What About Canned Fruit?

Food cans used to be soldered with lead compounds—so much so that people living off of canned food may have died from lead poisoning. Thankfully, this is no longer a problem in the United States. Lead contamination was one of the first priorities of the Food and Drug Administration back in 1906, before it was even called the FDA. Newspapers now have online archives going back a century so we can read about landmark historical events like “FDA Proposes Lead-Soldered Cans Be Banned” from way back yonder in…1993. So even though it was a priority in 1906, the ban didn’t actually go into effect until 1995. Evidently it was complicated because lead solder was “grandfathered” in as a “prior-sanctioned” substance.

Now that the lead is gone, though, are canned foods healthy? It depends primarily on what’s in the can. If it’s SPAM or another processed meat product, for instance, I’d probably pass.

What about canned fruit? We know fruits and vegetables in general may help protect us from dying of cardiovascular disease, and, when it comes to preventing strokes, fruit may be even more protective. But whether food processing affects this association was unknown, as I discuss in my video Is Canned Fruit as Healthy? One study found that unprocessed produce, mostly apples and oranges, appeared superior to processed produce. But that study focused mainly orange and apple juice. It’s no surprise whole fruit is better than fruit juice.

What about whole fruit when it is in a can? Dietary guidelines encourage eating all fruit whether it’s fresh, frozen, or canned, but few studies have examined the health benefits of canned fruit…until now. Canned fruit did not seem to enable people to live longer. In fact, moving from fresh or dried fruit to canned fruit might even shorten one’s life. Therefore, perhaps dietary guidelines should stress fresh, frozen, and dried fruit rather than canned.

Why the difference? While there’s no longer lead in cans these days, there is bisphenol A (BPA), the plastics chemical used in the lining of most cans. BPA can leach into the food and might counterbalance some of the fruits’ benefits. Recently, for example, blood levels of this chemical were associated with thickening of the artery linings going up to the brains of young adults. Canned fruit is often packed in syrup, as well, and all that added sugar and the canning process itself may diminish some nutrients, potentially wiping out 20 to 40 percent of the phenolic phytonutrients and about half of the vitamin C.

Maybe one of the reasons citrus appears particularly protective against stroke is its vitamin C content. It appears the more vitamin C in our diet and in our bloodstream, the lower the risk of stroke. And the way to get vitamin C into the bloodstream is to eat a lot of healthy foods, like citrus and tropical fruits, broccoli, and bell peppers. “Therefore, the observed effect of vitamin C on stroke reduction may simply be a proxy for specific foods (eg, fruits and vegetables) that causally lower stroke” risk. How could the researchers tell? Instead of food, they gave people vitamin C pills to see if they worked—and they didn’t.

This might be because citrus fruit have all sorts of other compounds associated with lower stroke risk, proving that the whole is greater than the sum of its parts. You can’t capture Mother Nature in a pill. It’s like the apocryphal beta-carotene story. Dozens of studies showed that people who ate more beta-carotene-rich foods, like greens and sweet potatoes, and therefore had more beta-carotene circulating in their system, had lower cancer risk. What about beta-carotene supplements instead of whole foods? Researchers tried giving beta-carotene pills to people. Not only did they not work, they may have even caused more cancer. I assumed the National Cancer Institute researcher who did this study would conclude the obvious: produce, not pills. But, no. Instead, the researcher questioned whether he should have tried lower dose pills, alpha-carotene pills, pills with other phytochemicals, or maybe multiple combinations. After all, he said, “[i]t is likely that neither the public nor the scientific community will be satisfied with recommendations concerned solely with foods…”

Check out my other videos on the can-lining chemical BPA, including:

Is fresh fruit really that healthy? See:

Is it possible to get too much of a good thing? See How Much Fruit Is Too Much?.

Now that there’s no more lead in the cans, are there any other ways we’re exposed to the toxic heavy metal? I did a whole series on lead, which you can watch. See also:

I close with yet another screed against reductionism. For more on that, see my videos Why Is Nutrition So Commercialized? and Reductionism and the Deficiency Mentality.

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:

Concerns About Bone Broth

There are toxicological issues associated with production and processing of meat, such as the presence of various toxic contaminants—from dioxins and PCBs to cooked meat carcinogens. Carcinogenesis, the development of cancer, may be the main concern, but there are a number of other toxic responses connected with the consumption of meat products. Lead, for example, can be toxic to the nerves, gastrointestinal tract, bone marrow, and kidneys.

Where is lead found in the food supply? In general terms, the highest levels of lead, as well as arsenic and mercury, are found in fish. Sardines have the most arsenic, but tuna may have sardines beat when it comes to mercury and lead.

The problem is that “fish-consumption advisories related to human health protection do not consider the fish by-products fed to farmed animals,” like farmed fish. If some tilapia are fed tuna by-products, they could bioaccumulate heavy metals and pass them onto us when we eat them. Researchers found the highest levels in frozen sole fillets, averaging above the legal limit for lead.

Lead exposure has been shown to have adverse effects on nearly every organ system in the body. Symptoms of chronic exposure range from memory loss and constipation to impotence and depression. These symptoms present after pretty hefty exposure, though. However, we now know that “[b]lood lead levels in the range currently considered acceptable are associated with increased prevalence of gout and hyperuricemia” (elevated levels of uric acid in the blood). According to the Centers for Disease Control and the World Health Organization, a blood lead level needs to be less than 25 micrograms per deciliter to be “non-elevated.” You’d assume that at values under 25, there’d be no relationship with health outcomes, but even throughout this “acceptable” range, lower lead means lower uric acid levels and lower gout risk. So, even blood lead levels 20 times below the acceptable level can be associated with increased prevalence of gout. “These data suggest that there is no such thing as a ‘safe’ level of exposure to lead.” 

Once lead gets into the body, it tends to stay in the body. It builds up in the bones such that it may take 30 years just to get rid of half. The best strategy? Don’t get exposed in the first place.

If lead builds up in bones, though, what about boiling bones for broth? As I discuss in my video Lead Contamination in Bone Broth, we know bones sequester lead, which can then leach from the bones. So, researchers suggested that “the bones of farmyard animals will sequester lead, some of which will then be released into broth during its preparation.” Who eats bone broth? Bone broth consumption is encouraged by many advocates of the paleo diet. Online, you can learn all about purported “benefits” of bone broth, but what they don’t tend to mention is the theoretical risk of lead contamination—or at least it was theoretical until now. Broth made from chicken bones was to have markedly high lead concentrations, up to a ten-fold increase in lead. Researchers concluded, “In view of the dangers of lead consumption to the human body, we recommend that doctors and nutritionists take the risk of lead contamination into consideration when advising patients about bone broth diets.”

But what if you only use bones from organic, free-range chickens? They did use only bones from organic, free-range chickens.

For more on the paleo diet, see:

Other products contaminated with lead include Ayurvedic supplements, protein powders, wild animals shot with lead ammunition, dairy products, and tea from China:

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:

Alzheimer’s Disease and Dietary Copper

Though the underlying cause of Alzheimer’s disease has yet to be found, there is increasing concern about the role of metals in the development of the disease, as I discuss in my video Alzheimer’s Disease, Copper, and Saturated Fat. “Iron and copper,” for example, “are strongly concentrated within the neuritic plaques and neurofibrillary tangles that represent the hallmarks of the [Alzheimer’s] brain.”

Alzheimer’s disease victims have higher levels of copper in their blood and in the fluid that surrounds their brain, as well as inside their brain. Researchers found that in a slice of Alzheimer’s-diseased brain tissue, the amyloid plaques correspond to copper hotspots. Copper may then make these amyloid plaques more toxic, “leading to increased oxidative stress.” “Free Cu [copper] is extremely efficient in the generation of free radicals,” and when copper is removed with a chelating (metal-binding) drug, the free radical oxidation drops.

Unfortunately, when researchers gave that drug to nine Alzheimer’s patients in a pilot study, it did not seem to have any effect on slowing the clinical progression of the disease. Perhaps we need to prevent the copper buildup in the first place?

“Organ meats and shellfish are the richest food sources of copper,” but should we also consider cutting down on plant sources, such as nuts, seeds, legumes, and whole grains? Copper intake only seems to be a problem when consumed with saturated fat or trans fat. In the Chicago Health and Aging Project, thousands of elderly Chicagoans were followed for six years. Those who were getting the highest copper doses, largely from multivitamin supplements, combined with a diet high in saturated fats, lost cognition as if they had aged 19 years in a period of 6 years, tripling their rate of cognitive decline. However, copper intake “was not associated with cognitive change when the diet was not high in saturated fats.”

Diet-induced high cholesterol “has been shown to increase the formation and progression of [amyloid] plaques in the brain.” As well, “dietary copper may interfere with clearance of [amyloid] from the brain and may further promote [the plaque] accumulation that results from elevated cholesterol levels.” Copper has been shown to interact badly with amyloid, causing its clumping and the production of hydrogen peroxide, a potent pro-oxidant neurotoxin.

This may explain why the higher the levels of copper, the quicker Alzheimer’s disease may progress, particularly among people with high cholesterol levels. What do we think may be happening? As cholesterol and copper levels rise, cholesterol is incorporated into the nerve cell membrane, causing it to stiffen. The amyloid protein in the membrane detaches to form plaques, at which point iron and copper generate neurotoxic free radicals. Inside the cell, similar havoc is created. Finally, cholesterol-enriched diets can lead to nerve cell death, DNA damage, and blood-brain barrier disruption.

“In conclusion, the present systematic review suggests that a diet rich in [copper and iron] might aggravate the detrimental effects of a high intake of cholesterol and [saturated fat] on the risk of developing [Alzheimer’s disease].” So, diets rich in saturated fat and deficient in antioxidants appear to promote the onset of the disease, while more plant-based diets would likely suppress its onset. There are compounds in plant foods that not only scavenge free radicals and prevent oxidative damage, but are also known to chelate, or bind up, metals, potentially making them additionally protective against the onset of Alzheimer’s. Therefore, the practical implications could be to eat lots of fruits and vegetables, avoid copper-containing supplements, and avoid high intakes of saturated fat and excessive iron intake.

Isn’t Alzheimer’s genetic? What about the “Alzheimer’s gene”? Just because we’ve been dealt some bad genetic cards doesn’t mean we can’t reshuffle the deck with diet. See The Alzheimer’s Gene: Controlling ApoE.

If the relationship between cholesterol and dementia is new to you, see Alzheimer’s and Atherosclerosis of the Brain and Cholesterol and Alzheimer’s Disease for more.

What else can we do to protect our brain? Check out:

It’s never too early to start eating healthier, because Alzheimer’s May Start Decades Before Diagnosis.

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: