New genetic evidence could strengthen the link between the role of dietary fats with colon cancer progression.
Because this cancer occurs in the digestive tract, scientists have often considered important links to diet. Now
new evidence verifies a connection to dietary fats, such as those found
in processed meats, butter, beef and pork fat, shortening, and
margarine. Dr. Raymond DuBois, of
Arizona State University, has
identified a molecule, called peroxisome proliferator-activated receptor
delta (PPAR delta), which, when deleted in mice with colon cancer,
stopped the progression of tumor growth.
The study was published in the April 21 early online edition of the
Proceedings of the National Academy of Sciences.
The DuBois research team has been in pursuit of uncovering the links
between inflammation and colon cancer for the past two decades.
Colorectal cancer is the second leading cause of cancer deaths in the
U.S.
Diet and cancer
Known risks for colorectal cancers — tumors affecting the colon and
the rectum are commonly grouped together as they affect the digestive
tract — include family history, inflammatory bowel disease, smoking, and
type 2 diabetes.
Foods high in saturated fats
may also increase risk and so general advice to help you avoid
colorectal cancer is to focus on your diet. Recent, large studies, for
instance, suggest that fiber, especially from whole grains, may lower
colorectal cancer risk. Doctors also recommend you limit your intake of
red and processed meats, eat more vegetables and fruits, watch your
weight (especially watch for gains around the midsection), avoid
excessive alcohol and get recommended levels of calcium and
vitamin D, which may work together to prevent these cancers.
The facts about fat
There are numerous types of fat. Your body makes its own fat from
taking in excess calories. Some fats are found in foods from plants and
animals and are known as dietary fat. Dietary fat is a macronutrients,
along with protein and carbohydrates, that provide energy for your body.
Fat is essential to your health because it supports a number of your
body's functions. Some vitamins, for instance, must have fat to dissolve
and nourish your body.
But there is a dark side to fat. Fat is high in calories and small
amounts can add up quickly. If you eat more calories than you need, you
will gain weight.
Excess weight is inked to poor health.
Research about the possible harms and benefits of dietary fat is
always evolving. And a growing body of research suggests that when it
comes to dietary fat, you should focus on eating healthy fats and
avoiding unhealthy fats. Simply stated, fat is made up of varying
amounts of fatty acids.
It's the type and amount of fatty acid found in
food that determines the effect of the fat on your health.
Harmful dietary fat
There are two main types of potentially harmful dietary fat — fat that is mostly saturated and fat that contains trans fat:
- Saturated fat. This is a type of fat that comes
mainly from animal sources of food, such as red meat, poultry and
full-fat dairy products. Saturated fat raises total blood cholesterol
levels and low-density lipoprotein (LDL) cholesterol levels. Saturated fat may also
increase your risk of type 2 diabetes and cancer.
- Trans fat. This is a type of fat that occurs
naturally in some foods in small amounts. But most trans fats are made
from oils through a food processing method called partial hydrogenation.
By partially hydrogenating oils, they become easier to cook with and
less likely to spoil than do naturally occurring oils. Research studies
show that these partially hydrogenated trans fats can increase unhealthy
LDL cholesterol and lower healthy high-density lipoprotein (HDL)
cholesterol. This can increase your risk of cardiovascular disease.
Most fats that have a high percentage of saturated fat or that
contain trans fat are solid at room temperature. Because of this,
they're
typically referred to as solid fats. They include beef fat, pork
fat, butter, shortening and stick margarine.
Healthier dietary fat
The types of potentially helpful dietary fat are mostly unsaturated:
- Monounsaturated fat. This is a type of fat
found in a variety of foods and oils. Studies show that eating foods
rich in monounsaturated fats (MUFAs) improves blood cholesterol levels,
which can decrease your risk of heart disease. Research also shows that
MUFAs may benefit insulin levels and blood sugar control, which can be
especially helpful if you have type 2 diabetes.
- Polyunsaturated fat. This is a type of fat
found mostly in plant-based foods and oils. Evidence shows that eating
foods rich in polyunsaturated fats (PUFAs) improves blood cholesterol
levels, which can decrease your risk of heart disease. PUFAs may also
help decrease the risk of type 2 diabetes.
- Omega-3 fatty acids. One type of
polyunsaturated fat is made up of mainly omega-3 fatty acids and may be
especially beneficial to your heart. Omega-3, found in some types of
fatty fish, appears to decrease the risk of coronary artery disease. It
may also protect against irregular heartbeats and help lower blood
pressure levels. There are plant sources of omega-3 fatty acids.
However, the body doesn't convert it and use it as well as omega-3 from
fish.
Foods made up mostly of
monounsaturated and polyunsaturated fats are
liquid at room temperature, such as olive oil, safflower oil, peanut oil
and corn oil. Fish high in omega-3 fatty acids include salmon, tuna,
trout, mackerel, sardines and herring. Plant sources of omega-3 fatty
acids include flaxseed (ground), oils (canola, flaxseed, soybean), and
nuts and other seeds (walnuts, butternuts and sunflower).
Tips for choosing foods with the best types of dietary fat
So now that you know which types of dietary fat are healthy or
unhealthy, and how much to include, how do you adjust your diet to meet
dietary guidelines?
First, focus on reducing foods high in saturated fat, trans fat and
cholesterol. Then emphasize food choices that include plenty of
monounsaturated fats (MUFAs) and polyunsaturated fats (PUFAs). But a
word of caution — don't go overboard even on healthy fats. All fats,
including the healthy ones, are high in calories. So consume MUFA-rich
and PUFA-rich foods instead of other fatty foods, not in addition to
them.
Here are some tips to help you make over the fat in your diet:
- Use the Nutrition Facts label when selecting foods. Read food
labels and look for the amount of trans fat listed. By law a serving of
food containing less than 0.5 grams of trans fat can be labeled as 0
grams. Therefore, it is important to also check ingredient lists for the
term "partially hydrogenated." It's best to avoid foods that contain
trans fat and those that have been partially hydrogenated.
- Prepare fish, such as salmon and mackerel, instead of meat at
least twice a week to get a source of healthy omega-3 fatty acids. Limit
sizes to 4 ounces of cooked seafood a serving, and bake or broil
seafood instead of frying.
- Use liquid vegetable oil instead of solid fats. For example,
saute with olive oil instead of butter, and use canola oil when baking.
- Use olive oil in salad dressings and marinades.
- Use egg substitutes instead of whole eggs when possible.
- Select milk and dairy products that are low in fat.
Sources: http://www.eurekalert.org/,
http://www.medicaldaily.com/,
http://www.mayoclinic.org/