A growing body of evidence implicates degenerative changes in the mitochondria of our cells as a major cause of aging. Mitochondria are organelles - specialized parts of our cells that function in a manner similar to the way in which organs serve our bodies. Mitochondria are the powerhouses of the cell. They generate stored forms of energy from the nutrients we consume. When we consume too much food, containing energy beyond our needs, free radicals and other compounds promoting oxidation may form in the mitochondria. This represents one theory as to why calorie (dietary) restriction diets increase longevity in almost all species of animals studied.
An important antioxidant enzyme is mitochondrial superoxide dismutase. Some experimental data suggest that having higher activity levels of this enzyme may help protect against chronic disease processes such as diabetic retinopathy and Alzheimer's disease. Mitochondrial superoxide dismutase requires the mineral manganese as a cofactor, so this enzyme is usually abbreviated MnSOD. If a person is deficient in manganese, there will be less superoxide dismutase activity in the mitochondria. The best dietary sources of manganese include whole grains, legumes, nuts, and tea. Leafy vegetables and fruit contain moderate amounts. It is difficult to determine whether a person is mildly deficient, however, because most of the manganese in the body is concentrated in organs, such as the liver, kidneys, and pancreas. It would require a biopsy to determine the manganese content of these organs. There is some manganese in the blood, although the concentration there does not necessarily reflect its concentration in the organs. For minerals like this, checking the activity of enzymes that require manganese is sometimes the best way to determine adequacy or deficiency.
A study has been reported in the British Journal of Nutrition (2008) that examines just this issue. It is titled, "Epigenetic Regulation of Human Buccal Mucosa Mitochondrial Superoxide Dismutase Gene Expression by Diet." Forty young adult vegetarians were compared with a group of nonvegetarians, and some elderly people were studied as well. The important finding was that the vegetarian group had "a 3-fold increase in the expression of the MnSOD gene" as compared with the nonvegetarian group. Although we cannot be certain of the reason, the most likely explanation is the better manganese status of the vegetarians because of the foods they consume. The superior manganese status of vegetarians has been documented in the past. This may explain some of the health benefits associated with a plant-based diet.
It is important to note, though, that simply following a vegetarian diet is not enough to insure adequate manganese intake. It must be a healthful diet, rich in the whole plant foods mentioned previously. For example, whole wheat flour contains over five times as much manganese as refined flour. Consuming a good variety of unrefined plant foods and avoiding the high fat/salt/sugar "immediate gratification" trap represent the keystones of the ideal diet.
Many doctors recommend calcium supplementation in the range of 1,000 to 1,500 mg a day to women who are developing or who are at risk for osteoporosis. Because calcium supplementation has been shown to have a favorable effect on blood lipids (fats), raising the ratio of HDL (good) cholesterol to LDL (bad) cholesterol in postmenopausal women, some have speculated that this may lower their risk of heart disease and stroke.
A randomized, controlled clinical trial in New Zealand examined this possibility (Bolland MJ, Barber PA, Doughty RN, et al. Vascular events in healthy older women receiving calcium supplementation: randomized controlled trial. BMJ 2008; Online First). The women in the experimental group took 1,000 mg of calcium citrate a day: 400 mg in the morning and 600 mg in the evening. Surprisingly, these researchers from the University of Auckland found a significantly increased risk of heart attack and stroke in the group receiving the calcium. The fact that calcium often forms part of atherosclerotic plaques (hardening of the arteries) suggests a possible mechanism for the observed result.
This illustrates a number of important points:
Following a report from The Women's Healthy [sic] Eating and Living (WHEL) Study, 1 news articles bearing blaring headlines declared that fruits and vegetables do not help women with breast cancer and that there was no need for such women to increase their consumption of such foods. It is obvious to scientifically-minded individuals that conclusions of this nature can hardly ever be drawn from the results of a single study, but it is not at all obvious to the general public. Such irresponsible journalism feeds the mindset that nutritional scientists are always flip-flopping on their recommendations and that their advice is best ignored. Scientists from all disciplines lament the increasingly poor scientific knowledge of news reporters and science writers, who often seem to be more interested in sensationalism than in getting the story right - even if their misstatements hurt people. No, the medical writers generally don't pore the scientific literature to find studies of interest. They are fed stories from the public relations departments of academic institutions. Once upon a time, there were ethical scientists who published their findings and allowed them to be subjected to the scrutiny of others. Now, they have public relations people to promote themselves and inflate the significance of their results. So much for reputation.
The WHEL study was a controlled trial in which one (intervention) group of women with breast cancer were to consume at least 5 vegetable servings, 3 fruit servings, and 1 pint of vegetable juice each day, all in the context of a moderately low-fat diet (15-20% of calories from fat). They received phone calls from "dietary counselors," and attended a few cooking classes, mainly in the first year of the study. A control group was asked to consume at least five servings of fruits and vegetables a day. Here's the rub, though. At baseline (before the study began), the women in both groups were consuming, on average, more than 7 servings of fruit and vegetables a day. Consider that the average American consumes about 1 serving of vegetables a day, which includes potatoes, such as French fries (the WHEL study excluded white potatoes)! Therefore, if the study participants were already consuming a diet so rich in fruits and vegetables, how much of an effect could one expect to see by increasing fruit and vegetable consumption by such a small amount?
In any study such as this, compliance is a major problem. Poor dietary habits are difficult to change when they're so much a part of our culture. Compliance was measured by phone calls in which the women were asked about their eating habits. Now if they've been told they're supposed to follow such and such a diet, what do you think they're going to say? Of course, many are going to lie and say they ate more fruits and vegetables than they did and that they consumed a lower fat and lower calorie diet than they did because they know what was expected of them and they're ashamed to admit the truth. It is well established that overweight people especially tend to underestimate the amount of food they actually eat. Therefore, the results of such telephone interviews cannot be trusted. The intervention and control groups gained similar amounts of weight during the study.
To overcome the aforementioned problem, the researchers in this study measured the concentrations in the blood plasma of a number of carotenoids - pigments present in most fruits and vegetables. These included beta-carotene, alpha-carotene, lutein and zeaxanthin, lycopene, and beta-cryptoxanthin. In a prior publication from this study, the researchers reported no significant changes in the laboratory results from the control group, but the intervention group showed a 223% increase in plasma alpha-carotene and an 87% increase in beta-carotene but only a 29% increase in lutein, a 17% increase in lycopene, and no significant change in beta-cryptoxanthin. The authors of this study claimed that these results provided objective evidence of the compliance of the women in the intervention group. But do they really? The main dietary sources of alpha-carotene are carrots, pumpkins, and, to a minor degree, winter squash. Since most people eat little pumpkin and squash, it's reasonable to assume that carrot consumption caused the large increase in plasma alpha-carotene. Because carrots are also rich in beta-carotene, they could be largely responsible for the 87% increase there. Considering that it is much easier to comply with drinking a pint of vegetable juice each day than it is to change one's whole dietary lifestyle, I would strongly suggest that the higher carotenoid concentrations seen in the intervention group were largely the result of consuming carrot-rich juice each day. Thus, I do not feel that the carotenoid data establishes the compliance of the intervention group.
Comments of some of the co-authors of this study also bear mentioning. One of the lead authors was quoted as saying that the women were placed on a "tough diet." Tough? What is so tough about following a diet moderately low in fat and rich in fruits and vegetables? The comment betrays the mindset of so many in the nutrition field. They're so entrenched in our culture of "If it feels good, eat it" that they're loath to recommend truly healthful, low-fat diets because of their own prejudice that such diets are not very palatable. How can we expect the population-at-large to adopt healthful eating habits if they're given the perception that such diets are "tough?" In reality, the intervention group should have been placed on a much more restricted diet, one not only rich in whole vegetables and fruits but also eliminating the animal products and the bulk of the saturated fat. They may actually have found it easier to comply with such a diet. It's much easier to backslide from a half-hearted dietary regimen than it is from one in which some foods are permitted while others are totally off-limits.
Another of the lead authors, a dietitian, was quoted in a press release (naturally) as claiming that this study showed how successful telephone counseling is in bringing about large differences in dietary lifestyle. I don't think so. The only thing this study should teach us is that we should be wary of anything we read in the news media.
There is a growing body of evidence that healthful plant-based diets, low in fat (especially saturated fat, derived mainly from animal products), can improve the quality of life and survival of women with breast cancer. Telephone calls by "trained counselors" are not enough to overcome the resistance to "regimen change" in our society. We need a system where physicians, aided by dietitians, can work with patients and provide the continuing support they need.
1Pierce JP, Natarajan L, Caan BJ, et al. Influence of a diet very high in vegetables, fruit, and fiber and low in fat on prognosis following treatment for breast cancer. JAMA 2007;298:289-298.
Looking at 17th century Dutch paintings, with the succulent table spreads and the plump visages of Jan Steen and his contemporaries, one might expect to get in Dutch with one's doctor if one followed a Dutch diet. But a study 1 just published in The American Journal of Clinical Nutrition indicates that "it ain't necessarily so." Over 5,400 women in their sixties were studied, and the relationship between their dietary patterns and their longevity was determined. These dietary patterns included a Traditional Dutch dietary pattern (high consumption of meat, potatoes, other vegetables, and alcoholic beverages); a Mediterranean-like pattern (high consumption of vegetables, grains, sauces, fish, and wine); and what the authors call a Healthy Traditional Dutch pattern (high consumption of vegetables, fruits, nonalcoholic beverages, and dairy products in general but low in butter and in alcoholic beverages). They found a 30% reduction in mortality risk (chance of dying) for those women following the Healthy Traditional Dutch diet as compared with those following either the Traditional Dutch or Mediterranean style diets.
Let us now put these results into context by comparing the Healthy Traditional Dutch diet with two other relatively healthful dietary patterns, the Mediterranean diet and the traditional Japanese diet. The Mediterranean diet is rich in vegetables, grains, olive oil, and red wine, with modest amounts of dairy and other animal products, whereas the Japanese diet is rich in vegetables and grains but low in fat and in all animal products. The Mediterranean diet receives the most publicity even though the Japanese are the longest-lived people in the world, most likely because the higher fat Mediterranean diet comes closer to the taste preferences of people used to the standard Western diet. But what components of the Mediterranean diet contribute to its reputed benefits? Is it the olive oil and the red wine as we are often led to believe? There is a certain plausibility to this claim, because both olive oil and red wine contain phytochemicals, the beneficial chemical compounds found throughout the plant kingdom. However, the common denominator of all of these diets is the high consumption of plant foods, in particular, vegetables.
Two other recent articles in this journal underscore the important of vegetable and fruit consumption. One Italian study,2 a meta-analysis of the results of sixteen previously performed studies, showed a very sharp reduction in the risk of oral cancer associated with both fruit and vegetable consumption. The other study3 showed a lower risk of non-Hodgkin's lymphoma, one of our major causes of death due to cancer, with higher consumption of vegetables, especially the dark leafy greens like kale, spinach, collards, chard, and mustard and turnip greens, which are rich in the carotenoid lutein.
The moral of the story, then, is that eating multiple servings of vegetables and fruit a day keeps the doctor away, the benefit from which should not be underestimated.
1Waijers PMCM, OckŽ MC, van Rossum CTM, et al. Dietary patterns and survival in older Dutch women. Am J Clin Nutr 2006;83:1170-1176.
2Pavia M, Pileggi C, Nobile CGA, Angelillo IF. Association between fruit and vegetable consumption and oral cancer: a meta-analysis of observational studies. Am J Clin Nutr 2006;83:1126-1134.
3Kelemen LE, Cerhan JR, Lim U, et al. Vegetables, fruit, and antioxidant-related nutrients and risk of non-Hodgkin lymphoma: a National Cancer Institute-Surveillance, Epidemiology, and End Results population-based case-control study. Am J Clin Nutr 2006;83:1401-1410.
Inflammation in the body is now believed to play a causative role in a number of chronic diseases, not just in obviously inflammatory conditions such as rheumatoid arthritis. It is now well established that inflammation serves as a risk factor for heart disease, stroke, and other blood vessel disease in the body. It may be related to adult-onset diabetes, and a growing body of evidence links inflammation with Alzheimer's disease and with the "wet" form of age-related macular degeneration, the main cause of poor vision among the elderly. Obesity carries with it an inflammatory tendency, but it hasn't always been clear to what degree it is the obesity itself rather than the overeating associated with the obesity that leads to the problem. As mentioned on the Dietary Restriction page, people who consume a low-calorie diet tend to have very low concentrations of biochemical markers of inflammation, such as C-reactive protein (CRP), in their blood. Theoretically, plant foods in and of themselves should be helpful. Fruit and vegetables are rich in phytochemicals with anti-inflammatory properties. A plant-based diet is also low in arachidonic acid, a pro-inflammatory omega-6 fatty acid that comes mainly from animal products.
Recent studies have added to our knowledge regarding the connection between diet and inflammation. When people are instructed to follow a low-fat, high-carbohydrate diet but are made to maintain the same intake of calories as before, nothing much happens. But when they aren't required to take in a certain minimum amount of food, their calorie intake drops, and so do their markers of inflammation.1 This study provides support for the role of caloric intake in inflammation.
Another study showed that the more fiber people consume, the lower their levels of CRP in their blood. 2 As with other studies involving fiber, it isn't clear whether the fiber itself is beneficial or whether it is just a marker for a healthful, plant-based diet, which tends to be lower in calories than the average diet and which is rich in fruits and vegetables with their potentially beneficial properties.
Still another study just out linked higher plasma vitamin C concentrations with evidence of reduced inflammation in the body. 3 As with fiber, vitamin C may just be a marker here for a plant-based diet.
Finally, although a high glycemic load, that is, the tendency of the foods one eats to raise one's blood sugar, has been linked with higher levels of CRP by some, it is premature to recommend avoiding foods with a high glycemic index (tendency to raise one's blood sugar). Glycemic load may just be a marker for an unhealthful diet in general. Indeed, a recent clinical trial showed that when sugar (sucrose) consumption was increased by 151% in one group of patients and reduced by 42% in another group, there was no significant effect on CRP levels.4
In summary, the flurry of recent studies supports the concept that the best way to minimize any inflammatory tendency in the body is to consume a high-fiber, low-fat, plant-based diet, which generally results in a lower intake of calories than the standard Western diet.
1Kasim-Karakas SE, Tsodikov A, Singh U, Jialal I. Responses of inflammatory markers to a low-fat, high-carbohydrate diet: effects of energy intake. Am J Clin Nutr 2006:83:774-779.
2Ma Y, Griffith JA, Chasan-Taber L, et al. Association between dietary fiber and serum C-reactive protein. Am J Clin Nutr 2006;83:760-766.
3Wannamethee SG, Lowe GDO, Rumley A, Bruckdorfer KR, Whincup PH. Associations of vitamin C status, fruit and vegetable intakes, and markers of inflammation and hemostasis. Am J Clin Nutr 2006;83:567-574.
4Sorensen LB, Raben A, Stender S, Astrup A. Effect of sucrose on inflammatory markers in overweight humans. Am J Clin Nutr 2005;82:421-427.