5) DIET TO AVOID HEART DISEASE
d) Benefits of Unsaturated Fats
There is strong indications from several studies, including the large Nurses study done at Harvard, that, IF THE TOTAL CALORIC INTAKE REMAINS THE SAME, unsaturated fats are beneficial to the heart. Indeed, the unsaturated fats seem to be better for the heart than what researchers term "carbohydrates". The study was a little misleading in that this same Harvard nurses study found that most nurses who consumed carbohydrates consumed "bad" high glycemic index carbohydrates or "refined carbohydrates". This same nurses' study showed that those who consumed low glycemic index carbohydrates had 50% of the heart disease of those who ate high glycemic index carbohydrates. So both high glycemic index carbohydrate foods and saturated fats are worse than unsaturated fats, calorie for calorie. But low glycemic index carbohydrates may be roughly equivalent to unsaturated fats, calorie for calorie. The technical details of the data are as follows (note "CHD" is coronary heart disease or a heart attack):
From the Harvard Nurses Study:
"More recently, using 14-year follow-up data from the Nurses' Health Study, Hu and colleagues [14] conducted detailed prospective analyses of dietary fat and CHD among 80,082 women aged 34 to 59. The study was particularly powerful because of large sample sizes and repeated assessments of diet. Hu et al. found a weak positive association between saturated fat intake and risk of CHD, but a significant and strong positive association with intake of trans fatty acids. Five percent of energy from saturated fat, compared with equivalent energy from carbohydrates, was associated with a 17 percent greater risk of CHD (relative risk=1.17, 95 percent confidence interval 0.97-1.41, p=0.10). Compared with equivalent energy from carbohydrates, the relative risk for two percent of energy from trans fat was 1.93 (1.43-2.61, p < 0.001); for five percent of energy from monounsaturated fat, 0.81 (0.65-1.00, p=0.05); and for five percent energy from polyunsaturated fat, 0.62 (0.46-0.85, p=0.002). Total fat was intake not significantly related to risk (for five percent energy 1.02, 0.97-1.07, p=0.55). It was estimated that replacement of five percent of energy from saturated fat by unsaturated fats would reduce risk by 42 percent (23-56, p < 0.001), and replacement of two percent of energy from trans fat by unhydrogenated unsaturated fats would reduce risk 53 percent (34-67, p < 0.001) (Fig. 1). These findings challenge the widely recommended low-fat high-carbohydrate diets because they suggest that replacing saturated and trans fats with unhydrogenated unsaturated fats is more effective in preventing CHD than reducing overall fat intake."From JAMA:
"Design, Setting, and Participants Randomized, 3-period, crossover feeding study (April 2003 to June 2005) conducted in Baltimore, Md, and Boston, Mass. Participants were 164 adults with pre-hypertension or stage 1 hypertension. Each feeding period lasted 6 weeks and body weight was kept constant.
Interventions: A diet rich in carbohydrates; a diet rich in protein, about half from plant sources; and a diet rich in unsaturated fat, predominantly monounsaturated fat.
Main Outcome Measures: Systolic blood pressure and low-density lipoprotein cholesterol.
Results: Blood pressure, low-density lipoprotein cholesterol, and estimated coronary heart disease risk were lower on each diet compared with baseline. Compared with the carbohydrate diet, the protein diet further decreased mean systolic blood pressure by 1.4 mm Hg (P = .002) and by 3.5 mm Hg (P = .006) among those with hypertension and decreased low-density lipoprotein cholesterol by 3.3 mg/dL (0.09 mmol/L; P = .01), high-density lipoprotein cholesterol by 1.3 mg/dL (0.03 mmol/L; P = .02), and triglycerides by 15.7 mg/dL (0.18 mmol/L; P<.001). Compared with the carbohydrate diet, the unsaturated fat diet decreased systolic blood pressure by 1.3 mm Hg (P = .005) and by 2.9 mm Hg among those with hypertension (P = .02), had no significant effect on low-density lipoprotein cholesterol, increased high-density lipoprotein cholesterol by 1.1 mg/dL (0.03 mmol/L; P = .03), and lowered triglycerides by 9.6 mg/dL (0.11 mmol/L; P = .02). Compared with the carbohydrate diet, estimated 10-year coronary heart disease risk was lower and similar on the protein and unsaturated fat diets.
Conclusion: In the setting of a healthful diet, partial substitution of carbohydrate with either protein or monounsaturated fat can further lower blood pressure, improve lipid levels, and reduce estimated cardiovascular risk."
Of course the big problem here is that unsaturated fats are loaded with calories on a gram weight or bulk basis. So it is difficult to control the calorie intake if a person substitutes unsaturated fats for carbohydrates. It's easier to control the calories of high fiber, low glycemic index carbohydrates as they are far more bulky and far more filling on a calorie for calorie basis. For instance, a level tablespoon of oil such as olive oil has 120 calories, the same as an entire cup of cooked oats or half a cup of beans. That is a huge difference in volume.
Also there is the problem that our ancestors did not eat large amounts of vegetable oils (unsaturated fats). At most it was 1% of their diet. With the prevalence of fried foods and salad dressing modern man probably consumes about 6% of his diet in vegetable oils. So, if someone has to eat fats, they should eat unsaturated fats. But no one should look at unsaturated fats as a healthy food if they are overweight, because unsaturated fats in even moderate amounts prevent weight loss. This point argues strongly for the Pritikin and the Ornish diets! There is no study we could find that tested low glycemic, fiber rich carbohydrates against unsaturated fat dietary intake. So that trade off is unknown at this time.
Calorie for calorie it appears that very low glycemic index carbohydrate, protein, and unsaturated fats are pretty much equivalent as far as being beneficial for a normal individual. The problem a person with diabetes has, of course, is that, by definition, their body cannot control blood sugar levels when they eat carbohydrates, so carbohydrates are not equivalent to protein and unsaturated fats for a person with diabetes. For a person with diabetes, protein and unsaturated fats are unquestionably the best calorie sources. The problem is that "complete" proteins and unsaturated fat are not found in the same foods! Fish, white meat chicken, nuts, beans and vegetables (especially spinach) is probably as close of a balance that we can get to.
Polyunsaturated fats (rich in omega 3's) are better than monounsaturated fats (rich in omega 6's), but the difference is difficult to take advantage of. Most polyunsaturated fats are processed out of the liquid vegetable oils found on the store shelves so realistically one is left with only monounsaturated oils for cooking. Refrigerated flaxseed from the health food store is a polyunsaturated fat rich in omega 3's and should be used for salad dressings whenever possible. Use canola oil (a 70% monounsaturated 30% polyunsaturated oil) in cooking if someone must cook with oil. Do not use olive oil or flax seed oil to cook with as they both decompose at too low a temperature and the decomposition products aren't healthy (and they taste bad). Note that there is nothing in the data to suggest that olive oil is a magic panacea or the "best" oil for anything (it is largely monounsaturated fats and it has very little polyunsaturated oil in it); the best oil for cold applications such as salads is clearly flaxseed oil and the best oil for cooking is definitely canola oil. If someone is trying to lose significant amounts of weight, don't overdo it; any oil is very calorie rich.
Current Chapter: 5) DIET TO AVOID HEART DISEASE
a) Introduction
b) Avoiding Saturated Fats
c) Avoiding Trans Fatty Acids
d) Benefits of Unsaturated Fats
e) Fats and Weight Loss
f) Benefits of Fiber
g) Avoiding High Glycemic Index Foods
h) Reducing Salt Intake
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