1. High intake of omega-6 oils, such as corn, safflower, sunflower, peanut, and soybean oils. This not only includes fried foods such as french fries, fried chicken, and fried vegetables, but also commercial foods made using these oils, such as breads, pastries, and chips.

2. High levels of sugar impair immunity, especially cellular immunity. This can include all forms of sugar, but especially high fructose corn syrup.

3. Low iron levels increase susceptibility to infections and difficulty curing infections. The immune system requires an adequate iron level for its function. Excessive iron also impairs immunity. The only way to know your iron status by getting an iron panel that includes such things as total iron binding capacity, transferrin, ferritin, and total and free iron levels. This blood test is especially important as one enters middle age.

4. Lack of quality sleep causes stress and activates the stress system. All stress, especially excessive and chronic stress, raises glucocorticoid levels in the blood and tissues and this suppresses immunity.

5. The vast majority of vaccines suppress cellular immunity. This is a special danger in older people and those who are very young. The closer together the vaccines are administered, the greater the danger they present. Mercury and aluminum, which are found in many vaccines (such as the flu shot), also alter cellular immunity.

6. Many pesticides, herbicides and fungicides alter immune function.

7. Deficiencies of vitamins B, C, and E, and especially folate and methylcobalamin deficiencies, will lower immunity