The Amount of Vitamin D Supplementation I Recommend

Randomized, controlled clinical trials have found that vitamin D supplements extend one’s lifespan. What is the optimal dose? What blood level is associated with living longest? In my nine-part video series on vitamin D from 2011, I noted that the relationship between vitamin D levels and mortality appeared to be a U-shaped curve, meaning low levels of vitamin D were associated with increased mortality, but so were levels that were too high, with the apparent sweet spot around 75 or 80 nmol/L based on individual studies. (See Vitamin D and Mortality May Be a U-Shaped Curve for more on this.)

Why might higher vitamin D levels be associated with higher risk? Well, the study I profile in my video How Much Vitamin D Should You Take? was a population study, so we can’t be sure which came first. Maybe the higher vitamin D higher risk, or perhaps higher risk led to higher vitamin D levels, meaning maybe those who weren’t doing as well were prescribed vitamin D. Maybe it’s because it was a Scandinavian study, where individuals tend to take a lot of cod liver oil as a vitamin D supplement, one spoonful of which could exceed the tolerable upper daily limit of intake for vitamin A, which could have negative consequences.

Anyway, the U-shaped curve is old data. An updated meta-analysis has shown that as population vitamin D levels go up, mortality appears to go down and stay down, which is good because then we don’t have to test to see if we’re hitting just the right level. Routine testing of vitamin D levels is not recommended. Why? Well, it costs money, and, in most people, levels come right up to where you want them with sufficient sun or supplementation, so what’s the point? As well, the test is not very good: Results can be all over the place. What happens when you send a single sample to a thousand different laboratories around the world? You’d perhaps expect a little variation, but results from the same sample ranged anywhere from less than 20 to over 100 nmol/L. Depending on what laboratory your doctor sent your blood sample to, the results could vary dramatically, so one could argue the test isn’t necessarily very helpful.

So, what’s a safe dose that will likely get us to the purported optimal level? A thousand units a day should get most people up to the target 75 nmol/L (which is 30 ng/mL), but by most people, researchers mean 50 percent of people. To get around 85 percent of the U.S. population up to 75 nmol/L would require 2,000 IU a day. Two thousand IU a day would shift the curve so that the average person would fall into the desired range without fear of toxicity. We can take too much vitamin D, however, but problems don’t tend to be seen until blood levels get up around 250 nmol/L, which would take consistent daily doses in excess of 10,000 IU.

Note that if you’re overweight, you may want to take 3,000 IU and even more than that if you’re obese. If you’re over age 70 and not getting enough sun, it may take 3,500 IU to get that same 85 percent chance of bumping up your levels above the target. Again, there’s no need for the average person to test and retest, since a few thousand IU per day should bring up almost everyone without risking toxicity.

Given this, why then did the Institute of Medicine set the Recommended Daily Allowance at 600 to 800 IU? In fact, official recommendations are all over the map, ranging from just 200 IU a day all the way up to 10,000 IU a day. I’ll try to cut through the confusion in my next post.


After all that work plowing through the new science, the same 2,000 IU per day recommendation I made in 2011 remains (for those not getting enough sun): http://nutritionfacts.org/2011/09/12/dr-gregers-2011-optimum-nutrition-recommendations/.

The other videos in this series include:

I also explore Vitamin D as it relates to specific diseases:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

What Are the Best and Worst Foods?

I’ve always pictured my role primarily as providing the latest science, but you can’t understand all the new discoveries without a good foundation. The Dietary Guidelines for Americans has a chapter on food components to reduce. But, when they say things like “reduce intake of solid fats (major sources of saturated and trans fatty acids),” what does that mean in terms of which foods to cut down on?

Similarly, there’s a chapter on nutrients we should increase our intake of, so-called “shortfall nutrients.” But, when they say we need more magnesium, for example, what does that mean in terms of actual food? There’s no magnesium aisle in the grocery store. In my video What Are the Healthiest Foods? I analyze 20 different types of foods to see, based on the federal guideline criteria, which are the healthiest and which are the least healthy. There are a lot of fascinating charts in the video, so I encourage you to check it out.

To give a better idea of which foods to eat and which ones to avoid, in the video I use traffic-light labeling, so imagine that a green light means to “go ahead and eat,” yellow or amber means “caution,” and red tells you to “stop and think before you put that in your mouth.” Note these don’t correspond to the more comprehensive Traffic Light designations I detail in my book How Not to Die. When considering what foods in our diet may contribute most of the added sugars we consume, as one would suspect, sweets and sodas are red-light foods, but there are often surprising levels of extra sugar even in savory snack foods, like Ritz crackers. So, what are the top five offenders? Soda contributes 36.6% of the added sugars we consume, with grain-based desserts like donuts contributing 11.7%, Kool-Aid-type beverages contributing 11.5%, dairy desserts including ice cream contributing 6.4%, and candy contributing 6.2%.

What about caloric density? Surveying which foods contain the most calories per serving, oils join desserts and processed snack foods as the worst, though eggs, meat (including fish and poultry), nuts, seeds, and soda can’t be considered low-calorie. The top five sources of calories in the American diet are basically desserts, which contribute 6.4% of our total calories, bread, which contributes 6.0%, chicken, which contributes 5.6%, soda and other sweetened beverages, which contribute 5.3%, and pizza, which contributes 4.5%.

Which foods contain the most cholesterol? Eggs, fish, chicken, and red meat all earn the red light, while desserts, dairy, and other meats earn the yellow. Which foods contribute the highest percentages of cholesterol intake to the American diet? Number one by far is eggs (24.6%), with chicken coming in second (12.5%), beef third (11.0%), cheese fourth (4.2%), and pork fifth (3.9%).

As for saturated fat, desserts, dairy, and snack foods are all designated as red light, with eggs, chicken, fish, and red meat getting the yellow light. Most of the saturated fat in the American diet comes from cheese (8.5%), pizza (5.9%), grain-based desserts (5.8%), dairy desserts (5.6%), and chicken (5.5%).  

Salt levels are highest in lunch meat and snack foods, which both get a red light. But, Americans get most of their sodium from bread (7.3%), chicken (6.8%), pizza (6.3%), pasta (5.1%), and lunch meat (4.5%).

Trans fats are present in many foods—naturally or artificially added or created. Snack foods earn red-light levels, while oils, animal products, and animal-derived products get yellow lights. The primary contributors of trans fat in the American diet are cakes, cookies, crackers, pies, doughnuts, and other grain-based processed foods (40%), followed by animal products (21%), margarine (17%), French fries (8%), and chips and microwave popcorn (5%).

Now, to the nutrients. If you fast-forward to the 3:00 minute mark of my What Are the Healthiest Foods? video, you can see which foods are the best sources of such nutrients as calcium, fiber, magnesium, potassium, and vitamins A, C, D, E, and K. Foods in the chart with a green designation are a high source of a particular nutrient, while pale green designees are a medium source and white entries are a poor source. Since the body’s food currency is in calories, not grams or food weight, nutrient density by calorie is a better way of making assessments. Our body monitors how much energy we eat, not how much weight (of food) we eat. We only have about 2,000 calories in the calorie bank to spend every day; so, to maximize our nutrient purchase, we want to eat the most nutrient-dense foods.

To look for trends in nutrient density by calorie, we can rank the foods in the chart from best to worst, which you can see at the 3:47 minute mark of the video.

The clear winners are unprocessed, unrefined, plant-derived foods, including vegetables, herbs and spices, fruit, mushrooms, legumes, whole grains, and nuts and seeds. In general, these foods lack the disease-promoting components we want to avoid and, as the Dietary Guidelines Committee states, “These foods contain not only the essential vitamins and minerals…but also hundreds of naturally-occurring phytonutrients…that may protect against cancer, heart disease, osteoporosis, and other chronic health conditions.” So, these foods also contain hundreds of phytonutrients found in whole plant foods that are largely missing from processed and animal-derived foods. Additionally, the lack of disease-preventing compounds may be compounded by the presence of disease-promoting compounds.

So this is why people eating more plant-based tend to end up eating a more nutrient-dense dietary pattern, closer to the federal dietary recommendations. The more plant-based we get, apparently, the better.


For more information on the best diet to maximize nutrient intake while minimizing the intake of harmful food components, check out my video What Is the Healthiest Diet?.  How low should one try to push their intake of some of the food components to avoid? See Trans Fat, Saturated Fat, and Cholesterol: Tolerable Upper Intake of Zero, How Much Added Sugar Is Too Much?, and, for sodium, High Blood Pressure May Be a Choice. Surprised that trans fats weren’t limited to partially hydrogenated junk? Check out Trans Fat in Meat and Dairy

And for an overview on why I do this work to publish the latest in health and nutrition, see my introductory series

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

How to Treat Dry Eye Disease Naturally with Diet

One of the most common eye disorders, dry eye disease, causes irritation or discomfort, and can decrease functional vision, sometimes causing a dramatic deterioration in the quality of life. About five million Americans over age 50 suffer from moderate-to-severe dry eyes, and tens of millions more have mild or episodic manifestations of the disease, at a cost of more than $50 billion.

In terms of treatment, there are several drops and drugs that can help. We spend hundreds of millions of dollars on things like artificial tears, but currently there is no therapy available to actually fix the problem. If drugs don’t work, doctors can try plugging up the outflow tear ducts, but that can cause complications, such as plugs migrating and eroding into the face, requiring surgical removal. Alternatively, surgeons can just cauterize or stitch up the ducts in the first place.

There has to be a better way.

What about prevention? Dry eyes can be caused by LASIK surgery, affecting about 20-40% of patients six months after the operation. With a million LASIK procedures performed annually, that’s a lot of people, and sometimes the long-term symptoms can be severe and disabling.

There’s a long list of drugs that can cause it, including antihistamines, decongestants, nearly all the antidepressants, anticonvulsants, antipsychotics, anti-Parkinson’s drugs, beta-blockers, and hormone replacement therapy, as well as a few herbal preparations.

In the developing world, vitamin A deficiency can start out as dry eyes and then progress to becoming the leading cause of preventable childhood blindness. Vitamin A deficiency is almost never seen in the developed world, unless you do it intentionally. There was a report in the 1960s of a guy who deliberately ate a vitamin A-deficient diet, living off of bread and lime juice for five years, and his eyes developed vascularization and ulceration of the cornea, which you can see (if you dare) in my Treating Dry Eye Disease with Diet: Just Add Water? video. That was better than what happened to an unfortunate woman who was the member of a cult and tried to live off of brown rice and herbal tea: Her eyes literally melted and collapsed.

There are also a couple case reports of autistic children who refused to eat anything but French fries or menus exclusively comprised of bacon, blueberry muffins, and Kool-Aid, and became vitamin A deficient. A case in the Bronx was written up as vegan diet and vitamin A deficiency, but it had nothing to do with his vegan diet—the kid refused to eat vegetables, consuming only potato chips, puffed rice cereal with non-fortified soymilk, and juice drinks. “His parents lacked particular skill in overcoming the child’s tendency to avoid fruits and vegetables.”

A plant-based diet may actually be the best thing for patients with dry eye disease, those who wear contact lenses, and those who wish to maximize their tear secretions. People with dry eyes should be advised to lower protein, total fat, and cholesterol intake, and do the following:

  • increase complex carbohydrates;
  • increase vitamin A content (by eating red, orange, yellow, and dark green leafy vegetables);
  • increase zinc and folate intake (by eating whole grains, beans, and raw vegetables, especially spinach);
  • ensure sufficient vitamin B6 and potassium intake (by eating nuts, bananas, and beans);
  • ensure sufficient vitamin C intake (by eating citrus);
  • eliminate alcohol and caffeine;
  • reduce sugar and salt intake; and
  • consume six to eight glasses of water per day.

We know dehydration can cause a dry mouth, but could dehydration cause dry eyes? It may seem kind of obvious, but evidently it was never studied until recently. Is the answer to just drink more water? We know that those suffering from dry eye are comparatively dehydrated, so researchers figured that tear secretion decreases with progressive dehydration just like saliva secretion decreases and gives us a dry mouth. And indeed, as one gets more and more dehydrated, their urine concentrates and so does the tear fluid. But one can reverse that with rehydration, raising the exciting prospect that improving whole-body hydration by getting people to drink more water might bring relief for those with dry eyes. The researchers recommend eight cups of water a day for women and ten cups a day for men.


Find more on the importance of proper hydration in my How Many Glasses of Water Should We Drink a Day?, Does a Drink Of Water Make Children Smarter?, and Can Dehydration Affect Our Mood? videos.

To learn more on other topics related to eye health, check out:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: