Vitamin B12 binds to the protein in the foods we eat. In the stomach, hydrochloric acid and enzymes unbind vitamin B12 into its free form. From there, vitamin B12 combines with a protein called intrinsic factor so that it can be absorbed further down in the small intestine.

Intrinsic factor is a protein that helps your intestines absorb vitamin B12. It is made by cells in the stomach lining.

The intrinsic factor (IF) is a glycoprotein produced by the parietal cells (oxyntic cells) located at the gastric body and fundus. Intrinsic factor plays a crucial role in the transportation and absorption of the vital micronutrient vitamin B12 (cobalamin, Cbl) by the terminal ileum.

These factors include a person’s age, organ function (e.g., liver, kidney, cardiovascular), and co-morbid diseases. Finally, intrinsic factors also include characteristics that can be influenced by both genetics and a person’s physiology/pathology, such as height, body weight, and receptor sensitivity.

Cyanocobalamin is a synthetic form of vitamin B12 that can be converted to the natural forms methylcobalamin and adenosylcobalamin. The body may absorb cyanocobalamin better, while methylcobalamin has a higher retention rate.

Vitamin C has been shown to enhance iron absorption. It captures non-heme iron and stores it in a form that’s more easily absorbed by your body ( 3 ). Foods high in vitamin C include citrus fruits, dark green leafy vegetables, bell peppers, melons and strawberries.

The following foods can interfere with iron absorption:

• tea and coffee.
• milk and some dairy products.
• whole-grain cereals.
• foods that contain tannins, such as grapes, corn, and sorghum.
• foods rich in gluten, such as pasta and other products made with wheat, barley, rye, or oats.

Grains, beans, nuts, and seeds All grains, legumes, seeds, and nuts contain phytic acid, or phytate, which reduces iron absorption. Eating foods high in phytates, such as beans, nuts, and whole grains, reduces the absorption of nonheme iron from plant foods. As a result, it may reduce total iron levels in the body.

For example, Cook et al. reported that soybean protein inhibited iron absorption more than egg white protein by a factor of about 5 [7]. Although the whole egg is a food that contains a large amount of iron [8], it is often cited as a food that inhibits iron absorption [9,10,11].

Although in vitro studies show that iron absorption can be inhibited by magnesium laxatives such as magnesium oxide, taking oral iron supplements with magnesium laxatives is not considered a clinical problem.

If you’re looking to get more vitamin D in your diet, take it with a side of magnesium. That mineral appears to help regulate levels of vitamin D, which in turn manages the levels of other minerals such as calcium and phosphorus.

Turmeric is among the spices known to inhibit iron absorption by 20%-90% in humans, reducing iron absorption in a dose-dependent manner [10].

Avoid taking more than one multivitamin product at the same time unless your doctor tells you to. Taking similar vitamin products together can result in a vitamin overdose or serious side effects. Many multivitamin products also contain minerals such as calcium, iron, magnesium, potassium, and zinc.

Combining supplements will not normally interfere with the way they work and in some cases may be beneficial, for example vitamin C helps iron absorption.

When to take supplements He suggests taking your dietary supplements at night isn’t advisable. “Digestion slows down during sleep, so taking your nutrient supplement late at night would not be associated with an efficient absorption.”

The results suggest that ascorbic acid does not affect the absorption of normal dietary levels of zinc and calcium.

Too much vitamin C or zinc could cause nausea, diarrhea, and stomach cramps.

Prompted by the observation that zinc deficiency is associated with bleeding and clotting abnormalities, there now is evidence that zinc serves as an effector of coagulation, anticoagulation and fibrinolysis.