Vitamin D: With Meals, or Without?
Vitamin D recently has risen in the vitamin ranks to superstar status: suddenly everybody seems to realize they need more of it in their lives. I've written several blogs about how the common habit of slathering up with sunscreen before going outside has created widespread vitamin D deficiencies and how those deficiencies may cause bone weakness and deformity, certain cancers, heart disease, autoimmune disorders, and so on. The recommended remedy has been to simply go out in the early morning or late afternoon sun for 10 to 15 minutes daily without the sunscreen, and to supplement with up to 2000 IU of vitamin D3 daily. Also, losing weight can enhance vitamin D absorption. Now, a new study adds another important element to the prescription.
Researchers at the Cleveland Clinic discovered that taking vitamin D with large meals boosts its absorption dramatically. It was a small study -- 17 subjects with an average age of 64 -- all of whom had borderline vitamin D deficiencies despite taking daily supplements. The research team postulated that because vitamin D is fat soluble, it needs plenty of fat in order to activate acid bile, and the acid bile expedites absorption. And so, the researchers asked the subjects to take the vitamin with the largest meal of the day.
The participants took doses of vitamin D ranging from 1000 IU to 50,000 IU a day, which far exceeds the currently recommended 400-600 IU daily. After several months, they had an average increase of 50 percent of vitamin D in their blood levels, no matter their daily dose -- a stunning increase given the fact that these people had been having a very difficult time getting blood levels of vitamin D up to the minimum level. Plus, it didn't matter whether they took an oil-based or solid vitamin D. Apparently, most of the participants had been taking the vitamin on empty stomachs or with light meals.
Increasing blood levels of vitamin D up to the recommended level of 50 ng/mL can be challenging for some people, say study directors Drs. Angelo Licata and Guy B. Mulligan, both of the Cleveland Clinic's Metabolic Bone Clinic. "In our practice, it is common to see patients treated with vitamin D supplements who do not achieve an appreciable rise in their serum 25OHD [i.e., vitamin D] level after therapy despite large prescribed doses," they write. "A consistent increase of 50% or greater was seen in the serum 25OHD concentration when patients consumed the vitamin with the largest daily meal."
Given that the Institute of Medicine sets the current upper tolerable level of vitamin D at 2,000 IU daily, and yet many patients don't absorb most of the vitamin D they take, the study provides good evidence that higher levels of vitamin D than the standard 400 IU daily may need boosting. The Institute of Medicine currently is reviewing its recommendations.
In any event, the study raises the question of whether all vitamins should be taken with meals. First, it's important to understand that the body doesn't really like to get its vitamins as isolated substances. It has trouble absorbing them this way and often treats them as toxic substances. Fat-soluble vitamins, for example need bile acid for absorption. So taking fat-soluble vitamins like A, D, E and K with a hefty meal is likely to make them absorb far more easily. Note: they get stored in body fat, and thus cause more concerns about toxicity at high doses.
In the case of water-soluble vitamins, the common perception is that the body absorbs these vitamins easily and excretes excess through the urine. If this is true, water-soluble vitamins need not be taken with a meal. Water-soluble vitamins include Vitamin C, biotin and the seven B vitamins -- thiamin (B-1), riboflavin (B-2), niacin (B-3), pantothenic acid (B-5), pyridoxine (B-6), folic acid (B-9) and cobalamin (B-12).
But the small intestine is where the body absorbs vitamins, minerals and the like. And based on small intestine physiology, I'd have to say that such claims are not necessarily wrong, but are definitely misleading. The body prefers water-soluble vitamins bound to carbohydrates since the receptor sites in the small intestine for absorbing vitamins are keyed to carbohydrates (monosaccharides) -- not the vitamins themselves. If they enter the body as isolates that are not bound to carbohydrates, there are severe limits to the amount of absorption that can take place. Plus, if absorbed in an isolated form, they are toxic to the body and are carried to the liver as "poisons." The liver then neutralizes their toxicity through a process called conjugation that combines them with proteins. Long story short, the issue is not one of whether they are taken with a meal or not, but rather, are they bound to carbohydrates. Given that, your best bet is to avoid isolate vitamins completely. As I've written before, food-based supplements or superfood combinations work better, or even better yet, choose an organic food matrix supplement that was grown using a live, biodynamic growing process.
As for vitamin D, if you really want bang for your buck as far as absorption is concerned, go get some sun. Even a few minutes of sun exposure can generate 2000-4000 or more IU. Obviously, limited amounts of early morning or late afternoon sun are your safest bet, as opposed to extended stays in the noonday sun. And if you supplement, my recommendation for years has been 1,000-2,000 IU of vitamin D3 -- taken with your largest meal of the day. Note: D2 (ergocalciferol) is the synthetic form of vitamin D, and is only marginally absorbable. In fact, it's virtually useless. By the way, most prescription vitamin D is synthetic D2. Why are we not surprised?