Antibiotic Resistance: A New Dietary Hazard
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For years, doctors were able to turn to a multitude of antibiotics that could stop virtually any type of bacterial infection. No longer. Several strains of bacteria have emerged that are resistant to the antibiotics we currently have. These so-called superbugs have appeared around the world, including in the United States.
The use of antibiotics in food production has contributed to the emergence of these superbugs.12 Antibiotics are often given to healthy animals to help them grow faster. That’s a recipe for creating antibiotic resistance. By allowing more opportunity for random mutations, giving healthy animals antibiotics for a long time allows bacteria that become resistant to the antibiotic mutations to thrive. This is truly evolution at work. Recognizing this problem, the FDA announced in 2016 a voluntary program to limit such routine use of antibiotics in food production.13 The major poultry producers have indicated they will stop routinely using antibiotics, and some quickly began to use this as a selling point to consumers, touting that their products were raised without antibiotics. Beef and pork producers are finding it harder to do the same thing, because cows and pigs live longer than poultry and they are raised in less sanitary conditions.
As a consumer, eating less meat will reduce the likelihood of your taking in antibiotic-resistant microbes. If you do plan on eating meat, try to find products without antibiotics. Some companies say that on the packaging; others don’t.
THE SCOOP ON SOY
At the turn of the twenty-first century, several research groups turned their attention to soybeans and soy protein. The media routinely churned out articles with provocative headlines like this one from the Washington Post—“Touting the Joys of Soy: Studies of the Protein-Rich Bean’s Positive Effects on Cholesterol May Be Only the Beginning”—trumpeting the “power” of soy to lower cholesterol, prevent heart disease, ease hot flashes and other menopause-related problems, preserve memory, and protect against breast, prostate, and other cancers. That work didn’t hold up.
• Soy and heart disease. Based largely on an analysis published in the New England Journal of Medicine that eating soy in place of red meat can reduce the level of harmful LDL cholesterol,14 the FDA approved a health claim for soy in 1999. Foods that contain at least 6.25 grams of soy per serving can claim on the label that “diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease.”
Fats in 11/2 Ounces of Various Nuts and Seeds
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Types (# pieces/11/2 ounces)
Calories
Total Fat (grams)
Saturated Fat (grams)
Mono- unsaturated Fat (grams)
Poly- unsaturated Fat (grams)
Ratio of Un- saturated to Satu- rated Fats
Hazelnuts (27–30)
275
26.5
1.9
19.8
3.6
12.3
Almonds (30–36)
246
22
1.7
14.1
5.5
11.5
Pine nuts
286
29.1
2.1
8
14.5
10.7
Flaxseeds
224
17.7
1.5
3.2
12.1
10.2
Pecans (27–30 halves)
293
31.6
2.7
18.7
8.7
10.1
Walnuts (12–16)
270
25.5
2.3
3.5
18.6
9.6
Pistachios (73–77)
243
19.5
2.4
10.4
5.7
6.7
Sesame butter (tahini, 2 tbsp.)
178
16.1
2.3
6.1
7.1
5.7
Sesame seeds
240
20.4
2.9
7.7
8.9
5.7
Mixed nuts (30–36)
258
22.7
3.4
14.7
4.2
5.6
Macadamia nuts (15-18)
32.3
32.2
5.1
25.2
0.6
5.1
Peanuts (42–45)
250
21.1
3.3
11.1
4.2
4.6
Cashews (24–28)
244
19.7
3.9
11.6
3.2
3.8
Peanut butter (smooth, 2 tbsp.)
191
16.4
3.3
8.3
4
3.7
Brazil nuts (9–12)
280
28.5
6.9
10.1
10.4
3.0
Source: USDA National Nutrient Database for Standard Reference, Release 28, 2016.
ndb.nal.usda.gov/ndb/foods.
Keep in mind that you would need to drink four 8-ounce glasses of soy milk (which would deliver a whopping 600 calories) or eat almost a pound of tofu to get 25 grams of soy protein a day. Soy alone can’t counteract a diet that’s high in calories and saturated fat, or for lack of exercise. And later studies don’t fully back this health claim for soy, with some trials showing that soy protein has little or no effect on cholesterol levels.
One problem with the soy research is that in nutrition, the issue of substitution—what you choose to eat instead of something you prefer not to eat—is vitally important. If you eat a soy food instead of red meat in an entrée, say, this will reduce the risk of heart disease, in part because of the much healthier mix of fatty acids in soy than in red meat.
Soy and breast cancer. Biologically speaking, there’s a good reason why soybeans and soy products may act against cancer. Soybeans are rich in compounds called phytoestrogens, literally plant estrogens. There are two main types of phytoestrogen, isoflavones and lignans. They act a bit like human estrogen, sometimes erroneously called the “female hormone.” Yet exactly what phytoestrogens do depends on the amount of them and where they are acting. In some tissues phytoestrogens mimic the action of estrogen, while in other tissues they block it. Estrogen stimulates the growth and multiplication of breast and breast cancer cells. So the estrogen-blocking effects of soy estrogens could protect against breast cancer.
Support for this idea comes from a 2009 cohort study in Shanghai, where soy intake has traditionally been much higher than in the United States.15 In Shanghai, women who ate more soy foods during both childhood and early adult life were less likely to develop breast cancer during their premenopausal years, when natural estrogens are high; no relation was seen for postmenopausal breast cancer. Women with the highest soy protein intakes throughout adolescence and early adulthood had nearly a 60 percent lower risk of premenopausal breast cancer than women with the lowest intakes.
In Western populations, little relation has been seen between soy consumption and breast cancer risk, possibly because the amounts of soy eaten by those groups are relatively low.
Soy and hot flashes. Menopause is a time of dwindling estrogen production. If the phytoestrogens that are thought to block the effects of estrogen in breast tissue can mimic the effects of estrogen elsewhere in the body, they could provide a natural way to cool hot flashes and ease other problems that plague many women during menopause. A recent meta-analysis of clinical trials of soy foods showed that eating these foods appeared to help reduce the frequency of hot flashes and may ease vaginal dryness but had no effect on night sweats.16 Yet the studies inclu
ded in the analysis had significant limitations, so it is hard to tell whether or not women in menopause should eat extra soy.
Soy and prostate cancer. Soy foods have also been promoted as a way to prevent prostate cancer by inhibiting the hormones that help this disease grow. A few prospective studies support this idea.17 However, more research is needed, since most of the studies have been small. We know little about how much soy would be needed to prevent prostate cancer and when in life one should start eating it for the biggest payoff.
Soy and the brain. Can soy keep your memory sharp as you get older? It’s an interesting idea. Naturally falling estrogen levels in both women and men have been suggested as one possible cause of aging-related memory loss and cognitive problems. A few studies, mostly using isoflavone supplements, suggest that getting more soy may preserve memory and thinking skills. Others say that more soy won’t make any difference.18
SOY MAY HAVE A DARK SIDE
The flip-flopping research on soy and health wouldn’t be a huge concern if eating soy protein was completely and totally safe and free of side effects. We don’t know if that’s the case. Two disconcerting reports suggest that, in some situations, overdoing soy protein could do more harm than good.
One showed that women with a suspicious breast lump who took a soy supplement containing 45 milligrams of isoflavones a day for the fourteen days until a scheduled breast biopsy had biopsies showing more cell growth and division than biopsies from women not taking soy.19 While this might suggest a possible link between soy and risk of breast cancer, the large study from Shanghai that I described earlier, as well as other prospective studies from Asia, provide reassurance that soy does not promote breast cancer.
The other, done among older individuals of Japanese ancestry living in Hawaii, showed that those who continued to eat a traditional soy-based diet were more likely to have memory loss and other cognitive problems than those who had made the switch to a more Western diet.20 Similar increases in cognitive problems have been seen in two other reports from Asia, but studies from the United States have generally shown no problems, and even possible benefits, from eating soy foods for maintaining memory.
These conflicting findings point out the absolutely critical need to learn more about how soy foods affect different tissues at different life stages. The estrogen-blocking activity of phytoestrogens may be beneficial for young women, whose breast, ovarian, and other tissues are bombarded by more human estrogens that may promote the development of cancer. But it would be a shame to make blanket recommendations for eating more soy as a way to prevent breast cancer if phytoestrogens also cause problems with memory later in life, when the natural output of estrogen is dwindling.
One thing we know for certain about soy is that the phytoestrogens it contains are potent biological agents. Whether they trigger, suppress, or have no effect on breast cancer, prostate cancer, or memory is unfortunately an open question. That’s why you should treat concentrated soy supplements or isoflavone pills with the same caution you would a totally untested new drug.
These findings don’t mean to steer you completely clear of soy. Instead, eat it now and then rather than several times a day.
PUTTING IT INTO PRACTICE
Protein is a key part of any diet. The average person needs about 7 grams of protein a day for every 20 pounds of body weight. Many people can get that amount without any trouble. What’s probably more important for health is the foods you turn to for protein. Red meat, poultry, eggs, fish, milk and dairy foods, and other animal sources can provide plenty of protein. So can beans, soy, nuts, seeds, and other plant sources.
There’s no need to go overboard on protein and eat it to the exclusion of everything else. By shunning fruits, vegetables, and whole grains, you would miss out on fiber, vitamins, minerals, and other phytonutrients you can’t get from protein. Supplements can add back some of the main phytonutrients, but they leave out hundreds of others that may be equally important for long-term health. You also need to pay attention to what’s coming along with your protein. A serving of salmon gives you 19 grams of protein plus 2 grams of unhealthy saturated fat and 7.4 grams of healthy unsaturated fats. A standard hamburger delivers the same amount of protein but with more than double the saturated fat (4.5 grams) and only 5 grams of unsaturated fat. Choosing high-protein foods low in saturated fat will help your heart even as it helps your waistline.
Here are suggestions for shaping your diet with the best protein choices:
• Get your protein from plants when possible. Eating beans, nuts, whole grains, and other plant sources of protein is good for your health and the health of the planet. If you enjoy milk and other dairy foods, do so in moderation. If you enjoy red meat, eat it in small amounts or on special occasions, as is done with traditional Mediterranean diets. Chicken, turkey, and fish are better options than red meat.
• Mix up your proteins. If most of your protein comes from plants, make sure you eat a mix of beans, nuts, whole grains, and vegetables to be sure that no essential components of protein are missing.
• Balance carbohydrates and protein. Eating more protein and cutting back on carbohydrates, especially refined carbohydrates, improves blood pressure, blood triglycerides, and protective HDL, all of which may reduce your odds of having a heart attack, stroke, or other form of cardiovascular disease. However, if that extra protein comes from red meat and dairy foods, you are likely to be increasing, not decreasing, your risks of cardiovascular disease and diabetes.
Fish, Mercury, and Fish Oil
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If you like to eat seafood, or think you should eat more of it, you may feel you’re caught between the devil and the deep blue sea. Fish is a great choice for many reasons: it tastes good, it’s a healthier source of protein than red meat, and the omega-3 fats in most types of seafood help the heart. Yet some species contain mercury, polychlorinated biphenyls (PCBs), and other contaminants. Should you stop eating fish? Cut back? Hold the line?
The answer depends on who you are.
Mercury and PCBs are definitely dangerous at the high doses you’d see in an industrial accident. In the small amounts found in fish, their effects aren’t as clear-cut.
Young children and women who are pregnant, who might become pregnant, or who are breastfeeding need to be the most careful about mercury. This metal, which comes from natural sources, industrial emissions, and coal-burning electricity plants, can harm the developing brain and nervous system. At the same time, getting enough omega-3 fats from fish and other foods is important during pregnancy and when breastfeeding, because they are essential building blocks for a developing child’s nervous system.
What about PCBs, which were banned in the 1970s but are still present in the environment? High doses kill fish and cause cancer in laboratory rats. Low doses may cause subtle developmental problems in babies. Studies in adults haven’t linked PCBs to cancer or other diseases.
To be on the safe side, children and women of childbearing age should stay away from high-mercury fish like shark, swordfish, king mackerel, and tilefish (sometimes called golden snapper or golden bass). It’s also wise to avoid eating fish caught near industrial areas, where PCBs are likely to be most abundant. Safe choices include cod, haddock, salmon, sardines, shrimp, and tilapia. The EPA’s and FDA’s “Advice About Eating Fish” sheet (www.fda.gov/downloads/Food/FoodborneIllnessContaminants/Metals/UCM536321.pdf) offers information about choosing healthy sources of seafood during pregnancy.
But that doesn’t mean avoiding seafood altogether. Instead, it’s best to eat up to twelve ounces (two average meals) a week of a variety of lower-mercury fish and shellfish such as salmon, pollock, catfish, and shrimp to get the omega-3s you need.
Canned tuna warrants special attention because it is easy and inexpensive, making it something that people tend to eat often. Unfortunately, it also contains intermediate amounts of mercury. To be prudent, eat canned light tuna, which has less mercury than canned white (albacore) tuna.
What about men and older women? If you’re old enough to worry about heart disease, the definite benefits from eating seafood greatly outweigh the possible (and possibly minuscule) risks from mercury and PCBs. It’s prudent to limit your seafood choices to species known to carry high levels of mercury to once a month, and you might not want to eat fish—even ones low in mercury—every single day.
The benefits of eating fish extend beyond the heart and arteries. It’s also good for your brain. The overall benefit of fish for brain health was vividly illustrated in a 2016 study by Martha Claire Morris at Rush University in Chicago. She autopsied brains from participants in her long-term study of diet and brain function who had died. Higher consumption of fish before death was associated with fewer of the harmful changes of Alzheimer’s disease. Fish consumption was also correlated to the amount of mercury in the brain, but it wasn’t linked to harmful changes.21
If you don’t like to eat fish or are worried about contamination, fish oil supplements are an alternative. They deliver plenty of two essential omega-3 fats, EPA and DHA, without the mercury; several chemical analyses of fish oil supplements show negligible amounts of the metal. However, they don’t deliver the same benefit as fish as a replacement for a less healthy source of protein such as steak. And you might consider talking with your doctor about taking a fish oil supplement that contains 600 to 800 milligrams of EPA plus DHA if you:
• have angina (chest pain), have had a heart attack, or are at high risk for one. (You can calculate your risk of having a heart attack using an online calculator provided by the Harvard T.H. Chan School of Public Health, www.diseaseriskindex.harvard.edu.)
• engage in high-intensity sports or activities. Even though the overall risk of heart disease is generally low among people who exercise hard, fatal heart rhythms can appear during and shortly after intense activity. Formal studies haven’t yet been done on the effect of fish oil supplements in this group. Even so, it’s prudent to have plenty of omega-3 fats aboard if you exercise or play hard.
Eat, Drink, and Be Healthy Page 19