Macronutrients that provide calories—carbs, proteins, and fats—are only a slice of the nutritional pie. I have not mentioned non-caloric nutrients at all yet. Vitamins, minerals, and other micronutrients—such as antioxidants and sterols—while having little effect on calories, have an enormous effect on health and longevity.

Vitamins, according to the article “Nutrition: vitamins on trial” by Melinda Moyer in Nature, were named so by biochemist Casimir Funk because he discovered that certain ones, such as thiamine (vitamin B1) and vitamin C, were “vital” for life. That the chemicals we know as vitamins are necessary components in the diet is certain; what is uncertain is how much we need and whether it is healthy to take supplements.

In some cases at least, only people who already have vitamin deficiencies benefit by taking supplements. Folic acid (vitamin B9) is important in preventing cancer and maintaining proper gene function throughout life. Moyer says that one study, in which folic acid supplements were given to patients with benign tumors in the colon, found that only patients who already ate folic acid-deficient diets reduced their risk of developing more tumors by taking the supplements. It appeared that vitamin supplements had no positive effect on tumor prevention in people who got all of the folic acid they needed from food.

Vitamin supplements, in fact, have been found to increase the risk of cancer in several groups of people who are already at risk. Moyer cites another study, this time of smokers, which found that supplementing beta-carotene, which is an antioxidant that humans convert into vitamin A, to three times the recommended daily value (RDA), increased risk of lung cancer by 18%. Another article in Nature, “Antioxidants speed cancer in mice,” by Heidi Ledford, found just that: giving mice that were predisposed to develop cancer supplements of vitamin E, which is both a vitamin and an antioxidant, at up to 50 times the RDA tripled their risk of developing cancer. These tests were not, however, performed in humans, so it is not clear that vitamin E would do the same to us, but vitamin E supplements aimed at humans can have up to 20 times the RDA.

Determining the RDA is itself a very imprecise process. Because of genetic differences between us, we all actually have different requirements for certain nutrients, according to Moyer. Studies that do not take these into account may report the average RDA, but not the RDA for a specific group of people, and may find that vitamin supplementation does not increase health in most people, when really there is a group of people who have a greater requirement for that vitamin that would benefit from supplementation. Averaging results can have dangerous consequences: for example, there is evidence that, on average, beta carotene supplements do decrease the risk of cancer, but they increase the risk in people who smoke and regularly drink.

What is really needed is a method for individuals to assess the effects of vitamin supplementation on themselves, if we want to know whether supplementation is worthwhile. Vitamin supplements are a multi-billion dollar industry, and it would be worth billions of dollars to develop such methods and determine if we are making wise purchases by buying vitamin supplements.

Google can tell us a lot about nutrition. It can tell us a lot that is correct and a lot that has no backing. But even if we can evaluate which sources are reliable, how do we find them in the first place?

I find two primary kinds of nutritional information for these blogs: clinical studies and nutrition facts. Most of the information that I trust comes from scientific journals—for clinical studies—or, for nutrition facts, from SELF Magazine’s Nutrition Data website, which takes its data from the USDA’s less user-friendly database and agrees with most Nutrition Facts labels I read.

While finding nutrition facts for common foods using Nutrition Data is easy, finding reliable information about the effects of nutrients on health is more challenging. My first search engine is usually Google Scholar, which automatically links to journal and newspaper articles and books and therefore provides a good starting place to find the most reliable information. Before I type my query, I consider what keywords will likely be in every article relevant to my topic. I don’t want ten thousand search results; it’s impossible that all of them are chock full of relevant information.

If I wanted to find information on a broad topic, such as how our insulin levels change after we eat, I would not search Google Scholar for “insulin levels after eating,” because that search returns about 300,000 results. The search engine is supposed to do the searching; you should not have to wade through ten pages of hits, searching for the useful ones. That being said, I would first ask myself to identify subtopics that will yield fewer results, such as how insulin responds to whole wheat vs. refined wheat: “postprandial blood levels insulin whole wheat” returns 18,000 results, specifically about how insulin levels change after one eats whole wheat, so every hit has a better chance of being useful. Using a rarer word, but one that is likely to occur in relevant results (like “postprandial,” which simply means “after a meal”), returns fewer and more useful hits.

When my searches return too many hits, I do several things to lower the number: I add more words to be more specific, I use quotes, and I use the Boolean operators AND and -. Putting a phrase in quotes means that that exact phrase must appear in the article. If my aforementioned query returned results about whole grains, refined wheat, and whole wheat, I would change it to “postprandial blood levels insulin ‘whole wheat’” (where the single quotes inside the double quotes actually represent double quotes) to specify that the wheat must be whole grain (this got 3,300 results). If I kept getting results that had a certain word that I didn’t want, like if many studies on insulin levels were in overweight people, but I wanted results for lean people, I could change the query to “postprandial blood levels insulin ‘whole wheat’ -overweight -obese” (587 results), and there, on the first page, is an article titled “Plasma glucose, insulin and lipid responses to high-carbohydrate low-fat diets in normal humans,” which provides some relevant information.

Additionally, I use OR in order to simultaneously use specific terminology but allow articles to contain any one of several specific terms. For instance, “blood” and “serum” both are used when describing the levels of insulin, so I could modify my query to “(postprandial OR ‘after eating’ OR ‘after the meal’) blood levels insulin ‘whole wheat’ -overweight -obese” (800 results), which brings up another article, “Plausible mechanisms for the protectiveness of whole grains,” that is relevant.

If Google Scholar does not find relevant information, there are other sources of scholarly work. Search sites like the NIH’s National Library of Medicine, which encompasses many databases, including the National Center for Biotechnology Information (NCBI), which in turn searches many databases, such as PubMed. In my experience, though, PubMed is limited in the number of nutrition-related articles of the kind I look up, so I prefer NCBI’s entire database search. Additionally, Web of Science and CAB Abstracts provide many articles, some of which are also found on Google Scholar. Students and faculty at Penn State can get articles that would normally cost money for free through Penn State Libraries. This site provides links to databases that are relevant to pretty much any major you can imagine on its research guides page.

There are abundant scholarly resources online to provide information on nutrition that is more reliable than most of the blather. Still, non-scholarly sites and Wikipedia are good places to start if you don’t know where to begin—I do start some searches on these types of sites, not by reading the information on the sites themselves, but by looking at their references and exploring the ones that seem promising.

Given the resources of the Internet, what can you learn about nutrition that I haven’t mentioned?

I have covered in my last five posts the five main macronutrients—fats, proteins, sugars, starches, and fiber—but I have only barely scratched the surface of the complexities behind how these nutrients affect our health. I have only barely discussed insulin-like growth factors (IGFs), for example, which are proteins that promote tissue growth (meaning they can either help you build muscle or tell tumor cells to “grow, grow, grow!”), but their levels increase after you eat sugars and complete proteins, so the health effects of these two macronutrients are inextricably related to the effects of IGFs. Since I can describe only a sliver of what is known, this week, I will discuss guidelines for finding information for yourself—how to search and how to judge your sources’ credibility.

Does your source provide references that lead back to actual scientific data? Knowledge ultimately comes from experiments on chemicals and studies on people. Even I am extremely tempted to read Google search results like (and these are real examples) “Food Manufacturers are Replacing Trans Fat with this Dangerous Alternative” (from InsidersHealth) and “5 Foods You Should Never Eat Again,” (from MyDiet), but neither of these sources lists references, while both of them have advertisements (InsidersHealth even advertises a weight-loss supplement in the text), which indicates that the source is trying to persuade you of something, that is biased, or that it is scientifically unfounded.

Articles published in reputable journals like Science, Nature, The American Journal of Clinical Nutrition, and other high-profile, peer-reviewed journals are generally trustworthy, unless they are about highly disputed topics like the lipid hypothesis (compare these contemporary articles from BC Medical Journal and Scandinavian Cardiovascular Journal).

Newspapers like the New York Times and other websites like ScienceDaily that cite reputable articles are also generally trustworthy. Two notes about Wikipedia: 1) Different sentences within a Wikipedia article may have differing degrees of credibility depending on their sources. 2) For controversial topics in nutrition, Wikipedia may present only one side of the issue, so you should always see if there is research that conflicts it.

Keep in mind that even sites that cite may cite only articles that support their points, so it is especially important that you look into controversial topics further. Opinions of doctors or other qualified people may be accurate, but because they are written by humans, they may just as likely be biased towards one side of the issue.

If you see a piece of information that seems wrong on a website, be wary. For example, I found on Livestrong.com this page describing food sources of ATP. However, according to David Nicholls and S. J. Ferguson in Bioenergetics 4 (published 2013), chapter 9, page 33, the equilibrium between ATP and ADP in water strongly favors ADP, so in dead cells that you would find in food, virtually all of the ATP would have degraded into ADP before you would eat it.

And my last, most important guideline for evaluating sources is thus: only trust nutrition blogs that cite their sources.

Fibers, though they do not give us energy, are important nutrients, according to this article of the American Dietetic Association, but most of us do not eat enough. In the intestines, fiber adds to stool bulk and speeds the passage of stool, which reduces the amount of time that enzymes have to break down starches in our food, according to Drs. Tharanathan and Mahadevamma. Also, fiber can physically block those enzymes from breaking down the starch. In two ways, fiber lowers the spike in blood sugar resulting from starch consumption, which has beneficial health effects (see the post on starch and the post on sugar).

Studies have shown that dietary fiber intake is associated with lowered risks of certain chronic diseases, although the evidence is not unequivocal. This meta-study authored by Drs. Teresa Norat et al. reported that higher fiber intake reduced the risk of colon cancer when data from 25 prospective studies were combined; however, this other study by Drs. Arthur Schatzkin et al. reported no overall reduction in colon cancer risk simply from fiber, though fiber from whole grains specifically did somewhat reduce colon cancer risk.

I speculate that the reason why whole grain cereal fiber, but not legume fiber, reduces cancer risk is that we absorb pure cereal starches very quickly, and whole grain cereals have more fiber than refined cereals, so our blood glucose spikes less when we eat whole grains than when we eat refined grains, and in this way, whole grain fiber is protective. However, because we digest legume starches more slowly and thus experience smaller blood glucose spikes from legumes, fiber that we eat with legumes will not reduce the spike in our blood glucose as much, so the fiber makes less of a difference in blood glucose levels for legumes.

Fiber, by tempering glucose levels, affects us in an opposite manner as sugar does. According to this article by Drs. James Anderson et al., dietary fiber intake is negatively associated with our risks of cardiovascular diseases, such as hypertension, coronary heart disease, and stroke. Thus it is vital, when we eat large amounts of starches, to consume fiber along with them in order to protect ourselves against diseases related to glucose spikes.

Because we do not break down and absorb fiber, bacteria in our large intestine instead ferment it for energy. Bacteria play an underappreciated role in our health. Each one of us hosts over one thousand different species of bacteria in our intestines, and we all have slightly different combinations of bacteria, which together are called the microbiome. Drs. Kieran Tuohy et al., in this article, explains that people with diseases like obesity, celiac disease, and diabetes have markedly abnormal microbiomes. Fiber promotes good bacteria to grow in our microbiomes, which protects us against these diseases.

Bacteria, the article says, provide us with a “second set of genes” to help us digest foods because they produce a large number of enzymes for breaking down carbohydrates that we do not have genes for. Some of their metabolic products, such as short-chain fatty acids (SCFAs), positively affect our health, and a healthy microbiome fed sufficient fiber produces more SCFAs than a fiber-starved microbiome. Additionally, depriving our microbiomes of fiber causes them to switch to amino acids for energy, and when they ferment amino acids, they produce amines, sulfides, and phenols, which can be carcinogenic. Though there is much awaiting research about how our diets affect our microbiomes and how our microbiomes affect our health, it is clear that dietary fiber consumption is beneficial for both us and our bacteria.

What foods are good sources of dietary fiber, and how much do we need? Current recommendations are to eat 25 grams of fiber per 2000 calories, although Drs. Kieran Tuohy et al. speculate that our ancestors benefitted from eating around 100 grams per day. According to nutritiondata.self.com, fiber-enriched breakfast cereals and wheat bran have among the highest amounts of fiber per mass of food—up to 50% fiber. Spices, such as oregano, rosemary, and fennel seed are over 40% fiber by mass, though one would probably not eat much of any spice at one time. Though I eat high-fiber cereal, my favorite sources of fiber are chia seeds and flax seeds, which respectively are 38% and 27% fiber by mass, and additionally are high in omega-3 fatty acids. I also eat apples and bananas, which, despite their reputations for being high-fiber foods, are only 2% to 3% fiber by fresh weight (an average apple or banana has 3 to 4 grams of fiber).

Because of the benefits of fiber on cardiovascular, intestinal, and microbiome health, it is important to eat enough fiber. Though I find getting enough to be difficult on my college meal plan, I go out of my way to buy high-fiber whole grain cereal and flax seeds because I view the cost of spending extra money on healthy food as an investment in my health later on, so that I will not have to spend money when I am 70 on exorbitantly expensive cancer medications. What information can you find about fiber, how much we need, how to get enough, and how it affects our health?

For most of us, starches provide us with most of the energy we get from our food. Given the amount of starches we consume, it’s important that we know how they affect our health. There exist high-carb, low-carb, and “no-carb” diets (but given the ubiquity of carbs in all plant products, even these diets have low amounts) that tout benefits, but before we commit to any such diet, we should know the scientific evidence behind our actions.

Starches, like fibers, are complex carbs, which are all made of simple sugar molecules—usually glucose—joined chemically together (see the post on sugar), but this simple rule yields sundry forms of complex carbs—and several different forms of starch. Starch consists of long chains of glucose molecules, and those chains can branch off into side chains. Starch with no branches is called amylose, while more branched starches are called amylopectin-C, -B, and -A, in order of increasing branching.

Starches give us energy because, according to this article by Drs. Lehmann and Robin, enzymes in our small intestine break them down into single molecules of glucose, which are then absorbed into our blood. As described in the post on sugar, rising levels of blood glucose trigger insulin production; chronically high insulin and insulin-like growth factor levels lead to many diseases, including diabetes, obesity, metabolic syndrome, and cancer.

It is unhealthy, then, to regularly dump large amounts of glucose into our blood, but we can do this by eating too much starch, as well as by eating too much sugar. Fortunately, some kinds of starch break down much more slowly than others and thus steadily release small amounts of glucose, which minimizes the insulin response. Based on the rate of release, scientists have created three classes of starches: rapidly digestible (RDS), slowly digestible (SDS), and resistant (RS), which, according to this article by Drs. Tharanathan and Mahadevamma, is only digested by bacteria in the large intestine and thus does not increase blood glucose.

Many factors determine which type of starch a food will have. The degree of branching affects digestibility because typically, the more branches, the faster the starch is broken down, so amylopectin content typically correlates with the rate of digestion. Physical factors, such as tight packing of starch molecules (as in spaghetti) or the presence of other components in the food, both of which block the enzymes that break down starch from getting to the starch, slow the rate of digestion. And factors in food preparation also determine which type of starch food has: cooking food in water can turn SDS into RDS, but desiccating the food can turn RDS back into SDS or even RS.

Typically, according to Drs. Tharanathan and Mahadevamma, cereal starches—those in bread, corn, and rice—are high in amylopectin-A and more quickly digested than those in tuberous vegetables like potatoes, which have amylopectin-B, which are in turn more quickly digested than amylopectin-C-rich starches in legumes like beans and chickpeas. However, before you give up eating cereals, consider that another factor—the presence of dietary fiber, which is found in whole grain cereals—lowers the rate at which starch is digested.

I will discuss the risks and benefits of low- and high-carbohydrate diets in a subsequent post, as well as the important role of fiber in regulating our health. No component of the diet acts in isolation—especially starch, as other components of food influence how quickly it is absorbed and can turn glucose-spiking starches into slowly digestible starch. What information can you find about the complexities of this complex carbohydrate?

Eat honey, agave nectar, or maple syrup. Call it “organic evaporated cane juice,” if you wish. It’s all sugar, and eating too much is unhealthy. But what evidence is there to blame sugar for our maladies? After all, fruits contain sugar, and all carbohydrates—from bread starch to chicory root fiber—are made of sugars. In fact, without one type of sugar—glucose (also known as blood sugar)—which most of our cells continuously use for energy, we would die within minutes.

The problem with sugar is that it is easy to get too much of a good thing. Excess consumption of sugar jeopardizes health by elevating three main conditions: glycemic loads, caloric intake, and inflammation. There are several different types of sugars, and each affects these conditions differently. Here is not the place to describe the chemical differences between different sugars—I encourage you to research these differences on your own; you may start with this link.

High Glycemic Loads and Insulin Resistance

What are glycemic loads? This link explains. When we eat digestible glucose-containing foods, like table sugar (sucrose) and starch, the glucose enters our blood. If blood glucose increases significantly, the pancreas secretes insulin to lower glucose levels; insulin stimulates liver, fat, and muscle cells to absorb glucose out of the blood. The more sugar released, the higher the glycemic load and the insulin response.

Habitually high glycemic loads have been linked to breast cancer, colorectal cancer, and pancreatic cancer, but other studies have not found associations. Interestingly, high glycemic loads have been shown to raise LDL cholesterol (the bad kind), lower HDL (the good kind), and raise triglycerides (fat in the blood), according to Drs. Christian Roberts and Simin Liu in their 2009 article, “Effects of Glycemic Load on Metabolic Health and Type 2 Diabetes Mellitus.” Thus sugar intake affects the amount and types of fat and cholesterol in the blood, and it is therefore important to reduce sugar consumption, along with improving the makeup of fats you eat (have you read my post on fats?), in order to improve cholesterol and triglycerides.

Another important result of high glycemic loads are chronically high insulin levels, which lead to insulin resistance—when cells stop absorbing glucose effectively. Insulin resistance, according to Dr. Gerald Reaven’s article, “Role of Insulin Resistance in Human Disease,” increases one’s risk of diabetes, coronary heart disease (CHD), and possibly hypertension.

Cancer may be related to insulin levels because, according to Dr. Barry Boyd’s 2003 article, “Insulin and Cancer,” insulin and a number of insulin-like growth factors stimulate cell growth, which is bad if those stimulated cells happen to be malignant or pre-malignant.

Caloric Intake

Sugar and insulin work together to make us fat. Sugar, like any carbohydrate, provides 4 calories per gram, and it’s easy to overeat: the CDC reported that between 2005 and 2010, the average adult man consumed 335 calories, and the average woman 239 calories, per day, from added sugars. For men and women, respectively, that works out to 89 and 60 grams of added sugars per day—which doesn’t include natural sugars in fruit, vegetables, and milk (12 grams per cup). Mind you that a 12-oz. Coca Cola has 39 grams of sugar.

When your blood glucose rises, insulin stimulates your liver, muscle, and fat cells to absorb glucose. The liver and muscles convert glucose into glycogen, while your fat cells convert it into—fat. Because of this, and because high sugar intake increases blood triglyceride levels, low-fat foods (and beware—when companies take out delicious fat, they have to replace it with something else delicious, like sugar, so as not to ruin the flavor) may actually lead to obesity if they are high in sugar; always check the nutrition facts label. The World Health Organization has recently recommended that we limit our consumption of added sugars to 25 grams per day.

This may be difficult, however, because Dr. Karen Teff et al. have shown that eating fructose—which is chemically combined with glucose in table sugar (sucrose)—results in higher levels of the appetite-stimulating hormone ghrelin and lower levels of the appetite-suppressing hormones leptin and insulin as compared with eating glucose. Eating a lot of fructose or sucrose, therefore, may make us eat more food—and more calories—than we would eat if we ate only glucose or starches (which are made of long chains of glucose).

Inflammation

Inflammation is a condition when cells produce a lot of chemicals that stimulate cell growth and immune system activity. While acute inflammation following a wound helps us fight off germs and repair tissue, chronic inflammation promotes cancer, autoimmune disorders, and a host of other diseases. Unfortunately, we can blame sugar and insulin for some of our inflammation: Drs. Roberts and Liu, mentioned above, associate high glycemic loads with elevated levels of the inflammatory chemicals interleukin-6, tumor necrosis factor receptor-2, C-reactive protein, adiponectin, and nuclear-factor kappa-B. This is not the place to explain what each of these does (researchers are, in fact, still determining their effects on our bodies), but I encourage you to read into the basics of inflammation.

Roberts and Liu also say that high blood glucose promotes oxidative stress, which is yet another complex condition. It damages DNA, promotes white blood cells to absorb cholesterol particles and stick to blood vessel walls, and contributes to atherosclerosis, cancer, and hypertension.

Learning about all of the problems that sugar-high diets can cause is what fanned my mild interest in healthy eating into a passion for researching nutrition. I credit Dr. Robert Lustig’s lecture, “Sugar: The Bitter Truth,” for first showing me how biochemistry and nutrition are related. In it, he explains that when the liver metabolizes fructose, it produces a number of inflammatory chemicals that ultimately harm the body. Though I think Dr. Lustig is overstating it by blaming fructose alone for the obesity epidemic, watching his lecture motivated me to more than halve my sugar consumption.

A Few Final Notes

High fructose corn syrup

I have to mention high fructose corn syrup (HFCS). HFCS is made of a mixture of chemically uncombined glucose and fructose (its composition varies but is generally around 50-50), whereas table sugar (sucrose) is chemically combined glucose and fructose. We have an enzyme—sucrase—that cleaves the chemical bond between glucose and fructose, so once inside the body, table sugar and HFCS are pretty much identical. And too much of any sugar is unhealthy.

Lactose

Lactose, which is glucose chemically combined to another sugar, galactose, has a lower glycemic index (65) than sucrose (87). People who are lactose intolerant do not produce lactase, an enzyme that, like sucrase, breaks lactose molecules up into individual glucose and galactose molecules, and they can therefore not digest lactose. The undigested lactose is broken down in the intestines by bacteria, which produce the discomfort associated with lactose intolerance.

Added sugar versus natural sugar

Sugar is sugar, as long as the composition of the sugar (glucose, fructose, galactose) is the same. Whenever my parents buy sweetened almond milk, which has 7 grams of added sucrose per cup but almost no naturally-arising sugar, I wonder if it is healthier to drink that or skim milk, which has 12 grams of lactose per cup but no added sugar. I have decided that the healthier sugar source is the one with a lower glycemic load, which is 6 per cup of almond milk and 9 per cup of skim milk. However, I do not just consider which sugar is healthier; I also have to consider the nutrients and toxins that come with the sugar. Skim milk has 8 grams of complete protein per cup, while almond milk has 1, and that single gram is incomplete protein. The almond milk has more calcium and vitamin E, but those were both added as supplements; I could just as well buy fortified skim milk. And what about antioxidants? Or rBST?

This is why nutrition is an endless stream of questions. I look forward to answering more in my next posts. But what can you find out in the meantime?

Proteins make life possible. We need them every day, and that raises the important question: are proteins from animals or vegetables better? Or is there even a difference? In a 2004 article, “Protein – Which is Best?” Jay Hoffman and Michael Falvo examined studies to answer this question.

First, the reason we all need protein is to obtain amino acids (AAs), which compose all proteins. We need to eat nine essential AAs to stay alive, to transport oxygen in blood, to repair and grow tissues, and to make enzymes, which carry out almost every bodily process that you can name. Animal proteins almost always have all nine essential AAs, and hence are “complete,” while plant proteins often lack one or two. Fortunately, different plants lack different AAs, so by eating brown rice, which is deficient in the AA lysine, with pinto beans or green peas, which are deficient in methionine and cysteine, vegans can eat complete protein.

If we eat animal flesh itself to obtain proteins, we will also be eating cholesterol and saturated fat. Though evidence that these cause cardiovascular disease is inconclusive, there is evidence, discussed in the post on fat, that replacing some saturated fats with unsaturated fats from whole vegetable products (not refined carbohydrates) decreases our risk of cardiovascular disease. In any case, skim milk and egg whites contain almost no fat and cholesterol, and “Protein – Which is Best” says that casein, the main protein in milk, is effective at building muscle. An equivalent mass of vegetable protein, however, is not as effective, according to the article.

The article mentions several different ways to compare protein quality: Net Protein Utilization (NPU), which measures what percent of the protein we eat we actually can use to make our own proteins, and Protein Digestibility Corrected Amino Acid Score (PDCAAS), which is calculated by seeing what percentage of each essential AA the food supplies, and then taking the lowest one, where a PDCAAS score of 100% indicates a complete protein. The article gives these measurements for several proteins. The ones with the best NPUs on the list are egg (94%), milk (82%) and beef (73%), all animal proteins. Wheat gluten (67%) and soy (61%) are the top vegetable proteins, but gluten has a PDCAAS score of only 25%, whereas soy is actually a complete protein. Egg and milk are also complete; beans (PDCAAS = 75%) and peanuts (PDCAAS = 52%) are not. Thus, in general, animal proteins are not only more complete, but also better absorbed, than vegetable proteins.

Complete proteins, however, can have large amounts of cysteine and methionine, essential AAs that contain sulfur. Metabolizing them converts the sulfur to small amounts of sulfuric acid, and to neutralize the sulfuric acid, the body draws calcium out of the bones. Some studies have shown than high animal protein diets decrease bone density in elderly women, young men, and rats, but other contradictory studies have shown that increasing animal protein and decreasing vegetable protein preserves bone density. This can be explained because, firstly, dairy products have calcium, which could replace the calcium lost from bones, and secondly, some vegetable proteins actually contain as much sulfur as animal proteins. According to nutritiondata.self.com, as a percentage of total protein, Brazil nuts and walnuts contain more cysteine and methionine than do eggs and milk. Oats, wheat, and rice also contain more than milk. Thus, it is not universally true that animal proteins contain more sulfur or increase bone loss; the amount of cysteine and methionine is more important than the source of the protein, as are the other nutrients, like calcium, consumed with the protein. Also, since these sulfur-containing AAs are essential, we all need to eat them, but in moderation.

Protein supplements appear to benefit athletes in both strength and endurance training. Whey, casein, and soy are common supplements, and of these, studies have shown that casein is most effective at providing us AAs for several hours that we can best use to rebuild muscle. However, there is evidence that high protein diets increase growth factors, such as insulin-like growth factor 1, which can promote cancer growth. For those of us who are not athletes, then, it seems like a good idea to avoid excessive protein consumption.

Certain foods famous for their protein content, such as milk and soy, exert additional effects on our bodies. Soy, for example, contains isoflavones that mimic estrogen and are thought to possibly reduce breast cancer risk, but that also promote oxidation of LDL cholesterol, which leads to atherosclerosis. These additional effects, however, result from other chemicals in the food, not the protein itself. Thus, it seems like it is more important, for the purpose of health, to ask not, “Animal protein or vegetable protein?” but to ask, “What are the effects of other chemicals are in this food?” Also, because there are many differences among proteins from animals and even more differences among proteins from plants, and because some plant proteins, like soy, are even more complete than some animal proteins, like beef, we cannot generalize all plant proteins into one category and all animal proteins into another. For those of us who are dedicated athletes, it may be advantageous to eat a lot of animal protein, as we tend to absorb it better. But for most of us, as long as we fulfill our protein requirements, there should not be much difference. We can choose to be carnivores or to be vegans. But as you decide, keep in mind the other nutrients and toxins that come with the protein you eat; these are more important than whether the protein originated in an animal or a vegetable.

Fat.

Like it or not, we all need to eat it to stay healthy. But it turns out that the type of fat makes all the difference—saturated, monounsaturated, polyunsaturated, trans fat—and probably is more important than how much total fat we eat, and it has a big effect on our risk of cardiovascular disease (CVD), a group of diseases that is the top killer in America. Though knowing which fats are healthiest is so important, determining which ones are has been protracted and controversial. For an explanation of what fatty acids are and what the terms saturated, monounsaturated, polyunsaturated, omega-3, and omega-6 mean, follow this link to the University of Utah.

It turns out that common recommendations for fat consumption may be unfounded—saturated fats may not be so bad after all. It appears that the Mediterranean diet, which includes a significant amount of fat, is one of the best diets to reduce risk of CVD. In general, combining the findings of many recent studies on fat and CVD, it seems good advice for someone following a typical Western diet to significantly increase omega-3 consumption, slightly increase omega-6 consumption, slightly decrease saturated fat consumption, and greatly decrease consumption of refined carbohydrates, especially white bread and sugar.

The Academy of Nutrition and Dietetics recommends that people limit saturated (SFA) and trans fatty acid (TFA) intake and focus on mono- (MUFA) and polyunsaturated (PUFA) fatty acids to reduce the risk of cardiovascular disease (CVD), which is in line with common knowledge. However, the authors of a 2013 article entitled “The role of dietary fats for preventing cardiovascular disease. A review,” point out that recent studies have shown that SFAs do not unequivocally increase one’s risk of CVD.

Whether or not SFA intake correlates with CVD risk seems to depend on what people eat more of to replace the lost SFAs. Several studies cited by the aforementioned article, including one I have also read, “Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease,” have shown that when people replace SFAs with PUFAs, their risk of CVD decreases, but when they replace SFAs with refined carbohydrates, their risk of CVD actually increases as they eat less SFAs, which is contrary to common knowledge. The effects of replacing SFAs with MUFAs are more ambiguous.

However, it is unclear whether it is better to replace SFAs with omega-6 fatty acids or not. Both omega-6 and omega-3 fatty acids are polyunsaturated, and they have been shown, respectively, to promote and mitigate inflammation, and to increase and decrease CVD risk. There is no officially recommended ratio of omega-6s to omega-3s, but the Mediterranean diet provides a ratio of about 2:1, while typical Western diets have ratios around 15:1, which increases CVD risk. Replacing SFAs with omega-6s has been shown in some studies to reduce CVD risk but to increase CVD risk in others.

Oils are pure liquid fats, but they differ markedly in composition; data can be found in the first article. Of two common oils with the most omega-3s, flaxseed oil is over 50% omega-3s and 20% omega-6s by mass, while rapeseed oil—which is actually cheaper than olive oil—is about 10% omega-3s and 20% omega-6s. Olive oil has almost no omega-3s, but it is only about 10% omega-6s, so eating it with either of the other two oils would still allow a low omega-6/omega-3 ratio.

In general, those following a Western diet should eat more omega-3s and a little more omega-6s, eat a little less saturated fat, and eat many fewer refined carbohydrates. The studies have shown that the Mediterranean diet seems to be very protective against CVD, so the more our diets resemble it, the more likely it seems that we can reduce our CVD risk and live healthier, longer lives.

If you attempt to eat a healthy diet like I do, then you know how many claims there are about what you should eat, and that though the more credible sources generally agree that the unhealthiest edible foods are fat-fried and delicious, they often disagree on what the healthiest foods are.

Being a fledgling biochemist myself, I will research which recommendations for healthy eating are supported by scientific evidence. The scientific evidence itself, however, is developing. Clinical studies contradict, and researchers are still elucidating how nutrients change the way enzymes work in our cells and how they turn genes on and off, a very complex and incompletely understood process called gene regulation. As I evaluate nutritional advice, I will research clinical studies on people and animals as well as research on metabolism and gene regulation.

I will begin with dietary guidelines that come from the top—the Academy of Nutrition and Dietetics, the world’s largest organization of nutrition professionals—to analyze guidelines that apply to most people, before looking at more niche-oriented diets, such as the paleo diet.

“Eating right isn’t complicated,” asserts the title of one page on the website. That page lists the following guidelines:

• Eat a multicolored variety of fruits and vegetables, at least three ounces of whole grains daily, lean dairy and meat products, and a variety of protein-rich foods that includes nuts, eggs, fish, poultry, and legumes.
• Limit sodium, cholesterol, added sugar, and saturated and trans fats.
• Monounsaturated and polyunsaturated fats should constitute the majority of dietary fat intake.

Over the next few weeks, I will locate studies that examine the effects of the suggested foods on human health, making sure to search for articles that refute the above recommendations, in the reverse order in which they are presented, as well as those that give support. By weighing evidence for and against these claims, I aim to understand which are valid and how scientists test their validity. But most importantly, I hope that everyone who is reading this blog and I will improve our diets and our lives.

You know how margarine is healthier than butter? Oh, wait—it’s not. Neither is agave nectar healthier than refined sugar, although it sure sounds more “natural.” If you’re looking for a good answer about which foods are healthiest, it will get lost somewhere between the doctors who write books about why their diet is better than everyone else’s and the magazines that say you can lose 10 pounds by eating speciously healthy snacks. Clinical studies do not paint a clear picture, either—an article by Patty W Siri-Tarino, Qi Sun, Frank B Hu, and Ronald M Krauss entitled “Meta-study of prospective cohort analyses evaluating the association of saturated fat with cardiovascular disease” examined 21 clinical studies; some of the studies found that eating more saturated fats increased risk of cardiovascular disease (conventional wisdom), but other studies found that eating more saturated fats decreased that risk. So before we let possibly flawed conventional wisdom dictate our eating habits, I would like to look at the best scientific evidence about dietary fads and putatively healthy or unhealthy foods and determine which facts hold up to scientific scrutiny, which are unsupported, and which are simply contradicted by most of the evidence available. In doing so, I hope to better understand the science that backs up nutritional claims and learn where the holes in our knowledge lie.

Is the computer you’re using to read this blog post Energy-Star certified? If it is, then you’re part of a growing movement to reduce the human carbon footprint. How did that movement get started? What methods do people use to conserve resources? Why should you care as well, and how can you get more involved? These are the questions I will answer in a blog about ways that you can help reduce environmental damage. You don’t have to be the one in charge of constructing fields of wind turbines or solar panels or designing hybrid automobiles to have a positive impact. Here’s how.