Few things change as often in nutrition as the party line on fat. But one thing has remained more or less constant: saturated fat spells trouble. And milk fat has lots of it: two thirds to be exact – much more than beef itself.It's not just that saturated fat elevates blood levels of artery-clogging LDL-cholesterol about three times as much as it boosts cardioprotective HDL-cholesterol. It also makes blood sticky, promoting clots that can plug cholesterol-narrowed arteries and cause heart attacks, strokes, and the thousand tiny brain insults that contribute to senile dementia. Controlled trials have shown that restricting saturated fats helps prevent these manifestations of cardiovascular disease (CVD).
Surprisingly, some studies suggest more milk means less CVD. In the Caerphilly Study of nearly 3000 Welsh men, those who drank one or more pints of milk a day had an 88% lower risk of heart attacks and strokes than those who drank none. The famous Honolulu Heart Program found that, compared to men who shunned milk, men who drank two or more glasses a day were only half as likely to be felled by a thromboembolic stroke (the most common kind).
Whaaaaat?
Well, there are some serious methodological criticisms. The Caerphilly study, for example, didn’t rule out any risk factors of the "he drinks milk and works out a lot; he drinks beer and smokes all day" kind. By far the most significant criticism of the better-controlled positive studies (which have usually found a very modest effect for milk) is that few if any have data on what kind of milk. But at least one study does, and its results are very suggestive.
But first, a little background.
When scientists ponder why skim- or low-fat milk might prevent, rather than cause CVD, they typically cite its high calcium content, its moderate contributions of magnesium and potassium, and its modest burden of sodium. All these factors (especially potassium) prevent high blood pressure, which is a major risk factor for CVD. For dairy dissenters, that's good news really. Calorie for calorie, whole unprocessed plant foods – especially fruits and vegetables – are as good, if not better than milk at producing this blood pressure-friendly mineral balance. In 1999, the Harvard Nurses' Health Study found that stroke risk fell by 6% for every serving of fruits or vegetables consumed.
Now to the study. Another dispatch from the famous Nurses' Health Study, this one found that women who drank the most whole milk (one or two glasses a day) had (respectively) a 48% and a 67% greater risk of fatal and nonfatal heart attacks than those who drank it almost never. In contrast, skim milk produced a modest, though nonsignificant, reduction in risk of up to 22% with increasing intake. The study appeared to neatly separate milk's cardiotoxic fat from its (perhaps) cardioprotective whey. But like the pro-milk studies, it too had an Achilles heal. The researchers had controlled for a posse of potential confounding factors - smoking, exercise, taking a vitamin E supplement, among others - but not the plant food portion of the nurses' diets. What if the throw-caution-to-the-wind whole milk drinkers had also neglected to eat their fruit and vegetables, and the "prudent" skim milk lovers had not? "It is possible the association with whole milk may be due to other factors," admits lead author Frank Hu, who says he and his associates are looking into the plant food connection. But, given what we know about saturated fat from a lode of other studies, Hu believes "a higher amount of saturated fat associated with regular milk may be also responsible for the positive association."
VERDICT: Because of its preponderance of saturated fat, it's a reasonable bet that whole milk is as inimical to your heart and blood vessels as any saturated fat source. In contrast, low-fat milk may actually be beneficial - just like fruit or vegetable juice.
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