Diet protects from Alzheimer’s disease
Vitamin D and breast cancer
Omega-3 oils and colon cancer
Soft drinks increase pancreatic cancer
Sugar increases cardiovascular risk
Soy foods are safe and healthy
Dietary patterns play a large role in the development of chronic, degenerative disease, as opposed to one particular food being most important. A recent study set out to see what dietary pattern might be associated with the risk of Alzheimer’s disease (AD). Researchers studied 2148 elderly subjects without dementia at the start of the study and evaluated them every 18 months for four years. Dietary patterns ranked seven potentially AD-related nutrients, including saturated fat, monounsaturated fat, omega-3 polyunsaturated fat, omega-6 polyunsaturated fat, vitamins E and B12, and folate.
The most protective dietary pattern included higher intakes of nuts, fish, tomatoes, salad dressing, cruciferous vegetables, fruits, poultry, and dark green leafy vegetables and a lower intake of red meat, organ meat, high-fat dairy products, and butter. Those subjects in the upper third of adherence to this dietary pattern had a 38 percent lower risk of AD than those in the lowest third of adherence. (Gu Y, et al., Food combination and Alzheimer disease risk: A protective diet. Arch Neurol. 2010 Apr 12. [Epub ahead of print].
From this research, it is not clear which of these foods are most protective, or indeed if some of them might not contribute at all to the benefits of the foods as a group, while others are so protective that they make up for the ones that are not (or may even be damaging). These are mostly the same foods that protect against heart disease, and it is likely that some of the same degenerative processes are involved in AD, vascular dementia, and cardiovascular disease.
Vitamin D is produced in the body by the action of ultraviolet light on a derivative of cholesterol in the skin. It is also found in a few food products (it is added to dairy and soy milks). With age, the formation of vitamin D in the skin declines, and production is also lower in months and latitudes with little sun. A Canadian population-based case-control study evaluated 3101 cases of breast cancer (aged 25 to 74 years old) and compared them to 3471 controls.
Dietary sources of vitamin D did not appear to be associated with reduced breast cancer risk, although in all categories the intake of vitamin D was relatively low. However, supplemental vitamin D of 400 IU or greater was associated with a 24 percent reduction in the risk of breast cancer. (Anderson LN, Vitamin D and calcium intakes and breast cancer risk in pre- and postmenopausal women. Am J Clin Nutr. 2010 Apr 14. [Epub ahead of print]
Even with supplements of 400 IU of vitamin D, most people will still be far below ideal levels. Measuring blood levels of 25-hydroxy vitamin D (25(OH)D) is the only way to know if you are getting enough. Levels should be at least 50 to 80 nanograms/ml. Typical doses of supplements to achieve this level range from 5000 to 10,000 IU per day of vitamin D3 (this is the natural form, cholecalciferol, as opposed to the synthetic D2, or irradiated ergosterol).
Higher dietary intake of omega-3 fatty acids appears to lower the risk of developing colon cancer. Among 1872 subjects, those with the highest levels of omega-3 fatty acids in the diet had half the risk compared to those with the lowest levels. Those with higher levels of omega-6 fatty acids had an increased risk. The risk association did not appear to be the same for African Americans in the study (there were fewer of them, so it might have been more difficult to detect a significant difference).
The higher colon cancer risk associated with omega-6 oils may be due to the common sources of those oils in the American diet, as the sunflower, soy, and corn sources are often heavily processed (and any polyunsaturated oils in the diet may require more nutrients to protect them from oxidation). (Kim S, et al., Intake of polyunsaturated fatty acids and distal large bowel cancer risk in whites and African Americans. Am J Epidemiol. 2010 May 1;171(9):969-79.) It is not clear whether oils that are not as heavily processed would have the same deleterious effects. Mono-unsaturated oils, such as olive oil, were not reported in this study.
The sources of omega-3 fatty acids include fish (containing EPA and DHA) and nuts and seeds (particularly flaxseeds and walnuts), which contain alpha-linolenic acid (ALA). Smaller amounts of ALA are found in leafy green vegetables. This is converted through enzymatic action into the other two omega-3 fatty acids. Unfortunately, this conversion is not always adequate, especially in older or infirm individuals, so some individuals would benefit from consuming fish or supplements of EPA and DHA.
Consuming soft drinks (sugar-sweetened, carbonated beverages) puts a large burden of glucose on the pancreas relative to other foods and beverages. The pancreas produces insulin to maintain a normal blood sugar level. A new study in Singapore of 60,524 Chinese men and women examined whether these drinks could be associated with an increased risk of pancreatic cancer. (Diet soft drinks, with their own health risks, are not commonly consumed in Singapore).
Participants were followed for 14 years. Researchers found that those consuming two or more such soft drinks per week had nearly double the risk of pancreatic cancer compared to those who did not drink them. Consuming fruit juice was not similarly associated with the same risks. Even though these drinks have a fairly high sugar content, it is not as high as the sodas, and they also have other nutrients that may mitigate the effects. (Mueller NT, Soft drink and juice consumption and risk of pancreatic cancer: the Singapore Chinese Health Study. Cancer Epidemiol Biomarkers Prev. 2010 Feb;19(2):447-55.)
Aside from the cancer risks of soft drinks, sugar consumption is associated with other health problems (in addition to the common ones of hypoglycemia and intestinal yeast overgrowth). One large source of dietary sugar is the amount consumed in processed and prepared foods (people may not realize the large amount of sugar that is present in things like commercial salad dressing, muffins, or ketchup). A new study has evaluated the relationship between these “hidden” sugars and blood lipids that are heart disease risk factors.
Researchers evaluated 6113 US adults over a period of seven years. They were divided into four groups: low hidden sugar consumption (less than five percent of calories), 5-17.5 percent, 17.5-25 percent, and over 25 percent of calories. (Welsh JA, et al., Caloric sweetener consumption and dyslipidemia among US adults. JAMA. 2010 Apr 21;303(15):1490-7.) The overall average hidden sugar consumption (which is in addition to sugars that people add themselves, such as in coffee or on cereals) was 16 percent of calories.
For each group, they measured the average blood levels of HDL-cholesterol, triglyceride, and LDL-cholesterol. The highest sugar consumption had an HDL of 47.7, compared to the lowest group with an HDL of 58.7 mg/dL. Triglyceride levels ranged from a low of 102 to a high of 114 mg/dL. In women only, LDL levels were higher in the high sugar consumption group. These are all risk factors for atherosclerotic diseases of the heart, brain, and legs.
The average American now consumes a total of about 21 teaspoons of sugar daily, equal to about 360 calories. Much of this is found in soft drinks, but also in cereals, jams and jellies, candy, ice cream, baked goods, and more. It makes it even more important to avoid processed foods and to read labels carefully to avoid health problems.
A patient asked me to relay my comments when she said she only went to the fast food restaurants to please the grandchildren. I said I could understand why she would not want to poison herself with this junk, but did not understand why she felt it was OK to feed it to the little ones. When she said they were very “picky eaters” I noted that if they are offered only healthy foods they will eventually choose to eat them rather than starve themselves. She just needs to put up with their complaints in the meantime. (Imagine a Chinese child whining “I don’t like vegetables!”)
I have often reviewed scientific articles reporting the benefits of soy foods in disease prevention. The overwhelming weight of the evidence shows that soy is a healthy food (if not heavily processed, as it is in making texturized vegetable protein or fake meats). It is valuable in prevention and treatment of breast and prostate cancer, and in January I wrote about reduction of lung cancer with high consumption of soy, and it reduces uterine fibroid risk. It is a good food, but it is not essential in the diet.
Still, rumors persist about the so-called dangers of soy foods. Critics usually say that Asians (whose low rates of certain diseases are partly related to soy) do not consume as much soy as we think, or that they mainly consume fermented soy. In the article I cited in January, the low-consumption group ate about one ounce of soy per day, while the high consumption group ate over 5 ounces per day on average. These include tofu and soymilk, which are not fermented (of course, tempeh is also healthful, and it is fermented). I have been to Japan many times, and I know they consume a lot of soy foods.
It has no adverse effects on thyroid or other hormones (although it might in mice). Most of the criticism I have seen misrepresents the vast clinical data on soy. The critics are almost always promoting the consumption of meat, milk, butter, cheese, and related foods, with their known hazards (you just have to look at the data!), which leads me to wonder if they are surreptitiously promoting those industries and perhaps get their funding from them. (I have no financial interest in any of these industries, including soy.)
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