Like other foods from animals, whole milk is a source of cholesterol and saturated fats that raise your risk of heart disease. To reduce the risk of heart disease, the National Cholesterol Education Project recommends following the Step I and Step II diets.
The Step I diet provides no more than 30 percent of total daily calories from fat, no more than 10 percent of total daily calories from saturated fat, and no more than 300 mg of cholesterol per day. It is designed for healthy people whose cholesterol is in the range of 200–239 mg/dL.
The Step II diet provides 25–35 percent of total calories from fat, less than 7 percent of total calories from saturated fat, up to 10 percent of total calories from polyunsaturated fat, up to 20 percent of total calories from monounsaturated fat, and less than 300 mg cholesterol per day. This stricter regimen is designed for people who have one or more of the following conditions:
- Existing cardiovascular disease
- High levels of low-density lipoproteins (LDLs, or “bad” cholesterol) or low levels of high-density lipoproteins (HDLs, or “good” cholesterol)
- Type 1 diabetes (insulin-dependent diabetes, or diabetes mellitus)
- Metabolic syndrome, a.k.a. insulin resistance syndrome, a cluster of risk factors that includes type 2 diabetes (non-insulin-dependent diabetes)
Lactose intolerance—the inability to digest the sugar in milk—is not an allergy. It is an inherited metabolic deficiency that affects two-thirds of all adults, including 90 to 95 percent of all Asians, 70 to 75 percent of all blacks, and 6 to 8 percent of Caucasians.
These people do not have sufficient amounts of lactase, the enzyme that breaks lactose (a disaccharide) into its easily digested components, galactose, and glucose. When they drink milk, the undigested sugar is fermented by bacteria in the gut, causing bloating, diarrhea, flatulence, and intestinal discomfort.
Some milk is now sold with added lactase to digest the lactose and make the milk usable for lactase-deficient people. Galactosemia. Lactose, the sugar in milk, is a disaccharide (“double sugar”) made of one molecule of glucose and one molecule of galactose. People with galactosemia, an inherited metabolic disorder, lack the enzymes needed to convert galactose to glucose. Babies born with galactosemia will fail to thrive and may develop brain damage or cataracts if they are given milk.
To prevent this, they are kept on a milk-free diet for several years, until their bodies have developed alternative ways by which to metabolize galactose. Pregnant women who are known carriers of galactosemia may be advised to avoid milk while pregnant, lest the unmetabolized galactose in their bodies damage the fetus.
Genetic counseling is available to identify galactosemia carriers. Allergic reaction. According to the Merck Manual, milk is one of the 12 foods most likely to trigger classic food allergy symptoms: hives, swelling of the lips and eyes, and upset stomach. The others are berries (blackberries, blueberries, raspberries, strawberries), chocolate, corn, eggs, fish, legumes (green peas, lima beans, peanuts, soybeans), nuts, peaches, pork, shellfish, and wheat (see wheat cereals).
Food poisoning. Raw (unpasteurized) milk may be contaminated with Salmonella and/or Listeria organisms. Poisoning with Salmonella organisms may cause nausea, vomiting, and diarrhea—which can be debilitating and potentially serious in infants, the elderly, and people who are ill.
Listeria poisoning is a flu-like illness that may be particularly hazardous for pregnant women or invalids who are at risk of encephalitis, meningitis, or infections of the bloodstream. Listeria may also be found in milk foods made from infected raw milk. Salmonella will also grow in pasteurized milk if the milk is not refrigerated.