Why Bioavailability Matters for Vitamins and Essential Nutrients
The vinegar test. No, not for dying Easter eggs, but for getting essential nutrients. Pour some vinegar in a cup. Heat it up. Drop in your vitamin. Watch the clock for 30 minutes, then peek to see what’s left. This test is supposed to show us what happens to a vitamin in our stomachs. Since the break down of vitamins can differ, many ask: “Should I even take vitamins?” If so, “What vitamins should I take?”
Even so, how do we know that what we put in our mouths ends up helping our bodies? The answer is Bioavailability. According to the National Institute of Health, bioavailability is “the relative absorption of a nutrient from the diet…and their accumulation of a nutrient into various tissues.” Many things, like age, gender, illnesses, the type of the nutrient, other foods in the diet, what’s eaten with the nutrients and the health of our stomachs all affect the bioavailability of the nutrients in the vitamin or food source.
So, you ask, what vitamins should be found through food, and which through supplements? Because many forms of calcium exist, because many foods contain calcium, and because calcium is better absorbed in divided doses with substances like proteins and vitamin D, foods remain the best source of calcium. Studies show that although those who take calcium supplements have a higher daily intake, those who get calcium from foods have stronger bones.
Vegans and those who eat primarily a plant-based diet benefit from supplementation because fiber, quite abundant in plant sources, reduces the bioavailability of Vitamin B-6. According to Gagne et al., eight different forms of vitamin E exist. While our diets consist of food rich in vitamin E, the form available in our typical meals remains less important to our health than other forms, like alpha-tocopherol, which remains poorly absorbed from dietary sources. Many factors, including harvesting, temperature, ripeness, and the amount of oxygen present during storage and transport of foods, greatly affect the availability of vitamin D in them.
Some vitamins and minerals need to be taken together, while others shouldn’t. For instance, vitamin D helps us to absorb calcium, magnesium and phosphate, which we should ingest together for most favorable bone health. These vitamins and minerals do not always exist together in natural food form. vitamin C improves iron absorption, and a lot of zinc in the diet will impede the absorption of iron and copper. The amount of food in the stomach affects the absorption of vitamin C (more food is better), modifying its absorption. Oxalic acid or oxalate in spinach may bind to minerals and make them less available, creating the need for supplementation. You can see it isn’t just as simple as eating the right foods. Even when we do, we are at risk for micronutrient deficiencies. Micronutrients are those nutrients, like vitamins, that we need in smaller amounts.
Understanding bioavailability is most important when we consider our age. While bioavailability is important for good vitamin and nutrient levels at any age, it becomes even more important during the stages of life when we are eating less or fewer foods, like in our first years of life, in our teen years, and when we are older. Our bodies need less food as we age, and getting the right nutrients from the little bit of food we do eat or from the vitamins we take is all that much more important.
New parents often ask their pediatrician: “What vitamins should I take if I’m nursing my child? What vitamins should I give my child as they grow?” In babies, children, and teens, the age of the gut, fast growth and limited diets affect the bioavailability of nutrients from food sources. Nutrient needs increase during times of growth in all of these stages.
Relying on one food source, such as breast milk in babies, or limiting foods, as with the diet of picky eaters, makes it more likely to have micronutrient deficiencies. Iron and zinc are very important for babies and children, and their iron levels decrease and bioavailable zinc levels fall in breast milk. Dietary supplements are often added to cereals and foods to keep iron and zinc levels healthy, and to promote proper growth in babies. Teens seem to eat diets high in fat and sugar, and to not eat foods that promote proper growth and bone calcium. This puts them at risk for micronutrient deficiencies. Teens’ lack of calcium-rich foods in their diets, their changes in hormones and their increased bone growth make getting enough calcium of vital importance.
So, which vitamins should you take? Here’s the good news. The Federal Drug Administration (FDA) closely watches food and supplement labels. Statements made by food or vitamin companies must be true, and the FDA must agree with the label in order for companies to avoid problems.
Diane Dean, RN-BC, LPC, CEG is a wellness expert who promotes true expression of others’ essence in every way, every day through insight-oriented coaching, counseling and health education.