How Plastics Can Affect Your Love Life

Most of the attention on phthalates, a group of hormone-disrupting chemicals found in PVC plastics, has been focused on fetal and child health, particularly regarding genital and behavioral development. Recent data have shown, for example, “incomplete virilization in infant boys” and reduced masculine play as they grow up, and for girls, an earlier onset of puberty. What about affecting hormonal function in adults? I explore this in my video Avoiding Adult Exposure to Phthalates.

Men exposed to high levels of phthalate had lower testosterone levels, but that was for workers in a plastics plant. In the general population, the evidence is mixed. A study in Sweden of men in their 20s found no effect on testosterone, whereas a U.S. study on men in their 30s did find an effect, even at levels of exposure much lower than those of factory workers. When there’s conflicting evidence like this, ideally we’d put it to the test, but you can’t ethically expose people to phthalates so scientists have come up with convoluted methods like implanting the testicles from human fetuses into mice to keep them growing. We want to know about the effects on adult, not fetal, testicles, which had been harder to procure… until recently. “[C]onsent was obtained from all donors.” Now, I’ve heard of blood donors, but this is a whole other level. Researchers obtained donated testicles from prostate cancer patients who underwent castration to control their disease and, indeed, were able to get direct evidence that phthalates can inhibit testosterone production at the kinds of levels one sees in general population studies.

What about breast cancer, the number-one cancer killer of young women? Women working in automotive plastics and food canning are at five times the odds of breast cancer, suggesting a link. In a petri dish, however, phthalates didn’t seem to accelerate breast cancer growth at the levels of exposure expected in the general population. More recently, though, phthalate exposure was found to boost breast cancer cell growth in vitro at the levels found circulating in the bodies of many women. Therefore, the maximum tolerable dose set by governments should be re-evaluated.

How do you avoid the stuff? Well, when you think of plastic chemicals, you may think of water bottles, but they appear to play only a minor role. Most phthalates come from food. How do we know this? If you take people and have them stop eating for a few days, you get a significant drop in the amount of phthalates spilling into their urine. Fasting isn’t exactly sustainable, though. Thankfully, we can see similar drops from simply eating a plant-based diet for a few days, which gives us a clue as to where most phthalates are found. There were a few cases of spikes within the fasting period after showers, however, suggesting contamination in personal care products.

We can counsel patients to reduce phthalate exposures by avoiding the use of scented personal care products, soaps, and cosmetics, since phthalates are used as a fragrance carrier. Phthalates can also be found in children’s toys, as well as adult toys. “On behalf of the Danish [Environmental Protection Agency] EPA, [the Danish Technological Institute] DTI has made inquiries about the consumption pattern in connection with the use of sex toys made of rubber or plastics” to see what kind of exposure one might get “based on worst case scenarios.” Those working behind the counters at sex shops “proved to possess very little knowledge of the materials,” so the researchers had to do their own testing. It turns out that “jelly” is plasticized PVC—up to two-thirds phthalates by weight. Though the use of water-based lubricants may reduce the health risks 100-fold, phthalate exposure through lubricants may still have the opposite of the intended effect. Women with the highest levels of phthalates flowing through their bodies “had over 2.5 times the odds of reporting a lack of interest in sexual activity,” and these weren’t women in a canning factory, rather they were at typical exposure levels in America.


To find out how to lower your exposure to phthalates, see What Diet Best Lowers Phthalate Exposure?

More on hormone-disrupting chemicals in our food supply in:

Interested in learning more about improving sexual health? See:

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:

Does Rye Bread Protect Against Cancer?

Previously, I’ve explored the beneficial effects of flaxseeds on prostate cancer (Flaxseeds vs. Prostate Cancer), as well as breast cancer prevention and survival (Flaxseeds & Breast Cancer Prevention and Breast Cancer Survival & Lignan Intake). The cancer-fighting effect of flaxseeds is thought to be because of the lignans, which are cancer-fighting plant compounds found in red wine, whole grains, greens (cruciferous vegetables), and especially sesame seeds and flaxseeds, the most concentrated source on Earth. But this is based on per unit weight. People eat a lot more grains than seeds. Of the grains people eat, the highest concentration of lignans is found in rye. So, can rye intake decrease the risk of cancer? Theoretically yes, but unlike flaxseeds, it’s never been directly put to the test… until now.

In my video Does Rye Bread Protect Against Cancer?, I discuss the evidence that does exist. If you measure the levels of lignans in the bloodstream of women living in a region where they eat lots of rye, the odds of breast cancer in women with the highest levels do seem to be just half that of women with the lowest levels. But lignans are also found in tea and berries, so we couldn’t be sure where the protection is coming from. To get around this, researchers decided to measure alkylresorcinol metabolites, a class of phytonutrients relatively unique to whole grains.

Researchers collected urine from women with breast cancer and women without, and the women with breast cancer had significantly lower levels compared to those without. This suggests that women at risk for breast cancer consume significantly lower amounts of whole grains like rye. But if we follow older women in their 50s through 60s, the intake of whole grain products was not associated with risk of breast cancer. A similar result was found in older men for prostate cancer. Is it just too late at that point?

We know from data on dairy that diet in our early life may be important in the development of prostate cancer, particularly around puberty when the prostate grows and matures. If you look at what men were drinking in adolescence, daily milk consumption appeared to triple their risk of advanced prostate cancer later in life. (Learn more about milk and prostate cancer in my video Prostate Cancer and Organic Milk vs. Almond Milk.) So, researchers looked at daily rye bread consumption during adolescence.

Those who consumed rye bread daily as kids did appear to only have half the odds of advanced prostate cancer. This is consistent with immigrant studies suggesting that the first two decades of life may be most important for setting the pattern for cancer development in later life. These findings are certainly important for how we should feed our kids, but if we’re already middle-aged, is it too late to change course? To answer this question, researchers in Sweden put it to the test.

Researchers took men with prostate cancer and split them into two groups. One group got lots of rye bread, while the other got lots of high-fiber, but low-lignan, wheat bread. There’s been some indirect evidence that rye may be active against prostate cancer—like lower cancer rates in regions with high rye consumption—but it had never been directly investigated… until this study. Biopsies were taken from the subjects’ tumors before and after three weeks of bread eating, and the number of cancer cells that were dying off were counted. Though there was no change in the cancer cell clearance of the control bread group, there was a 180% increase in the number of cancer cells being killed off in the rye group. A follow-up study lasting 6 weeks found a 14% decrease in PSA levels, a cancer marker suggesting a shrinkage of the tumor.

The researchers note they used very high rye bread intakes, and it remains to be tested if more normal intake levels would have effects that are of clinical importance. As a sadly typical American, my lack of intimate familiarity of the metric system did not flag the “485 grams” of rye bread a day as far out of the ordinary, but that translates to 15 slices! Rather than eating a loaf a day, the same amount of lignans can be found in a single teaspoon of ground flaxseeds.


I’ve created several videos on flaxseeds for both breast cancer prevention and treatment, including Flaxseeds & Breast Cancer Prevention, Breast Cancer Survival and Lignan Intake, Flaxseeds & Breast Cancer Survival Epidemiological Evidence, and Flaxseeds & Breast Cancer Survival: Clinical Evidence.

What’s more, flaxseeds may help with cyclical breast pain (Flaxseeds for Breast Pain), prostate cancer (Flaxseed vs. Prostate Cancer), diabetes (Flaxseeds vs. Diabetes), and hypertension (Flaxseeds for Hypertension).

And if you’re wondering Which Are Better: Chia Seeds or Flaxseeds?, get the answer in the video!

The wonders of whole grains are also discussed in Whole Grains May Work as Well as Drugs, Can Oatmeal Reverse Heart Disease?, and Can Oatmeal Help Fatty Liver Disease?.

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:

Comparing Pollutant Levels Between Different Diets

The results of the CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas) study were published recently. This study of a California birth cohort investigated the relationship between exposure to flame retardant chemical pollutants in pregnancy and childhood, and subsequent neurobehavioral development. Why California? Because California children’s exposures to these endocrine disruptors and neurotoxins are among the highest in the world.

What did they find? The researchers concluded that both prenatal and childhood exposures to these chemicals “were associated with poorer attention, fine motor coordination, and cognition” (particularly verbal comprehension) by the time the children reached school age. “This study, the largest to date, contributes to growing evidence suggesting that PBDEs [polybrominated diphenyl ethers, flame retardant chemicals] have adverse impacts on child neurobehavioral development.” The effects may extend into adolescence, again affecting motor function as well as thyroid gland function. The effect on our thyroid glands may even extend into adulthood.

These chemicals get into moms, then into the amniotic fluid, and then into the breast milk. The more that’s in the milk, the worse the infants’ mental development may be. Breast milk is still best, but how did these women get exposed in the first place?

The question has been: Are we exposed mostly from diet or dust? Researchers in Boston collected breast milk samples from 46 first-time moms, vacuumed up samples of dust from their homes, and questioned them about their diets. The researchers found that both were likely to blame. Diet-wise, a number of animal products were implicated. This is consistent with what’s been found worldwide. For example, in Europe, these flame retardant chemical pollutants are found mostly in meat, including fish, and other animal products. It’s similar to what we see with dioxins—they are mostly found in fish and other fatty foods, with a plant-based diet offering the lowest exposure.

If that’s the case, do vegetarians have lower levels of flame retardant chemical pollutants circulating in their bloodstreams? Yes. Vegetarians may have about 25% lower levels. Poultry appears to be the largest contributor of PBDEs. USDA researchers compared the levels in different meats, and the highest levels of these pollutants were found in chicken and turkey, with less in pork and even less in beef. California poultry had the highest, consistent with strict furniture flammability codes. But it’s not like chickens are pecking at the sofa. Chickens and turkeys may be exposed indirectly through the application of sewer sludge to fields where feed crops are raised, contamination of water supplies, the use of flame-retarded materials in poultry housing, or the inadvertent incorporation of fire-retardant material into the birds’ bedding or feed ingredients.

Fish have been shown to have the highest levels overall, but Americans don’t eat a lot of fish so they don’t contribute as much to the total body burden in the United States. Researchers have compared the level of PBDEs found in meat-eaters and vegetarians. The amount found in the bloodstream of vegetarians is noticeably lower, as you can see in my video Flame Retardant Pollutants and Child Development. Just to give you a sense of the contribution of chicken, higher than average poultry eaters have higher levels than omnivores as a whole, and lower than average poultry eaters have levels lower than omnivores.

What are the PBDE levels in vegans? We know the intake of many other classes of pollutants is almost exclusively from the ingestion of animal fats in the diet. What if we take them all out of the diet? It works for dioxins. Vegan dioxin levels appear markedly lower than the general population. What about for the flame retardant chemicals? Vegans have levels lower than vegetarians, with those who’ve been vegan around 20 years having even lower concentrations. This tendency for chemical levels to decline the longer one eats plant-based suggests that food of animal origin contributes substantially. But note that levels never get down to zero, so diet is not the only source.

The USDA researchers note that there are currently no regulatory limits on the amount of flame retardant chemical contamination in U.S. foods, “but reducing the levels of unnecessary, persistent, toxic compounds in our diet is certainly desirable.”

I’ve previously talked about this class of chemicals in Food Sources of Flame Retardant Chemicals. The same foods seem to accumulate a variety of pollutants:

Many of these chemicals have hormone- or endocrine-disrupting effects. See, for example:

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: