My monthly Food Matters column in the San Francisco Chronicle answers readers’ questions and these tend to be about nutrition rather than food politics.   Today’s column is about diets aimed at controlling the amount of acid excreted in urine:

Low acid diet may not prevent bone loss

Q: I’ve just read “Building Bone Vitality: A Revolutionary Plan to Prevent Bone Loss and Reverse Osteoporosis,” by Amy Lanou and Michael Castleman.

The writers contend that a high acid diet causes bone loss and other negative health outcomes. The book is so well documented and the theory so logically explained that I find it compelling.

However, I am not a scientist and would appreciate your opinion.

A: Ordinarily I would not bother to read a book with the word “Revolutionary” in its title. In diet books, “revolutionary” invariably means using a grain of scientific truth to construct a dietary theory that contradicts current thinking but cannot be proven by current research.

But two readers asked about this book and I was curious about it for another reason. Last year, I gave a talk at a spa where I was seated at dinner next to a couple who announced that they were following a low-acid diet. To my amazement, they excused themselves during the meal to measure the pH of their urine.

Stay with me: pH is a measure of acidity or hydrogen ion concentration. pH 7 is neutral. Above 7 is basic or alkaline. Below 7 is acidic.

I could not believe that anyone would bother to measure urine pH, let alone leave dinner to do so. The pH of blood is tightly regulated and must stay within a slightly alkaline range of 7.36 to 7.4. Bicarbonate buffering systems keep it that way, and excreting excess acid is exactly what the kidney is supposed to do.

The authors are proponents of vegan diets. Here, they argue that small increases in blood acidity cause calcium to be leached from bones to help neutralize it. Over time, these small losses weaken bones and lead to osteoporosis.

Adding calcium to the diet, they claim, is not enough to replace the losses. They parse the results of 1,200 research studies to argue that dairy foods cannot protect against osteoporosis. Instead, low acidity – meaning too much meat – provides the best current explanation for worldwide rates of osteoporosis.

The authors provide an entertaining list of the acid-producing potential of more than 100 foods. As they put it, “flesh foods”- beef, chicken and fish – produce the most acid, with grains coming in second.

Dairy, oddly, is low-acid, except for cheeses. They produce the most. Four ounces of Parmesan, for example, yield 34 milliequivalents (mEq). Compare this to 4 ounces of trout (11 mEq), beef (8), cornflakes (6) or yogurt (1).

Acidity depends largely, but not exclusively, on protein content. All proteins form acid, but “flesh” proteins yield more. They contain more sulfurous amino acids than do plant proteins. Meat and grains also have more acid-forming phosphates.

In contrast, fruits and vegetables contain loads of alkali-producing potassium and magnesium. They have minus numbers: apples (-2 mEq), potatoes and cauliflower (-4), and avocados (-8), with the alkali prize going to raisins (-21).

To prove this theory, research must demonstrate four things: foods have differential effects on urine pH, acid-producing diets cause calcium to be excreted, calcium excretion reflects loss of calcium from bones, and acid-induced calcium losses lead to osteoporosis.

Research easily confirms that animal foods and grains produce more acid than do fruits and vegetables and cause calcium to be excreted in urine. Evidence for everything else, however, is much less certain. Although some studies find bone losses with high-acid diets, a recent “meta-analysis” published in the Journal of Bone Mineral Research concluded that urine calcium does not reflect bone calcium. It found little justification for the idea that alkaline foods prevent bone calcium losses.

Kidney specialists agree. I asked Dr. Jerome Lowenstein, author of “Acids and Basics: A Guide to Understanding Acid-Base Disorders,” for comment. He says bone calcium is involved in maintaining normal blood pH, but so are many other factors.

Normal kidneys maintain normal blood pH over a very wide range of diets. Diet may affect acid-base balance in people with damaged or diseased kidneys, but matters less to people with normal kidneys. Bone losses do occur in kidney disease but not because bone serves as an acid buffer.

“If it did, patients with advanced kidney disease would become invertebrate within a couple of years,” he says.

How to make sense of this? To prevent osteoporosis, the authors promote a vegan diet based on low-acid fruits, vegetables and beans, with no or minimal acid-producing meat, poultry, fish, eggs, cheese and grains.

Revolutionary? Hardly.

Last month’s report from the 2010 Dietary Guidelines Advisory Committee called for a shift in food intake patterns to a more plant-based diet, one with more vegetables, beans, fruits, whole grains, nuts, seeds, seafood and low-fat milk products, and only moderate amounts of lean meats, poultry and eggs.

Eat healthfully, and you automatically eat low-acid.

So: eat vegetables with your meat, forget about pH testing, and enjoy your dinner.

By analogy with cigarettes, taxes on sodas might discourage people—especially young people—from consuming sugary drinks.  This might help with weight issues.

According to a new analysis by USDA economists,

A tax-induced 20-percent price increase on caloric sweetened beverages could cause an average reduction of 37 calories per day, or 3.8 pounds of body weight over a year, for adults and an average of 43 calories per day, or 4.5 pounds over a year, for children. Given these reductions in calorie consumption, results show an estimated decline in adult overweight prevalence (66.9 to 62.4 percent) and obesity prevalence (33.4 to 30.4 percent), as well as the child at-risk-for-overweight prevalence (32.3 to 27.0 percent) and the overweight prevalence (16.6 to 13.7 percent).

Soft drink companies know this all too well.  Hence, intense industry lobbying.  In the case of New York State, the lobbying succeeded.  Soda taxes are history (for now).

As the New York Times explains:

Final lobbyist filings are not yet in, but estimates of the amount spent…range from $2.5 million, by Mr. Finnegan’s count, to $5 million, by the beverage industry’s count. The American Beverage Association spent $9.4 million in the first four months of the year to oppose New York’s soda tax, according to a search of public lobbying records by the New York State Healthy Eating and Physical Activity Alliance. Most of the money was spent on advertising, media and strategy.

This is a setback, but probably temporary.  Sooner or later, soda taxes will come.  Bring on the research!

Addition, July 5: Harvard researchers have just published a paper in the American Journal of Public Health showing that raising the price of sodas in a hospital cafeteria does indeed discourage sales.

In preparation for eating over the 4th of July weekend, here’s what’s happening on the salt frontier.

The CDC says fewer than 10% of Americans meet sodium recommendations. Only 5.5% of adults who should be consuming low sodium diets(≤1,500 mg/day) actually do so.  Less than 20% of adults consume the amount currently recommended for healthy adults, ≤2,300 mg/day. Overall, only 9.6% of adults met their applicable recommended limit.

The British Food Standards Agency (FSA) says the U.K. is making great progress on reducing salt consumption. Even though UK salt intakes are still above the target of 6g/day after seven years of campaigning, FSA is happy about what the campaign achieved: a 10% reduction in average daily intakes from 9.5g/day to 8.6g/day.  This is substantial progress, given “the complexity of the task and the FSA’s modest budget.”

The New York Times explains part of the complexity: food industry resistance.  In an article titled, “The hard sell on salt” (May 29), the Times interviews food company executives who talk about why they must, must use salt and lots of it in processed foods.

The Salt Institute attacks the Dietary Guidelines Advisory Committee report. The report recommends a limit of 1,500 mg/day sodium because 70% of the U.S. population is at risk of high blood pressure. According to Food Chemical News (June 16), the Salt Institute claims that reducing salt intake to recommended levels would only make the obesity epidemic worse: “Most nutritionists agree that reduced sodium in food preparations will very likely increase the obesity crisis because individuals will consume more calories just to satisfy their innate sodium appetite.”

Most?  I don’t think so.  Because 77% of salt (sodium chloride) is in processed and restaurant foods, I see the salt issue as one of consumer choice.  Consumers can always add salt to foods.  They cannot take it out.

Enjoy a happy, healthy, safe, and lower salt 4th of July!

I’ve just read an enlightening paper in the July issue of the American Journal of Public Health (see Note below) about the tobacco industry’s role in and funding of “We Card,” a program ostensibly aimed at discouraging smoking among young people by encouraging retail cigarette sellers to “card” underage buyers.

The paper is an analysis of internal food company discussions about this program in cigarette company documents released as part of the 1998 Master Settlement Agreement.  These documents are now publicly available on the University of  California San Francisco (UCSF) website.

This analysis demonstrates that the actual purpose of tobacco industry support for the program was to make the industry look good (public relations) and to convince legislators and health officials that regulation would be unnecessary.

The industry effectively recruited astonishing numbers of private business, retail, and trade groups (expected) and state health, legal, and police agencies (which should have known better) as partners in this program.  The paper lists these groups in tables that take up nearly five pages.

As the paper explains:

Economic theory predicts that industry self-regulation will achieve social benefits far smaller than those gained from government regulation, although governments increasingly view self-regulation as a means to achieve public goals without public spending. However, industries and governments may have competing agendas, suggesting that public health advocates should be wary of self-regulation strategies…. This program’s success in reaching tobacco retailers and attracting independent allies has made We Card one of the tobacco industry’s major public relations achievements. However, despite industry claims that the program is effective, internal industry evidence suggests that We Card has not reduced tobacco sales to minors and that it was not designed to do so. Instead, We Card was explicitly structured to improve the industry’s public image and to thwart regulation and law enforcement activity.

The authors’ conclusion: “Policymakers should be cautious about accepting industry self-regulation at face value, both because it redounds to the industry’s benefit and because it is ineffective.”

Proponents of food industry self-regulation and of partnerships and alliances with food companies should read this study carefully.

Note: Only the Abstract is available to non-subscribers.  The reference is Apollonio DE, Malone RE, The “We Card” Program: Tobacco Industry “Youth Smoking Prevention” as Industry Self Preservation.. Am J Public Health 2010;100:1188-1201.

The National Academies have just released Toward Sustainable Agricultural Systems in the 21st Century. You can read it online, one page at a time.  Otherwise, you have to come up with the $76.50 it costs in print (electronic versions are somewhat cheaper).

Sustainability, it says, has four goals:

• Satisfy human food, feed, and fiber needs, and contribute to biofuel needs.
• Enhance environmental quality and the resource base.
• Sustain the economic viability of agriculture.
• Enhance the quality of life for farmers, farm workers, and society as a whole.

To get there, the report proposes “two parallel and overlapping efforts:”

The incremental approach would be directed toward improving the sustainable performance of all farms, irrespective of size or farming system type….

The transformative approach would apply a systems perspective to agricultural research to identify and understand the significance of the linkages between farming components and how their interconnectedness and interactions with the environment make systems robust and resilient over time.

The report’s main conclusion:

If U.S. agricultural production is to meet the challenge of maintaining long-term adequacy of food, fiber, feed, and biofuels under scarce or declining resources and under challenges posed by climate change…agricultural production will have to substantially accelerate progress toward the four sustainability goals.

Take that, industrial agriculture!

With the politics out of the way (see yesterday’s post), let’s talk about what’s superb in the Dietary Guidelines Advisory Committee Report: the scientific review and analysis.

This was based on reviews produced by the Nutrition Evidence Library (NEL), which apparently recruited dozens of people to identify articles, assess their quality by uniform criteria, and rank the overall evidence as limited, moderate, or strong and consistent or inconsistent.

I particularly like the way the report organizes the research review by questions (of which there are 56, if I counted right).  The questions cover a great range of topics.  Examples:

• What nutrients and dietary components are overconsumed by the general public?
• Can a daily multivitamin/mineral supplement prevent chronic disease?
• What is the role of prebiotics and probiotics in health?
• What are health effects related to consumption of nuts?
• What are the health effects related to consumption of chocolate?
• How do the health outcomes of a vegetarian diet compare to those of a diet which customarily includes animal products?
• How are non-caloric sweeteners related to energy intake and body weight?
• What amount of water is recommended for health?

Questions are followed immediately by Conclusions, Implications, and Review of the Evidence. All of this is written with great clarity, accompanied by thoughtful comments, and packed with useful information.

Here is just one example (I’ve emphasized the evaluative words):

What is the Relationship between Vegetable Protein and/or Soy Protein and Selected Health Outcomes? Few studies are available, and the limited body of evidence suggests that vegetable protein does not offer special protection against type 2 diabetes, coronary heart disease, and selected cancers. Moderate evidence from both cohort and cross-sectional studies show that intake of  vegetable protein is generally linked to lower blood pressure. Moderate evidence suggests soy protein may have small effects on total and low density lipoprotein cholesterol in adults with normal or elevated blood lipids, although results from systematic reviews are inconsistent. A moderate body of consistent evidence finds no unique benefit of soy protein on body weight. A limited and inconsistent body of evidence shows that soy protein does not provide any unique benefits in blood pressure control.

Readers may disagree with the committee’s research interpretations, but its conclusions deserve serious consideration.

And, if anyone wants to know the state of the available science on any of a large number of questions in nutrition, this report is the place to look first.

Student alert: I will be using this report in classes.

I’ve heard rumors that some members of the Dietary Guidelines Advisory Committee (DGAC) believe that commentators did not give a fair shake to their recently released report (see previous post).

I complained that the DGAC report is difficult to read because its pieces are presented online in a great many individual pdf files that must be downloaded separately.  Fortunately, Cornell student Daniel Green created a single Web-based file.

I have now read the report, or at least browsed through its 699 pages, and I agree that it is better than it first appeared and deserves a revisit (which I am doing in two parts, the second tomorrow).

As with previous Dietary Guidelines, both politics and science underlie this report.  The science components of this report are stunning—as good as such things get—and make this document an invaluable resource.

Why did everyone, including me, miss this?  Politics, of course.  The politics appear unchanged from previous versions (for that, see Food Politics).

The science in this report gives clear guidance for action.  But the report obfuscates its most important messages.

The Executive Summary makes the advice seem dull. The Summary is the part everyone reads first and often the only part anyone reads.  Try this:

The 2010 DGAC report concludes that good health and optimal functionality across the life span are achievable goals but require a lifestyle approach including a total diet that is energy balanced and nutrient dense…SoFAS (added sugars and solid fats) contribute approximately 35 percent of calories to the American diet….Reducing the intake of SoFAS can lead to a badly needed reduction in energy intake and inclusion of more healthful foods into the total diet.

Obesity, it says, is a big problem.  The food environment is a big problem.  What to do about them?  SoFAS.

The report introduces a new euphemism, SoFAS (Solid Fats and Added Sugars).  The meaning of added sugars is obvious.  But what are solid fats?  For that, you must wait until page 183 (on the Daniel Green file):

Solid fats are fats that are solid at room temperature. Solid fats come from many animal foods and can be made from vegetable oils through hydrogenation. Some common solid fats are butter, beef tallow (tallow, suet), chicken fat, pork fat (lard), stick margarine, and shortening. Foods high in solid fats include many cheeses, creams, ice cream, well-marbled cuts of meats, regular ground beef, bacon, sausages, poultry skin, and many baked goods (such as cookies, crackers, donuts, pastries, and croissants).

Earlier (p. 24), the report listed the principal food sources of SoFAS:

Solid fats (percent of solid fat intake)

• Grain-based desserts, including cakes, cookies, pies, doughnuts, and granola bars (10.9%)
• Regular cheese (7.7%)
• Sausage, franks, bacon, and ribs (7.1%)
• Pizza (5.9%)
• Fried white potatoes, including French fries and hash browns (5.5%)
• Dairy-based desserts, such as ice cream (5.1%)

Added sugars (percent of added sugars intake)

• Soda (36.6%)
• Grain-based desserts (11.7%)
• Fruit drinks (11.5%)
• Dairy-based desserts (6.4%)
• Candy (6.2%)

The report does not say to eat less of these foods; it talks about nutrients.  In various places in the report, the report says [with my comments in brackets]:

• Significantly reduce intake of foods containing added sugars and solid fats because these dietary components contribute excess calories and few, if any, nutrients. In addition, reduce sodium intake and lower intake of refined grains, especially refined grains that are coupled with added sugar, solid fat, and sodium. [Nutrients, not foods].
• Eat less of these: calories from SoFAS, added sugars, solid fats, refined grains, sodium, saturated fat. [Ditto]
• Significantly lower excessive calorie intake from added sugars, solid fats, and some refined grain products. [Ditto]
• Strategies to prevent childhood obesity should include efforts to reduce surplus energy intake, especially energy from foods and beverages that provide empty calories from added sugars and solid fats. [Ditto]
• Intake of caloric beverages, including SSB [sugar-sweetened beverages], sweetened coffee and tea, energy drinks, and other drinks high in calories and low in nutrients should be reduced in consumers needing to lower body weight.  [Only overweight people need to worry about these foods?]

Only once does the report say the clear and simple: “Avoid sugar-sweetened beverages” (p. 65).  Nowhere does it explicitly say to eat less steak, hamburger, French fries, pizza, cookies, or ice cream.

Like previous editions of the Dietary Guidelines, this one talks about foods in the context of eat more (fruits and vegetables).  For eat less advice, it switches to nutrients.  I’d call this obfuscation (and politics).

But the report—for the first time—emphasizes environmental influences on obesity:

The 2010 DGAC recognizes that the current food environment does not adequately facilitate the ability of Americans to follow the evidence-based recommendations outlined in the 2010 DGAC Report. Population growth, availability of fresh water, arable land constraints, climate change, current policies, and business practices are among some of the major challenges that need to be addressed in order to ensure that these recommendations can be implemented nationally.

What business practices?  It doesn’t say.  It does, however, recommend:

• Improve foods sold and served in schools, including school breakfast, lunch, and afterschool meals and competitive foods so that they meet the recommendations of the IOM report on school meals….
• Increase comprehensive health, nutrition, and physical education programs and curricula in US schools and preschools, including food preparation, food safety, cooking, and physical education classes and improved quality of recess….
• Remove sugar-sweetened beverages and high-calorie snacks from schools, recreation facilities, and other places where children gather.
• Develop and enforce responsible zoning policies for the location of fast food restaurants near schools and places where children play….

This is excellent advice.  But how about some suggestions about what individuals might do about it?

The report says little about food marketing.  Beyond “Develop and enforce effective policies regarding marketing of food and beverage products to children…,” the report says virtually nothing about the well documented impact of food marketing on children’s food choices, dietary intake, and health.  Unless I missed it someplace, the research review does not cite the Institute of Medicine’s 2006 landmark report, Food Marketing to Children and Youth: Threat or Opportunity.

It buries the need for policy changes in long wordy lists.  It states the needs for low-income Americans to have access to and afford healthier foods; to produce fruits, vegetables, and grains sustainably; to ensure household food security; to promote sustainable aquaculture; and to encourage the food service industry to serve healthier foods and smaller portions.  It does not—and perhaps cannot—recommend policy changes to achieve these important goals.

Overall, the report contains plenty of material for food, nutrition, and health advocates to work with, but you have to read between the lines to find it.

Recall the process.  This committee’s report is advisory. From 1980 through 2000,  dietary guidelines advisory committees actually wrote the final Dietary Guidelines.   No more.  Since 2005, the sponsoring agencies decide what the Dietary Guidelines will say.

The report is open for public comment until July 8.  If you think the Dietary Guidelines should provide clear, unambiguous advice about how people should eat to avoid obesity and how we can create a healthier food environment, now would be a good time to express your opinion.  Here’s how.

Tomorrow: The reason why this report is an invaluable resource—its science review.

Bill Marler, the Seattle attorney whose firm represents victims of foodborne illness, has seen the best and worst of company behavior when faced with pressures to “voluntarily” recall tainted products.  Here is his guide to good corporate behavior under difficult circumstances.  It begins with “don’t produce tainted products in the first place.”   But, alas, if you do:

First, have a pre-existing relationship with the folks that regulate you. If someone holds your business in the palm of his or her hand, you should at least be on a first name basis. No, I am not suggesting that you can influence your way out of the outbreak, but knowing who is telling you that your company has a problem allows you the ability to get and understand the facts. Do regulators and their investigators make mistakes? Perhaps, but not very often and not often enough to waste time arguing that your company did not poison customers.

Second, stop production of the implicated product and initiate a recall of all products at risk immediately. This procedure should have been practiced, and practiced, and practiced before. All possibly implicated suppliers should be alerted and all retailers should be offered assistance. Consumers need to be engaged too. The goal now is to get poisoned product out of the marketplace and certainly out of the homes of consumers.

Third, launch your own investigation with two approaches, and at the same time. Are the regulators correct? And, what went wrong? Tell everyone to save all documents (you have to anyway). The goal here is to get things right. If it really is not your product, what has happened is bad, but survivable. If it really was your product, then learning what happened helps make sure it is likely to never happen again. More than anything, be transparent. Tell everyone what you find–good or bad.

Fourth, assuming that the outbreak is in fact your fault, publicly admit it. If it is not your fault, then fight it. However, pretending that you are innocent when you are actually at fault will get you nowhere. Asking for forgiveness is not a bad thing when you have something to be forgiven for. Saying you are sorry is not wrong when you are in fact wrong.

Fifth, do not blame your customers. If your food has a pathogen it is not your customers’ responsibility to handle it like it will likely kill them or a member of their family. Hoping that the consumer will fix your mistake takes your eye off of avoiding the mistake in the first place.

Sixth, reach out to your customers and consumers who have been harmed. Offering to pay legitimate losses will save money and your company’s reputation in the long run.

Seventh, teach all what you have learned. Do not hide what you have learned. Make your knowledge freely available so we all limit the risk that something similar will happen again.

In other words, do the right thing.  Excellent advice.

But Mr. Marler cites no examples.  I wonder if there are companies that actually did all this?  It would be good to know who they are.