How to Maximize Nutrient Absorption

Unhealthy lifestyle behaviors associated with an increased risk of premature death include smoking, excessive alcohol drinking, and not eating enough greens. The best way to get your greens is in whichever way you’ll eat the most of them, and one way to sneak extra greens into your daily diet is with whole-food smoothies, “a potent blend of good nutrition” in a quick, portable, delicious form.  

The Mayo Clinic offers a basic green smoothie recipe, combining the healthiest of fruits and the healthiest of vegetables, berries and dark green leafies, respectively. It calls for 2 ounces of baby spinach, which is about a cup and a half. Consider adding in some curly parsley, another mild beginner green to start with. Surprisingly, the sweetness of the fruit masks any bitterness from the greens such that the pickiest of children love these smoothies, as do adults who otherwise would not consume dark green leafy vegetables—or even fruit—for breakfast. Indeed, the average teen may only get about 1/20th of a serving of fruit otherwise—and Froot Loops don’t count. 

Offering smoothies can have a dramatic effect on fruit consumption for “students who do not want to take time peeling or chewing fruits.” (Who doesn’t have time to chew a fruit?!) The milkshake-y texture of smoothies may not only boost the quantity of fruit and vegetable consumption, but also the quality. 

Carotenoid phytonutrients, like beta-carotene and lycopene, can exist as microscopic crystals trapped inside the cell walls of fruits and vegetables. They’re only released when the cells are disrupted, which is why we have to chew really well. We either have to chew better or choose plants that are easier to chew. For example, while tomatoes have more beta-carotene than watermelon does, watermelon’s beta-carotene is more bioaccessible because its cell walls are wimpy compared with the smaller and tougher cell walls of other fruits and vegetables. To maximize nutrient release, food particle size would ideally be reduced to smaller than the width of the individual plant cells, but you can’t do that with chewing. Most vegetable particles end up greater than two millimeters when you chew them, whereas if we broke open all the cells, we could release much more nutrition, as you can see in my video, Are Green Smoothies Good for You?. The particle size distribution from chewing is about what you’d get blending in a food processor for about five seconds or one of those high-speed blenders for maybe half a second. Just 40 seconds in a blender can break down spinach to a subcellular level. 

Why does that matter? Let’s look at folate, the B vitamin in greens that is especially important for women of child-bearing age. Feed people a cup of spinach a day for three weeks and their folate goes up compared to control. What happens if you eat finely chopped spinach instead of whole leaves? You end up with more than twice as much in your bloodstream and the same absorption-boosting effect with lutein, the green nutrient so important for our eyesight.

It’s not what you eat—it’s what you absorb.  

The boost for lutein was only 14%, so a few extra bites of the whole leafy greens would have given you just as much. Some other nutrients, such as vitamin C, aren’t affected by pre-chopping at all. This is also less of an issue with cooked vegetables. If you boil carrots for three minutes, regular chewing can release about ten times more beta-carotene bioaccessibility than eating them raw, but not as much as blended. Intense cooking, like boiling for 25 minutes, so damages the cell walls so even gulping down large particles can result in significant absorption. But, blending may double carotenoid availability, explaining why we may be able to absorb three times the alpha- and beta-carotene from pureed cooked carrots compared to mashed cooked carrots. So, blending vegetables—raw or cooked—into soups, sauces, or smoothies can maximize nutrient absorption. Whether you went to the store and bought it, or toiled in your garden to grow it, you might as well take full advantage of it.  


Check out my other videos that touch on smoothies:

For other tips on getting children of all ages to eat healthier, see Tricks to Get Kids to Eat Healthier at Home and Tricks to Get Adults to Eat Healthier.

Finally, learn more about the effect of cooking on nutrient loss and absorption from these videos: Best Cooking Method, Raw Food Nutrient Absorption, and Sometimes the Enzyme Myth Is True.

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:

Foods to Avoid to Help Prevent Diabetes

We’ve known that being overweight and obese are important risk factors for type 2 diabetes, but, until recently, not much attention has been paid to the role of specific foods. I discuss this issue in my video, Why Is Meat a Risk Factor for Diabetes?

A 2013 meta-analysis of all the cohorts looking at the connection between meat and diabetes found a significantly higher risk associated with total meat consumption––especially consumption of processed meat, particularly poultry. But why? There’s a whole list of potential culprits in meat: saturated fat, animal fat, trans fats naturally found in meat, cholesterol, or animal protein. It could be the heme iron found in meat, which can lead to free radicals and iron-induced oxidative stress that may lead to chronic inflammation and type 2 diabetes, or advanced glycation end (AGE) products, which promote oxidative stress and inflammation. Food analyses show that the highest levels of these so-called glycotoxins are found in meat—particularly roasted, fried, or broiled meat, though any foods from animal sources (and even high fat and protein plant foods such as nuts) exposed to high dry temperatures can be potent sources of these pro-oxidant chemicals.

In another study, researchers fed diabetics glycotoxin-packed foods, like chicken, fish, and eggs, and their inflammatory markers––tumor necrosis factor, C-reactive protein, and vascular adhesion molecules––shot up. “Thus, in diabetes, environmental (dietary) AGEs promote inflammatory mediators, leading to tissue injury.” The good news is that restriction of these kinds of foods may suppress these inflammatory effects. Appropriate measures to limit AGE intake, such as eliminating meat or using only steaming and boiling as methods for cooking it, “may greatly reduce the already heavy burden of these toxins in the diabetic patient.” These glycotoxins may be the missing link between the increased consumption of animal fat and meats and the development of type 2 diabetes.

Since the 2013 meta-analysis was published, another study came out in which approximately 17,000 people were followed for about a dozen years. Researchers found an 8% increased risk for every 50 grams of daily meat consumption. Just one quarter of a chicken breast’s worth of meat for the entire day may significantly increase the risk of diabetes. Yes, we know there are many possible culprits: the glycotoxins or trans fat in meat, saturated fat, or the heme iron (which could actually promote the formation of carcinogens called nitrosamines, though they could also just be produced in the cooking process itself). However, we did learn something new: There also appears to be a greater incidence of diabetes among those who handle meat for a living. Maybe there are some diabetes-causing zoonotic infectious agents––such as viruses––present in fresh cuts of meat, including poultry.

A “crucial factor underlying the diabetes epidemic” may be the overstimulation of the aging enzyme TOR pathway by excess food consumption––but not by the consumption of just any food: Animal proteins not only stimulate the cancer-promoting hormone insulin growth factor-1 but also provide high amounts of leucine, which stimulates TOR activation and appears to contribute to the burning out of the insulin-producing beta cells in the pancreas, contributing to type 2 diabetes. So, it’s not just the high fat and added sugars that are implicated; critical attention must be paid to the daily intake of animal proteins as well.

According to a study, “[i]n general, lower leucine levels are only reached by restriction of animal proteins.” To reach the leucine intake provided by dairy or meat, we’d have to eat 9 pounds of cabbage or 100 apples to take an extreme example. That just exemplifies the extreme differences in leucine amounts provided by a more standard diet in comparison with a more plant-based diet.

I reviewed the role endocrine-disrupting industrial pollutants in the food supply may play in a three-part video series: Fish and Diabetes, Diabetes and Dioxins, and Pollutants in Salmon and Our Own Fat. Clearly, the standard America diet and lifestyle contribute to the epidemic of diabetes and obesity, but the contribution of these industrial pollutants can no longer be ignored. We now have experimental evidence that exposure to industrial toxins alone induces weight gain and insulin resistance, and, therefore, may be an underappreciated cause of obesity and diabetes. Consider what’s happening to our infants: Obesity in a six-month-old is obviously not related to diet or lack of exercise. They’re now exposed to hundreds of chemicals from their moms, straight through the umbilical cord, some of which may be obesogenic (that is, obesity-generating).

The millions of pounds of chemicals and heavy metals released every year into our environment should make us all stop and think about how we live and the choices we make every day in the foods we eat. A 2014 review of the evidence on pollutants and diabetes noted that we can be exposed through toxic spills, but “most of the human exposure nowadays is from the ingestion of contaminated food as a result of bioaccumulation up the food chain. The main source (around 95%) of [persistent pollutant] intake is through dietary intake of animal fats.”


For more on the information mentioned here, see the following videos that take a closer look at these major topics:  

AGEs: Glycotoxins, Avoiding a Sugary Grave, and Reducing Glycotoxin Intake to Prevent Alzheimer’s.

TOR: Why Do We Age?, Caloric Restriction vs. Animal Protein Restriction, Prevent Cancer From Going on TOR, and Saving Lives By Treating Acne With Diet

Viruses: Infectobesity: Adenovirus 36 and Childhood Obesity

Poultry workers: Poultry Exposure and Neurological Disease, Poultry Exposure Tied to Liver and Pancreatic Cancer, and Eating Outside Our Kingdom

Industrial pollutants: Obesity-Causing Pollutants in Food, Fish and Diabetes, Diabetes and Dioxins, and Pollutants in Salmon and Our Own Fat

The link between meat and diabetes may also be due to a lack of sufficient protective components of plants in the diet, which is discussed in my videos How May Plants Protect Against Diabetes?, Plant-Based Diets for DiabetesPlant-Based Diets and Diabetes, and How Not to Die from Diabetes.

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: