Stolen Minerals: The Story of Anti-Nutrients

I’m a big fan of healthy eating. I believe it is some of the best medicine available, and without it, no other treatments will work very well.

I love to keep it simple when I talk to people about how to eat well, and I love Michael Pollan’s recommendation to “Eat food, not too much, mostly plants.” : ) For people who are just starting out on the journey of learning how to care for their body with a wholesome diet, this advice is overly simplistic, but it covers some important points.

So, my goal with bringing up the concept of anti-nutrients is not to make you feel like you’re doing it all wrong, or to make your life more complicated. It’s an important topic, especially for folks with mineral deficiencies, and there are some fairly simple things you can do to help your body extract more minerals out of that healthy food you are so lovingly feeding yourself and your family.  

First of all, what are anti-nutrients?

Anti-nutrients are compounds found in plant foods that prevent animals from extracting nutrition from them. These compounds likely evolved as a defensive system developed by plants (who can’t fight or run away) to help prevent them from being eaten in the first place, or to help their seeds survive intact as they pass through animals’ digestive systems.

There are a number of anti-nutrients including oxalic acid, tannins, enzyme inhibitors and phytic acid. This article will focus on phytic acid for simplicity’s sake, and because it’s a particularly big issue in the American diet.

Definitions and language:

This is a technical distinction, but phytic acid, once it’s bound to minerals is called phytate. To avoid confusion, I’ll be using the term phytic acid throughout this article. Phytase is an enzyme that is prepackaged in seeds, nuts and grains that, once activated, breaks down phytic acid. Grains and nuts are both technically a type of seed, so I’ll mostly be using the word seed as a general term for all three of these foods.

Phytic acid and why it’s a problem

Phytic acid is found in large quantities in nuts, seeds and grains, especially in the bran or outer hull. It’s a snowflake-shaped molecule with an important job. It is a storage molecule that holds onto phosphorus in the middle of the snowflake and keeps it stable until the seed sprouts and needs the phosphorus to grow into a new plant. It holds onto that phosphorus so tightly, that when seeds are eaten by animals, they remain intact, and the phosphorus inaccessible all the way through the digestive tract.

Here is the issue. Unless dealt with appropriately, phytic acid not only doesn’t let us extract phosphorus from our food (which we need for cell growth and repair, and bone health), but the arms of the 'snowflake' actually bind to other minerals such as iron, zinc, magnesium and calcium, and make them much more difficult to absorb, thus taking a healthy diet and depleting it of minerals.

To be clear, phytic acid doesn’t target your ability to absorb protein, fat or fiber (the macronutrients) or vitamins from your food, just the minerals. However, phytic acid also inhibits the activity of our digestive enzymes, so on top of making our food less nutritious, it makes our digestion less efficient.

To give you an idea of the scale of the issue, in a meal free of phytic acid, you will absorb approximately 20% more zinc (1) and 60% more magnesium from your food. (2)

It's actually a bit ironic, because we’ve been told for years that whole grains are healthier than white bread/grains. But unless those whole grains are prepared properly, there’s not much nutritional difference between white bread and whole wheat bread because the phytic acid makes the minerals in whole grains much less accessible.

Who needs to worry about this?

This is a particularly big deal for people struggling with issues of calcium metabolism such as osteopenia, osteoporosis and frequent cavities (Though there is actutally a lot more going on with these conditions than calcium deficiency). But we all need magnesium for nervous system and heart health, and small amounts of trace minerals including iron, cobalt, chromium, copper, iodine, manganese, selenium, zinc and molybdenum for countless other daily tasks our bodies must perform for us to thrive. Deficiencies in any of these minerals can cause all sorts of symptoms.

I won’t get into all the problems that can be caused by deficiencies in each of these minerals, but as an example, deficient magnesium can result in headaches, muscle cramps, high blood pressure, and irregular heart beats.

I think you get the point that paying attention to phytic acid is important.

As an interesting note, there is some research linking dietary phytic acid to decreased risk of colon cancer. This may be because it can actually bind to or chelate excess iron and harmful metals and remove them from the body, in essences aiding in detoxification. It may also act as an antioxidant.

So this tells us that perhaps we don’t need to panic that we all get some phytic acid in our diet, we just need to be conscious of its presence and make sure we’re not getting too much. 

So, what can you do about it?

Solutions fall into two categories:

1.     Preparing food in a way that breaks down phytic acid.

2.     Optimizing digestion and food choices to help prevent mineral depletion.

How much is too much phytic acid?

It is neither practical, nor likely necessary to remove all phytic acid from your diet. So let’s get practical. According to Ramiel Nagel in his article “Living With Phytic Acid”, the average phytic acid intake in the U.S. and the U.K. rages from 631 to 746 mg per day; the average in Finland is 370 mg; the average in Italy is 219 mg; and in Sweden it is 180 mg per day. (11)

In the context of a balanced diet taking into account my other suggestions listed below for optimizing mineral absorption, most people should do ok with 400-600 mg of phytic acid daily. For anyone who struggles with bone loss, tooth decay or other mineral deficiencies, I would recommend a total of 150-400mg per day as a healthy guideline. (11)

This means preparing your foods to decrease phytic acid content, and sticking to 2-3 servings of phytic acid containing foods per day. For example, a small handful of nuts, two slices of true sourdough bread, and one serving of properly prepared oatmeal.

Problems arise when whole grains, nuts or beans are eaten with every meal and make up the main sources of calories. Regular consumption of granola or commercial cereals for breakfast is also problematic.

Check out this table for an idea of phytic acid content of various foods without special preparation.

Reference (5)

 

Preparation Techniques

Our ancestors figured out through trial and error how to deal with phytic acid through food preparation. Some helpful techniques that decrease phytic acid are soaking, sprouting and fermenting grains, nuts and seeds. Fermenting is the most affective and soaking the least affective, with sprouting somewhere in between. Basically the goal is to recreate the conditions under which the plant would naturally sprout (warmth, acidity and moisture), because under these conditions, the seed produces an enzyme called phytase, which breaks down the phytate, releasing the phosphorus within.

Soaking

Soaking can begin the process of waking up the phytase enzyme and other enzymes stored in the seed to break down the phytic acid as well as complex sugars that might cause gas. It still leaves lots of phytic acid intact, however.

Sprouting

Sprouting not only activates the phytase enzyme which begins to break down phytic acid, but the process of germination also produces vitamin C and increases the B vitamin content and carotene content. Complex sugars (which would otherwise cause intestinal gas) begin to be broken down, and naturally occurring enzymes found in the seed, bean or grain are activated which work synergistically with our own digestive enzymes to improve our digestion.

Fermentation

Fermenting nuts, seeds and grains has the most dramatic effect on increasing their nutritional value and decreasing phytic acid content. The proliferation of lactobacilli bacteria in fermented foods significantly increases digestibility and increases vitamin levels. These probiotic bacteria produce copious enzymes that improve our digestion as well as substances that encourage growth of healthy bacteria, and discourage growth of unhealthy bacteria in the digestive tract.

Preparing foods for maximal removal of phytic acid can be a bit of a rabbit hole. Scroll to the bottom of this article for some basic preparation techniques for common foods, but if you want to investigate further, the Weston A. Price foundation and the cookbook Nourishing Traditions by Sally Fallon are good places to start. Look here for a more in depth exploration of this topic.

Optimizing digestion and food choices

1. Optimize stomach acid

Apple cider before meals – Drink 1 tsp of apple cider vinegar in a little water before meals to help optimize your stomach acid. Stomach acid is vital for absorbing minerals.

2. Have one paleo meal per day

For example, have a breakfast of eggs or sausage and a plate of vegetables. No toast, no grains at all, and no nuts, seeds or legumes. Alternatively, you could have meat and veggies for dinner. I don’t believe that most people need to follow a strict paleo diet, but one meal per day gives your body an anti-nutrient free meal, allowing for better mineral absorption.

3. Take your vitamin D or get enough sun

Sufficient vitamin D is associated with stronger bones regardless of diet. Obviously a healthy diet is crucial too : ) Aim for 2000 IU of vitamin D daily, bumping your dose up to 4,000 IU daily during the winter.

4. Get enough absorbable calcium

Getting good forms of calcium in your food helps prevent bone loss from phytic acid. This might explain why cultures that traditionally eat bread, often eat it with cheese. The calcium in the dairy helps offset the calcium losses from the bread.

Great sources of calcium include raw cheeses and milk, yogurt, bone broth, and dark leafy greens. If you need to take a supplement, consider a food based calcium like this one or this one.

5. Eat vitamin C -rich foods with your grains, nuts and seeds

Vitamin C helps keep the iron in your food absorbable, so it doesn’t get stolen by phytic acid.

Good sources of vitamin C include bell peppers, dark leafy greens, strawberries and citrus. Vitamin C gets rapidly destroyed when cooked, so this is a good reason to eat some of your veggies raw.

6. Eat foods rich in vitamin A and beta carotene

These compounds can also help keep iron soluble and prevent phytic acid from binding to it. (8)

Foods rich in vitamin A include organ meats, grass fed butter, cod liver oil, milk and eggs. Foods rich in beta carotene are orange and green vegetables such as carrots, sweet potatoes, squash, kale, collards, broccoli and chard. 

7. Eat plenty of probiotic rich foods, and make sure your digestion is healthy.

The extent to which phytic acid inhibits mineral absorption varies somewhat from person to person, with some people severely affected, and others seemingly immune. This likely has to do with each person's specific gut flora, as certain probiotic bacteria can break down phytic acid. Making probiotic rich foods like sauerkraut, kimchi, yogurt, kombucha and other fermented foods a regular part of your diet can help cultivate a healthy gut. 

8. Ask for help

If you’re struggling with compromised bone health or frequent cavities and need further support, schedule a complimentary 15-minute consultation to discover how I can help.

 

Specific Food Prep Tips for removing phytic acid

Brown Rice

Soak brown rice in filtered water for 24 hours at room temperature without changing the water. Reserve 10% of the soaking liquid (should keep for a long time in the fridge). Discard the rest of the soaking liquid; cook the rice in fresh water.

The next time you make brown rice, use the same procedure as above, but add the soaking liquid you reserved from the last batch to the rest of the soaking water.

Repeat the cycle. The process will gradually improve until 96% or more of the phytic acid is degraded at 24 hours. (

Quinoa

Process                                                                                   Phytate Reduction

Cook for 25 minutes at 212 degrees F                                           15-20 %

Soak for 12-14 ours at 68 degrees F, then cook                              60-77%

Sprouted quinoa is available as well. 

Oats and Corn

Some grains such as oats and corn are high in phytic acid, but naturally low in phytase, the enzyme that breaks down phytic acid under the right conditions. So even when soaked or sprouted, their phytic acid levels do not reduce much.

One option is to add a tablespoon or two of freshly ground rye flour (keep whole rye kernels around and grind some in a coffee grinder as needed) to your oats or cornmeal, then soak overnight (12 hrs) in an acidic medium. Soak your grain in 2 cups of warm water plus 2 TBSP of whey, lemon juice, yogurt or vinegar, and 2 TBSP of rye flour. Once processed this way, your oatmeal will only take about 5 minutes to cook the next day.

Breads

  • Sourdough starter is significantly more effective than packaged yeast at reducing phytate content.
  • Heat-treating flours destroys the phytase enzyme that breaks down phytic acid during fermentation. Therefore look for breads made with stone ground flour.
  • Phytic acid content decreases about 60% after 2 hours of leavening, and 80-85% after 48 hours of leavening. So make your own bread with non-heat treated flour, or look for a bakery near you who follows these guidelines.
  • Sprouted bread such as Ezekiel brand is widely available as well.

Beans

Soak for 24 hours, changing the water at least twice, then cook over low heat. This removes about 50% of the phytate. Sprouting would likely be even better. 

Some types of beans are available pre-sprouted, or you can sprout your own.

Lentils

Consider buying sprouted lentils or sprouting your own. This removes about 50% of the phytic acid.

Nuts and seeds

  • Nuts and seeds contain significantly more phytic acid than grains.
  • It’s unknown how much phytic acid is removed by various preparation techniques.
  • Roasting probably removes a significant percentage of phytic acid (since it does so in grains and soy nuts), but this hasn’t been studied.
  • Consuming large amounts of raw nuts, nut butters or nut flours like almond flour is likely problematic for long-term health due to mineral depletion.
  • Consider buying sprouted and dehydrated nuts like these.
  • Sprouted nut butters are also available and likely a better choice.
  • Don’t go overboard eating a ton of nuts. Keep it to occasional snacks, and don’t eat them with every meal, or handfuls at a time.

Coconut

While coconut does contain phytates, they actually have an extremely low mineral binding capacity, and therefore you don’t need to worry about soaking or otherwise processing your coconut.

Tofu

Limit tofu consumption, and purchase organic, sprouted tofu. 

*Note that if you soak your phytic acid-containing foods, you don’t need to throw out the soaking water, because the phytic acid has simply been broken down by the phatase enzyme. It is no longer present.

Resources:

Thrive market offers discounts on wholesome non-perishable food items like sprouted lentils, brown rice, pumpkin seeds, etc.

Nourishing Traditions by Sally Fallon

The Weston A. Price Foundation, and this blog post in particular.

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Citations

  1. Barbro, N., Sandström, B., & ÅKE, C. (1985, January). Reduction of the phytate content of bran by leavening in bread and its effect on zinc absorption in man. British Journal of Nutrition, 53(1), 47-53. http://dx.doi.org.nunm.idm.oclc.org/10.1079/BJN19850009
  2.  Bohn, T., Davidsson, L., Walczyk, T., & Hurrell, R. F. (2004). Phytic acid added to white-wheat bread inhibits fractional apparent magnesium absorption in humans. The American Journal of Clinical Nutrition, 79, 418-423.
  3.  Ellis, R., Kelsay, J. L., Reynolds, R. D., Morris, E. R., Moser, P. B., & Frazier, C. W. (1987, August). Phytate:zinc and phytate X calcium:zinc millimolar ratios in self-selected diets of Americans, Asian Indians, and Nepalese. Journal of the American Dietetic Association, 87(8), 1043-1047. Retrieved October 20, 2016.
  4.  Fallon, S., Enig, M. G., Murray, K., & Dearth, M. (2001). Nourishing traditions: The cookbook that challenges politically correct nutrition and the diet dictocrats. Brandywine, MD: NewTrends Pub.
  5. Figures collected from various sources. Inhibitory effect of nuts on iron absoprtion. American Journal of Clinical Nutrition 1988 47:270-4; J Anal At Spectrum. 2004 19,1330 –1334; Journal of Agriculture and Food Chemistry 1994, 42:2204-2209.
  6. Guyenet, Stephan. http://wholehealthsource.blogspot.com/2009/04/new-way-to-soak-brown-rice.html.
  7.  Kresser, C. (2011, September 23). Another reason you shouldn’t go nuts on nuts. Retrieved October 20, 2016, from https://chriskresser.com/another-reason-you-shouldnt-go-nuts-on-nuts/
  8. Layrisse, M., Garcia-Casal, M. N., Solano, L., Baron, M. A., Arguello, F., Llovera, D., . . . Tropper, E. (2000, September). New property of vitamin A and beta-carotene on human iron absorption: Effect on phytate and polyphenols as inhibitors of iron absorption. Archivos Latinoamericanos De Nutricion, 50(3), 243-248. Retrieved October 20, 2016. 
  9.  Liang, J., Han, B., Nout, M. R., & Hamer, R. J. (2008, October 15). Effects of soaking, germination and fermentation on phytic acid, total and in vitro soluble zinc in brown rice. Food Chemistry, 110(4), 821-828. doi:10.1016/j.foodchem.2008.02.064
  10. Mensah, P., & Tomkins, A. (2003). Household-level Technologies to Improve the Availability and Preparation of Adequate and Safe Complementary Foods. Food and Nutrition Bulletin, 24(1), 104-125. doi:10.1177/156482650302400106
  11. Nagel, R. (2010, March 26). Living With Phytic Acid. Retrieved October 20, 2016, from http://www.westonaprice.org/health-topics/living-with-phytic-acid/
  12. Zhou, J. R., & Erdman, J. W. (1995). Phytic acid in health and disease. Critical Reviews in Food Science and Nutrition, 35(6), 495-508. doi:10.1080/10408399509527712