Most of the nutrients in the food you eat -- such as protein, fats, carbohydrates and fat-soluble vitamins -- need to undergo some amount of digestion before they can be absorbed. But some nutrients, such as some minerals and the water-soluble B vitamins and vitamin C, are absorbed directly into your bloodstream without the need for additional digestion or chemical changes.
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Most B Vitamins
B vitamins are a group of water-soluble vitamins that includes thiamin, riboflavin, niacin, pantothenic acid, folate, vitamin B-6, vitamin B-12 and biotin. These vitamins help your body transform the food you eat into energy.
For the most part, the B vitamins are absorbed directly into the bloodstream in your stomach or small intestines. The exception is vitamin B-12, which must be bound to something called intrinsic factor for absorption.
Vitamin C is also a water-soluble vitamin that is absorbed directly into your bloodstream in your small intestines after it has been freed from food. Vitamin C is essential for good health and plays a number of important roles in your body. For example, it helps make connective tissue, assists in the absorption of iron and, as an antioxidant, supports immune health by protecting your white blood cells from oxidative damage.
Potassium and Calcium
The absorptive process of major minerals, which includes potassium, calcium, chloride, sodium, magnesium and phosphorus, varies. Potassium, for example, is absorbed directly in the bloodstream. Calcium, however, in most cases requires a transporter, but when levels are low, it may be directly absorbed into the bloodstream. Potassium helps regulate fluid balance, while calcium supports bone health.
Iron and Copper
How trace minerals, such as iron and copper, are absorbed also varies. Iron may go through changes before absorption, but some heme iron, which is the iron found in animal foods, is absorbed directly into the blood, says Colorado State University. Copper, like calcium, may also be absorbed directly into circulation if levels are low. You need iron to carry oxygen in your body, and copper is needed to make a number of enzymes.