“Eat your vegetables!” Mother may have told you. And innumerable researchers are backing up that exhortation with hard facts. But what would they say about pizza? Could you ever believe that the most favorite food of youth in America might actually be healthful… well, parts of it at least?
If you throw away the acidifying dough, the heart clogging meats and acid forming, carcinogenic cheese, the tomato sauce might actually be good. It contains lycopene, the red pigment of tomatoes, watermelon, papaya, pink grapefruit, guava and apricots. Among the group, tomatoes are the most concentrated food source of lycopene, a non-vitamin A forming member of the family of carotenoids that include alpha carotene, beta-carotene, lutein, astaxanthin, and beta-cryptoxanthin to name a few.
With research beginning in the 1980s, lycopene is one of those recently identified bioactive food substances that must be obtained either from dietary or supplemental sources. Moreover, unlike many other nutrients that are destroyed in various phases of food processing, processed foods actually deliver more lycopene than fresh foods. It appears that tomato soup, juice, sauce and paste as well as salsa and ketchup, are better sources of lycopene than fresh tomatoes. Heating lycopene during food processing converts it to a form that is more easily absorbed by the body! Studies that looked at lycopene levels in the blood found that levels were higher after people ate cooked tomatoes than after they ate raw tomatoes or drank tomato juice, indicating a higher level of absorption and bioavailability from processed foods. Eating lycopene-rich vegetables and fruits together with a small amount of oil (e.g. olive oil or coconut oil [I don’t recommend seed oils]) or fat, as from the cheese on a friendly pizza, increases the amount of lycopene absorbed.
Researchers Stahl and Sies found that that drinking tomato juice that had been heated with a 1% concentration of corn oil doubled or tripled serum concentrations of lycopene, and there were significant differences among the human test subjects. No increase occurred with the consumption of unheated juice, however .
Serum and lymph lycopene is delivered on the backs of large, super low-density lipoproteins called chylomicrons. First though, the lycopene must be micellized, that is, reduced to a collection of submicroscopic aggregates of molecules capable of suspension within a colloidal solution. This fancy language simply means that the lycopene must be broken down into minute groups of a few lycopene molecules that will be tiny enough to be vacuumed up by and incorporated into chylomicrons. Micellarization occurs in the presence of dietary fat. Olive, peanut, or rapeseed oils [as well as other dietary fats from animals and plants] have been shown to significantly enhance carotenoid micellarization in a non-dose-dependent manner, meaning that some oil improves the formation of micelles but ingesting large amounts of oil does not necessarily improve micellarization and subsequent absorption.
Chylomicrons are formed during digestion from fats present in the diet. They are the commuter buses that carry fat-soluble vitamins (A, D, E and K), some cholesterol, lycopene and other carotenoids cross the mucosal barrier of the intestinal lining and into circulation. Chylomicrons are usually dismantled and metabolized within 24 hours after a meal is eaten. But in order for chylomicrons to form, there must be some fat in the diet. And the ability of chylomicrons to form is not only regulated by dietary fat but also by gene expression.
The human variability in lycopene bioavailability noted by Stahl and Sies in 1992 reflects the test subjects’ individual genetics. Although lycopene absorption is strongly impacted by dietary composition, most especially the amount of fat in the diet, circulating lycopene (carried through the blood and lymph in lipoproteins), genetic influence cannot be discounted. Genes related to the way an individual manages (absorbs and metabolizes) fats can control uptake and distribution throughout the body. They can dictate the expression of and variations among lipoprotein receptors on cell membranes, cholesterol transporters and carotenoid metabolizing enzymes. All these influences can impact lycopene accumulation in target tissues. The primary repositories for lycopene are adipose tissue, liver, and blood, while testes, prostate, adrenal glands, and the liver contain the greatest concentrations of lycopene. In consideration of dietary supplementation, combining lycopene with phosphatidylcholine from soy, egg [or sunflower lecithin] can improve absorption.
Among tomato products, tomato paste and tomato sauce seem to provide the greatest quantities of lycopene. It is presumed that the physical process of chopping and puréeing tomatoes breaks down the cell walls of the plant, releasing lycopene to the outside world of human digestion. Indeed, uptake from processed tomato paste and tomato sauce was shown to be 2 1/2 times (250%) greater than that of fresh tomatoes. And, whereas the processing of tomatoes into paste and sauce enhances its bioavailability, two other carotenoids in tomatoes, alpha carotene and beta-carotene, were increased by only about 50%.
Undoubtedly cooking had something to do with the results. In a test to evaluate the stability, isomeric form, bioavailability, and in vivo antioxidant properties of lycopene, lycopene content of tomatoes remained unchanged during the multistep processing operations for the production of juice or paste and, surprisingly, remained stable for up to 12 months of storage at ambient temperature! Moreover, subjecting tomato juice to cooking temperatures in the presence of corn oil resulted in the formation of the cis isomeric form, which was more bioavailable than trans isomeric forms. Lycopene was absorbed readily from processed juice and paste, but not so well from fresh tomato. Oxidation of blood serum lipids and low-density lipoprotein (LDL) cholesterol, the “bad” form of cholesterol, were significantly reduced after the consumption of the tomato products containing lycopene.
There are three implications to these findings: 1.) That lycopene easily survives the processing and heating of food products, 2.) That lycopene bioavailability is enhanced by processing, and 3.) That lycopene can be expected to benefit cardiovascular health.
©Mark Timon, M.S. May, 2014