I recently read Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating. As I understand, it’s the book that does the best job of representing the mainstream scientific perspective on nutrition for a lay audience. Here are the notes I took.

Last updated 2024-05-31.

I wrote down info that I found personally useful, which often doesn’t translate to other people. For example, if the book gave a nutrition fact that I already confidently believed, I didn’t write it down, but someone else might have benefited from reading that fact.

Unless otherwise specified, these notes represent my interpretation of the author’s perspective and first-person pronouns represent the author, not me. Any sentence preceded by “me:” is my perspective.

Contents

• Contents
  • Chapters 1–3: Healthy Eating Matters
  • Chapter 4: Healthy Weight
  • Chapter 5: Straight Talk About Fat
  • Chapter 6: Carbohydrates for Better and Worse
  • Chapter 7: Choose Healthier Sources of Protein
  • Chapter 8: Eat Plenty of Fruits and Vegetables
  • Chapter 9: You Are What You Drink
  • Chapters 10–11: Vitamins and Minerals
• Notes from Red Pen Reviews
• Footnotes

Chapters 1–3: Healthy Eating Matters

• Soybean oil and canola oil are healthy¹
• The association between “healthy” foods and good health can’t be explained by socioeconomic status or conscientiousness because Greeks are healthier but poorer, and people who followed USDA guidelines did worse than people who followed “good” diets
• American diets are getting healthier over the last 20 years. (me: so why are people getting fatter?)
• RCTs are expensive. A nutrition and breast cancer study cost $2 billion and got inconclusive results. We mainly do cohort studies which follow a group of people for a time, they have less room for bias than retrospective self-reports / asking people with a disease about their eating habits
• Nurses’ Health Study is good because nurses are more diligent and accurate about reporting what they eat
• Japanese migrants in America have American levels of heart disease, which shows it’s not genetic
• Moderate alcohol does actually prevent heart disease. Experiments show it raises HDL

Chapter 4: Healthy Weight

• me: I examined BMI in more detail in What’s the Healthiest BMI?. Eat, Drink, and Be Healthy primarily cites the same two meta-analyses that I cited (and the book’s primary author also co-authored one of the meta-analyses (along with 61 other authors lol))
• Higher BMI is worse even within the healthy weight range, see Nurses’ Health Study
  • me: the reported data looks at CVD and diabetes and stuff but not at respiratory disease
• Guidelines say BMI should be 18.5 to 25, that’s the cohort with lowest death rate after controlling for smoking etc. But really health starts getting worse at BMI > 22
• BMI = weight (kg) / height (m)^2 or weight (lbs) / height (in)^2 * 703
• BMI under 18.5 is bad if you’re sick but it’s fine if you’re just thin
  • me: for my perspective on this, see What’s the Healthiest Body Composition?, especially the bits about Lee et al. (2018). the claim appears to be true, but there are approximately zero people with healthy lean mass and a BMI under 18.5

Chapter 5: Straight Talk About Fat

• Belly fat is worse than hip/butt fat. Unclear why, maybe because it affects hormones more
• Controlling weight is the most important component of diet. Luckily, a healthy diet is a subset of diets that make it hard to overeat (me: fad diets can be good for controlling weight but aren’t optimal for health). Ex: fiber is satiating and also good for digestive health
• Insulin makes your body convert calories to fat and reluctant to burn fat; people with high insulin will be hungry even if they have plentiful fat stores. That’s a reason to prefer foods with low glycemic index
• Proteins/fats stay in the stomach for longer which reduces hunger
• 45% of a database of people who lost weight didn’t use a Diet, they “did it themselves”²
• Unsaturated fat lowers LDL (“bad”) cholesterol and raises HDL (“good”) cholesterol (compared to carbs); saturated raises both; trans raises LDL
• Fat is not water soluble, so it is transmitted through bloodstream by protein packages (lipoproteins)
• Saturated fats have varying effects. Coconut oil raises HDL more than beef or butter fat, but its effect on LDL still makes it net unhealthy
• LDL accumulates in blood vessels—it’s low density so it’s more likely to get stuck. HDL removes LDL from blood vessels
• Omega-6 doesn’t increase inflammation, it reduces it. The 3:6 ratio didn’t matter in the Nurses’ Health Study
• Eggs are fine. Low in saturated fat
• Nuts beat olive oil in RCTs
• Red meat is bad for colon cancer, which could be b/c of fat content or b/c of chemicals generated by cooking at high temperatures. But biggest risk factor for colon cancer is being overweight
• ALA associated with prostate cancer, but likely b/c ALA-rich fats used to be partially hydrogenated most of the time. Walnuts are high in ALA and aren’t associated with prostate cancer. Future studies will see if the ALA-cancer connection persists now that trans fats are mostly gone from diets, But you probably shouldn’t worry about ALA
• Dietary fat has no detectable association with cancer. Saturated and trans fats are bad for heart disease so that’s what we should focus on

Chapter 6: Carbohydrates for Better and Worse

• Grains are optional
• Carbs looked healthy in old China studies but don’t look healthy in the west. Likely due to (1) Chinese were more physically active and (2) they ate whole or lightly refined grains. The badness of carbs mainly comes when you don’t burn them off (?)
• Simple vs complex carb isn’t that important. Glycemic index (GI) and refined vs whole are more important. Glycemic index, not carb complexity, determines blood sugar
• Potatoes and corn are fast digesting. Corn is technically whole grain but it’s been bred to be fast digesting so it’s more like white rice
• Fast digesting carbs spike blood sugar then spike insulin so your body quickly absorbs the blood sugar, now you have low blood sugar which triggers hunger
• Table sugar and corn syrup have the same impact on blood sugar and metabolism
• Insulin resistance means cells resist the signal telling them to absorb sugar, so blood sugar stays elevated for longer. Insulin-producing cells in the pancreas get overworked and stop working
• Contributors to diabetes: obesity; sedentariness, because muscles are good at consuming glucose; low polyunsaturated fatty acid (PUFA) and high saturated fat; genetics
• Finely ground whole wheat is high GI but it’s still healthy due to fiber and nutrients
• Low-GI foods help prevent diabetes
• High-fiber cereal helps prevent diabetes
• Early studies showed fiber reduced gut cancer, but later studies e.g. Nurses’ Health showed no effect
• Whole grains have 1:10 or 1:5 fiber:carb ratio
• Added fiber like cellulose isn’t as good as whole fiber b/c it’s missing micronutrients and it doesn’t encapsulate the carbs to slow digestion (book calls added fibers “fake fiber”)
• Eat whole grain cereal for breakfast. Ex: Wheaties, Grape Nuts, Kashi, Shredded Wheat, Wheat Chex

Chapter 7: Choose Healthier Sources of Protein

• BCAAs turn up IGF-1 which helps muscles grow but also cancer
• Processed meat causes cancer; red meat probably causes cancer. Mainly colorectal
• Country-level data shows plant proteins associated with less cancer than animal proteins, but country data is highly confounded. It’s probably the stuff that comes with the protein that matters, not the pure protein
• ALA reduces clotting
• Soy effect on heart disease is overstated. What studies actually show is that heart disease is reduced when you replace red meat with soy
• Soy contains phytoestrogens which may prevent breast cancer. Phytoestrogens act like estrogen in some places and block it in others. It appears it blocks estrogen in cancer cells and estrogen stimulates growth
• Some fish contain mercury but many species (e.g. salmon) don’t have concerning amounts. Don’t worry about it unless you’re a child or pregnant. Fish oil supplements have less mercury than fish but don’t show the same health benefits

Chapter 8: Eat Plenty of Fruits and Vegetables

• The effects of the vast majority of plant chemicals have yet to be determined. We don’t even know most of the chemicals that are in plants
• Fruit and veg, especially greens and citrus (including juice), lower blood pressure and reduce stroke. Folic acid supplements work too. Fruit and veg shown to reduce blood pressure in RCT
• Cataracts and macular degeneration may be caused by free radicals
• 1/3 of cancer is explained by diet. Possibly an overestimate
• One study found that fruit in adolescence does more to prevent cancer than fruit in middle age
• Berries are S tier fruit, especially blueberries
• Fiber sticks to cholesterol and you poop it out
• Newest studies show fiber doesn’t help with colon cancer. But it does still stabilize blood sugar which reduces diabetes, lowers triglycerides, and improves gut microbiome
• It looks like many diseases like CVD and cancer are driven by deficiencies in some phytonutrients, but we don’t know which. Folate is probably one
• Eat a variety of colors. Get one serving a day each of: dark leafy greens, yellow/orange fruit/veg, red fruit/veg, legumes, citrus
• Cooked tomatoes are better than raw b/c your body has a hard time absorbing lycopene from raw tomatoes
• Some veggies have chemicals that are bad if you eat too much, but it’s hard to eat too much
• Juice and smoothies are bad because (1) easy to over-eat and (2) juice makes sugar absorb faster (me: they didn’t say if smoothies do that)
  • me: I spent a little time online trying to determine if smoothies are healthy or not (ignoring calorie content), my main concern being whether blending destroys fiber/nutrients. I found zero relevant papers on Google Scholar. I found various people, including dietitians (e.g. on Hopkins Medicine) asserting without evidence that blending doesn’t destroy nutrients. So I assume smoothies are healthy but I don’t really know

Chapter 9: You Are What You Drink

• Milk in adolescence increases height which increases hip fractures
• Coffee and tea reduce gallstones, possibly b/c they stimulate gall bladder activity
• Coffee, even decaf, reduces diabetes. Possibly due to antioxidants
• Coffee reduces Parkinson’s
• Tea has flavonoids which may reduce CVD
• Alcohol raises HDL. CVD benefit at 1-2 drinks per day for men. Can be any kind of alcohol. Benefits of wine specifically are unproven
• Alcohol raises breast cancer risk in women even at half a drink per day. Folate counteracts this
• Alcohol is net harmful for young men due to low CVD risk, and net beneficial for older men. Unclear for women, probably net positive unless you have family history of breast cancer

Chapters 10–11: Vitamins and Minerals

• Hard to tell how much calcium people need because outer shells of bones can absorb calcium quickly but without increasing inner bone density
• Insufficient vitamins can contribute to CVD and cancer even without deficiency disease
• Folic acid started being added to grains to prevent birth defects but it accidentally reduced CVD and cancer too
• Vitamin A helps regulate cell division and thus prevent cancer
• Beta carotene isn’t vitamin A but your body turns it into vitamin A
• Excess pre-formed vitamin A blocks vitamin D. Better to get vitamin A from beta carotene than from pre-formed vitamin A (retinol)
• Free radicals are positively charged so they can steal electrons from DNA or cholesterol or other important things in your body
• Early studies showed benefits but recent large RCTs don’t find benefits to antioxidant supplements
• James Watson suggests antioxidant supplements are bad because free radicals kill cancer cells
• Antioxidants are good if you get them from food
• Excess iron generates free radicals. Some evidence suggests excess iron causes heart disease and cancer, but jury is still out
• Body does a good job of passing on unneeded iron when it comes from plants but not when it comes from meat (me: what about supplements?)
• I recommend taking a multivitamin that doesn’t contain iron
• Sodium RDA is 2300mg but most people need less than 1000mg
• American Heart Association recommends a max of 1500mg sodium
• Selenium probably doesn’t matter
• Take a multivitamin that contains the nutrients people tend to miss: beta carotene, B6, B12, folic acid, D, E, iron, zinc (me: what about earlier claim to not supplement iron?). No more than 2000IU pre-formed vitamin A
• Basic One multivitamin is good. Menstruating women get the version with iron, others don’t need the iron
  • me: Compared to normal multivitamins, Basic One has considerably more D3, E, and B6, and way more B12; added selenium, chromium, and lycopene (an antioxidant found in many red fruits/veggies); and its vitamin A comes exclusively in the form of beta carotene (no pre-formed vitamin A)

Notes from Red Pen Reviews

This section was added on 2024-05-31.

Red Pen Reviews, a website that reviews the scientific accuracy of books on nutrition, reviewed Eat, Drink, and Be Healthy and gave it the highest score of any book it’s reviewed.³ It did, however, have some minor quibbles with the book. It disputed one claim from the book, found that the book overstated the strength of evidence in two of its references, and sort-of disputed the book’s position on multivitamins.

Claim from the book: “Protein sources from plants and lean meats such as chicken or fish are likely more beneficial than protein from red and processed meat. Protein from soy, however, is less well-understood.”

There’s mixed evidence on whether plants and lean meats are better for cardiovascular disease than red meat. It seems broadly true but there’s some conflicting evidence. In addition, the skepticism about soy is based on old studies, and more recent studies find that soy is beneficial.

Reference from the book: “In an analysis my colleagues and I did among more than 43,000 men, intake of total protein was minimally associated with heart disease risk, while intake of protein from meat was associated with higher risk.”

Among all participants, the correlation between protein source and heart disease risk was non-significant. The correlation only became significant when the analysis was restricted to “healthy” patients.

Reference from the book: “Dark leafy green vegetables contain two pigments, lutein and zeaxanthin, that accumulate in the eye. These two, along with phytochemicals called carotenoids, can snuff out free radicals before they can harm the eye’s sensitive tissues.”

The cited study established that lutein and zeaxanthin are good for eye health, but the study did not examine mechanisms. The proposed mechanism is plausible, but not supported by the cited study.

Claim from the book: “Take a daily multivitamin.”

Some, such as the president of the Australian Medical Association, say multivitamins are a waste. Some good studies showed multivitamins had no beneficial effects. But other good studies showed multivitamins did have beneficial effects. So the claim that you should take a multivitamin is controversial.

My personal take: multivitamins are cheap and easy, so they clearly pass a cost-benefit analysis, even if there’s a good chance that they don’t work.

Footnotes