortfall.

Magnesium is also difficult to obtain from food. Nuts and seeds are the highest source, but they also contain phytic acid, which inhibits magnesium absorption. (This can be addressed, at least to some degree, by soaking the nuts and seeds for 18 hours, and then roasting or dehydrating them prior to consumption). Another issue is that magnesium levels in food have dropped as modern soils have become increasingly depleted. What this means is that if you’re not supplementing with magnesium, you’re probably not getting enough.

And magnesium deficiency is no small thing. It has serious—even fatal—consequences. It produces symptoms like muscle cramps, heart arrhythmias, tremor, headaches, and acid reflux, and it’s associated with CVD, hypertension, metabolic syndrome, diabetes, migraines, PMS, asthma, and hypothyroidism. In fact, it’s hard to find a modern disease that magnesium deficiency isn’t associated with.

Because of this, I think most people would benefit by supplementing with magnesium. Intake of 500–600 mg/d from a combination of food and supplements is an optimal range to shoot for. Since most people get less than 250 mg/d from food, a dose of 250– 350 mg/d in supplement form is ideal. I recommend using chelated forms of magnesium like glycinate and malate because they’re better absorbed and tend to have fewer side effects.


EPA and DHA are omega-3 fats found primarily in cold-water fish like salmon, mackerel, herring, sardines, anchovies, and halibut.

EPA and DHA play an important role in fetal development, cardiovascular and immune health, weight management, cognitive function, and much more. Low intake of these important nutrients has been associated with a wide range of health problems, including:

  • Depression and bipolar disorder.
  • Heart disease.
  • High blood pressure.
  • High cholesterol.
  • Autoimmune diseases like rheumatoid arthritis and lupus.
  • Behavioral disorders like ADHD and autism spectrum disorder.
  • Infections like chronic hepatitis.
  • Cognitive disorders like Alzheimer’s and Parkinson’s.

It’s possible to meet EPA and DHA needs by eating about 12–16 ounces a week of coldwater, fatty fish (such as those I listed above).

However, if you’re not eating this much of these types of fish, it’s a good idea to supplement so that you obtain approximately 500–1,000 mg/d of EPA and DHA combined.

Again, I think cod liver oil is a good choice, because it not only contains EPA and DHA, it also contains fat soluble vitamins like vitamin A and D.


Probiotics (“pro” = for, “biotic” = life) are live microorganisms that are beneficial to humans. Studies suggest that consuming probiotic organisms have a wide range of positive effects, including reducing inflammation, treating diarrhea and constipation, improving the immune system, minimizing or reversing lactose intolerance, and even reducing anxiety and improving cognitive function.

For some people, consuming fermented foods (which are rich in probiotic bacteria) on a daily basis will be enough to restore and maintain healthy gut flora. However, for those that have significantly compromised gut microbiota due to a history of antibiotic use, poor diet, intestinal infections, or conditions like IBS or inflammatory bowel disease, supplementing with additional probiotics may be necessary.

There are many choices when it comes to probiotics. However, the best probiotics will meet these seven criteria:

  • It should survive the passage through the stomach and thrive in the large intestine.
  • It should contain a broad spectrum of microorganisms.
  • It should be effective for both constipation and loose stools or diarrhea.
  • It should be safe to take when conditions like small intestinal bacterial overgrowth (SIBO) are present.
  • It should be shelf-stable (i.e. doesn’t require refrigeration, maintains potency over time).
  • It should be backed by peer-reviewed, published clinical studies.
  • It should be gluten- and dairy-free.

Many commercially available probiotics do not meet all of these criteria. For example, only a small percentage of Lactobacillus and Bifidobacterium strains (which are among the most commonly used probiotics) are viable in the presence of stomach acid and bile, and thus have a chance of making it to the large intestine where they belong. Many probiotics require refrigeration, which makes traveling with them difficult, or lose potency quickly. Other products are effective for diarrhea, but can make constipation worse. And many probiotics that are sold in stores or online have little research behind them. This probably explains why studies have found that most probiotics do not cause substantive changes in the quantity or number of species of gut bacteria.

In general, I favor probiotics that contain soil-based organisms (SBOs). These are particular species of microflora found in the soil that humans have been exposed to throughout the vast majority of our evolutionary history. Unfortunately, changes in the soil after the industrialization of agriculture and differences in food handling have decreased our exposure to these important symbiotic organisms. SBOs are typically strains found in the human gut (such as Bacillus species), they survive the passage through the gastrointestinal tract and are adapted for colonization of the gut (because they are normal residents), and they exist in lower concentrations than Lactobacilli and Bifidobacterium (and are thus easier to influence via supplementation). Soil-based organisms have been shown to be effective for IBS, diarrhea, constipation, and other digestive conditions in randomized, placebo-controlled trials—including one trial that lasted for a year, which is an exceptionally long period for a probiotic study.

Another reason I prefer soil-based organisms is that they are safer and more effective for patients with small intestinal bacterial overgrowth (SIBO)—a condition which many people with gut issues have. SIBO often involves an overgrowth of bacteria that produce D-lactic acid, such as Lactobacillus acidophilus. If you have SIBO and you take a probiotic with L. acidophilus in it (which the majority of commercial probiotics do contain), it could worsen your condition. Many of my patients with gut issues are surprised when they have adverse reactions to probiotics, since they are so universally regarded as helpful. This is often the explanation for their reaction.

Finally, I’ve found that soil-based organisms tend to work well for people with both constipation and diarrhea, whereas many typical commercial probiotics can make constipation worse.

The best approach with probiotics is to take a “broad spectrum” blend that contains species from all four of the phyla found in the human digestive tract, including Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria. As a result of the Human Microbiome Project, we now know that the gut contains thousands—rather than hundreds—of microbial species. This underlines the importance of a multi-strain product that contains many different genera of bacteria that are capable of colonizing the human gut.


Most people in the US get enough protein without supplementing. However, there are certain groups of people that may benefit from supplementing with additional protein. High protein intakes can be effective for:

  • Improving performance and recovery for athletes.
  • Weight loss.
  • Stabilizing blood sugar.
  • Helping with tissue regeneration in people with injuries or chronic illness.
  • Improving stress tolerance and “adrenal fatigue.”

Sometimes simply increasing your intake of animal products like meat, fish, eggs, and dairy is enough to meet your protein needs. However, in some cases this isn’t a viable option. For example, you might have trouble digesting too much meat, or maybe you simply don’t want to eat animal products three times a day.

Unfortunately, plants are much lower in protein, and the protein they do contain is much less bioavailable than animal protein. This means that plant protein sources like hemp and pea are not a great choice.

Whey protein powder is one of the most popular ways to supplement with protein, and can be a great option. Unfortunately, whey tends to cause bloating and discomfort in a significant number of people—especially those with dairy sensitivity.

The protein powder I recommend to patients, and the one I use myself, is made from hydrolyzed hormone- and antibiotic-free beef. When a protein is hydrolyzed it means it is partially “digested” or broken down, which increases its bioavailability and absorption. In fact, the particular product I use is even more bioavailable than whey protein.

I like the beef powder because it is well-tolerated by most people and can be safely used by those with dairy sensitivities (unlike whey). And in case you’re wondering, it doesn’t taste like beef! It has a pleasant sweet flavor that mixes well with almond milk or fresh vegetable juice.

Those are the basic maintenance supplements that I think are worth considering. As you may have gathered, there are several important considerations when choosing the right product in each case. I’ve provided the criteria above if you’d like to source them yourself. But I know that many of you are busy and don’t have time to do that kind of research.

The good news is I’ve already done this legwork, and I continue to review new options as they become available. If you’d rather just use the same products that I use myself and prescribe to my patients, you can purchase them from my online store using the links below:

Action Summary

  • Consider supplementing with vitamin A, vitamin D, magnesium, EPA and DHA, probiotics, and cod liver oil—depending on your diet, circumstances and goals.
Follow me

Chris Kresser L.Ac

Founder at ChrisKresser.com
Chris Kresser, M.S., L.Ac is a globally recognized leader in the fields of ancestral health, Paleo nutrition, and functional and integrative medicine. He is the creator of ChrisKresser.com, one of the top 25 natural health sites in the world, and the author of the New York Times best seller, Your Personal Paleo Code (published in paperback in December 2014 as The Paleo Cure).
Chris Kresser L.Ac
Follow me

Latest posts by Chris Kresser L.Ac (see all)



Comments are closed.

©2022 Life.Institute a place to grow


We're not around right now. But you can send us an email and we'll get back to you, asap.

85% of Americans Malnourished
Do you want to receive the free e-book?
Never display this again

Log in with your credentials

Forgot your details?