Micronutrients blocking each other's absorption


Apparently Calcium blocks some or all of the absorption of iron, or the other way around, and for that reason Iron and Calcium supplements shouldn’t be taken at the same time.

Does anyone know about any others blocking each other that we all should be aware of? :slight_smile:

Some Calcium compositions => block iron, manganese, magnesium, flouride, phosphorus, zinc
Lack of dietary fiber => everything shoots right through, leaving not enough time for stuff to be ideally absorbed
Magnesium overdoses => can lead to strong diarrhea, leaving not enough time for other nutrients to be absorbed ideally


Nice thought!


Nice article! I thought it was JUST iron, but other sources confirm that too.

Calcium => blocks iron, manganese, magnesium, flouride, phosphorus, zinc. Definitely take that one at other times than soylent. :smiley:


As far as I know, magnesium and iron are also blocking each other. At least my doctor told me so last week after my blood test.
Strange thing is: I had always a problem with low iron, and for one year know, I had taken a Once Daily supplement with Calcium, Iron, Magnesium, Zinc etc. - If calcium would completly block iron, I should be (again) low in iron, but I’m not.

I’m no professional, but could it be that these minerals are not “blocking” each other, but just lowering the effectiveness?


Yes, that’s what I mean by blocking.
The way I understand it, only high doses of one blocks the other.

I would call getting the full recommended amount of calcium a high dosage, since average people get much less through their food, so it might indeed be beneficial to take some things at other times than soylent.

Time is the important word here:
You might have taken pills that contained iron and calcium, and the calcium at the same time as the iron might have blocked/lowered the absorption of the iron from the pills - but you still would have had some iron in the rest of your diet, taken throughout the day, and this might have been absorbed.


Yes, I think that’s it. But had Rob any deficiency syndromes with testing a diet of (almost) pure soylent? If I’m not mistaken he mixed everything in a batch for the whole day - next week I’m starting in the same procedure, and I want to try a month almost pure on soylent.

Tricky. Because I use a multivitamin for my soylent, this could become difficult. I will keep a look at my blood values and report here if I notice something special.


I wanted to bring this back up because it seems pretty important. Why waste all this time/money trying to get all the micronutrients I need if simple timing is keeping me from actually absorbing them.

I get my iron from my multivitamin, which also contains some calcium and magnesium. How are these not blocking each other when I’m taking them at the exact same time? I add more calcium and magnesium to my soylent. Would it be more helpful to drink the soylent all day and then take the multi at night so the iron is not being blocked by the rest? Or should I leave it all out of the mix and remember to take my multi in the morning, and then calcium and magnesium in the afternoon and evening? (they are in a capsule which I empty into the soylent).

I second countermassive’s confusion that if rob was mixing everything together and drinking an even mix of it throughout the day, how did he avoid these issues?


I’m starting tomorrow with my own soylent mixture and using Multivitamins - I did a bloodtest a week ago and will do another test in about a month.
If some micronutrients are clearly blocking each other, I should see it in my test results.

I’m still convinced that these micronutrients are just blocking a certain amount, so maybe if you take a tablet with 500mg Calcium and 200mg Magnesium, that you absorb just 400mg Calcium and 150 Magnesium - just as an example. I think this issue is quite complex, and maybe the absorbtion depends on bioavailability and digestive enzymes as well.


From sources I have read, but sadly didn’t save. If you are taking more of some nutrients than you need, then it will affect the absorption of other nutrients. Where as, if you are taking precisely as much as you need, you will absorb all your nutrients adequately. Sorry I don’t have the sources of that information, I have tried searching for it again, but it seems to be in vain. The closest one I could find was

"High calcium intake can cause constipation. It might also interfere with the absorption of iron and zinc, though this effect is not well established [1]."

But then I find,

"Calcium competes with iron in normal doses, and the two nutrients should not be taken at the same time."

Adding more information as I go…

"When taken without food, calcium carbonate did not inhibit the absorption of ferrous sulphate with doses of either 300 mg Ca and 37 mg Fe or 600 mg Ca and 18 mg Fe. However, at the latter levels, calcium citrate and calcium phosphate reduced iron absorption significantly…"

Then this one disputes the claims of 300 Ca…

And the information goes on and on in both directions. The thing about all these experiments is they are done while the subjects are sustaining a normal diet of solids. We are all practicing a whole new diet. Our bodies should not be reliant on sources of nutrients from any other sources while doing this, so the absorption of everything is going to be affected differently. My conclusion on the idea is that taking these two (calcium and iron) together in the Soylent should be all right if that is your only source of these two. If not, you may have some absorption issues. My plan and budget only allows me to go full into soylent so I will be reliant on Soylent alone. If you have complications with iron deficiency already, you may want to keep a close eye on your blood tests and consider making separate drinks for the sake of maximum absorption…


maybe one can try to get a hint on absorption blocking in soylent by testing their own urine for the micronutrients. If there are more than usual, they do not get absorbed right.


what’s the cheapest, most reliable, quick, easy to do method for such a urine testing?

could there be a diy ‘thing’ for these kinds of tests?

the normal way would be in a lab I guess, which should be expensive?


Google suggests that such non-lab urine tests only are available for a few nutrients.


I just go by taste.

I’m very sorry, I couldn’t resist.


Found this as a newsletter from the Harvard Medical School in my mailbox . I will post it here as I have recieved it . If you feel to comment , or to disagree , please do so .

Nutrients that work together—and that you should eat together

Nutrition guidelines can make things look very cut and dry. They tell us to get this amount of that vitamin and that amount of this mineral. Separating out nutrients this way makes the guidelines relatively easy to understand. And this kind of thinking probably helps us avoid diseases of nutritional deficiency, such as scurvy (not enough vitamin C) or pellagra (not enough niacin).

But most nutrients don’t fly solo. They interact—sometimes they join forces, other times they cancel each other out. You have probably heard before that eating vitamin-rich foods is better for you than taking a vitamin supplement. One reason why this is true is that food contains a mixture of nutrients that interact with one another in each mouthful.

The following is a list of nutrients that work in pairs. It’s just a sampler, and far from a complete catalog. But hopefully it will help you when you’re choosing what to eat.

Vitamin D and calcium

Like most nutrients, calcium is mostly absorbed in the small intestine. Calcium is important because it strengthens bones, but the body often needs vitamin D’s assistance to absorb the nutrient. Vitamin D also has many other benefits throughout the body.

There’s debate these days about whether to raise the daily intake goal for vitamin D. Right now, the official nutrition guidelines recommend that adults get 1,000 milligrams (mg) of calcium and 400 international units (IU) of vitamin D daily. For older adults, the recommended daily allowance is a bit higher: 1,200 mg of calcium starting in your 50s, and 600 IU of vitamin D starting in your 70s.

To give you an idea of how much that is, an 8-ounce glass of milk contains 300 mg of calcium and, because of fortification, 100 IU of vitamin D.

Sodium and potassium

Sodium is one essential nutrient that most Americans consume more of each day than they need (mostly in the form of salt).

Excess sodium interferes with the natural ability of blood vessels to relax and expand, increasing blood pressure—and increasing the chances of having a stroke or heart attack.

But potassium encourages the kidneys to excrete sodium. Many studies have shown a connection between high potassium intake and lower, healthier blood pressure. According to the current guidelines, adults are supposed to get 4,700 mg of potassium and 1,200 mg to 1,500 mg of sodium daily.

To meet these criteria, you need to follow general healthy eating guidelines. To increase potassium intake, load up on fruits and vegetables. To decrease sodium intake, cut back on cookies, salty snacks, fast foods, and ready-made lunches and dinners.

Vitamin B12 and folate

Vitamin B12 and folate (also one of the eight B vitamins) form one of nutrition’s best couples. B12 helps the body absorb folate, and the two work together to support cell division and replication, which allow the body to replace cells that die. This process is important during times of growth in childhood, and throughout the body of adults as well. Cells that line the stomach and the cells of the hair follicle, for example, divide and replicate often.

Good food sources of vitamin B12 include:

• meat

• eggs

• milk

Natural sources of folate include:

• leafy green vegetables

• beans

• other legumes

Nutrition guidelines recommend 2.4 micrograms of B12 and 400 micrograms of folate daily. This can usually be achieved easily by eating a reasonably well-balanced diet.

However, vegans—people who don’t eat meat and other animal-based products—may have B12 deficiencies. And people who eat poorly or drink too much alcohol may have folate deficiencies.

Folate deficiencies can be corrected with multivitamins or folic acid pills. For a B12 deficiency, you can get injections every few months or take a pill daily.

Deficiency in either or both vitamins may cause a form of anemia called macrocytic anemia. B12 deficiencies can also cause mild tingling sensations and memory loss.

Zinc and copper

Copper and zinc don’t work together—they actually compete for places to be absorbed in the small intestine. If there’s a lot of zinc around, copper tends to lose out and a copper deficiency may develop.

One way the knowledge of the copper-zinc interaction has been put into practice is in treating people with an eye condition called macular degeneration. Some people with the condition are prescribed a special vitamin-mineral combination, called AREDS. The combination has been shown to slow down progression of the disease, which can cause blindness. The AREDS pills include 80 mg of zinc, enough to cause a copper deficiency, so 2 mg of copper were added to the pills.

Niacin and tryptophan

Niacin is one of the B vitamins, although it rarely goes by its B-vitamin moniker, B3. The daily niacin requirement is 16 mg for men and 14 mg for women. Niacin deficiency causes pellagra, a disease that causes a bad rash, diarrhea, and dementia. Tryptophan, an amino acid, is a source of niacin. So one way to avoid niacin shortfalls is to eat foods that contain a lot of tryptophan, including chicken and turkey